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Giramondi, N. (2021). Diffusive Combustion of Ethanol in a Dual-Fuel Direct Injection Compression Ignition Engine. (Doctoral dissertation). Stockholm: KTH Royal Institute of Technology
Open this publication in new window or tab >>Diffusive Combustion of Ethanol in a Dual-Fuel Direct Injection Compression Ignition Engine
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The impact of climate change due to global warming necessitates rapid and extensive measures to enhance the sustainability of the energy and transport sectors. In this context, there are large environmental and societal benefits to be gained by replacing diesel with renewable fuels for road freight transport. This solution may facilitate and expedite the transition towards fossil-free, carbon-neutral transport, while the electrification process takes shape. Short-chain alcohol fuels have favorable properties for the enhancement of engine performance and the abatement of pollutant emissions, however, they necessitate ignition aid systems in compression ignition engines. The present research investigates a novel concept of dual-fuel combustion for heavy-duty compression ignition engine applications by means of engine tests and three-dimensional combustion simulations. This concept involves the direct injection of pure ethanol as main fuel through a centrally mounted injector, and minimal quantities of diesel as pilot fuel via a separate injector. The objective is to achieve diffusive combustion of ethanol in a process analogous to conventional diesel combustion throughout the entire engine load range, with a higher thermal efficiency and lower pollutant emissions. Single-cylinder engine tests were carried out to evaluate the influence of combustion characteristics and performance with respect to dual-injection strategy, engine load, ethanol ratio and configuration of the diesel pilot injector. The characteristics and performance of ethanol-diesel direct injection compression ignition (DICI) combustion were compared to two sets of baselines, that are conventional diesel combustion and dual-injections of diesel via the main and pilot injector in the same proportion as in the dual-fuel test points. At low load conditions, increasing the separation between the diesel pilot and ethanol main injection enabled the achievement of diffusive combustion of ethanol, avoiding combustion instability and partial misfire thanks to minimal quantities of diesel injected. At high load conditions, a minimum main-pilot separation was instead required to limit the degree of ethanol premixing at ignition. Using a diesel pilot injector having a lower number of sprays with a wider hole diameter promoted a more robust ignition of ethanol, while also causing a reduction of engine performance. Parallel to the experimental work, three-dimensional combustion simulations were carried out in order to investigate the interaction between diesel and ethanol sprays during ignition at various engine operating conditions, from low to full load. At the operating conditions investigated during engine tests, the ignition of a subset of ethanol sprays was locally triggered by the contact with the products of diesel combustion. Subsequently, ignition propagated towards the neighboring ethanol sprays, until reaching the furthest ones from the diesel pilot injector. The coupling between experimental and numerical results highlighted the noteworthy predictive capability of the adopted combustion model with respect to the ethanol combustion characteristics. In conclusion, the present research work provides a solid starting point for future studies on diffusive combustion of alcohol fuels in compression ignition engines. The structured knowledge built in the course of the doctoral project lays the foundation for the development of a fuel-flexible engine for heavy-duty applications.

Abstract [sv]

