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  • 11401.
    Zhang, Yang
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik. Ningbo RK Solar Tech. Ltd., China.
    Lundblad, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik. Mälardalen University, Sweden.
    Campana, Pietro Elia
    Yan, Jinyue
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik. Mälardalen University, Sweden.
    Comparative Study of Battery Storage and Hydrogen Storage to Increase Photovoltaic Self-sufficiency in a Residential Building of Sweden2016Ingår i: PROCEEDINGS OF RENEWABLE ENERGY INTEGRATION WITH MINI/MICROGRID (REM2016) / [ed] Yan, J Zhai, Y Wijayatunga, P Mohamed, AM Campana, PE, ELSEVIER SCIENCE BV , 2016, s. 268-273Konferensbidrag (Refereegranskat)
    Abstract [en]

    Photovoltaic (PV) is promising to supply power for residential buildings. Battery is the most widely employed storage method to mitigate the intermittence of PV and to overcome the mismatch between production and load. Hydrogen storage is another promising method that it is suitable for long-term storage. This study focuses on the comparison of self-sufficiency ratio and cost performance between battery storage and hydrogen storage for a residential building in Sweden. The results show that battery storage is superior to the hydrogen storage in the studied case. Sensitivity study of the component cost within the hydrogen storage system is also carried out. Electrolyzer cost is the most sensitive factor for improving system performance. A hybrid battery and hydrogen storage system, which can harness the advantages of both battery and hydrogen storages, is proposed in the last place.

  • 11402.
    Zhang, Yang
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Lundblad, Anders
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Campana, Pietro Elia
    Yan, Jinyue
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Employing Battery Storage to Increase Photovoltaic Self-sufficiency in a Residential Building of Sweden2016Ingår i: CUE 2015 - APPLIED ENERGY SYMPOSIUM AND SUMMIT 2015: LOW CARBON CITIES AND URBAN ENERGY SYSTEMS, Elsevier, 2016, s. 455-461Konferensbidrag (Refereegranskat)
    Abstract [en]

    Photovoltaic (PV) or hybrid PV-battery systems are promising to supply power for residential buildings. In this study, the load profile of a multi apartment building in Gothenburg and the PV production profile under local weather conditions are compared and analyzed. Three different types of batteries, including lead acid, NaNiCl (Sodium-Nickel-Chloride) and Lithium ion, are studied in combination with the PV systems. It is found that Lithium ion battery system is superior in achieving higher Self-Sufficiency Ratio (SSR) with the same Life Cycle Cost (LCC). Achieving high SSR with the hybrid PV-battery system is unrealistic because of the seasonal mismatch between the load and electricity production profile. The capacity match between the PV and battery to maximize SSR was investigated, showing different trends under system LCC range of 0.1-40 Million SEK (1SEK approximate to 0.12USD). The system LCC should be lower than 10.6 Million SEK (at the SSR of 36%) in order to keep the payback time positive.

  • 11403.
    Zhang, Yantong
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Escribano, Pedro
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Active Forwarder Cab Suspension2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The forest industry plays an important role in Sweden, and forest machine manufactures are underconstant pressure to achieve both high productivity and comfortable operating environment in its products. A forwarder is a forestry vehicle that carries logs which are cut by a harvester. It suffers alot of low frequency and high amplitude vibrations during the operation because of the rough terrainin forests. Therefore, it is necessary and vital to introduce an active cab suspension system in orderto reduce the whole vibrations in the forwarder cab.The main purposes of this thesis are to develop, implement and test a feasible control strategy forthe active cab suspension system as well as verify the controller’s performance in terms of vibrationreduction and power consumption. This project is focused on the available mechanical rig installedat KTH lab hall, instead of a real forwarder.A deep study has been carried out on a new valve prototype. Exhausted tests were made to testthe performance of this valve under different conditions. From the test results, the valve was tunedin order to get the best performance out of it. Once the valve has been well calibrated, a model ofthe whole system was estimated by using Black-box estimation. The model has a 96% of matchingbetween the stimulation data and the validation data. Different controllers were designed with thismodel, and the best one was designed by the gain scheduling method.The system has a delay of 36 ms, therefore, it was studied how the performance of this controllerwould increase if this delay was reduced. The study shows that reducing the delay to around 0-2ms, the suspension system is able to reduce the vibration from 60% to 90%. Smith Predictor wasimplemented into the gain scheduling controller in order to reduce the effect of the delay. The resultsdemonstrated a better and more robust performance of the controller with Smith Predictor.Several test cases were implemented to seek a wide range of possible vibrations that a forwardercould handle in the forest. These tests have been done both in a test rig and in a simulationenvironment. The final test was conducted by using a real track test model obtained from Skogforsk.This track is used for testing different systems in a test forwarder since it simulates the terrain ina forest. Based on the simulation result, the total disturbance reduction percentages of SmithPredictor controller are 75% for heave, 68% for pitch and 73% for roll, which shows the systemreduces the cab vibration. Moreover, the maximum amount of power needed during the forwarderoperation is 11.63 kW which is feasible for implementing this system on the actual forwarder.

  • 11404. Zhang, Yingfeng
    et al.
    Liu, Sichao
    Key Laboratory of Contemporary Design and Integrated Manufacturing Technology, School of Mechanical Engineering, Northwestern Polytechnical University, Shaanxi, China.
    Liu, Yang
    Li, Rui
    Smart box-enabled product–service system for cloud logistics2016Ingår i: International Journal of Production Research, ISSN 0020-7543, E-ISSN 1366-588X, Vol. 54, s. 6693-6706Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Modern logistics takes significant progress and rapid developments with the prosperity of E-commerce, particularly in China. Typical challenges that logistics industry is facing now are composed by a lack of sharing, standard, cost-effective and environmental package and efficient optimisation method for logistics tasks distribution. As a result, it is difficult to implement green, sustainable logistics services. Three important technologies, Physical Internet (PI), product–service system (PSS) and cloud computing (CC), are adopted and developed to address the above issues. PI is extended to design a world-standard green recyclable smart box that is used to encapsulate goods. Smart box-enabled PSS is constructed to provide an innovative sustainable green logistics service, and high-quality packaging, as well as reduce logistics cost and environmental pollution. A real-time information-driven logistics tasks optimisation method is constructed by designing a cloud logistics platform based on CC. On this platform, a hierarchical tree-structure network for customer orders (COs) is built up to achieve the order-box matching of function. Then, a distance clustering analysis algorithm is presented to group and form the optimal clustering results for all COs, and a real-time information-driven optimisation method for logistics orders is proposed to minimise the unused volume of containers. Finally, a case study is simulated to demonstrate the efficiency and feasibility of proposed cloud logistics optimisation method.

  • 11405. Zhang, Yingfeng
    et al.
    Liu, Sichao
    Department of Industry Engineering, Northwestern Polytechnical University, Xi'an, China.
    Si, Shubin
    Yang, Haidong
    Production System Performance Prediction Model Based on Manufacturing Big Data2015Ingår i: ICNSC 2015 - 2015 IEEE 12th International Conference on Networking, Sensing and Control, IEEE, 2015, s. 277-280Konferensbidrag (Refereegranskat)
    Abstract [en]

    Existing production systems are short of real-time performance status of production process active perception, resulting in the production abnormal conditions processed lag, leading to the frequency problems of deviations in production tasks execution and planning. To address this problem, in this research, an advanced identification technology is extended to the manufacturing field to acquire the real-time performance data. Based on the sensed real-time manufacturing data, this paper presents a prediction method of production system performance by applying the Dynamic Bayesian Networks (DBN) theory and methods. It aims to achieve the prediction of the performance status of production system and potential anomalies, and to provide the important and abundant prediction information for real-time production control.

  • 11406. Zhang, Yingfeng
    et al.
    Liu, Sichao
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion, Produktionssystem.
    Sun, Shudong
    Clustering and Genetic Algorithm Based Hybrid Flowshop Scheduling with Multiple Operations2014Ingår i: Mathematical problems in engineering (Print), ISSN 1024-123X, E-ISSN 1563-5147Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This research is motivated by a flowshop scheduling problem of our collaborative manufacturing company for aeronautic products. The heat-treatment stage (HTS) and precision forging stage (PFS) of the case are selected as a two-stage hybrid flowshop system. In HTS, there are four parallel machines and each machine can process a batch of jobs simultaneously. In PFS, there are two machines. Each machine can install any module of the four modules for processing the workpeices with different sizes. The problem is characterized by many constraints, such as batching operation, blocking environment, and setup time and working time limitations of modules, and so forth. In order to deal with the above special characteristics, the clustering and genetic algorithm is used to calculate the good solution for the two-stage hybrid flowshop problem. The clustering is used to group the jobs according to the processing ranges of the different modules of PFS. The genetic algorithm is used to schedule the optimal sequence of the grouped jobs for the HTS and PFS. Finally, a case study is used to demonstrate the efficiency and effectiveness of the designed genetic algorithm.

