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Optical Investigation on the Combustion Process Differences between Double-Pilot and Closely-Coupled Triple-Pilot Injection Strategies in a LD Diesel Engine

Lund University-Alexios Matamis, Zhenkan Wang, Per Tunestal, Mattias Richter, Öivind Andersson
Volvo Car Corp.-Michael Denny, Håkan Persson
Published 2019-01-15 by SAE International in United States
The combustion processes of three injection strategies in a light-duty (LD) diesel engine at a medium load point are captured with a high speed video camera. A double-pilot/main/single-post injection strategy representative of a LD Euro 6 calibration is considered as the reference. There is a modest temporal spacing (dwell) after the first pilot (P1) and second pilot (P2). A second strategy, “A,” adds a third pilot (P3). The dwell after both P2 and P3 are several times shorter than in the reference strategy. A third strategy, “B,” further reduces all dwells. Each injection has its own associated local peak in the heat release rate (HRR) following some ignition delay. Between these peaks lie local minima, or dips. In all three cases, the fuel from P1 combusts as a propagating premixed flame. For all strategies, the ignition of P2 primarily occurs at its interface with the existing combustion regions. Extinguishing of the prevailing combustion by the fuel jets of later injections is noted in all strategies. This phenomenon is confirmed by comparing the timing of each…
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Lift-Off Lengths in an Optical Heavy-Duty Engine Operated at High Load with Low and High Octane Number Fuels

Lund University-Marcus Lundgren, Alexios Matamis, Zhenkan Wang, Pablo Garcia Valladolid, Mattias Richter, Oivind Andersson
Volvo Global Truck Tech Powertrain Eng-Arne Andersson
Published 2018-04-03 by SAE International in United States
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…
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Ultra-High Speed Fuel Tracer PLIF Imaging in a Heavy-Duty Optical PPC Engine

Istituto Motori CNR-Ludovica Luise, Bianca Maria Vaglieco
Lund University-Zhenkan Wang, Panagiota Stamatoglou, Marcus Lundgren, Oivind Andersson, Marcus Alden, Mattias Richter
Published 2018-04-03 by SAE International in United States
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…
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Transition from HCCI to PPC: Investigation of Fuel Distribution by Planar Laser Induced Fluorescence (PLIF)

SAE International Journal of Engines

Lund University-Zhenkan Wang, Sara Lonn, Alexios Matamis, Oivind Andersson, Martin Tuner, Marcus Alden, Mattias Richter
  • Journal Article
  • 2017-01-0748
Published 2017-03-28 by SAE International in United States
In a previous study, in order to investigate the effect of charge stratification on combustion behavior such as combustion efficiency and combustion phasing which also largely affects the emissions, an experiment was conducted in a heavy-duty compression ignition (CI) metal engine. The engine behavior and emission characteristics were studied in the transition from HCCI mode to PPC mode by varying the start of injection (SOI) timing. To gain more detailed information of the mixing process, in-cylinder laser diagnostic measurements, namely fuel-tracer planar laser induced fluorescence (PLIF) imaging, were conducted in an optical version of the heavy-duty CI engine mentioned above. To the authors’ best knowledge, this is the first time to perform fuel-tracer PLIF measurements in an optical engine with a close to production bowl in piston combustion chamber, under transition conditions from HCCI to PPC mode. Results show that four mixing schemes can be distinguished as the SOI timings are varied during the transition. They are linked to the results presented in the reference paper, where emissions were varied in different zones. For SOI…
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Effects of Post-Injections Strategies on UHC and CO at Gasoline PPC Conditions in a Heavy-Duty Optical Engine

Lund University-Marcus Olof Lundgren, Zhenkan Wang, Alexios Matamis, Oivind Andersson, Mattias Richter, Martin Tuner, Marcus Alden
Volvo AB-Andersson Arne
Published 2017-03-28 by SAE International in United States
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…
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High-Speed Particle Image Velocimetry Measurement of Partially Premixed Combustion (PPC) in a Light Duty Engine for Different Injection Strategies

Dantec Dynamics A/S-Hua Wang
Lund University-Zhenkan Wang, Slavey Tanov, Mattias Richter, Bengt Johansson, Marcus Alden
Published 2015-09-06 by SAE International in United States
It has been proven that partially premixed combustion (PPC) has the capability of high combustion efficiency with low soot and NOx emissions, which meet the requirements of increasingly restricted emission regulations. In order to obtain more homogenous combustion and longer ignition delay in PPC, different fuel injection strategies were employed which could affect the fuel air mixing and control the combustion. In the present work, a light duty optical diesel engine was used to conduct high speed particle image velocimetry (PIV) for single, double and triple injections with different timings. A quartz piston and a cylinder liner were installed in the Bowditch configuration to enable optical access. The geometry of the quartz piston crown is based on the standard diesel combustion chamber design for this commercial passenger car engine, including a re-entrant bowl shape. The severe image distortions caused by the optical piston shape are minimized through recordings of reference targets and an image dewarping algorithm. To the authors knowledge this is the first time the flow field inside such realistic re-entrant piston bowl has…
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Effects of Injection Strategies on Fluid Flow and Turbulence in Partially Premixed Combustion (PPC) in a Light Duty Engine

Slavey Tanov
Dantec Dynamics A/S-Hua Wang
Published 2015-09-06 by SAE International in United States
Partially premixed combustion (PPC) is used to meet the increasing demands of emission legislation and to improve fuel efficiency. With gasoline fuels, PPC has the advantage of a longer premixed duration of the fuel/air mixture, which prevents soot formation. In addition, the overall combustion stability can be increased with a longer ignition delay, providing proper fuel injection strategies.In this work, the effects of multiple injections on the generation of in-cylinder turbulence at a single swirl ratio are investigated. High-speed particle image velocimetry (PIV) is conducted in an optical direct-injection (DI) engine to obtain the turbulence structure during fired conditions. Primary reference fuel (PRF) 70 (30% n-heptane and 70% iso-octane) is used as the PPC fuel. In order to maintain the in-cylinder flow as similarly as possible to the flow that would exist in a production engine, the quartz piston retains a realistic bowl geometry. The distortion caused by the complex shape of the optical piston is corrected by an advanced image-dewarping algorithm. The in-cylinder charge motion is evaluated and investigated over a range of crank…
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