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  • 1. Adlercreutz, Ludvig
    et al.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Andersen, J.
    Ogink, R.
    Optimizing the Natural Gas Engine for CO2 reduction2016In: SAE Technical Papers, SAE International , 2016, Vol. 2016-April, no AprilConference paper (Refereed)
    Abstract [en]

    With alternative fuels having moved more into market in light of their reduction of emissions of CO2 and other air pollutants, the spark ignited internal combustion engine design has only been affected to small extent. The development of combustion engines running on natural gas or Biogas have been focused to maintain driveability on gasoline, creating a multi fuel platform which does not fully utilise the alternative fuels' potential. However, optimising these concepts on a fundamental level for gas operation shows a great potential to increase the level of utilisation and effectiveness of the engine and thereby meeting the emissions legislation. The project described in this paper has focused on optimising a combustion concept for CNG combustion on a single cylinder research engine. The ICE's efficiency at full load and the fuels characteristics, including its knock resistance, is of primary interest - together with part load performance and overall fuel consumption. In the process of increasing the efficiency of the engine the following areas have been of primary interest, increased compression ratio, thermal load at high cylinder pressure and the use of EGR to further increase efficiency. The overall goal in the project was to reduce the CO2-emissions while maintaining the performance and characteristics of the engine. The ambition is to reduce specific tail-pipe CO2-emissions in g/kWh by 50% compared to a modern gasoline engine. The goal was close to being reached at 45% reduction at full load and 25-34% on part load. This was done by theoretically downsizing the engine and increasing the specific performance of the engine.

  • 2. Adlercreutz, Ludvig
    et al.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlåås, Ola
    Particle Emission Measurements in a SI CNG EngineUsing Oils with Controlled Ash Content2019In: SAE Technical Papers, 2019Conference paper (Refereed)
    Abstract [en]

    Clean combustion is one of the inherent benefits of using a high methane content fuel, natural gas or biogas. A single carbon atom in the fuel molecule results, to a large extent, in particle-free combustion. This is due to the high energy required for binding multiple carbon atoms together during the combustion process, required to form soot particles. When scaling up this process and applying it in the internal combustion engine, the resulting emissions from the engine have not been observed to be as particle free as the theory on methane combustion indicates. These particles stem from the combustion of engine oil and its ash content. One common practice has been to lower the ash content to regulate the particulate emissions, as was done for diesel engines. For a gas engine, this approach has been difficult to apply, as the piston and valvetrain lubrication becomes insufficient. However, the low particle emissions from the combustion of CNG does allow for an investigation of particle contribution from engine oil ash content with only a minor particle contribution from the fuel itself. The hypothesis for this study is that there is a relationship between the engine oil ash content and the particulate emissions from a CNG engine. The investigation was conducted for several operating points with varying engine speeds and load on a single cylinder engine. The single cylinder approach was chosen to reduce sources of engine oil intrusion in the combustion chamber. The obtained results were not in line with the hypothesis, the particle emissions from the lower ash content oil did not decrease in number but the size of the particles did. The results also showed a spiking behavior in the particulate emissions, originating from the lubrication oil consumption past the piston rings. Mass flow through the engine proved to affect the particle size distribution as well as the total number of particles for all levels of oil ash content.

  • 3. Adlercreutz, Ludvig
    et al.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlåås, Ola
    Variation in Squish Length and Swirl to Reach Higher Levels of EGRin a CNG Engine2019Conference paper (Refereed)
    Abstract [en]

    Gaseous methane fuel for internal combustion engineshave proved to be a competitive source of propulsionenergy for heavy duty truck engines. Using biogascan even reduce the carbon footprint of the truck to near-zerolevels, creating fully environmentally friendly transport. Gasengines have already been on the market and proved to be apopular alternative for buses and waste transport. However,for long haulage these gas engines have not been on par withthe equivalent diesel engines. To improve the power and efficiencyof EURO VI gas engines running stoichiometrically, adirect way forward is adding more boost pressure and sparkadvance in combination with more EGR to mitigate knock.Using in-cylinder turbulence to achieve higher mixing rate,the fuel can still be combusted efficiently despite the increasedfraction of inert gases. In this paper, previous findings onin-cylinder air flows for diesel engine simulations are investigatedfor the applicability on to stoichiometric gas combustion.Two key parameters were identified, swirl and squish.By varying the levels of swirl with different squish lengths inthe piston design, the in-cylinder flow motion is altered toinvestigate its effect on stoichiometric gas combustion. Thetesting was performed on a single cylinder research engineoperated in the equivalent multi cylinder engine operatingpoints. The results show that previous modelling findings areverified on the pre-mixed gas combustion studied. By choosingswirl and squish for the design of the gas engine, it is possibleto increase the combustion speed and thus the fraction of EGRin the combustion charge, without the latter having a negativeimpact on the combustion.

  • 4.
    Binder, Christian
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. Scania CV AB.
    Abou Nada, Fahed
    Lund University.
    Richter, Mattias
    Lund University.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Norling, Daniel
    Scania CV AB.
    Heat Loss Analysis of a Steel Piston and a YSZ Coated Piston in a Heavy-Duty Diesel Engine Using Phosphor Thermometry Measurements2017In: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 10, no 4, p. 1954-1968Article in journal (Refereed)
    Abstract [en]

    Diesel engine manufacturers strive towards further efficiency improvements. Thus, reducing in-cylinder heat losses is becoming increasingly important. Understanding how location, thermal insulation, and engine operating conditions affect the heattransfer to the combustion chamber walls is fundamental for the future reduction of in-cylinder heat losses. This study investigates the effect of a 1mm-thick plasma-sprayed yttria-stabilized zirconia (YSZ) coating on a piston. Such a coated piston and a similar steel piston are compared to each other based on experimental data for the heat release, the heat transfer rate to the oil in the piston cooling gallery, the local instantaneous surface temperature, and the local instantaneous surface heat flux. The surface temperature was measured for different crank angle positions using phosphor thermometry. The fuel was chosen to be n-heptane to facilitate surface temperature measurements during non-skip-fire, thermally stabilized operating conditions. Assuming one-dimensional heat transfer inside each piston, the local instantaneous surface heat flux was calculated using the heat transfer rate to the oil in the piston cooling gallery and the surface temperature measurements. The results from this study show that the surface temperature variation is similar for both pistons. The instantaneous heat flux during combustion is however significantly greater for the steel piston than the coated piston. The heat release analysis also indicates that combustion is slower for the piston with the yttria-stabilized zirconia coating.