  • 11407. Zhang, Yingfeng
    et al.
    Liu, Sichao
    Key Laboratory of Contemporary Design and Integrated Manufacturing Technology, School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi, China.
    Zhu, Zhenfei
    Si, Shubin
    Agent-based intelligent medical diagnosis system for patients2015Ingår i: Technology and Health Care, ISSN 0928-7329, E-ISSN 1878-7401, Vol. 23, s. S397-S410Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    BACKGROUND: According to the analysis of the challenges faced by the current public health circumstances such as the sharp increase in elderly patients, limited medical personnel, resources and technology, the agent-based intelligent medical diagnosis system for patients (AIMDS) is proposed in this research. OBJECTIVE: Based on advanced sensing technology and professional medical knowledge, the AIMDS can output the appropriate medical prescriptions and food prohibition when the physical signs and symptoms of the patient are inputted. METHODS: Three core modules are designed include sensing module, intuition-based fuzzy set theory/medical diagnosis module, and medical knowledge module. RESULTS: The result shows that the optimized prescription can reach the desired level, with great curative effect for patient disease, through a case study simulation. CONCLUSION: The presented AIMDS can integrate sensor technique and intelligent medical diagnosis methods to make an accurate diagnosis, resulting in three-type of optimized descriptions for patient selection.

  • 11408. Zhang, Yingfeng
    et al.
    Wang, Jin
    Liu, Sichao
    Key Laboratory of Contemporary Design and Integrated Manufacturing Technology, Ministry of Education, Northwestern Polytechnical University, Shaanxi, 710072, China.
    Qian, Cheng
    Game theory based real-time shop floor scheduling strategy and method for cloud manufacturing2017Ingår i: International Journal of Intelligent Systems, ISSN 0884-8173, E-ISSN 1098-111X, Vol. 32, nr 4, s. 437-463Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the rapid advancement and widespread application of information and sensor technologies in manufacturing shop floor, the typical challenges that cloud manufacturing is facing are the lack of real‐time, accurate, and value‐added manufacturing information, the efficient shop floor scheduling strategy, and the method based on the real‐time data. To achieve the real‐time data‐driven optimization decision, a dynamic optimization model for flexible job shop scheduling based on game theory is put forward to provide a new real‐time scheduling strategy and method. Contrast to the traditional scheduling strategy, each machine is an active entity that will request the processing tasks. Then, the processing tasks will be assigned to the optimal machines according to their real‐time status by using game theory. The key technologies such as game theory mathematical model construction, Nash equilibrium solution, and optimization strategy for process tasks are designed and developed to implement the dynamic optimization model. A case study is presented to demonstrate the efficiency of the proposed strategy and method, and real‐time scheduling for four kinds of exceptions is also discussed.

  • 11409. Zhang, Yingfeng
    et al.
    Wang, Wenbo
    Liu, Sichao
    School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an 710072, China.
    Xie, Gongnan
    Real-time shop-floor production performance analysis method for the internet of manufacturing things2014Ingår i: Advances in Mechanical Engineering, ISSN 1687-8132, E-ISSN 1687-8140, Vol. 6, artikel-id 270749Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Typical challenges that manufacturing enterprises are facing now are compounded by lack of timely, accurate, and consistent information of manufacturing resources. As a result, it is difficult to analyze the real-time production performance for the shopfloor. In this paper, the definition and overall architecture of the internet of manufacturing things is presented to provide a new paradigm by extending the techniques of internet of things (IoT) to manufacturing field. Under this architecture, the real-time primitive events which occurred at different manufacturing things such as operators, machines, pallets, key materials, and so forth can be easily sensed. Based on these distributed primitive events, a critical event model is established to automatically analyze the real-time production performance. Here, the up-level production performance analysis is regarded as a series of critical events, and the real-time value of each critical event can be easily calculated according to the logical and sequence relationships among these multilevel events. Finally, a case study is used to illustrate how to apply the designed methods to analyze the real-time production performance.

  • 11410.
    Zhang, Youpeng
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Wallenius, Janne
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorfysik.
    Upper limits to americium concentration in large sized sodium-cooled fast reactors loaded with metallic fuel2014Ingår i: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 70, s. 180-187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Transient analysis of a large sized sodium-cooled reactor loaded with metallic fuel modified by different fractions of americium have been performed. Unprotected loss-of-offsite power, unprotected loss-of-flow and unprotected transient-over-power accidents were simulated with the SAS4A/SASSYS code based on the geometrical model of an IFR1 with power rating of 2500 MW th, using safety parameters obtained with the SERPENT Monte Carlo code. The Ti-modified austenitic D9 steel, having higher creep rupture strength, was considered as the cladding and structural material apart from the ferritic/martensitic HT9 steel. For the reference case of U-12Pu-1Am-10Zr fuel at EOEC, the margin to fuel melt during a design basis condition UTOP is about 50 K for a maximum linear rating of 30 kW/m. In order to maintain a margin of 50 K to fuel failure, the linear power rating has to be reduced by ∼3% and 6% for 2 wt.% and 3 wt.% Am introduction into the fuel respectively. Hence, an Am concentration of 2-3 wt.% in the fuel would lead to a power penalty of 3-6%, permitting a consumption rate of 3.0-5.1 kg Am/TW hth. This consumption rate is significantly higher than the one previously obtained for oxide fuelled SFRs.

  • 11411.
    Zhang, Yuwei
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Abuammuna, Abdalgani
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Energy Systems Modeling for Eco-Cities with Focus on Renewable Energy Integration2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Syftet med rapporten är att undersöka vad den potentiella elektricitetsproduktionen samt kostnaden är för att installera förnyelsebara energikällor i den svensk-kinesiska ekostaden i New Taihu City, som är belägen i Wuxi, Kina. Den förnyelsebara energiteknologin som ska implementeras är solceller.

     

    Rapporten börjar med att presentera förnyelsebara energikällors nuvarande marknadsläge i Kina och fortsätter med en studie av solceller och dess tillämpningar och ekonomiska och  marknadsmässiga aspekter. For att få en bättre bild av hur solceller kan bli integrerad i en store skala har fallundersökningar av andra städer som har lyckats med detta gjorts.

     

    Resultaten som presenteras i den senare delen av rapporten tyder på att det finns bra avkastningspotential i ekostaden med solceller. Men rent kostnadsmässigt är implementeringen av  solceller mycket beroende av ekonomiska incitament från den kinesiska staten.

     

    For att priset för elektriciteten producerad med solceller ska kunna vara onkurrenskraftig måste 91% av solcellernas elektricitetspris sänkas för att kunna komma i närheten av Wuxis elpris.

  • 11412. Zhang, Z.
    et al.
    Kabral, R.
    Nilsson, B.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Revisiting the cremer impedance2017Ingår i: Proceedings of Meetings on Acoustics, Acoustical Society of America , 2017, nr 1Konferensbidrag (Refereegranskat)
    Abstract [en]

    In a classical paper (Acustica 3, 1953) Cremer demonstrated that in a rectangular duct, with locally reacting walls, there exits an impedance (”the Cremer impedance”) that maximizes the propagational damping for the lowest mode. Later (JSV 28, 1973) Tester extended the analysis to include a plug flow and ducts of both circular and rectangular cross-section. One limitation in the work of Tester is that it simplified the analysis of the effect of flow only considering high frequencies or well cut-on modes. This approximation is reasonable for large duct applications, e.g., aero-engines, but not for many other cases of interest. Kabral et al. (Acta Acustica united with Acustica 102, 2016) removed this limitation and investigated the’exact’ Cremer impedance for circular ducts including flow effects. As demonstrated in that paper the exact solution exhibits some special properties at low frequencies, e.g., a negative real part of the wall impedance. In this paper the exact Cremer impedance is further analyzed and discussed. Also, the exact solution for rectangular ducts is presented. 