Klimatförändringarna, som en följd av den globala uppvärmningen, gör det nödvändigt med effektiva och omfattande åtgärder för att göra transport- och energisektorn mer hållbara. Både ur miljö och socialt perspektiv, finns det stora fördelar med att ersätta diesel med förnyelsebara bränslen för godstransport på väg. En sådan lösning underlättar och påskyndar övergången till fossilfri, kolneutral transport, under tiden elektrifieringen av transportsektorn utvecklas. Korta alkoholer som biobränsle har fördelaktiga egenskaper som kan öka motorprestandan samt minska utsläppen av hälsovådliga avgaser. Dock är det i kompressionsantända motorer nödvändigt med hjälpmedel för antändning av dessa bränslen. Detta projekt undersöker ett nytt koncept med förbränning av dual-fuel för framtida användning i tunga kompressionsantända motorer. Detta undersöks genom motorexperiment av konceptet, samt tredimensionell simulering av förbränningsförloppet. Konceptet innefattar direktinsprutning av etanol, som huvudbränsle, genom en centralt monterad insprutare. I kombination med ytterst små mängder av Dieselbränsle som pilotbränsle genom en separat insprutare. Målet är att uppnå diffusiv förbränning av etanol i en förbränningsprocess, likt den av konventionell diesel, för alla lastpunkter med en ökad termisk verkningsgrad och låga utsläpp av föroreningar. Motorprov i en en-cylindrig motor genomfördes för att utvärdera förbränningsegenskaperna och prestanda med avseende på en dual-fuel strategi, last, etanolmängd, och dieselinsprutarens konfigurering. Förbränningsegenskaper samt prestanda av etanol-diesel direktinsprutad kompressionsantänd (DICI) förbränning jämfördes med konventionell dieselförbränning samt dubbel insprutning av diesel i samma konfiguration och mängd som etanol-diesel insprutningen. Vid låga laster gjorde en ökad separation mellan dieselpiloten och den huvudsakliga etanolinsprutningen att diffusiv föorbränning av etanol lättare kunde uppnås. Detta gjorde att förbränningsinstabilitet och missantändning kunde undvikas då ytterst små mängder av diesel injiceras. Vid höga laster behövdes en kort separation mellan de två olika bränsleinsprutningseventen för att begränsa förblandningen av etanol innan antändning. En dieselinsprutare med färre strålar och med större håldiameter gav en mer robust förbränning av etanol, men det försämrade också motorns prestanda. Parallellt med det experimentella arbetet genomfördes tredimensionell simulering av förbränningen där interaktionen mellan diesel- och etanolstrålarna vid antändning undersöktes vid olika lastförhållanden, från låg last till full last. Vid de driftsförhållanden som undersöktes genom motorexperiment visade simuleringen att antändning av etanolen delvis triggades genom lokala interaktioner med förbränningsprodukter från dieselförbränningen. Därefter propagerade förbränningen till de närliggande etanolstrålarna och så vidare tills att förbränningen propagerat även till etanolstrålarna längst bort från dieselinsprutaren. Kombinationen mellan experimentella och numeriska resultat framhäver den anmärkningsvärda prediktiva kapaciteten av den antagna förbränningsmodellen med hänsyn till förbränningsegenskaperna hos etanol. Sammanfattningsvis, projektet ger en stabil startpunkt till framtida studier av diffusiv förbränning av alkoholbränslen i kompressionsantända motorer. Kunskapen som utvecklats under doktorandprojektets gång ger en grund för framtida utveckling av tillämpning av flexi-fuel i tunga förbränningsmotorer.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2021. p. 93
Series
TRITA-ITM-AVL ; 2021:25
National Category
Other Mechanical Engineering
Research subject
Machine Design
Identifiers
urn:nbn:se:kth:diva-294329 (URN)978-91-7873-893-9 (ISBN)
Public defence
2021-06-11, https://kth-se.zoom.us/j/64427961704, Stockholm, 10:00 (English)
Opponent
Supervisors
Available from: 2021-05-18 Created: 2021-05-17 Last updated: 2022-06-25Bibliographically approved
Giramondi, N., Konstanzer, D. & Christiansen Erlandsson, A. (2021). Evaluation of the Ethanol-Diesel Spray Interaction during Ignition in a Dual-Fuel DICI Engine Using an Experimentally Validated CFD Model. In: SAE Technical Paper 2021-01-0521: . Paper presented at SAE WCX Digital Summit. SAE International
Open this publication in new window or tab >>Evaluation of the Ethanol-Diesel Spray Interaction during Ignition in a Dual-Fuel DICI Engine Using an Experimentally Validated CFD Model
2021 (English)In: SAE Technical Paper 2021-01-0521, SAE International , 2021Conference paper, Published paper (Refereed)
Abstract [en]

The ignition dynamics of an ethanol-diesel direct injection compression ignition engine is investigated based on 3D RANS simulations. Experimental results of a previous test campaign on a single-cylinder research engine equipped with two direct injectors are used to validate the CFD model. Four reference engine conditions are considered, including split and overlapped injections of ethanol and diesel at low and high load. Combustion driven by the separate direct injection of pure ethanol and diesel as pilot fuel is simulated with AVL Fire and AVL Tabkin adopting the flamelet generated manifold combustion model. The in-cylinder pressure and apparent rate of heat release traces computed in the simulations are found to be consistent with the corresponding experimental results. The influence of several simulation input parameters on ethanol combustion characteristics is evaluated, highlighting a high sensitivity to the initial in-cylinder temperature and a limited impact of the swirl number. The spatial and temporal interaction between ethanol and diesel sprays during ignition is investigated based on simulation results of in-cylinder flow features. Under the engine conditions considered in this study, ethanol ignition is found to originate within the spray plumes adjacent to the burning diesel sprays and to subsequently propagate towards the other ethanol sprays. The peak sequence identified in the ARoHR traces of experiments and simulations corresponds to the ignition sequence of the ethanol sprays. The coupling between experimental and simulation results allowed to achieve a detailed understanding of the ignition dynamics of an ethanol-diesel DICI engine. The validated simulation model will enable the performance evaluation of alternative hardware configurations of the dual-injector system.