  • 5.
    Binder, Christian
    et al.
    Scania CV AB.
    Vasanth, E.
    Norling, Daniel
    Scania CV AB.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Experimental Determination of the Heat Transfer Coefficient in Piston Cooling Galleries2018In: SAE Technical Papers, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    Piston cooling galleries are critical for the pistons’ capability to handle increasing power density while maintaining the same level of durability. However, piston cooling also accounts for a considerable amount of heat rejection and parasitic losses. Knowing the distribution of the heat transfer coefficient (HTC) inside the cooling gallery could enable new designs which ensure effective cooling of areas decisive for durability while minimizing parasitic losses and overall heat rejection. In this study, an inverse heat transfer method is presented to determine the spatial HTC distribution inside the cooling gallery based on surface temperature measurements with an infrared (IR) camera. The method utilizes a piston specially machined so it only has a thin sheet of material of a known thickness left between the cooling gallery and the piston bowl. The piston - initially at room temperature - is heated up with warm oil injected into the cooling gallery. The transient of the piston’s outer surface temperature is captured with an IR camera from the top. Combining the temperature transient of each pixel, the HTC is later obtained through an inverse heat transfer solver based on one-dimensional heat conduction inside the piston material. To the authors’ knowledge, the current study presents the first application of an inverse heat transfer method for spatially resolved and experimentally determined heat transfer coefficients inside a piston cooling gallery. Preliminary measurements at standstill to demonstrate the method display an area of increased heat transfer where the entering oil jet impinges onto the wall of the cooling gallery.

  • 6.
    Crescenzo, Domenico
    et al.
    KTH.
    Olsson, Viktor
    KTH.
    Arco Sola, Javier
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Wu, Hongwen
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Lycke, Eric
    Leufven, O.
    Stenlåås, Ola
    Turbocharger Speed Estimation via Vibration Analysis2016In: SAE technical paper series, ISSN 0148-7191, Vol. 2016-April, no AprilArticle in journal (Refereed)
    Abstract [en]

    Due to demanding legislation on exhaust emissions for internal combustion engines and increasing fuel prices, automotive manufacturers have focused their efforts on optimizing turbocharging systems. Turbocharger system control optimization is difficult: Unsteady flow conditions combined with not very accurate compressor maps make the real time turbocharger rotational speed one of the most important quantities in the optimization process. This work presents a methodology designed to obtain the turbocharger rotational speed via vibration analysis. Standard knock sensors have been employed in order to achieve a robust and accurate, yet still a low-cost solution capable of being mounted on-board. Results show that the developed method gives an estimation of the turbocharger rotational speed, with errors and accuracy acceptable for the proposed application. The method has been evaluated on a heavy duty diesel engine.

  • 7.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    A computer-controlled bowing machine (MUMS)1992In: STL-QPSR, Vol. 33, no 2-3, p. 61-66Article in journal (Other academic)
    Abstract [en]

    MUMS is a  bowing machine, i.e., a  machine that bows (plays) a  violin in a controlled  and  repeatable  manner  by  mechanical means. Traditionally, the main application of bowing machines has  been in studying  string vibrations and violins under  reproducible conditions. MUMS uses  a normal bow to  excite  the violin, which also allows a comparison of different bows and their influence on the string vibrations. The position and velocity of the bow and the force between bow and string ("bow pressure") can be specified and controlled within close limits. MUMS consists of two parts; a converted printer which contains the mechanical support of the bow and motors for bow motion and force, and a PC-computer which controls the motion by software servos.

  • 8.
    Cronhjort, Andreas
    KTH.
    Droplet Velocities in a Sliced Diesel Spray2001Conference paper (Refereed)
    Abstract [en]

    This paper gives a summary of particle image velocimetry (PIV) measurements performed in a sliced diesel spray. The slicing of the spray was necessary to achieve good image quality in the more dense regions of the spray. The images were double exposed to allow auto-correlation based velocimetry. The exposure time of each exposure was 100 ns, as that was the shortest possible exposure with the camera used. The illumination was achieved with a flashlight located at the opposite side of the spray, consequently the droplets were visible as dark shadows. The long exposure time limited the possibilities to measure high velocities, and therefore the velocities in the very rapidly moving spray core could not be measured, as the images were smeared out in the direction of the velocity. The resulting velocities were compared to velocities in the corresponding unsliced spray in the points where both sprays gave velocity data. The results were also compared with computer simulations. Some disagreements were found, and possible reasons for these are discussed.

  • 9.
    Cronhjort, Andreas
    Scania CV AB.
    Optical Studies in a Direct Injected Diesel Engine2005Conference paper (Other academic)
    Abstract [en]

    A heavy-duty diesel engine with optical access through an extended piston has been used to study diesel spray combustion. Conventional photography using a solid-state camera was adopted to image the flames. The images were parameterized using image processing software. Due to extended crevices and reduced stiffness as compared to the original engine, the effective compression ratio was slightly lower in the optical cylinder. To compensate for the lowered compression ratio, the inlet pressure as well as the inlet temperature were increased. As top dead center conditions regarding gas density and temperature were desired to be maintained, this approach resulted in an increased overall air to fuel ratio. However, despite these drawbacks, the engine allows for spray combustion studies under realistic diesel engine conditions regarding pressure and temperature. The inlet pressure was kept at 400 kPa absolute and the temperature was 325 K. To predict the air mass in the cylinder as accurately as possible, the exhaust back pressure was always kept equal to the inlet pressure. To minimize the thermal load on the piston, fuel was injected only when an image was to be exposed. This was also beneficial when estimating the air mass in the cylinder, as the temperature of the rest gas was quite low. A nozzle with eight orifices fitted to a common-rail injector was used to generate the sprays. The rail pressures used were 160 MPa and 220 MPa, the injected amount of fuel was varied between 80 mg and 240 mg.

  • 10.
    Cronhjort, Andreas
    KTH, Superseded Departments (pre-2005), Machine Design. Scania CV AB.
    Spray Visualization Using a Mechanical Slicing Device2000Conference paper (Refereed)
    Abstract [en]

    This paper describes a concept for gaining photographic access, at a high magnification level, to quite dense regions in liquid sprays, aiming primarily at photographic investigations of the spray and studies of the trailing edge with its associated large droplets. The slicing of the spray is achieved with two sharp edges, which cut out a thin sheet of the spray. The sheet of droplets is visualized with conventional shadow photography. The images acquired with the slicer are compared with images acquired without it, and even though some ligaments are identified as originating from the edges of the slit, the method is still considered as being beneficial, as the quality of the images is significantly enhanced.