  • 11413.
    Zhang, Zhe
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Optimal damping and slow sound in ducts2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Denna avhandling har till syfte att öka kunskapen om akustiska problem i kanaler, inklusive: 1) optimal dämpning av lågfrekvent ljud och; 2) utveckling och tillämpning av ‘slow sound’.När det gäller det första problemet, har ‘Cremer-impedansen’, som föreslogs för mer än ett halvt sekel sedan studerats och vidareutvecklats. Detta möjliggör nya tillämpningar svarande mot lågfrekvent ljud som insugnings- och avgassystem för fordon samt ventilationssystem. En ‘exakt’ lösning av Cremer-impedansen för rektangulära kanaler med en ljuddämpande vägg giltig i lågfrekvensområdet har härletts. En väsentlig förbättring av lågfrekvent dämpning har uppnåtts med denna lösning vilket även validerats med mätningar.Emellertid har den exakta lösningen av Cremer-impedansen en negativ realdel (‘resistans’) i lågfrekvensområdet, vilket betyder att en aktiv väggbeklädnad är nödvändig för att åstadkomma optimal dämpning. Två undersökningar av den negativa resistansen har genomförts för att studera om dessa lösningar är realiserbara. I den första ändrades randvillkoret för att inkludera gränsskikt i strömningen. Resultatet visade att negativ resistans erhålls i de flesta fall även med det modifierade randvillkoret. I den andra studerades lösningens giltighet i det komplexa vågtalsplanet. Resultatet visade att lösningen nedströms alltid är giltig medan vissa lösningar uppströms i lågfrekvensområdet är ogiltiga. Detta resultat gäller i princip för alla vågor eller moder i en kanal.När det gäller det andra problemet undersöktes möjligheterna att skapa ‘slow sound’, dvs ljud som utbreder sig mycket långsammare än normalt, genom att utnyttja ett resonant periodiskt system i en kanal i lågfrekvensområdet. Detta kan ses som ett s.k. akustiskt metamaterial och kan nyttjas för att med hjälp av starka ljudvågor påverka små partiklar som tvingas att kollidera och bli större. En studie om denna metod för sammanslagning av partiklar (‘particle agglomeration’) kan nyttjas för avgasrening har genomförts. Metoden är teoretiskt möjlig men begränsad av att tekniken för att skapa ‘slow sound’ inte bara saktar ned ljudvågen utan även dämpar dess amplitud och därigenom minska ljudvågens påverkan på partiklar.

  • 11414.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    The Cremer Impedance: An Investigation of the Low Frequency BehaviorManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    The Cremer impedance, first proposed by Cremer (1953) and then extended by Tester (1973), is supposed to give the maximum propagation damping in an infinitely long waveguide. Previous works including a uniform grazing flow have shown negative resistance in the low frequency range for both circular and 2-D rectangular waveguides, i.e., implying an active boundary. In order to further analyze the low frequency behaviour of the Cremer impedance, especially the negative resistance, two investigations are conducted in the current work. First, the previously used Ingard-Myers boundary condition is replaced by the Brambley boundary condition with the introduction of a thin inviscid boundary layer, and results obtained with the two boundary conditions are compared to see the effect of a sheared flow. The frequency range where the two boundary conditions can be applied is also analyzed. Second, discussions regarding the validity of the low frequency result in both the up- and downstream directions from the perspective of mode-merging are presented. This analysis is further extended from the fundamental mode to higher order modes in the frequency range where they are ‘just cut-on’.

  • 11415.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    The Cremer impedance: An investigation of the low frequency behavior2019Ingår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 459, artikel-id 114844Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Cremer impedance concept based on mode merging is one method that can substantially improve the axial damping in a waveguide. Previous works on the Cremer impedance including a uniform grazing flow have exhibited unexpected phenomenon such as negative resistance in the low frequency range. The current paper is a continuation of earlier works by the authors to extend the investigation of the Cremer impedance with a focus on the low frequency range. Two independent investigations from the perspective of boundary layer effects and mode merging patterns are conducted to better understand the low frequency behavior of the Cremer impedance.

  • 11416.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Lin, D.
    Xiaodong, J.
    Investigation of the 'exact' cremer impedance2018Ingår i: 25th International Congress on Sound and Vibration 2018, ICSV 2018: Hiroshima Calling, International Institute of Acoustics and Vibration, IIAV , 2018, s. 1810-1817Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Cremer impedance, first proposed by Cremer (Acustica 3, 1953) and then improved by Tester (JSV 28, 1973), refers to the locally reacting boundary condition that can maximize the attenuation of a certain acoustic mode in a uniform waveguide. One limitation in Tester's work is that it simplified the analysis on the effect of flow by only considering high frequencies or the 'well cut-on' modes. This approximation is reasonable for large duct applications, e.g., aero-engines, but not for many other cases of interest such as the vehicle intake and exhaust systems. A recent modification done by Kabral et al. (Acta Acustica united with Acustica 102, 2016) has removed this limitation and investigated the 'exact' solution of Cremer impedance, which reveals an appreciable difference between the exact and classic solution in the low frequency range. A measurement campaign is here carried out to experimentally demonstrate such difference. In addition, the exact solution is found to exhibit some special properties at very low frequencies, e.g., a negative resistance. One can question if this negative resistance is physically correct or an artefact of the assumption of a plug flow profile and the use of the so-called Ingard-Myers boundary condition. To investigate this the Cremer solution is here extended to the case with a more general and realistic flow profile, using a modified version of the Ingard-Myers condition suggested by Brambley (AIAA J 49(6), 2011).

  • 11417.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Tiikoja, Heiki
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Experimental analysis of whistle noise in a particle agglomeration pipe2018Ingår i: INTER-NOISE 2018 - 47th International Congress and Exposition on Noise Control Engineering: Impact of Noise Control Engineering, Institute of Noise Control Engineering , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    A self-sustained sound, more usually known as a whistle, refers to a distinct tonal noise created due to the interaction between the sound and flow field. When a positive feedback loop is formed between the two fields, the energy in the mean flow will be transferred into the sound wave, thus giving rise to a whistle. In engineering practice, whistles are destructive as they can produce high sound and vibration levels and may result in risk for mechanical failures. In this work, a flow-related high level tonal noise was found during a measurement on a particle agglomeration pipe, which is a quasi-periodic corrugated structure designed for the exhaust system of heavy-duty trucks. The purpose of the pipe is to enhance particle agglomeration to increase the size of exhaust gas particles. To investigate the origin of the detected tonal noise additional measurements were carried out. Based on the measurement result, the aero-acoustic coupling in the agglomeration pipe was analyzed, revealing that the pipe has a large potentiality to amplify the incident sound power in the presence of a mean flow. Furthermore, the Nyquist stability criterion was applied to confirm the existence of exponentially growing modes in the system at certain conditions.

  • 11418.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    ‘Double-’ and ‘Triple-root’ Cremer Impedancefor a Rectangular Duct with Opposite Lined WallsManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    To achieve high low frequency damping in an infinitely long double-lined rectangular duct with zero mean flow, the optimization of axial sound attenuation in the sense defined by Cremer (i.e., using the ‘Cremer impedance/solution’ concept) is examined for the fundamental mode. Two double-root Cremer impedance solutions that merge a mode pair into a single mode are presented. Different mode-merging patterns due to symmetry are found for these two solutions. As an extension, two triple-root Cremer impedance solutions (including one with a negative resistance) that merge three modes are also provided by extending the optimum condition proposed by Cremer. The two triple root solutions are theoretically advantageous in damping compared with the double root solutions, and the advantage is explained from the perspective of mode-merging.

  • 11419.
    Zhang, Zhe
    et al.
    KTH, Skolan för teknikvetenskap (SCI).
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Karlsson, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Katoshevski, D.
    Particle Number Reduction in Automotive Exhausts Using Acoustic Metamaterials2017Ingår i: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 10, nr 4, s. 1566-1572Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Air pollution caused by exhaust particulate matter (PM) from vehicular traffic is a major health issue. Increasingly strict regulations of vehicle emission have been introduced and efforts have been put on both the suppression of particulate formation inside the engine cylinders and the development of after-treatment technologies such as filters. With modern direct injected engines that produce a large number of really small sub-micron particles, the focus has increased even further and now also includes a number count.The problem of calculating particle trajectories in flow ducts like vehicle exhaust systems is challenging but important to further improve the technology. The interaction between particles and oscillating flows may lead to the formation of particle groups (regions where the particle concentration is increased), yielding a possibility of realizing particle agglomeration. The oscillating flow may simply be hydrodynamic or as assumed here: the flow oscillations are created by sound propagation rather than hydrodynamic approaches. An analysis is presented which gives the relationship between the speed of sound, the mean flow velocity and the amplitude of the acoustic particle velocity for particle agglomeration to be feasible. It is shown that it can be achieved if the convective speed of sound is reduced to the same order as the mean flow velocity. It is therefore suggested to use the so-called acoustic metamaterials, which can help control, direct and manipulate sound waves. At this stage a phenomenological 1D model is used for the analysis, which allows the authors to build an understanding of the effect of the sound waves and flow oscillations on particle motion and paves the way for further analysis on particle agglomeration.