Place, publisher, year, edition, pages
SAE International, 2021
Series
SAE Technical Paper, ISSN 0148-7191, E-ISSN 2688-3627
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-293518 (URN)10.4271/2021-01-0521 (DOI)2-s2.0-85106983987 (Scopus ID)
Conference
SAE WCX Digital Summit
Note

QC 20210520

Available from: 2021-04-27 Created: 2021-04-27 Last updated: 2022-06-25Bibliographically approved
Giramondi, N., Jäger, A., Norling, D. & Christiansen Erlandsson, A. (2021). Influence of the diesel pilot injector configuration on ethanol combustion and performance of a heavy-duty direct injection engine. International Journal of Engine Research, Article ID 146808742110012.
Open this publication in new window or tab >>Influence of the diesel pilot injector configuration on ethanol combustion and performance of a heavy-duty direct injection engine
2021 (English)In: International Journal of Engine Research, ISSN 1468-0874, E-ISSN 2041-3149, article id 146808742110012Article in journal (Refereed) Published
Abstract [en]

Thanks to its properties and production pathways, ethanol represents a valuable alternative to fossil fuels, with potential benefits in terms of CO2, NOx, and soot emission reduction. The resistance to autoignition of ethanol necessitates an ignition trigger in compression-ignition engines for heavy-duty applications, which in the current study is a diesel pilot injection. The simultaneous direct injection of pure ethanol as main fuel and diesel as pilot fuel through separate injectors is experimentally investigated in a heavy-duty single cylinder engine at a low and a high load point. The influence of the nozzle hole number and size of the diesel pilot injector on ethanol combustion and engine performance is evaluated based on an injection timing sweep using three diesel injector configurations. The tested configurations have the same geometric total nozzle area for one, two and four diesel sprays. The relative amount of ethanol injected is swept between 78 – 89% and 91 – 98% on an energy basis at low and high load, respectively. The results show that mixing-controlled combustion of ethanol is achieved with all tested diesel injector configurations and that the maximum combustion efficiency and variability levels are in line with conventional diesel combustion. The one-spray diesel injector is the most robust trigger for ethanol ignition, as it allows to limit combustion variability and to achieve higher combustion efficiencies compared to the other diesel injector configurations. However, the two- and four-spray diesel injectors lead to higher indicated efficiency levels. The observed difference in the ethanol ignition dynamics is evaluated and compared to conventional diesel combustion. The study broadens the knowledge on ethanol mixing-controlled combustion in heavy-duty engines at various operating conditions, providing the insight necessary for the optimization of the ethanol-diesel dual-injection system.

Place, publisher, year, edition, pages
SAGE Publications, 2021
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-293515 (URN)10.1177/14680874211001260 (DOI)000654539200001 ()2-s2.0-85103877223 (Scopus ID)
Note

QC 20210518

Available from: 2021-04-27 Created: 2021-04-27 Last updated: 2022-06-25Bibliographically approved
Giramondi, N., Jäger, A., Mahendar, S. K. & Christiansen Erlandsson, A. (2020). Combustion Characteristics, Performance and NOx Emissions of a Heavy-Duty Ethanol-Diesel Direct Injection Engine. In: : . Paper presented at SAE 2020 International Powertrains, Fuels and Lubricants Meeting, PFL 2020, Online, Poland, 22-24 September 2020. SAE International
Open this publication in new window or tab >>Combustion Characteristics, Performance and NOx Emissions of a Heavy-Duty Ethanol-Diesel Direct Injection Engine
2020 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Diffusive combustion of direct injected ethanol is investigated in a heavy-duty single cylinder engine for a broad range of operating conditions. Ethanol has a high potential as fossil fuel alternative, as it provides a better carbon footprint and has more sustainable production pathways. The introduction of ethanol as fuel for heavy-duty compression-ignition engines can contribute to decarbonize the transport sector within a short time frame. Given the resistance to autoignition of ethanol, the engine is equipped with two injectors mounted in the same combustion chamber, allowing the simultaneous and independent actuation of the main injection of pure ethanol and a pilot injection of diesel as an ignition source. The influence of the dual-fuel injection strategy on ethanol ignition, combustion characteristics, engine performance and NOx emissions is evaluated by varying the start of injection of both fuels and the ethanol-diesel ratio. The results are compared against two baselines, i.e. conventional diesel combustion and dual-injections of diesel. Diesel substitution ratios above 80% on an energy basis are investigated, as the objective is to minimize diesel consumption while keeping stable and complete ethanol combustion. A minimum separation between ethanol and diesel injections is found to be necessary in order to limit the degree of premixing of ethanol at high load and avoid partial ethanol misfire causing combustion instability at low load, respectively. At low load, shortening the ethanol-diesel injection separation causes an increase in HC and CO emissions leading to lower combustion efficiencies. At high load, NOx emissions grow at higher degrees of premixing of ethanol. A slight reduction in NOx emissions occurs when increasing the relative amount of ethanol injected. Higher gross indicated efficiencies are observed for the ethanol-diesel cases compared to conventional diesel combustion. In conclusion, stable mixing-controlled combustion of ethanol is achieved with minimal diesel pilot quantities within a broad engine load range.