  • 11.
    Cronhjort, Andreas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. Scania CV AB.
    Dahlén, Lars
    Diesel Flame Studies in an Optical Engine2004Conference paper (Refereed)
    Abstract [en]

    A diesel engine with optical access through an extended piston has been developed. It is based on a heavy duty truck engine and the purpose is to generate calibration data for computer simulation of spray combustion, hereby facilitating reliable combustion prediction using Computational Fluid Dynamics (CFD). Conventional photography using a solid-state camera was adopted to image the combustion. As the upper surface of the glass window in the piston is flat, the compression ratio of the engine is reduced to 12:1, in order to avoid that the spray plumes hit the glass surface. To compensate for the lowered compression ratio, the inlet pressure as well as the inlet temperature were increased. As top dead center conditions regarding gas density and temperature are desired to be maintained, this approach results in an increased overall air-to-fuel ratio. Additionally, the cylinder pressure decay due to the piston movement becomes slower than it should be at the present engine speed. However, despite these drawbacks, the engine allows for spray combustion studies under realistic diesel engine conditions regarding pressure and temperature. In the preliminary study the inlet pressure was 400 kPa absolute and the temperature was 450 K, resulting in a compression pressure of about 8.6 MPa at top dead center when the engine runs at 1200 rpm. To predict the air mass in the cylinder as accurately as possible, the exhaust back pressure is always kept equal to the inlet pressure. To minimize the thermal load on the piston, fuel is injected only during cycles when an image is exposed. This is also beneficial when estimating the air mass in the cylinder, as the temperature of the rest gas from the preceding cycle is quite low. In the preliminary study a nozzle with eight orifices fitted to a common-rail injector was used to generate the sprays. The orifice diameter was 190 µm. The rail pressure was 160 MPa and the injected amount of fuel was 80 mg. The resulting combustion was dominated by diffusion flames.

  • 12.
    Cronhjort, Andreas
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Gåsste, Jan
    Konstanzer, Dennis
    Advanced control system for optical diesel spray analysis in a pressurized vessel1997Conference paper (Refereed)
    Abstract [en]

    An advanced control system to enable systematic photographic studies of diesel injections has been developed. The system automatically generates series of photos under predefined conditions. The injections are made in a pressurized vessel. The temperature in the vessel can be varied between 30 °C and 100 °C and the gas pressure between 0.1 MPa and 5 MPa. The entire system is controlled by a computer, and therefore the safety level is very high when performing experiments under extreme conditions. During the injection sequence the system can be remote controlled and monitored from another computer. The timing of the image acquisition is adjustable with an accuracy of 1 µs. Up to four separate flashes can be used to achieve multiple exposures of the film. The four flashes can also be fired simultaneously in order to increase the optical energy in the flash. When using double exposure at a low level of optical magnification the spray tip velocity can be determined. If the double exposure facility is used in conjunction with a high magnification the droplet speed can be measured.

    The system has been used to study the spray penetration into air at 60 °C and 4.2 MPa. The air density corresponds to full load conditions in a direct injected 2 liter per cylinder heavy duty diesel engine. The peak injection pressure was 140 MPa. To minimize the influence of cycle to cycle variations the median values of several images have been used. The results have been compared with computer simulations.

  • 13.
    Cronhjort, Andreas
    et al.
    KTH.
    Konstanzer, Dennis
    Scania (CFD).
    Analysis of a Diesel Spray Using a Mechanical Slicing Device2001Conference paper (Refereed)
    Abstract [en]

    This paper gives a summary of image velocimetry measurements performed in a sliced diesel spray. The slicing of the spray was necessary to achieve sufficient image quality in the more dense regions of the spray. The images were double exposed to allow auto-correlation based velocimetry. The illumination was achieved with a xenon flashlight behind the spray and consequently the droplets were visible as dark shadows. Images were acquired from different points downstream from the nozzle, and a number of different radii were employed at every position. In the images the smaller droplets seem to be spherical, while the larger ones are distorted due to high weber numbers. Computer simulations indicate that large droplets may reach high weber numbers when passing through the slit, and that some of these large droplets break up.

  • 14.
    Cronhjort, Andreas
    et al.
    KTH.
    Sjöberg, Henrik
    Diesel spray droplet analysis using a long distance microscope1996Conference paper (Refereed)
    Abstract [en]

    An injection test rig suitable for optical analysis of diesel fuel injections has been developed. The system is based upon an injector with an internal hydraulic pressure booster. The system has been tested at a temperature of 300 K and a peak injection pressure of 98 MPa. The ambient pressure was 100 kPa. The entire system is controlled by a computer. The spray is backlighted with a flashlight. A long distance microscope magnifies the image of the injection. The distance between the object and the first lens is approximately 230 mm. The magnification is continuously variable between unity and 50 times magnification. The resolution of the system is approximately 5 µm when using the largest magnification. The depth of focus depends on the selected magnification. With the largest magnification engaged the depth of focus is 800 µm. The pictures were analyzed using commercially available software. The droplet size distribution as well as the concentration of droplets were calculated. The system was also used to study the early breakup of the spray.

  • 15.
    Cronhjort, Andreas
    et al.
    Scania CV AB.
    Wåhlin, Fredrik
    Scania CV AB.
    Segmentation Algorithm for Diesel Spray Image Analysis2004In: Applied Optics, ISSN 1559-128X, E-ISSN 2155-3165, Vol. 43, no 32, p. 5971-5980Article in journal (Refereed)
    Abstract [en]

    An algorithm for segmentation of diesel spray images has been developed. Its most important feature is robustness against experimental setups that fail to guarantee images whose histograms show two distinct peaks. According to the approach presented, only the peak from the background is used, and it is assumed that the background peak is narrow enough not to include too much of the spray. The algorithm has proved successful for evaluation of images from a pressurized vessel as well as from an engine with optical access, with no need for adjusting the tuning parameters. By adjusting them, one may tune the noise sensitivity.