  • 11420.
    Zhang, Zhi
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    On the Study of a Liquid Steel Sampling Process2010Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The liquid steel sampling method is one of the commonly used procedures in monitoring the steelmaking process. Besides it can be used for analyzing the dissolved alloys, hydrogen content and oxygen content, it can be also employed to monitor the inclusion characteristics at the steelmakings. Here, a crucial point is that the steel sampler should be filled and the metal solidifies without changing the inclusion characteristics. Therefore, the objective of this work is to fundamentally understand the liquid steel sampling process by means of analyzing and modeling the two-phase flow during the sampler filling process, and verifying the mathematical model by using the experimental data.

    The present dissertation presents an experimental and theoretical study of the filling process of both the lollipop-shaped sampler and the rectangular-shaped sampler. Firstly, a physical modeling by using a water model has been carried out to fundamentally investigate the flow pattern inside the sampler vessels during its filling. The flow patterns were obtained by a PIV system. Then, a mathematical model has been built to theoretically understand the phenomena. The commercial CFD code was used. Here, different turbulence model have been compared between the realizable k-ε turbulence model and Wilcox k-ω turbulence model. It concludes that the Wilcox k-ω turbulence model agrees well with the PIV measurements.HH

    Thus, the preferred it was further employed to predict the turbulent flow inside the production lollipop-shaped sampler fillings. It is important to find that the average collision volume in the production steel sampler without solidification at filling is about 30 times higher than that in a ladle furnace.

    In the end, the whole sampling system was modeled. The initial solidification during the filling was taken into account. Focus was on the influence of the initial solidification on the inclusion concentrations. A discrete phase model was used to simulate the movement of inclusions in the liquid steel. Some selected different sized primary inclusions that exist in the ladles at a steelmaking process were simulated.

    The same method of studying the filling procedure of the lollipop-shaped sampler was further applied to comprehensively investigate the rectangular-shaped sampler.

  • 11421.
    Zhao, Guo-Hua
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Aune, Ragnhild E.
    Espallargas, Nuria
    Tribocorrosion studies of metallic biomaterials: The effect of plasma nitriding and DLC surface modifications2016Ingår i: Journal of The Mechanical Behavior of Biomedical Materials, ISSN 1751-6161, E-ISSN 1878-0180, Vol. 63, s. 100-114Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The medical grade pure titanium, stainless steel and CoCrMo alloy have been utilized as biomaterials for load-bearing orthopedic prosthesis. The conventional surgery metals suffer from a combined effect of wear and corrosion once they are implanted, which may significantly accelerate the material degradation process. In this work, the tribocorrosion performance of the metallic biomaterials with different surface modifications was studied in the simulated body fluid for the purpose of investigating the effect of the surface treatments on the tribocorrosion performance and eventually finding the most suitable implantation materials. The metals were subjected to surface modifications by plasma nitriding in different treatment temperatures or physical vapor deposition (PVD) to produce diamond-like carbon (DLC) coating, respectively. The dry wear and tribocorrosion properties of the samples were evaluated by using a reciprocating ball-on-disc tribometer equipped with an electrochemical cell. Prior to the tribocorrosion tests, their electrochemical behavior was measured by the potentiodynamic polarization in phosphate buffer saline (PBS) solution at room temperature. Both stainless steel and CoCrMo after low temperature nitriding kept their passive nature by forming an expanded austenite phase. The DLC coated samples presented the low anodic corrosion current due to the chemical inertness of the carbon layer. During the tribocorrosion tests at open circuit potential, the untreated and low temperature nitrided samples exhibited significant potential drop towards the cathodic direction, which was a result of the worn out of the passive film. Galvanic coupling was established between the depassivated (worn) area and the still passive (unworn) area, making the materials suffered from wear-accelerated corrosion. The DLC coating performed as a solid lubricant in both dry wear and tribocorrosion tests, and the resulting wear after the tests was almost negligible.

  • 11422. Zhao, Ruikai
    et al.
    Deng, Shuai
    Zhao, Li
    Liu, Yinan
    Tan, Yuting
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Energiprocesser.
    Energy-saving pathway exploration of CCS integrated with solar energy: Literature research and comparative analysis2015Ingår i: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 102, s. 66-80Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of main technical barriers to a large-scale application of carbon capture and storage (CCS) technology is a significant amount of required energy, e.g., regeneration heat of solvent in the chemical absorption system. Thus, energy consumption and corresponding high operation cost become two primary challenges for the promotion of CCS technology. Meanwhile, energy from the solar source in various forms has already been successfully used as an effective alternative supply in the industrial section for drying, heating and even cooling. Thus, integrating solar energy utilization into the CCS process could be a reasonable option for a sustainable development. A comparative analysis of CCS integrated with solar energy was presented in this paper based on the existing researches. The current status on typical configuration structure, feature and energy-efficiency performance of integrating options is reviewed for post-combustion, pre-combustion and oxygen-combustion systems. Based on these typical CO2 capture systems, a theoretical analysis is conducted for an energy-efficient comparison. Then four typical structures of the post-combustion system, which are highlighted in the review, are chosen as comparative objects for energy-saving and techno-economic evaluation. The results show that systems with a solar-assisted thermal energy and power generation have comparative advantages in term of carbon emission intensity, but the economic cost is increased under the current conditions of the equipment price. Compared to that of baseline case, carbon emission intensity of the case integrated with solar Organic Rankine Cycle can be reduced with a maximum decline of 9.73%, meanwhile the levelized costs of electricity increases 0.01 USD/kW h correspondingly.

  • 11423.
    Zhao, Ruikai
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Liu, Longcheng
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Kemiteknik.
    Zhao, Li
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    Deng, Shuai
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    Li, Shuangjun
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    Zhang, Yue
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    Li, Hailong
    Malardalen Univ, Sch Business Soc & Engn, SE-72123 Vasteras, Sweden..
    Thermodynamic exploration of temperature vacuum swing adsorption for direct air capture of carbon dioxide in buildings2019Ingår i: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 183, s. 418-426Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abrupt climate change such as the loss of Arctic sea-ice area urgently needs negative emissions technologies. The potential application of direct air capture of carbon dioxide from indoor air and outdoor air in closed buildings or crowded places has been discussed in this paper. From the aspects of carbon reduction and indoor comfort, the ventilation system integrating a capture device is of great value in practical use. For ultra-dilute carbon dioxide sources, many traditional separation processes have no cost advantages, but adsorption technologies such as temperature vacuum swing adsorption is one of suitable methods. Thermodynamic exploration has been investigated regarding minimum separation work and second-law efficiency at various concentrations in the air. The influence of concentration, adsorption temperature, desorption temperature and desorption pressure on the energy efficiency has also been evaluated. Results show that the minimum separation work for the level of 400 ppm is approximately 20 kJ/mol. The optimal second-law efficiencies are 44.57%, 37.55% and 31.60%, respectively for 3000 ppm, 2000 ppm and 1000 ppm. It means that a high energy-efficiency capture device in buildings merits attention in the exploration of the possibility of approaching negative carbon buildings.

  • 11424.
    Zhao, Shuang
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Wallmark, Oskar
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Leksell, Mats
    KTH, Skolan för elektro- och systemteknik (EES), Elektrisk energiomvandling.
    Low-Speed Sensorless Control With Reduced Copper Losses for Saturated PMSynRel Machines2013Ingår i: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 28, nr 4, s. 841-848Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Permanent-magnet-assisted synchronous reluctance (PMSynRel) machines are generally well suited for sensorless operation at all speeds since the rotor topology possesses a magnetic saliency. However, magnetic saturation can result in a vanishing differential saliency which renders sensorless control at certain operating points difficult (or even impossible) at low speed. In this paper, an optimization procedure, based on results from finite-element (FEM)-based simulations, is proposed. As output, current reference trajectories are obtained in which copper losses are kept at minimum, while the capability for sensorless control is still maintained. The results from the FEM-based simulations are in good agreement with the corresponding experimental results. For the experimental prototype in consideration, the torque limit when operating sensorless at low speed is increased substantially from below 45% to around 95% of its rated value with only slightly increased copper losses. Additionally, the impact of position-dependent harmonics on the magnetic cross saturation (affecting the steady-state position estimation error) is found to be substantial. This highlights that this spatial variation should be taken into consideration for accurate prediction of performance during sensorless operation even if the winding of the machine is of the conventional distributed type.

