| 1. |
- Lundgren, Marcus, et al.
(författare)
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Lift-Off Lengths in an Optical Heavy-Duty Engine Operated at High Load with Low and High Octane Number Fuels
- 2018
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2018-April
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the ignition quality of diesel-and gasoline-like fuels on the lift-off length of the jet were investigated in an optical heavy duty engine. The engine was operated at a load of 22 bar IMEPg and 1200 rpm. A production type injector with standard holes were used. The lift-off length was recorded with high speed video Different injection pressures and inlet temperatures were used to affect conditions that consequently affect the lift-off length. No matter which fuel used nor injection pressure or inlet temperature, all lift-off lengths showed equal or close to equal lift-off length when stabilized. The higher octane fuel had a longer ignition delay and therefore the fuel penetrate the combustion chamber before auto ignition. This gave a longer lift-off length at the initial stage of combustion before reaching the same stabilized lift-off length. These results indicate that the hot combustion gases are a dominant factor to the lift-off length. Also, that possible soot reductions using high octanes fuels are feasible because of a longer ignition delay that allow more premixing, and an initially longer lift-off length due to longer penetration into the combustion chamber.
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| 2. |
- Lundgren, Marcus Olof, et al.
(författare)
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Effects of Post-Injections Strategies on UHC and CO at Gasoline PPC Conditions in a Heavy-Duty Optical Engine
- 2017
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2017:March
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Tidskriftsartikel (refereegranskat)abstract
- Gasoline partially premixed combustion (PPC) has shown potential in terms of high efficiency with low emissions of oxides of nitrogen (NOx) and soot. Despite these benefits, emissions of unburned hydrocarbons (UHC) and carbon monoxide (CO) are the main shortcomings of the concept. These are caused, among other things, by overlean zones near the injector tip and injector dribble. Previous diesel low temperature combustion (LTC) research has demonstrated post injections to be an effective strategy to mitigate these emissions. The main objective of this work is to investigate the impact of post injections on CO and UHC emissions in a quiescent (non-swirling) combustion system. A blend of primary reference fuels, PRF87, having properties similar to US pump gasoline was used at PPC conditions in a heavy duty optical engine. The start of the main injection was maintained constant. Dwell and mass repartition between the main and post injections were varied to evaluate their effect. All points were run at 7 bar IMEPg. High-speed imaging of the natural combustion luminescence was performed together with measurements of performance and engine out emissions. Results show reduction in both CO and UHC with close coupled injections. A large close coupled post injection show the largest reduction in UHC. Analysis show that a post injection prior to combustion reduces the dribble and increases the recirculation in the downstream region of the fuel jet, hence reaching more of the UHC in the area near the injector. General observations show that the partition of fuel between the injections have the largest impact on the CO while the dwell time affects UHC emissions. Injector dribble seems to be a significant contributor to the UHC emissions.
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| 3. |
- Wang, Zhenkan, et al.
(författare)
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Ultra-High Speed Fuel Tracer PLIF Imaging in a Heavy-Duty Optical PPC Engine
- 2018
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2018-April
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Tidskriftsartikel (refereegranskat)abstract
- In order to meet the requirements in the stringent emission regulations, more and more research work has been focused on homogeneous charge compression ignition (HCCI) and partially premixed combustion (PPC) or partially premixed compression ignition (PCCI) as they have the potential to produce low NOx and soot emissions without adverse effects on engine efficiency. The mixture formation and charge stratification influence the combustion behavior and emissions for PPC/PCCI, significantly. An ultra-high speed burst-mode laser is used to capture the mixture formation process from the start of injection until several CADs after the start of combustion in a single cycle. To the authors' best knowledge, this is the first time that such a high temporal resolution, i.e. 0.2 CAD, PLIF could be accomplished for imaging of the in-cylinder mixing process. The capability of resolving single cycles allows for the influence of cycle-to-cycle variations to be eliminated. This ability to study individual cycles aids the understanding of the mixture formation process as well as the cycle-to-cycle variations. Strong air entrainment at the boundary layer can be clearly observed and followed as the mixing process progresses. The formation of eddies created by the shear force and their rotational motion can be continuously observed during the mixing process. The interaction between two adjacent spray plumes in the recirculation zone is well captured and studied. In addition, the mixing process resulting in the stratified fuel charge being located in the recirculation zone before the SOC while the areas along the original spray axis are leaned out after the end of injection, can be followed in one time sequence. Moreover, the auto-ignition position and early flame development can be studied, from the high-speed chemiluminescence imaging, together with the fuel distribution in the combustion chamber.
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| 4. |
- Chartier, Clement, et al.