  • 16.
    Cronhjort, Andreas
    et al.
    KTH.
    Ångström, Hans-Erik
    Optical analysis of diesel sprays1996Conference paper (Other academic)
    Abstract [en]

    An injection test rig suitable for optical analysis of diesel fuel injections in a constant volume pressurized vessel has been developed. Optical access to the vessel is obtained with two quartz glasses. The injection system is based upon an electronically controlled injector with an internal hydraulic pressure booster. The injection system has been tested at a temperature of 300 K and a peak injection pressure of 98 MPa. The gas pressure in the vessel was varied between 100 kPa and 4 MPa. The entire system is controlled by a computer. The spray is backlighted with a flashlight. A long distance microscope magnifies the image of the injection. The magnification is continuously variable between unity and 50 times magnification. The resolution of the system is approximately 5 µm when using the largest magnification. The pictures were analyzed using commercially available software.

  • 17.
    Cronhjort, Andreas
    et al.
    KTH.
    Ångström, Hans-Erik
    Optical analysis of diesel sprays1997Conference paper (Other academic)
    Abstract [en]

    An advanced control system to enable systematic photographic studies of diesel injections has been developed. The system automatically generates series of photos under predefined conditions. The injections are made in a pressurized vessel. The temperature in the vessel is variable between 30 °C and 100 °C and the gas pressure between 0.1 MPa and 5 MPa. The entire system is controlled by a computer, and therefore the safety level is very high when performing experiments under extreme conditions. During the injection sequence the system can be remote controlled from another computer. The timing of the image acquisition is adjustable with an accuracy of 1 µs. Up to four separate flashes can be used to achieve multiple exposures of the film. The four flashes can also be fired simultaneously in order to increase the optical energy in the flash. When using double exposure at a low level of optical magnification the spray tip velocity can be determined. If the double exposure facility is used in conjunction with a high magnification the droplet speed can be measured.

    The system has been used to study the spray penetration into air at 60 °C and 4.2 MPa. The air density corresponds to full load conditions in a direct injected 2 liter per cylinder heavy duty diesel engine. The peak injection pressure was 120 MPa. To minimize the influence of cycle to cycle variations the median values of several images have been used. The results have been compared with computer simulations. Droplet volume distributions and velocities, with double exposure technique, have been studied under the same ambient conditions.

  • 18. Desantes, José
    et al.
    Arrègle, Jean
    López, Javier
    Cronhjort, Andreas
    Scania CVAB, Advanced Combustion. Engine Development, SE - 151 87 Södertälje, Sweden.
    Scaling Laws for Free Turbulent Gas Jets and Diesel-Like Sprays2006In: Atomization and sprays, ISSN 1044-5110, E-ISSN 1936-2684, Vol. 16, no 4, p. 443-474Article in journal (Refereed)
    Abstract [en]

    Scaling laws for free turbulent gas jets and diesel-like sprays are deduced and experimentally validated. The analysis is based on basic conservation equations and experimental evidence. As a new contribution, the effect of the Schmidt number on the scaling laws is analyzed and included, which leads to a more general set of normalized parameters. By analyzing the scaling laws, it is possible to obtain a clear comprehension of gas-jet or diesel-spray behavior, as well as an understanding of the relationship between input and output parameters. Two new parameters are introduced that characterize mass and momentum transfer in the radial direction of the gas jet or diesel spray, thus providing valuable information about the mixing process.

  • 19.
    Gundmalm, Stefan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Divided Exhaust Period: Effects of Changing the Relation between Intake, Blow-Down and Scavenging Valve Area2013In: SAE World Congress 2013, 2013Conference paper (Refereed)
    Abstract [en]

    In a previous paper we showed the effects of applying the Divided Exhaust Period (DEP) concept on two heavy-duty diesel engines, with and without Exhaust Gas Recirculation (EGR). Main findings were improved fuel consumption due to increased pumping work, improved boost control and reduced residual gas content. However, some limitations to the concept were discovered.  In the case of high rates of short route EGR, it was apparent that deducting the EGR flow from the turbine manifold impaired optimal valve timing strategies. Furthermore, for both of the studied engines it was clear that the size and ratio of blow-down to scavenging valve area is of paramount importance for engine fuel efficiency.

    In this paper, the DEP concept has been studied together with a long route EGR system. As expected it gave more freedom to valve timing strategies when driving pressure for EGR is no longer controlled with the valve timing, as in the short route case. However, when evaluating different combinations of intake, blow-down and scavenging valve area, the optimal relation proves to be strongly dependent on the current EGR system and EGR rates. Hence, for different engine setups the trade-off between total intake and total exhaust area needs to be re-evaluated for optimal engine fuel efficiency. This paper also presents general trends in how different valve timing strategies and EGR rates affect both pumping work and boost pressure.

  • 20.
    Gundmalm, Stefan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Divided Exhaust Period: Effects of Changing the Relation between Intake, Blow-Down and Scavenging Valve Area2013In: SAE International Journal of Engines, ISSN 1946-3936, Vol. 6, no 2, p. 739-750Article in journal (Refereed)
    Abstract [en]

    In a previous paper we showed the effects of applying the Divided Exhaust Period (DEP) concept on two heavy-duty diesel engines, with and without Exhaust Gas Recirculation (EGR). Main findings were improved fuel consumption due to increased pumping work, improved boost control and reduced residual gas content. However, some limitations to the concept were discovered. In the case of high rates of short route EGR, it was apparent that deducting the EGR flow from the turbine manifold impaired optimal valve timing strategies. Furthermore, for both of the studied engines it was clear that the size and ratio of blow-down to scavenging valve area is of paramount importance for engine fuel efficiency. In this paper, the DEP concept has been studied together with a long route EGR system. As expected it gave more freedom to valve timing strategies when driving pressure for EGR is no longer controlled with the valve timing, as in the short route case. However, when evaluating different combinations of intake, blow-down and scavenging valve area, the optimal relation proves to be strongly dependent on the current EGR system and EGR rates. Hence, for different engine setups the trade-off between total intake and total exhaust area needs to be re-evaluated for optimal engine fuel efficiency. This paper also presents general trends in how different valve timing strategies and EGR rates affect both pumping work and boost pressure.