  • 11425.
    Zhao, Xiaoyu
    KTH, Skolan för industriell teknik och management (ITM), Maskinkonstruktion (Inst.).
    Condition Monitoring of Hydraulic Systems2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Syftet för detta projekt är att utreda och föreslå ett system för tillståndsövervakning och analys av en skogsmaskins hydraulsystem baserat på tillgängliga data från ombordmonterade partikelsensorer. Den maskin som studerats är Ponsse Scorpion King, som är utrustad med partikelsensorn Icount PDR från Parker. Data samlades in under en två veckor lång fälttest. Maskinoperationerna och mätdata från partikelräknaren samlades in, och orsakerna till avbrott längre än fem minuter loggades manuellt. Resultatet av detta examensarbete presenterar relationerna mellan tre faktorer: partikelantal hos hydrauloljan, maskinens verksamhet och de avbrott som inträffade. Denna avhandling avser också föreslå hur informationen från Icount PDR skall presenteras för operatören och hur förebyggande maskinunderhåll skall kunna planeras.

  • 11426. Zhao, Y.
    et al.
    Xiong, D. -B
    Qin, Haiying
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Gao, F.
    Inui, H.
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi.
    Nanocomposite electrode materials for low temperature solid oxide fuel cells using the ceria-carbonate composite electrolytes2012Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, nr 24, s. 19351-19356Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low temperature solid oxide fuel cell (LTSOFC, 300-600 °C) is one of the hot areas in recent fuel cell developments. In order to develop high performance LTSOFCs, compatible electrodes are highly demanded. We used NANOCOFC (nanocomposites for advanced fuel cell technology) approach to develop nanocomposite electrodes based on metal oxides Ni-Cu-Zn-oxide and samarium doped ceria (SDC). It was found that the materials consist of individual metal oxide and SDC phase, indicating the material as a composite with a homogenous distribution for all constituent components. Highly homogenous distribution of the particles enhanced the catalyst function for electrode applications in LTSOFC devices. We constructed the devices using the SDC-carbonate nanocomposite (NSDC) as the electrolyte and above as prepared composite as electrodes in a symmetrical configuration. We found that the prepared composite electrodes had good catalytic function for both H2 and O2, to prove its anode and cathode functions. Based on the material properties, the LTSOFC devices have reached a power output more than 730 mW cm-2 at 550 °C.

  • 11427. Zhao, Yicheng
    et al.
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. Hubei University, China.
    Lund, Peter
    Basile, Angelo
    Li, Yongdan
    Preface to the special issue section on "The 2nd International Symposium on Catalytic Science and Technology in Sustainable Energy and Environment (EECAT 2016), October 11-14th 2016, Tianjin, China"2017Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 42, nr 27, s. 17339-17340Artikel i tidskrift (Refereegranskat)
  • 11428. Zhao, Yufeng
    et al.
    He, Yunjuan
    Fan, Liangdong
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Hubei, Peoples R China.
    He, Jing
    Xiong, Ding-Bang
    Gao, Faming
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Kraft- och värmeteknologi. Hubei Univ, Fac Phys & Elect Sci, Hubei Collaborat Innovat Ctr Adv Organ Chem Mat, Wuhan 430062, Hubei, Peoples R China.
    Synthesis of hierarchically porous LiNiCuZn-oxide and its electrochemical performance for low-temperature fuel cells2014Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, nr 23, s. 12317-12322Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, hierarchically porous composite metal oxide LiNiCuZn-oxide (LNCZO) was successfully synthesized through a sol-gel method with a bio-Artemia cyst shell (AS) as a hard template. The phase and morphology of the products were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM). The as-synthesized material was used as symmetrical electrodes, anode and cathode, for the SDC-LiNaCO3 (LNSDC) electrolyte based low temperature solid oxide fuel cell (LTSOFCs), achieving a maximum power density of 132 mW cm(-2) at 550 degrees C. Besides, a single-component fuel cell device was also demonstrated using a mixture of as-prepared LNCZO and ionic conductor LNSDC, and a corresponding peak power output of 155 mW cm(-2) was obtained, suggesting that the hierarchically porous product has high prospective in the single-component fuel cell.

  • 11429. Zhe, Yuan
    et al.
    Qizhao, Lin
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Thermodynamic analysis of ITSOFC co-generation system fueled by ethanol2011Ingår i: International journal of energy research (Print), ISSN 0363-907X, E-ISSN 1099-114X, Vol. 35, nr 12, s. 1025-1031Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solid oxide fuel cell (SOFC) is a true multi-fuel energy conversion device that produces electricity directly from fuel through electrochemical reactions. In this paper, the performance of intermediate temperature SOFC (ITSOFC) fueled by ethanol was analyzed. The exhaust gas of SOFC has high value in use. So SOFC is integrated into a hybrid system with other power system for co-generations. Based on a mathematical model of ITSOFC, the steady-state model of each designed system was presented. Results show that a co-generation system can achieve high efficiency. The research on SOFC fueled by ethanol is useful for the application of new and renewable energy. The results of this research can be useful in design and application for SOFC in co-generations.

  • 11430. Zhe, Yuan
    et al.
    Qizhao, Lin
    Zhu, Bin
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
    Thermodynamic analysis of ITSOFC hybrid system for polygenerations2010Ingår i: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 35, nr 7, s. 2824-2828Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solid oxide fuel cell (SOFC) is an energy conversion device that produces electricity directly from fossil fuels through electrochemical reactions. Intermediate and low temperature SOFCs (IT/LT, 300-800 C SOFCs) are the main strains of the world SOFC R&D now. The exhaust gas of SOFC has high value in use. So SOFC is often integrated into a hybrid system with other power systems. Research shows that the electrical efficiency and the total efficiency of a hybrid system can be about 60% and 80% higher than an independent one. In this paper, the performance of intermediate temperature SOFC hybrid system was analyzed. Based on presenting a steady-state mathematical model of ITSOFC, the steadystate model of each designed system was presented. Results show that a hybrid system can achieve high efficiency. The results of this research can be useful in design and application for polygenerations integrated by SOFCs.

  • 11431.
    Zhendong, Liu
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, Spårfordon.
    Stichel, Sebastian
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Anders, Rønnquist
    NTNU Norwegian University of Science and Technology.
    Numerical Study on the Dynamic Behaviour of Railway Catenary Overlap Section for Higher Speed2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    The dynamic behaviour in the contact between pantograph and catenary decides the quality of power transmission, the component service life and the maximum operational speed. The catenary system is desired to be built smooth and uniform in geometry and elasticity along the train-running direction, but due to electric concerns and tensile force retention, the entire catenary is made up by many tensioning sections. To make a pantograph smoothly shift between the neighbouring sections, an overlap of several spans is introduced to work as a transition zone. However, when the pantograph is passing through the overlap section, its dynamic behaviour can be heavily changed and cannot sustain as good contact as in the middle spans of each tensioning section. To clarify the dynamic behaviour in this special section and to ensure a stable contact between pantograph and catenary, a numerical study on catenary section overlap is performed based on a 3D pantograph-catenary finite element (FE) model. The following issues are discussed in this paper: operational speed, wire gradient, damping ratio, and spacing distance in multi-pantograph operation. The results show that the gradient of wires in overlap sections and the damping ratio have great influence on the dynamic performance, especially at high speed and in multi-pantograph operation. In practice, in the overlap section the gradient should be properly designed and some additional damping is beneficial to ensure good dynamic performance for higher speed.  

  • 11432. Zheng, H.
    et al.
    Wang, C.
    Liu, Qingming
    KTH, Skolan för industriell teknik och management (ITM), Energiteknik, Tillämpad termodynamik och kylteknik. Guangdong University of Technology, China.
    Tian, Z.
    Fan, X.
    Thermal performance of copper foam/paraffin composite phase change material2018Ingår i: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 157, s. 372-381Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Phase change materials are promising options for thermal energy storage and thermal energy devices. However, their low thermal conductivity lowers their charging and discharging rate. In this paper, copper foam was utilized to enhance the thermal performance of the paraffin. A visible experimental device was built to investigate the melting behavior of paraffin with and without copper foam. The effect of the heating position on the thermal performance of copper foam/paraffin composite phase change material (CPCM) was also discussed. The heat transfer characteristics including solid-liquid interface development, temperature distribution and wall temperature of the heater were tested and recorded. In addition, a numerical model was established using one-temperature volume averaging method to analyze the melting process of the CPCM. The experimental results showed that the total melting time of the CPCM was 20.5% shorter than that of pure paraffin, and the CPCM heated at the top melted slowest and reached the biggest temperature difference in the three heating conditions, so the effect of natural convection on the melting process of the CPCM could not be neglected. A two dimensional numerical simulation was also performed to analyze the melting behavior of CPCM, and the numerical results were well consistent with the experimental data.