(författare)
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Air-Entrainment in Wall-Jets Using SLIPI in a Heavy-Duty Diesel Engine
- 2012
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Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3936 .- 1946-3944. ; 5:4, s. 1684-1692
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Tidskriftsartikel (refereegranskat)abstract
- Mixing in wall-jets was investigated in an optical heavy-duty diesel engine with several injector configurations and injection pressures. Laser-induced fluorescence (LIF) was employed in non-reacting conditions in order to quantitatively measure local equivalence ratios in colliding wall-jets. A novel laser diagnostic technique, Structured Laser Illumination Planar Imaging (SLIPI), was successfully implemented in an optical engine and permits to differentiate LIF signal from multiply scattered light. It was used to quantitatively measure local equivalence ratio in colliding wall-jets under non-reacting conditions. Mixing phenomena in wall-jets were analyzed by comparing the equivalence ratio in the free part of the jet with that in the recirculation zone where two wall-jets collide. These results were then compared to φ predictions for free-jets. It was found that under the conditions tested, increased injection pressure did not increase mixing in the wall-jets. Comparisons with free-jet predictions further indicated that mixing in wall-jets is less effective than in free-jets for identical conditions and downstream distances. The confined nature of the wall-jet in the optical engine is suspected to be the reason for these observations. A rapid leaning-out of the jet after end of injection was observed for all cases, but this enhanced mixing was not transmitted to the wall-jet.
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| 5. |
- Dahlström, Jessica, et al.
(författare)
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Experimental Comparison of Heat Losses in Stepped-Bowl and Re-Entrant Combustion Chambers in a Light Duty Diesel Engine
- 2016
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- Heat loss is one of the greatest energy losses in engines. More than half of the heat is lost to cooling media and exhaust losses, and they thus dominate the internal combustion engine energy balance. Complex processes affect heat loss to the cylinder walls, including gas motion, spray-wall interaction and turbulence levels. The aim of this work was to experimentally compare the heat transfer characteristics of a stepped-bowl piston geometry to a conventional re-entrant diesel bowl studied previously and here used as the baseline geometry. The stepped-bowl geometry features a low surface-to-volume ratio compared to the baseline bowl, which is considered beneficial for low heat losses. Speed, load, injection pressure, swirl level, EGR rate and air/fuel ratio () were varied in a multi-cylinder light duty engine operated in conventional diesel combustion (CDC) mode. Temperature measurements in the engine cooling media were used to set up the engine energy balance and find out how much heat was lost to cooling media in different parts of the engine. Based on these calculations and heat release analysis, conclusions could be drawn regarding how heat losses in different parts of the engine were affected by changes in these parameters. Results were compared to previously published CFD simulations and it was concluded how the heat transfer characteristics differ between the two piston designs.
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| 6. |
- Fatehi, Hesameddin, et al.
(författare)
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A Numerical Study on the Sensitivity of Soot and NOx Formation to the Operating Conditions in Heavy Duty Engines
- 2018
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2018-April
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, computation fluid dynamics (CFD) simulations are employed to describe the effect of flow parameters on the formation of soot and NOx in a heavy duty engine under low load and high load. The complexity of diesel combustion, specially when soot, NOx and other emissions are of interest, requires using a detailed chemical mechanism to have a correct estimation of temperature and species distribution. In this work, Multiple Representative Interactive Flamelets (MRIF) method is employed to describe the chemical reactions, ignition, flame propagation and emissions in the engine. A phenomenological model for soot formation, including soot nucleation, coagulation and oxidation with O2 and OH is incorporated into the flamelet combustion model. Different strategies for modelling NOx are chosen to take into account the longer time scale for NOx formation. The numerical results are compared with experimental data to show the validity of the model for the cases under study. A good agreement is achieved between the model results and the pressure and heat release rate from the experiment. For soot and NOx, the model is able to correctly predict the trends between different cases. The effect of number of RIFs on the behaviour of the model is discussed.
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| 7. |
- Fatehi, Hesameddin, et al.
(författare)
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Effects of In-Cylinder Flow Structures on Soot Formation and Oxidation in a Swirl-Supported Light-Duty Diesel Engine
- 2019
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Ingår i: 14th International Conference on Engines & Vehicles: Technical paper. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- In this paper, computation fluid dynamics (CFD) simulations are performed to describe the effect of in-cylinder flow structures on the formation and oxidation of soot in a swirl-supported light-duty diesel engine. The focus of the paper is on the effect of swirl motion and injection pressure on late cycle soot oxidation. The structure of the flow at different swirl numbers is studied to investigate the effect of varying swirl number on the coherent flow structures. These coherent flow structures are studied to understand the mechanism that leads to efficient soot oxidation in late cycle. Effect of varying injection pressure at different swirl numbers and the interaction between spray and swirl motions are discussed. The complexity of diesel combustion, especially when soot and other emissions are of interest, requires using a detailed chemical mechanism to have a correct estimation of temperature and species distribution. In this work, Representative Interactive Flamelets (RIF) method is employed to describe the chemical reactions, ignition, flame propagation and emissions in the engine. The CFD simulations are validated using experimental measurement of light-duty diesel engine at two different loads. A good agreement is achieved between the model results and the pressure, heat release rates and emissions from the experiment. These cases are considered as the base-line for the parameter study cases.
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| 8. |
- Gong, Miaoxin, et al.
(författare)
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An Optical Study of the Effects of Diesel-like Fuels with Different Densities on a Heavy-duty CI Engine with a Wave-shaped Piston Bowl Geometry
- 2023
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Ingår i: SAE Technical Paper. - 0148-7191.