  • 21.
    Gundmalm, Stefan
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Ångström, Hans-Erik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Divided Exhaust Period on Heavy-Duty Diesel Engines2012Conference paper (Refereed)
    Abstract [en]

    Divided Exhaust Period (DEP) has previously been studied on SI engines while results fromHD diesels are scarcer. In this paper the DEP concept has been numerically simulated on two HD dieselengines; one without EGR and one with high rates of short route EGR. The aim is to reduce fuelconsumption, residual gas content and to improve boost control, while current EGR rates are maintained.

    The central idea of the DEP concept is to let the initial high energy blow-down pulse feed theturbocharger, but bypass the turbine during the latter part of the exhaust stroke when back pressuredominates the pumping work. The exhaust flow from the cylinder is divided between two exhaust manifoldsof which one is connected to the turbine, and one bypasses the turbine. The flow split betweenthe manifolds is controlled with a variable valve train system.

    Results show a reduction of pumping losses for both engine configurations. In the non-EGRcase, the DEP concept offers the possibility to control the mass flow and pressure ratio over the turbine.This allows the turbocharger to operate in a high efficiency mode for a wide range of engine loadpoints. For the EGR case, there is less freedom in control of turbine mass flow, since the blow-downphase is used for both turbine work and EGR flow. Therefore the fuel consumption benefit is reduced.

    The conclusion of this paper is that the simulations of the DEP concept show improvements toengine performance and efficiency. In the case of high EGR rates it is shown that the EGR flow shouldnot be deducted from the blow-down phase.

  • 22. Gåsste, Jan
    et al.
    Cronhjort, Andreas
    KTH.
    Konstanzer, Dennis
    Photographic investigation of a sliced diesel spray1997Conference paper (Refereed)
    Abstract [en]

    Due to the high density of a diesel spray, normally no visualization of the spray core can be done by backlightning. By slicing the spray into a ”spray-sheet”, the phenomena inside the spray can be optically studied in the same way as the outer regions of the spray.

    Special spray slicers with very thin gaps have been designed and tested. By taking photos of the sliced sprays, the geometry and structure of the spray in the center of the spray have been studied.

    Comparisons with ”unsliced” sprays and with fire® cfd simulations have been done to study if the results of a sliced spray are representative of an ordinary diesel spray. The tests have been performed in an injection test rig equipped with an optical system which enables high resolution. Measurements were performed with the diesel spray injected into a pressurized vessel. The peak injection pressure was 140 MPa. The vessel pressure was set to 4.2 MPa and the vessel temperature to 60 ºC

    Photos of the spray tip just leaving the slicer have been taken to study the structure of the spray tip. Studies whether the ”spray-sheet” remains unaffected downstream from the slicer, or if it turns into a more normal spray shape, have been done. Prestudies have been made to investigate the internal spray structure.

  • 23.
    Holmberg, Ted
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlaas, O.
    Pressure Amplitude Influence on Pulsating Exhaust Flow Energy Utilization2018In: SAE technical paper series, ISSN 0148-7191, Vol. 2018-AprilArticle in journal (Refereed)
    Abstract [en]

    A turbocharged Diesel engine for heavy-duty on-road vehicle applications employs a compact exhaust manifold to satisfy transient torque and packaging requirements. The small exhaust manifold volume increases the unsteadiness of the flow to the turbine. The turbine therefore operates over a wider flow range, which is not optimal as radial turbines have narrow peak efficiency zone. This lower efficiency is compensated to some extent by the higher energy content of the unsteady exhaust flow compared to steady flow conditions. This paper experimentally investigates the relationship between exhaust energy utilization and available energy at the turbine inlet at different degrees of unsteady flow. A special exhaust manifold has been constructed which enables the internal volume of the manifold to be increased. The larger volume reduces the exhaust pulse amplitude and brings the operating condition for the turbine closer to steady-flow. The operating points are defined by engine speed and boost pressure. From these values the isentropic turbine work is calculated and with the measured compressor work the mean turbine efficiency is estimated. The results show that more energy has to be provided to the turbine at larger exhaust manifold volumes to maintain a constant boost pressure, indicating that the efficiency of the turbine decreases. 

  • 24.
    Holmberg, Ted
    et al.
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlaas, O.
    Pressure Ratio Influence on Exhaust Valve Flow Coefficients2017In: SAE technical paper series, ISSN 0148-7191, Vol. 2017-March, no MarchArticle in journal (Refereed)
    Abstract [en]

    In one dimensional engine simulation software, flow losses over complex geometries such as valves and ports are described using flow coefficients. It is generally assumed that the pressure ratio over the valve has a negligible influence on the flow coefficient. However during the exhaust valve opening the pressure difference between cylinder and port is large which questions the accuracy of this assumption. In this work the influence of pressure ratio on the exhaust valve flow coefficient has been investigated experimentally in a steady-flow test bench. Two cylinder heads, designated A and B, from a Heavy-Duty engine with different valve shapes and valve seat angles have been investigated. The tests were performed with both exhaust valves open and with only one of the two exhaust valves open. The pressure ratio over the exhaust port was varied from 1.1:1 to 5:1. For case A1 with a single exhaust valve open, the flow coefficient decreased significantly with pressure ratio. This trend was not replicated for the other single valve case B1, as pressure ratio only had a small influence on the flow coefficient. For the twin valve case A2, the pressure ratio influence was confined to the lower range of valve lifts as the limiting factor was the exhaust port outlet at higher valve lifts. The flow coefficient for the twin valve case B2 increased with pressure ratio in the mid-range of valve lifts.

  • 25.
    Holmberg, Ted
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlåås, Ola
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Dynamic Exhaust Valve Flow 1-D Modelling During Blowdown Conditions2019In: SAE Technical Papers, 2019Conference paper (Refereed)
    Abstract [en]

    To conduct system level studies on internal combustionengines reduced order models are required in order tokeep the computational load below reasonable limits.By its nature a reduced order model is a simplification of realityand may introduce modeling errors. However what is of interestis the size of the error and if it is possible to reduce the errorby some method. A popular system level study is gas exchangeand in this paper the focus is on the exhaust valve. Generallythe valve is modeled as an ideal nozzle where the flow lossesare captured by reducing the flow area. As the valve movesslowly compared to the flow the process is assumed to be quasisteady,i.e. interpolation between steady-flow measurementscan be used to describe the dynamic process duringvalve opening. These measurements are generally done at lowpressure drops, as the influence of pressure ratio is assumed tobe negligible. As it is very difficult to measure time-resolvedmass flow it is hard to test validity of these modeling assumptions.Experimental data indicates that the model overestimatesvalve flow during the blowdown event. As the blowdown pulsecontains a significant portion of the energy in the cylinder atexhaust valve opening, it is therefore of importance to modelthis correctly. In this paper experimental results from previouslypublished research have been compared to simulationresults and the deviation from quasi-steady behavior has beenquantified. The deviation appears to be a function of pressureratio over the valve and valve opening speed. A model isproposed to compensate for the observed effects.