  • 11433.
    Zheng, Miaomiao
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Härmark, Johan
    KTH, Skolan för teknik och hälsa (STH), Naturvetenskap och biomedicin, Strukturell bioteknik.
    Grishenkov, Dmitry
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik.
    Janerot Sjöberg, Birgitta
    CLINTEC, Department of Medical Imaging and Technology, Karolinska Institute.
    Polymer-Shelled Ultrasound Contrast Agents with controlled size and polydispersity.2011Ingår i: Nanomedicine: Nanotechnology, Biology & Medicine, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ultrasound imaging techniques can be greatly improved by the use of ultrasound contrast agents (UCAs). Gas bubbles encapsulated into biocompatible polymer shell are of particular interest of this work. Shell of the bubbles produced from Poly-Vinyl-Alcohol (PVA) offers considerable chemical versatility and stability. However, questions regarding the size and polydispersity of the microbubbles must be further investigated. The ideal UCAs should not obstruct the blood flow in pulmonary capillaries which diameter is less than 10 μm. From the technical perspective UCAs should modify the acoustic properties of a region of interest, by increasing backscattered efficiency. In order to enhance the ultrasound response UCAs should be engineered with narrow size distribution. In the present work PVA-shelled UCAs with controlled size and polydispersity is manufactured under varied parameters of the manufacturing protocol. It was observed that temperature of the surrounding atmosphere has major effect on the size of the UCAs, while polydispersity is regulated by geometry and speed of the disperser. Finally, the acoustic response of these microbubbles is tested using developed ultrasound test rig. The enhancement of the backscattered power of about 25 dB from a suspension of the microbubbles is observed at 5 MHz ultrasound frequency. Keeping in mind that in clinical practice ultrasound scatter from the blood is of about 30 dB weaker than scatter from surrounding tissue, introduction of novel PVA microbubbles will potentially improve diagnosis of the cardiovascular patients.

  • 11434. Zhong, R. Y.
    et al.
    Wang, Lihui
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion, Produktionssystem.
    Xu, X.
    An IoT-enabled Real-time Machine Status Monitoring Approach for Cloud Manufacturing2017Ingår i: Manufacturing Systems 4.0 – Proceedings of the 50th CIRP Conference on Manufacturing Systems, Elsevier, 2017, Vol. 63, s. 709-714Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cloud Manufacturing (CMfg) has attracted large number of attentions from both academia and practitioners. One of the key concepts in CMfg is service sharing which is based on the availability of various manufacturing resources. This paper introduces an Internet of Things (IoT) enabled real-time machine status monitoring platform for the provision of resource availability. IoT technologies such as RFID and wireless communications are used for capturing real-time machines' statuses. After that, such information is visualized through a graphical dashboard after being processed by various data models and cloud-based services over smart phones. A demonstrative case is given to illustrate the feasibility and practicality of the proposed system. In this case, IoT devices are deployed in a CMfg environment such as shop floors to capture machine data firstly. Secondly, cloud-based services are designed and developed for making full use of the captured data to facilitate end-users' production operations and behaviors. Thirdly, '5w' questions are answered by using both real-time and historic data generated from the frontline CMfg sites.

  • 11435. Zhong, Ray
    et al.
    Xu, Xun
    Wang, Lihui
    KTH, Skolan för industriell teknik och management (ITM), Industriell produktion.
    Food supply chain management: systems, implementations, and future research2017Ingår i: Industrial management + data systems, ISSN 0263-5577, E-ISSN 1758-5783, Vol. 117, nr 9, s. 2085-2114Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Purpose - The purpose of this paper is to review the food supply chain management (FSCM) in terms of systems and implementations so that observations and lessons from this research could be useful for academia and industrial practitioners in the future. Design/methodology/approach - A systematical and hierarchical framework is proposed in this paper to review the literature. Categorizations and classifications are identified to organize this paper. Findings - This paper reviews total 192 articles related to the data-driven systems for FSCM. Currently, there is a dramatic increase of research papers related to this topic. Looking at the general interests on FSCM, research on this topic can be expected to increase in the future. Research limitations/implications - This paper only selected limited number of papers which are published in leading journals or with high citations. For simplicity without generality, key findings and observations are significant from this research. Practical implications - Some ideas from this paper could be expanded into other possible domains so that involved parties are able to be inspired for enriching the FSCM. Future implementations are useful for practitioners to conduct IT-based solutions for FSCM. Social implications - As the increasing of digital devices in FSCM, large number of data will be used for decision-makings. Data-driven systems for FSCM will be the future for a more sustainable food supply chain. Originality/value - This is the first attempt to provide a comprehensive review on FSCM from the view of data-driven IT systems.

  • 11436.
    Zhou, Chunguang
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Gasification and Pyrolysis Characterization and Heat Transfer Phenomena During Thermal Conversion of Municipal Solid Waste2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The significant generation of municipal solid waste (MSW) has become a controversial global issue. Pyrolysis and gasification technologies for treating rejects from solid waste disposal sites (SWDSs), for which over 50 % of MSW is attributed to combustible species, have attracted considerable attention. MSW is an alternative energy source that can partly replace fossil resources; there is an increasing awareness that global warming caused by the utilization of fossil resources is occurring.

    The goal of this thesis is to realize the efficient and rational utilization of MSW and decrease the harmful impact of pollutants, such as dioxin, HCl, and CO2, on the environment. To achieve this goal, some fundamental studies have been experimentally and numerically conducted to enhance the understanding of the properties of municipal solid waste thermal conversion.

    In this thesis, the pyrolysis behaviors of single pelletized recovered fuel were tested. A detailed comparison of the pyrolysis behaviors of typical recovered solid waste and biomass particles was conducted. A swelling phenomenon with a swelling ratio of approximately 1.6 was observed on the surface of pelletized recovered fuels. Subsequently, a particle model was constructed to describe the thermal conversion process for large recovered fuel particles that are composed of a high fraction of polyethylene (PE) and a comparable low fraction of cardboard. The results indicate that an understanding of the heat transfer mechanism in highly porous and molten structures and the selection of a heat transfer model are crucial for accurate prediction of the conversion process.

    MSW pyrolysis is a promising method for producing liquid products. With the exception of lignocellulosic materials, such as printing paper and cardboard, PE, polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) are the six main polymers in domestic waste in Europe. Characterization studies of the products obtained from these individual components, such as PE, PET, PVC, printing paper, and cardboard, have been conducted on a pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) system and a fixed-bed reactor. The possible pathways for the formation of the main primary/secondary products in rapid and conventional pyrolysis were also discussed.

    MSW steam gasification with CaO was performed in a batch-type fixed-bed gasifier to examine the effect of CaO addition on the heat transfer properties, pollutant removal, and devolatilization and char gasification behaviors in the presence of steam.

    A new carbon capture and recycle (CCR) system combined with an integrated municipal solid waste system was proposed. The foundation of the system is the development of a novel method to remediate CO2 using a high-temperature process of reforming CH4 and/or O2 and/or H2O without catalysts. Thermodynamic and experimental studies were performed. High temperatures significantly promoted the multi-reforming process while preventing the problem of catalyst deactivation. Potential improvements in the efficiency of the novel technology can be achieved by optimizing the reforming reactants. Landfill gas (LFG) and fuel gas from bio-waste treatment contain a considerable fraction of CH4, which may be a source of CH4 for this process.  