Place, publisher, year, edition, pages
SAE International, 2020
Series
SAE Technical Paper, ISSN 0148-7191, E-ISSN 2688-3627
Keywords
Carbon footprint, Diesel engines, Dual fuel engines, Ethanol, Ethanol fuels, Fossil fuels, Ignition, Nitrogen oxides, Powertrains, Combustion characteristics, Combustion efficiencies, Combustion instabilities, Compression ignition engine, Direct injection engines, Heavy-duty single cylinder engines, Mixing controlled combustions, Sustainable production, Direct injection
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-291413 (URN)10.4271/2020-01-2077 (DOI)2-s2.0-85092710319 (Scopus ID)
Conference
SAE 2020 International Powertrains, Fuels and Lubricants Meeting, PFL 2020, Online, Poland, 22-24 September 2020
Note

QC 20210520

Available from: 2021-03-24 Created: 2021-03-24 Last updated: 2022-06-25Bibliographically approved
Giramondi, N., Mihaescu, M., Christiansen Erlandsson, A. & Jäger, A. (2019). CFD-Driven Preliminary Investigation of Ethanol-Diesel Diffusive Combustion in Heavy-Duty Engines. In: SAE (Ed.), : . Paper presented at 2019 JSAE/SAE Powertrains, Fuels and Lubricants (pp. 15). , Article ID 019-01-2192.
Open this publication in new window or tab >>CFD-Driven Preliminary Investigation of Ethanol-Diesel Diffusive Combustion in Heavy-Duty Engines
2019 (English)In: / [ed] SAE, 2019, p. 15-, article id 019-01-2192Conference paper, Published paper (Refereed)
Abstract [en]

The introduction of renewable alcohols as fuels for heavy-duty engines may play a relevant role for the reduction of the carbon footprint of the transport sector. The direct injection of ethanol as main fuel and diesel as pilot fuel in the engine combustion chamber through two separate injectors may allow good combustion controllability over the entire engine operating range by targeting diffusive combustion. Closed-cycle combustion simulations have been carried out using AVL FIRE coupled to AVL TABKIN for the implementation of the Flamelet Generated Manifold (FGM) chemistry reduction technique in order to investigate the influence of the injection system geometry and the injection strategy of pure ethanol and diesel fuel on ignition characteristics and combustion at different operating conditions.

National Category
Mechanical Engineering Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-272694 (URN)10.4271/2019-01-2192 (DOI)2-s2.0-85084468507 (Scopus ID)
Conference
2019 JSAE/SAE Powertrains, Fuels and Lubricants
Note

QC 20200427

Available from: 2020-04-24 Created: 2020-04-24 Last updated: 2022-12-07Bibliographically approved
Mahendar, S. K., Giramondi, N., Venkataraman, V. & Christiansen Erlandsson, A. (2019). Numerical Investigation of Increasing Turbulence through Piston Geometries on Knock Reduction in Heavy Duty Spark Ignition Engines. SAE technical paper series
Open this publication in new window or tab >>Numerical Investigation of Increasing Turbulence through Piston Geometries on Knock Reduction in Heavy Duty Spark Ignition Engines
2019 (English)In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed) Published
Abstract [en]

Knock in heavy duty (HD) spark ignition (SI) engines is exacerbated by a large bore diameter and a higher flame travel distance. An increase in turbulence close to TDC can improve combustion speed and reduce knock through low residence time for end gas auto-ignition. Since HD SI engines are usually derived from diesel engines, it is common to have a swirl motion that does not dissipate into turbulence. To increase flame speed and limit knock, squish can be used to produce turbulence close to TDC. In this study, two different piston bowl geometries are examined: The re-entrant and quartette. The influence of squish area on turbulence production by these piston geometries were investigated using motored simulations in AVL FIRE. The effect of increased turbulence on knock reduction was analyzed using a calibrated 1D GT-Power model of a HD SI engine and the performance improvement was estimated. The effect of clearance height and input swirl level on turbulence was studied for both piston geometries to determine their sensitivity. A lower squish area quartette piston provided the same knock advantage corresponding to a higher squish area re-entrant piston due to additional turbulence production by swirl breakdown. With zero swirl, there was no difference in the turbulence produced by re-entrant and quartette pistons, however, a considerable increase in TKE was observed compared to the baseline swirl level re-entrant case as piston driven flow imparted more turbulence early in the compression stroke. 

Place, publisher, year, edition, pages
SAE International, 2019
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-274068 (URN)10.4271/2019-01-2302 (DOI)2-s2.0-85084518608 (Scopus ID)
Note

QC 20210504

Available from: 2020-07-01 Created: 2020-07-01 Last updated: 2022-06-26Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-7078-2517

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