  • 26.
    Kerres, Bertrand
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). Competence Center for Gas Exchange.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. Competence Center for Gas Exchange.
    A Comparison of On-Engine Surge Detection Algorithms Using Knock AccelerometersManuscript (preprint) (Other academic)
    Abstract [en]

    On-engine surge detection could help in reducing the safety margintowards surge, thus allowing higher boosting pressures and ultimatelylow-end torque. In this paper, experimental data from a truckturbocharger compressor mounted on the engine is investigated. Ashort period of compressor surge is provoked through a sudden, largedrop in engine load. The compressor housing is equipped with knockaccelerometers. Different signal treatments are evaluated for theirsuitability with respect to on-engine surge detection: the signal rootmean square, the power spectral density in the surge frequency band,the recently proposed Hurst exponent, and a closely related conceptoptimized to detect changes in the underlying scaling behavior of thesignal. For validation purposes, a visual observation of the air filtervibrations are also used to diagnose surge. The four signal treatmentsare compared with respect to their reliability as surge indicator andthe time delay between surge onset and indication. Results show thatthe signal power in the surge frequency band has reasonably goodproperties as surge indicator. The normal Hurst exponent isproblematic, since periodic vibrations from engine firing dominatethe scaling behavior. Root mean square and the above mentionedscaling exponent do not measure vibrations caused by surge directly,but rather the reduction in housing vibrations due to the engine loaddrop; nevertheless, it was found to be possible to design an indicatorthat gives good results based on the change in scaling behavior.

  • 27.
    Kerres, Bertrand
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.). KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).
    Experimental investigation of upstream installation effects on the turbocharger compressor map2016In: The 12th International Conference on Turbochargers and Turbocharging, London, UK, 17-18 May, 2016, 2016Conference paper (Refereed)
    Abstract [en]

    This paper experimentally investigates the effects of an upstream bended pipe on the compressor speedline slopes and surge line. Different orientation angles for the incoming bended pipe relative to the compressor scroll are investigated. The tests were carried out on a cold gas stand on a passenger car sized turbocharger. A bended pipe upstream of the compressor leads to an increase of the surge margin. This effect does not depend on the orientation of the bend. Comparisons with a straight inlet with artificially generated pressure losses indicate that the increase in operating range is an effect of the pressure losses generated in the bend.

  • 28. Kerres, Bertrand
    et al.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Stenlåås, Ola
    A comparison of on-engine surge detection algorithms using knock accelerometers2017In: SAE Technical Papers, 2017Conference paper (Refereed)
    Abstract [en]

    On-engine surge detection could help in reducing the safety margintowards surge, thus allowing higher boost pressures and ultimatelylow-end torque. In this paper, experimental data from a truckturbocharger compressor mounted on the engine is investigated. Ashort period of compressor surge is provoked through a sudden, largedrop in engine load. The compressor housing is equipped with knockaccelerometers. Different signal treatments are evaluated for theirsuitability with respect to on-engine surge detection: the signal rootmean square, the power spectral density in the surge frequency band,the recently proposed Hurst exponent, and a closely related conceptoptimized to detect changes in the underlying scaling behavior of thesignal. For validation purposes, a judgement by the test cell operatorby visual observation of the air filter vibrations and audible noises, aswell as inlet temperature increase, are also used to diagnose surge.The four signal treatments are compared with respect to theirreliability as surge indicator and the time delay between surge onsetand indication. Results show that the signal power in the surgefrequency band has reasonably good properties as surge indicator.The normal Hurst exponent is problematic, since periodic vibrationsfrom engine firing dominate the scaling behavior. Root mean squareand the above mentioned scaling exponent do not measure vibrationscaused by surge directly, but rather the reduction in housingvibrations due to the engine load drop. Nevertheless, it was found tobe possible to design an indicator that gives good results based on thechange in scaling behavior.

  • 29.
    Kerres, Bertrand
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Optics and Photonics, OFO.
    Nair, Vineeth
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Mihaescu, Mihai
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx). KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Analysis of the Turbocharger Compressor Surge Margin Using a Hurst-Exponent-based Criterion2016In: SAE International Journal of Engines, ISSN 1946-3936, E-ISSN 1946-3944, Vol. 9, no 3Article in journal (Refereed)
    Abstract [en]

    Turbocharger compressors are limited in their operating range at low mass flows by compressor surge, thus restricting internal combustion engine operation at low engine speeds and high mean effective pressures. Since the exact location of the surge line in the compressor map depends on the whole gas exchange system, a safety margin towards surge must be provided. Accurate early surge detection could reduce this margin. During surge, the compressor outlet pressure fluctuates periodically. The Hurst exponent of the compressor outlet pressure is applied in this paper as an indicator to evaluate how close to the surge limit the compressor operates. It is a measure of the time-series memory that approaches zero for anti-persistence of the time series. That is, a Hurst exponent close to zero means a high statistical preference that a high value is followed by a low value, as during surge. Maps of a passenger-car sized turbocharger compressor with inlet geometries that result in different surge lines are measured on a cold gas stand. It is demonstrated that the Hurst exponent in fact decreases as the compressor moves towards surge, and that a constant value of the Hurst exponent can be used as a threshold for stable operation. Transient pressure signals of the compressor entering surge are analyzed in order to evaluate the time lag until surge can be detected using the Hurst exponent. Two surge cycles are usually needed to detect unstable operation. However, since the amplitude of these oscillations is relatively small for the first cycles, detection is possible before the oscillations grow into deep surge.