  • 11437.
    Zhou, Chunguang
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Rosén, Christer
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Engvall, Klas
    KTH, Skolan för kemivetenskap (CHE), Kemiteknik, Kemisk teknologi.
    Biomass oxygen/steam gasification in a pressurized bubbling fluidized bed: Agglomeration behavior2016Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 172, s. 230-250Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, the anti-agglomeration abilities of Ca- and Mg-containing bed materials, including dolomite and magnesite, in a pressurized bubbling fluidized bed gasifier using pine pellets and birch chips as feedstock, is investigated. The most typical bed material-silica sand-was also included as a reference for comparison. The sustainability of the operation was evaluated via analyzing the temperatures at different levels along the bed height. During the performances, the aim was to keep the temperature at the bottom zone of the reactor at around 870 °C. However, the success highly depends on the bed materials used in the bed and the temperature can vary significantly in case of agglomeration or bad mixing of bed materials and char particles. Both Glanshammar and Sala dolomites performed well with no observed agglomeration tendencies. In case of magnesite, the bed exhibited a high agglomeration tendency. Silica sand displayed the most severe agglomeration among all bed materials, even when birch chips with a low silica content was fed at a relatively low temperature. The solid samples of all the bed materials were inspected by light microscopy and Scanning Electron Microscopy (SEM). The Energy Dispersive Spectroscopy (EDS) detector was used to detect the elemental distribution in the surface. The crystal chemical structure was analyzed using X-ray Diffraction (XRD). Magnesite agglomerates glued together by big molten ash particles. There was no coating layer detected on magnesite particles at bed temperatures - below 870 °C. But when the temperature was above 1000 °C, a significant amount of small molten ash particles was deposited on the magnesite particles, indicating a pronounced tendency for formation of a coating layer in case of long-term operation. An increasing trend of Si on the surface of dolomite particles was observed. Simultaneously, potassium deposition on the surface is not obvious. The analyses, based on the XRD diffraction and the K2O-SiO2-MgO and K2O-SiO2-CaO ternary diagrams, suggest that the observed decreases in the risks for agglomeration using dolomite, cannot be attributed to formation of alkali-containing compounds with higher melting points, but to the reaction between dolomite and silica, consuming a considerable portion of silicon and thus hinder the formation of low-melting potassium silicate, as well as its ability to stabilize the temperatures under pressurized conditions.

  • 11438.
    Zhou, Chunguang
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Effect of heat transfer model on the prediction of refuse-derived fuel pyrolysis process2015Ingår i: Fuel, ISSN 0016-2361, E-ISSN 1873-7153, Vol. 142, s. 46-57Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Heat transfer models using to estimate the effective thermal conductivity have been developed and included in a model for the pyrolysis of refuse-derived fuel or solid recovered fuel particles composed of cardboard and polyethylene. Both the predictions from the Kunii and Smith model and the Breitbach and Barthels model were presented and compared with the experimental data. The possible mechanisms of heat transfer in the porous solid particles were discussed. Compared to the conduction mode by solid matrix and gas phase, radiation heat flux between the neighboring voids and from particle surface and neighboring particle surface are considered as the main mechanisms at the temperatures presented in this paper. The porosity has been reported to serve as an important role in the accurate estimation of the radiation exchange factor for the radiation term in heat transfer model in a highly porous medium. Refuse-derived fuel particle with a high plastic concentration exhibits a rapid increase of porosity with the continuous thermal conversion of plastic. Thus, a coefficient as a function of porosity was applied to the radiation exchange factor in the Kunii and Smith model, which was constructed and based on a simplified model of heat transfer in packed bed. Moreover, the effect of the contact surface area between solid particles on the heat transfer of conduction mode was also considered in the Breitbach and Barthels model. Both modified models were further validated with experimental results obtained at different temperature, with different PE content and initial porosity.

  • 11439.
    Zhou, Chunguang
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Blasiak, Wlodzimierz
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Characteristics of waste printing paper and cardboard in a reactor pyrolyzed by preheated agents2013Ingår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 116, s. 63-71Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We studied the characteristics of waste printing paper and cardboard particles in a reactor pyrolyzed by preheated agents with the aim of simulating a real case in a fixed-bed gasifier. A TGA/DSC was first used to study of the kinetics and enthalpy change of the printing paper and cardboard pyrolysis. Pyrolitic conversion was further carried out in a batch-type reactor with non-electrical heating. Syngas, tar and char were produced and characterized from printing paper and cardboard pyrolysis at 400 degrees C, 500 degrees C and 600 degrees C. Different flow rates of carrier gas were applied to study the effect of residence time on the products distribution. When the flow rate increased, the relative mass change of gas agrees with that of tar. With increase in temperature, the yield of furfural, olefins and other non-aromatic compounds in tar decreased, while phenols and heavier aromatic hydrocarbons increased. The evolution of CO2, CO and other gas species in the syngas was presented. Van Krevelan diagram of chars was also presented in the paper.

  • 11440.
    Zhou, Chunguang
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Zhang, Qinglin
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Arnold, Leonie
    Yang, Weihong
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    Blasiak, Wlodzimierz
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
    A study of the pyrolysis behaviors of pelletized recovered municipal solid waste fuels2013Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 107, s. 173-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pelletized recovered solid waste fuel is often applied in gasification systems to provide feedstock with a stabilized quality and high heating value and to avoid the bridging behavior caused by high moisture content, low particle density, and irregular particle size. However, the swelling properties and the sticky material generated from pyrolysis of the plastic group components also tend to trigger bridging in the retorting zone. It is well known that the plastic group materials, which occupy a considerable proportion of municipal solid waste, can melt together easily even under low temperature. This study investigates the pyrolysis behaviors of typical recovered solid waste pellets, including the devolatilization rate, heat transfer properties, char properties, and swelling/shrinkage properties, in a small fixed-bed facility over a wide temperature range, from 900 degrees C to 450 degrees C. The results are also compared with those from wheat straw pellets, a typical cellulosic fuel. Moreover, the SEM images and BET analysis of the char structure are further analyzed to provide additional explanation for the mechanisms of swelling/shrinkage phenomena observed during heating.

  • 11441. Zhou, H.
    et al.
    Lopez-Arteaga, Ines
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. Eindhoven University of Technology, Netherlands.
    Nijmeijer, H.
    Broadband planar nearfield acoustic holography based on one-third-octave band analysis2016Ingår i: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 109, s. 18-26Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Planar nearfield acoustic holography (PNAH) is usually based on narrow-band, single frequency analysis, which is time consuming when the source behavior over a broad frequency range is of interest, as is the case with many industrial sources. In this paper a method, broadband planar nearfield acoustic holography based on one-third-octave band analysis (BPNAH), is described. Data relating to the complex band pressure on the hologram is obtained by combining the root-mean-square pressure corresponding to a one-third-octave band with the phase of the pressure corresponding to a single frequency line. Numerical simulations and measurements show that the BPNAH method allows a significant reduction in processing time, while keeping a similar accuracy to the conventional reconstruction, which is based on the summation of frequency by frequency in the corresponding band. As a simple, time-saving and robust technique, the BPNAH method is particularly well adapted to industrial studies.

  • 11442. Zhou, J.
    et al.
    Karlsson, Mikael
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Åbom, Mats
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Study of thermoacoustic engine for automotive exhaust waste heat recovery2019Ingår i: SAE technical paper series, ISSN 0148-7191, Vol. 2019-April, nr AprilArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the travelling-wave thermoacoustic engine (TAE) and its application for recovery of waste heat from automotive exhaust systems is investigated. The aim is to give some insight into the potential, but also limitations of the technique for practical applications. This includes packaging, physical boundary conditions as heating and cooling available, but also system perspectives as influence of legislative drive cycles and degree of hybridization. First, the travelling-wave TAE is described as a low-order acoustic network in the frequency domain. Models, including non-linear effects, are set up for every component in the network to describe the propagation and dissipation of acoustic waves. For a TAE with looped structure, the continuity of pressure and volumetric velocity is employed to determine the saturation pressure, as well as the stable operating point. These models are validated against experimental data available in the literature [1]. This is an engine designed for high-temperature application, but is well documented and yields a good reference for the models and to further the understanding of the TAE. Next, an optimized design for a system to be adapted to the operating conditions typical for heavy-duty systems is studied and proposed. No actual physical prototype has been built and verified, but the design is based on, and is of the same efficiency, as machines that have been reported in the literature. The proposed design and the original TAE are then used to discuss the practical implementation for heavy- and light-duty vehicles on a system level. To improve the utilization of the available exhaust waste heat, a configuration of system heat exchangers combining a self-circulating loop with multiple TAE modules is preliminarily studied. Further research for this configuration is needed for practical implementation although current simulation results are encouraging.