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Konferensbidrag (refereegranskat)abstract
- The novel wave-shaped bowl piston geometry design with protrusions has been proved in previous studies to enhance late-cycle mixing and therefore significantly reduce soot emissions and increase engine thermodynamic efficiency. The wave-shaped piston is characterized by the introduction of evenly spaced protrusions around the inner wall of the bowl, with a matching number with the number of injection holes, i.e., flames. The interactions between adjacent flames strongly affect the in-cylinder flow and the wave shape is designed to guide the near-wall flow. The flow re-circulation produces a radial mixing zone (RMZ) that extends towards the center of the piston bowl, where unused air is available for oxidation promotion. The waves enhance the flow re-circulation and thus increase the mixing intensity of the RMZ. This flame-wall interaction is related to the momentum of the injected fuel sprays and therefore it is reasonable to investigate the impact of fuels of different densities that contain varied momentums. Conventional diesel and n-Heptane are tested in a single-cylinder optical heavy-duty compression ignition engine, as the fuels have similar characteristics but different densities. The spray and combustion processes are visualized by natural luminescence, captured by high-speed video. The experiment results indicate that there is a correlation between fuel densities and the flame-wall interaction.
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| 9. |
- Ibron, Christian, et al.
(författare)
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Effect of injection timing on the ignition and mode of combustion in a HD ppc engine running low load
- 2019
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Ingår i: Technical Paper - WCX SAE World Congress Experience. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2019
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Konferensbidrag (refereegranskat)abstract
- This work aims to study the effect of fuel inhomogeneity on the ignition process and subsequent combustion in a compression ignition Partially Premixed Combustion (PPC) engine using a primary reference fuel (PRF) in low load conditions. Five cases with injection timings ranging from the start of injection (SOI) at -70 crank angle degrees (CAD) to -17 CAD have been studied numerically and experimentally in a heavy duty (HD) piston bowl geometry. Intake temperature is adjusted to keep the combustion phasing constant. Three dimensional numerical simulations are performed in a closed cycle sector domain using the Reynolds Averaged Navier-Stokes (RANS) formulation with k-ϵ turbulence closure and direct coupling of finite rate chemistry. The results are compared with engine experiments. The predicted trends in required intake temperature and auto-ignition location for a constant combustion phasing are consistent with experiments. The simulations show that the auto-ignition is critically dependent on both fuel and temperature stratification. The ignition occurs in fuel-lean regions but the mixing of the fuel with the cylinder gas and the cylinder gas temperature stratification (prior to injection) determines the ignition location. A higher heat release rate is observed in the later injection cases, which is attributed to the higher equivalence ratio of the mixture inside the bowl. Negative temperature coefficient (NTC) heat release behaviour of the studied fuel plays a role in shortening the ignition wave propagation but the impact of the effect varies among the injection cases. A sensitivity study of combustion efficiency with regard to the intake temperature is performed on two of the cases (SOI of -30 CAD and of -63 CAD). While the combustion phasing is slower and correctly predicted in the simulations of the advanced injection cases the combustion efficiency is found to be very sensitive to the intake temperature. This is attributed to the high sensitivity of the ignition delay time to equivalence ratio and temperature.
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| 10. |
- Larsson, Peter, et al.
(författare)
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A Droplet Size Investigation and Comparison Using a Novel Biomimetic Flash-Boiling Injector for AdBlue Injections
- 2016
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2016-Octobeer
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Tidskriftsartikel (refereegranskat)abstract
- Increased research is being driven by the automotive industry facing challenges, requiring to comply with both current and future emissions legislation, and to lower the fuel consumption. The reason for this legislation is to restrict the harmful pollution which every year causes 3.3 million premature deaths worldwide [1]. One factor that causes this pollution is NOx emissions. NOx emission legislation has been reduced from 8 g/kWh (Euro I) down to 0.4 g/kWh (Euro VI) and recently new legislation for ammonia slip which increase the challenge of exhaust aftertreatment with a SCR system. In order to achieve a good NOx conversion together with a low slip of ammonia, small droplets of Urea solution needs to be injected which can be rapidly evaporated and mixed into the flow of exhaust gases. In most of today's solutions this process is enhanced with flow restricting mixers or longer path lengths but if these can be removed and shortened the flow losses can be reduced, leading to higher efficiency and lower fuel consumption as well as a more compact exhaust system. The μMist® injector, inspired by nature, takes the concept from the Bombardier beetle which induces flash-boiling in its effective defence mechanism by spraying a plume of hot poisonous fine droplets with great accuracy towards an attacker [3]. By heating up the fluid in a constant volume chamber above the saturation temperature and induce flash evaporation by opening the nozzle, the liquid breaks up into fine droplets which flow out into the target environment. This paper presents a study comparing the different effects of spray behaviour at different ratios between the saturation pressure and the target pressure. In this study the target pressure is atmospheric. The aim for the study is to gain a better understanding of the droplet sizes and the injector flow rates for different pressures and also present a limited benchmarking study of current market leading AdBlue injectors. Current testing has shown that this novel injector has the ability to produce 33% smaller droplets in SMD and 87% reduction in DV50.
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