  • 30. Konstanzer, Dennis
    et al.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Diesel spray analysis using FIRE1997Conference paper (Other academic)
    Abstract [en]

    This paper focuses on numerical studies and experimental investigations of dieselsprays. The commercial CFD-software package FIRE® has been used to describedynamic flow properties of the fluid in a pressurized vessel with optical access.The temperature in the vessel can be varied in the interval 300-370 K and the pressurecan be set to between 0.1 MPa and 5 MPa.An advanced control system [1], which automatically generates systematic series ofphotographs under predefined conditions has been used. In addition a long distancemicroscope [2] was employed, which allows magnifications up to 50 times at theimage plane. The maximum resolution is 5 mm and depth of focus is approximately800 mm. Local droplet size distributions can be measured with these pictures [3].The timing of the image acquisition is adjustable with an accuracy of 1 ms and the flashduration is 250 ns. Four separate flashes can be used to achieve multiple exposures ofthe film, or be fired simultaneously to increase the intensity of the light. Using doubleexposure at low level magnification provides means to determine the spray tip velocity,whereas at high magnification the velocity of single droplets can be determined.This way the control system is able to provide powerful help to verify and validatecalculated CFD-data.The system has been used to study diesel spray injections into air at 330 K and4.2 MPa (i.e. gas density equivalent to full load conditions in a heavy duty directinjected diesel engine with a displacement of 2 litre per cylinder).The peak injection pressure was 140 MPa.Since the dense diesel spray core cannot be visualized by the employed back lightingmethod, special mechanical spray slicers [4] have been designed and tested. The slicerextracts a thin sheet from the spray, which can then be studied.Calculations using the default settings of FIRE® have been carried out and comparedwith the experimental data. Ordinary sprays as well as horizontally and verticallysliced sprays have been studied. The spray contour and penetration length have beencompared at different stages of the first 200 ms of the injection.The results show a small over-prediction of the penetration length. However, it shouldbe emphasized that it is difficult to estimate the amount of liquid fuel required toensure detection on a photograph, which render a uncertainty in the experimentallydetermined penetration lengths.Thus the algorithm used for automatic evaluation of penetration length may needmodification to become compatible with calculated CFD-data.In order to eliminate some of the cycle-to-cycle variations, the average value of 16pictures have been calculated and compared with FIRE® calculations.

  • 31.
    Puttige, Anjan Rao
    et al.
    KTH.
    Hamberg, Robin
    KTH.
    Linschoten, Paul
    KTH.
    Reddy, G.
    KTH.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Stenlåås, Ola
    Surge Detection Using Knock Sensors in a Heavy Duty Diesel Engine2017In: SAE technical paper series, ISSN 0148-7191, Vol. 2017Article in journal (Refereed)
    Abstract [en]

    Improving turbocharger performance to increase engine efficiency has the potential to help meet current and upcoming exhaust legislation. One limiting factor is compressor surge, an air flow instability phenomenon capable of causing severe vibration and noise. To avoid surge, the turbocharger is operated with a safety margin (surge margin) which, as well as avoiding surge in steady state operation, unfortunately also lowers engine performance. This paper investigates the possibility of detecting compressor surge with a conventional engine knock sensor. It further recommends a surge detection algorithm based on their signals during transient engine operation. Three knock sensors were mounted on the turbocharger and placed along the axes of three dimensions of movement. The engine was operated in load steps starting from steady state. The steady state points of operation covered the vital parts of the engine speed and load range. The collected data was analysed with the objective of extracting information of a surging or non-surging compressor. In the charging system studied, the knock sensors detected a profound frequency peak between 5.0 Hz to 7.0 Hz. Another surge related frequency component of about 25 kHz was also observed, dependent on the turbocharger speed. Two surge detection algorithms were evaluated, one based on short time Fourier transform (STFT) and one based on the correlation integral (CI). These algorithms where then validated against temperature measurements at the compressor inlet and visual observation of oscillations of the air inlet piping. The surge detection algorithms were compared for accuracy and repeatability. The accuracy of the methods was found to be 73 % and 71 % respectively when compared to the temperature rise in the compressor inlet.

  • 32.
    Rantanen, Pekka
    et al.
    Helsinki University of Technology.
    Valkonen, Antti
    Helsinki University of Technology.
    Cronhjort, Andreas
    KTH. Scania CV AB.
    Measurements of a Diesel Spray with a Normal Size Nozzle and a Large Scale Model1998Conference paper (Refereed)
    Abstract [en]

    Advantages of the large scale modeling of diesel sprays based on dimensional analysis were studied. Measurements of the spray tip penetration, opening angle, droplet size and velocity in a diesel spray have been made with a small nozzle and a large scale model of the same nozzle. Measurements were made with image analysis, diffraction drop size analyzer and laser Doppler anemometer. Results show that scaling might give us new possibilities to research diesel sprays.

  • 33.
    Rantanen, Pekka
    et al.
    Helsinki University of Technology.
    Valkonen, Antti
    Helsinki University of Technology.
    Cronhjort, Andreas
    KTH. Scania CV AB.
    Measurements of a Diesel Spray with a Normal Size Nozzle and a Large-Scale Model1999In: International Journal of Heat and Fluid Flow, ISSN 0142-727X, E-ISSN 1879-2278, Vol. 20, p. 545-551Article in journal (Refereed)
    Abstract [en]

    Advantages of the large-scale modeling of diesel sprays based on dimensional analysis were studied. Measurements of the spray tip penetration, spray angle, droplet size and velocity in a diesel spray have been made with a small nozzle and a large-scale model of the same nozzle. Measurements were made with image analysis, diffraction drop size analyzer and laser Doppler anemometer. Results show that scaling might give us new possibilities to research diesel sprays.

  • 34. Sjoeberg, Henrik
    et al.
    Manneberg, Goran
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Long-working-distance microscope used for diesel injection spray imaging1996In: Optical Engineering: The Journal of SPIE, ISSN 0091-3286, E-ISSN 1560-2303Article in journal (Refereed)
    Abstract [en]

    An optical system for analysis of diesel spray penetration and atomization has been developed. The basic system is based on a microscope with a long working distance (230 mm) and a modest resolution. The magnification is variable between 1:1 and 50:1 on the camera plane. This enables the study of individual droplets with a diameter of 5 mm. A number of different techniques have been used together with the basic system to study different parts of the spray. They include the darkground technique, double exposure, and ordinary magnification. The size, speed, and direction of propagation of the individual droplets have been calculated using the elongation of the droplet image caused by the duration time of the flash.