  • 11443.
    Zhou, Jiewei
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Attitude Determination and Control of the CubeSat MIST2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Systemet for attitydstyrning och -bestamning i nanosatelliten MIST reekterar sma satelliters begransningarna i utrymme, elkraft och omborddatorkapacitet. Regleringen ar begransad till styrning med magnetspolar som genererar kraftmoment. For attitydbestamningen anvands magnetometrar och solsensorer trots under-manovrering och -bestamning vid solformorkelse. Vanligtvis misslyckas sma satelliter med liknande reglersystem och hoga krav, sa om MIST lyckas skulle den bli ett referenskoncept. Malen med detta examensarbete ar att utfora en genomforbarhetsstudie av ett reglerkoncept for att mota de nominella kraven for MIST samt undersoka av alternativa reglersystem. E ekten av gravitationsstabilisering och olika masstroghetskongurationer har analyserats med hjalp av linjariserade stabilitetsregioner for en nadirpekande satellit. Stabilitetsregionerna forstoras da ett roterande hjul infors i ett alternativt stabiliseringskoncept eftersom det roterande hjulet paverkar de e ektiva masstroghetsmomentet. Regleringsalgoritmen som utvarderats i detta arbete ar baserad pa teorin om Asymptotisk Periodisk Linjar Kvadratisk Regulering (AP LKR), den som ar mest anvand samt e ektiv for ren magnetisk styrning av sma satelliter. En utformning av ett koncept baserat pa Linjar Kvadratisk Reglering med numerisk optimering, vilket inte tidigare verkar anvants for ett riktigt rymduppdrag, har undersokts och jamforts med AP LKR-regleringen. Nar det galler attitydbestamningen sa har ett linjart Kalmanlter utformats for AP LKR-regleringen. Slutligen sa har en robusthetsanalys gjorts genom Monte Carlo-simuleringar for styrnings- och bestamningsstrategierna.

  • 11444.
    Zhou, Lin
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strömningsakustik.
    Acoustic characterization of orifices and perforated liners with flow and high-level acoustic excitation2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis is motivated by the need for noise control in aircraft engine with orifices and perforated liner. The presence of high-level acoustic excitation, different flow situations either bias flow, grazing flow or any combination in the aircraft engine, makes the acoustic behavior complex due to the interaction between sound and flow over the lined wall. Both systematic acoustic prediction of aircraft engines and liner optimization necessitate progress in impedance measurement methods by including the effect of the complex flow situations. The aim of the present thesis is to experimentally study the change in acoustic properties of orifices and perforated liners under bias or grazing flow.

    In order to study the effect of different combinations of bias flow and high-level acoustic excitation, an in-duct orifice has been investigated with finely controlled acoustic excitation levels and bias flow speeds. This provides a detailed study of the transition from cases when high-level acoustic excitation causes flow reversal in the orifice to cases when the bias flow maintains the flow direction. Nonlinear impedance is measured and compared, and a scattering matrix and its eigenvalues are investigated to study the potentiality of acoustic energy dissipation or production. A harmonic method is proposed for modelling the impedance, especially the resistance, which captures the change in impedance results at low frequencies compared with experimental results.

    The presence of grazing flow can increase the resistance of acoustic liners and shift their resonator frequency. So-called impedance eduction technology has been widely studied during the past decades, but with a limited confidence due to the interaction of grazing flow and acoustic waves. A comparison has been performed with different test rigs and methods from the German Aerospace Center (DLR). Numerical work has been performed to investigate the effect of shear flow and viscosity. Our study indicates that the impedance eduction process should be consistent with that of the code of wave propagation computation, for example with the same assumption regarding shear flow and viscosity. A systematic analysis for measurement uncertainties is proposed in order to understand the essentials for data quality assessment and model validation. The idea of using different Mach numbers for wave dispersion and in the Ingard-Myers boundary condition has been tested regarding their effect on impedance eduction. In conclusion, a local Mach number based on friction velocity is introduced and validated using both our own experimental results and those of previous studies.  

  • 11445.
    Zhou, Lin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    A systematic uncertainty analysis for liner impedance eduction technology2015Ingår i: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 356, s. 86-99, artikel-id 12557Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Abstract The so-called impedance eduction technology is widely used for obtaining acoustic properties of liners used in aircraft engines. The measurement uncertainties for this technology are still not well understood though it is essential for data quality assessment and model validation. A systematic framework based on multivariate analysis is presented in this paper to provide 95 percent confidence interval uncertainty estimates in the process of impedance eduction. The analysis is made using a single mode straightforward method based on transmission coefficients involving the classic Ingard-Myers boundary condition. The multivariate technique makes it possible to obtain an uncertainty analysis for the possibly correlated real and imaginary parts of the complex quantities. The results show that the errors in impedance results at low frequency mainly depend on the variability of transmission coefficients, while the mean Mach number accuracy is the most important source of error at high frequencies. The effect of Mach numbers used in the wave dispersion equation and in the Ingard-Myers boundary condition has been separated for comparison of the outcome of impedance eduction. A local Mach number based on friction velocity is suggested as a way to reduce the inconsistencies found when estimating impedance using upstream and downstream acoustic excitation.

  • 11446.
    Zhou, Lin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Effect of viscosity on impedance eduction and validation2016Ingår i: 21st AIAA/CEAS Aeroacoustics Conference, American Institute of Aeronautics and Astronautics, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Acoustic liners are a key part for reducing aircraft engine noise. Simulation and optimization of liner properties are critically relying on impedance measurement results, so called impedance eduction technology. Traditionally the effect of viscosity has been assumed to have negligible influence. However this paper shows that viscosity has noticeable influence even at low frequencies. The investigation is based on a comparison study using Linearized Euler equations and Linearized Navier-Stokes equations solved by finite element simulations. In the process of impedance eduction a one-dimensional straightforward method is proposed. Normal velocity and displacement have been obtained and discussed. Impedance results are further implemented into a two-dimensional wave propagation code. Finally simulation results have been compared and validated against experimental data.

  • 11447.
    Zhou, Lin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx). KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Effect of viscosity on impedance eduction and validationManuskript (preprint) (Övrigt vetenskapligt)
  • 11448.
    Zhou, Lin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx). KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Experimental investigation of an in-duct orifice with bias flow under medium and high level acoustic excitation2014Ingår i: International Journal of Spray and Combustion Dynamics, ISSN 1756-8277, Vol. 6, nr 3, s. 267-292Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper experimentally investigates the acoustic properties of an orifice with bias flow under medium and high sound level excitation. Orifices with two different edge configurations were tested. The study includes a wide range of bias flow velocities, various acoustic excitation levels and different frequencies. The nonlinear acoustic scattering matrix was identified by a finely controled two-source method. Aeroacoustic modal analysis was introduced based on eigenvalue-decomposition. Acoustic properties, such as impedance, nonlinear scattering matrix and the eigenvalues were compared and discussed. Experimental results also show that bias flow makes the acoustic properties more complex compared to the no bias flow case, especially when the velocity ratio between acoustic particle velocity and mean flow velocity is near unity.

  • 11449.
    Zhou, Lin
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx). KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    The effect of combined high level acoustic excitation and bias flow on the acoustic properties of an in-duct orifice (AIAA 2013-2128)2013Ingår i: 19th AIAA/CEAS Aeroacoustics Conference, American Institute of Aeronautics and Astronautics, 2013, s. 1-13Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates the acoustic properties of an orifice with bias flow under medium and high sound level excitation. Orifices with two different edge configurations were tested experimentally.The study includes a wide range of bias flow velocities, various acoustic excitation levels and different frequencies. The so-called Cummings equation was the starting point for the theoretical modelling. It was modified and a novel orifce acoustic discharge coefficient model was developed both for cases with and without bias flow. The model was experimentally validated. With this model the acoustic resistance is obtained by the harmonic balance method, and the results agree fairly well with the experimental results for low frequencies. Experimental results also show that bias flow makes the acoustic properties much more complex compared to the no bias flow case, especially when the velocity ratio between acoustic particle velocity and mean flow velocity is near unity.  

  • 11450.
    Zhou, Lin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för industriell teknik och management (ITM), Centra, Competence Center for Gas Exchange (CCGEx).
    Bodén, Hans
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Lahiri, Claus
    Bake, Fredrich
    Enghardt, Lars
    Comparison of impedance eduction results using different methods and test rigs2014Ingår i: 20th AIAA/CEAS Aeroacoustics Conference, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    The last twenty years has seen a large development in inverse techniques for the determination of liner impedance under grazing flow conditions, so called impedance eduction techniques. This paper contribute to a continuing effort to gain confidence in results obtained using different test rigs as well as different impedance eduction techniques. The latter includes the use of different equations for solving for the sound field in the lined section. The DLR reference liner sample HR-S2 studied is a locally reacting single degree of freedom Helmholtz resonator liner which has previously been tested at DLR and NASA Langley. In this study it is tested in a smaller scale facility at KTH, but under similar mean flow and sound pressure level conditions as in the previous studies. A good agreement has been obtained for different method under the same plug flow assumption. The same trend but not identical effects of nonlinearity have been obtained with high levels of acoustic excitation. The effect of different flow Mach number assumptions are discussed in connection with the use of the Ingard-Myers boundary condition.

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