  • 35.
    Tsironas, Sotirios
    et al.
    Scania CV AB.
    Stenlåås, Ola
    Scania CV AB.
    Apell, Magnus
    Scania CV AB.
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Heavy-duty engine intake manifold pressure virtual sensor2019Conference paper (Refereed)
    Abstract [en]

    Increasing demands for more efficient engines and stricter legislations on exhaust emissions require more accurate control of the engine operating parameters. Engine control is based on sensors monitoring the condition of the engine. Numerous sensors, in a complex control context, increase the complexity, the fragility and the cost of the system. An alternative to physical sensors are virtual sensors, observers used to monitor parameters of the engine thus reducing both the fragility and the production cost but with a slight increase of the complexity. In the current paper a virtual intake manifold cylinder port pressure sensor is presented. The virtual sensor is based on a compressible flow model and on the pressure signal of the intake manifold pressure sensor. It uses the linearized pressure coefficient approach to keep vital performance behaviors while still conserving calibration effort and embedded system memory. The virtual sensor approach is evaluated from the perspectives of accuracy and robustness. The design and evaluation of the virtual sensor are based on a heavy-duty diesel engine experiment series. The virtual sensor provides promising results indicating its future use in real-time intake manifold cylinder port pressure estimation.

  • 36.
    Wu, Hongwen
    et al.
    KTH.
    Brunberg, Johan
    Altimira, Mireia
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Bratt, Niclas
    Nyberg, Henrik
    Cronhjort, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines.
    Peciura, Justinas
    Semi-Empirical CFD Transient Simulation of Engine Air Filtration Systems2016In: SAE International Journal of Passenger Cars - Mechanical Systems, ISSN 1946-3995, E-ISSN 1946-4002, Vol. 9, no 1, p. 310-320Article in journal (Refereed)
    Abstract [en]

    To improve fuel efficiency and facilitate handling of the vehicle in a dense city environment, it should be as small as possible given its intended application. This downsizing trend impacts the size of the engine bay, where the air filter box has to be packed in a reduced space, still without increased pressure drop, reduced load capacity nor lower filtering efficiency. Due to its flexibility and reduced cost, CFD simulations play an important role in the optimization process of the filter design. Even though the air-flow through the filter box changes as the dust load increases, the current modeling framework seldom account for such time dependence. Volvo Car Corporation presents an industrial affordable model to solve the time-dependent dust load on filter elements and calculate the corresponding flow behavior over the life time of the air filter box. The implemented semi-empirical simulation algorithm integrates several sub-models derived from different studies on flows over pleated filters. This work also introduces an experimental method to record the dust pattern on the filter element in order to validate the numerical results. Test results show that the overall dust load as well as its distribution within the filter element can be estimated accurately.

  • 37.
    Wåhlin, Fredrik
    et al.
    Scania CV AB.
    Cronhjort, Andreas
    Scania CV AB.
    Fuel Sprays for Premixed Compression Ignited Combustion: Characteristics of Impinging Sprays2004In: SAE 2004 World Congress & Exhibition Technical Papers: Diesel Fuel Injection & Sprays (Part 3 & 4), 2004, Vol. 01-1776, p. 2004-01-1776-Conference paper (Refereed)
    Abstract [en]

    For homogeneous charge compression ignition (HCCI) engines with direct-injected fuel (also called PCI, Pre-mixed Compression Ignition), it is important to achieve a lean and homogeneous mixture before ignition. For this purpose, impinging diesel sprays have proven to be useful. In this study, an evaluation of the overall air/fuel ratio of such sprays was made in a test rig. The test rig consists of a pressurized vessel with optical access and a Common Rail (CR) fuel injection system. The investigation was made for impinging spray nozzles with different impingement angles and orifice diameters. Three gas back pressures and three injection pressures were evaluated. The evaluation was based on images of the fuel sprays taken in the test rig. The fuel spray images were automatically processed using in-house developed software. The results of the investigation points out some important factors to obtain a lean spray, (a high air/fuel ratio). The investigation also points out some factors that give a low spray penetration for a certain injected mass of fuel.

  • 38.
    Wåhlin, Fredrik
    et al.
    Scania CV AB.
    Cronhjort, Andreas
    Scania CV AB.
    Impinging Diesel Sprays2008In: Atomization and sprays, ISSN 1044-5110, E-ISSN 1936-2684, Vol. 18, no 2, p. 97-127Article in journal (Refereed)
    Abstract [en]

    Diesel fuel sprays from a common-rail injector have been optically investigated with respect to their macroscale characteristics. The tested nozzle designs were of standard plain orifice type, as well as the impinging-spray type, in which two orifices intersect at a specific angle at the exit. Testing was conducted using a pressurized vessel at room temperature. The impinging sprays were found to be low penetrating and widely dispersed compared to the nonimpinging sprays. The shape of the impinging sprays was as one homogeneous spray with no trace of individual sprays. It was found that impinging diesel sprays can be predicted in a manner similar to standard nonimpinging sprays, using a dimensionless penetration correlation. The cone angle of the impinging sprays increases with the impingement angle, and in contrast to nonimpinging sprays, appears insensitive to ambient density. The results indicate that the impinging spray has a larger spray volume at lower ambient densities. However, at higher ambient densities, the volume of the nonimpinging sprays is larger.

  • 39.
    Wåhlin, Fredrik
    et al.
    Scania CV AB.
    Cronhjort, Andreas
    Scania CV AB.
    Olofsson, Ulf
    KTH, Superseded Departments (pre-2005), Machine Design.
    Ångström, Hans-Erik
    KTH, Superseded Departments (pre-2005), Machine Design.
    Effect of Injection Pressure and Engine Speed on Air/Fuel Mixing and Emissions in a Pre-Mixed Compression Ignited (PCI) Engine using Diesel Fuel2004In: 2004 Powertrain & Fluid Systems Conference & Exhibition Technical Papers, 2004, Vol. 01-2989, p. 2004-01-2989-Conference paper (Refereed)
    Abstract [en]

    PCI combustion of diesel fuel was accomplished in a direct-injected heavy-duty single-cylinder research engine. An impinging spray nozzle combined with a shallow bowl piston design offered a short air/fuel mixing time. Low HC and CO emissions were observed compared to fully premixed operation using n-heptane. A method for evaluating the air/fuel mixing process has been established by quantifying the in-cylinder air/fuel heterogeneity with the NOx emission. The results indicate that high injection pressure and engine speed are favorable for a fast mixing process. The injection pressure had a small impact on HC and CO emissions, while the engine speed had a larger impact. There were no correlation between air/fuel mixing time and HC and CO emissions.

1 - 39 of 39
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