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Investigation of Late Stage Conventional Diesel Combustion - Effect of Additives

Eindhoven University of Technology-P.C. Bakker, Robbert Willems, Nico Dam, Bart Somers
Shell Global Solutions (UK)-Caroline Wakefield, Mark Brewer, Roger Cracknell
Published 2018-09-10 by SAE International in United States
The accepted model of conventional diesel combustion [1] assumes a rich premixed flame slightly downstream of the maximum liquid penetration. The soot generated by this rich premixed flame is burnt out by a subsequent diffusion flame at the head of the jet. Even in situations in which the centre of combustion (CA50) is phased optimally to maximize efficiency, slow late stage combustion can still have a significant detrimental impact on thermal efficiency.Data is presented on potential late-stage combustion improvers in a EURO VI compliant HD engine at a range of speed and load points. The operating conditions (e.g. injection timings, EGR levels) were based on a EURO VI calibration which targets 3 g/kWh of engine-out NOx. Rates of heat release were determined from the pressure sensor data. To investigate late stage combustion, focus was made on the position in the cycle at which 90% of the fuel had combusted (CA90).An EN590 compliant fuel was tested. To this fuel was added an organic compound, commonly encountered in sunscreen products, that was designed to absorb ultraviolet light.…
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Heavy-Duty Diesel Engine Spray Combustion Processes: Experiments and Numerical Simulations

Eindhoven University of Technology-Noud Maes, Nico Dam, Bart Somers
FPT Motorenforschung AG-Gilles Hardy
Published 2018-09-10 by SAE International in United States
A contemporary approach for improving and developing the understanding of heavy-duty Diesel engine combustion processes is to use a concerted effort between experiments at well-characterized boundary conditions and detailed, high-fidelity models. In this paper, combustion processes of n-dodecane fuel sprays under heavy-duty Diesel engine conditions are investigated using this approach. Reacting fuel sprays are studied in a constant-volume pre-burn vessel at an ambient temperature of 900 K with three reference cases having specific combinations of injection pressure, ambient density and ambient oxygen concentration (80, 150 & 160 MPa - 22.8 & 40 kg/m3-15 & 20.5% O2). In addition to a free jet, two different walls were placed inside the combustion vessel to study flame-wall interaction. Experimentally, low- and high-temperature reaction product distributions are imaged simultaneously using single-shot planar laser-induced fluorescence (PLIF) of formaldehyde and high-speed line-of-sight imaging of the chemically-excited hydroxyl radical (OH*). Interference of soot incandescence in experimental OH* recordings is assessed to improve interpretation of the results. Interference by poly-cyclic aromatic hydrocarbon (PAH) LIF and soot radiation is mostly evaded by evaluating flame…
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Effects of Injection Timing on Fluid Flow Characteristics of Partially Premixed Combustion Based on High-Speed Particle Image Velocimetry

SAE International Journal of Engines

Dantec Dynamics A/S-Hua Wang
Eindhoven University Of Technology-Mohammad Izadi Najafabadi, Bart Somers, Nico Dam
  • Journal Article
  • 2017-01-0744
Published 2017-03-28 by SAE International in United States
Partially Premixed Combustion (PPC) is a promising combustion concept ,based on judicious tuning of the charge stratification, to meet the increasing demands of emission legislation and to improve fuel efficiency. Longer ignition delays of PPC in comparison with conventional diesel combustion provide better fuel/air mixture which decreases soot and NOx emissions. Moreover, a proper injection timing and strategy for PPC can improve the combustion stability as a result of a higher level of fuel stratification in comparison with the Homogeneous Charge Compression Ignition (HCCI) concept. Injection timing is the major parameter with which to affect the level of fuel and combustion stratification and to control the combustion phasing and the heat release behavior. The scope of the present study is to investigate the fluid flow characteristics of PPC at different injection timings. To this end, high-speed Particle Image Velocimetry (PIV) is implemented in a light-duty optical engine to measure fluid flow characteristics, including the flow fields, mean velocity and cycle-resolved turbulence, inside the piston bowl as well as the squish region with a temporal resolution…
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Transient Flame Development in a Constant-Volume Vessel Using a Split-Scheme Injection Strategy

SAE International Journal of Fuels and Lubricants

Eindhoven University Of Technology-Noud Maes, P.C. Bakker, Nico Dam, Bart Somers
  • Journal Article
  • 2017-01-0815
Published 2017-03-28 by SAE International in United States
Multiple-injection strategies are characterized by a complex and transient interplay between high- and low-temperature reactions. Tracking low-temperature reaction products such as formaldehyde (CH2O) is particularly important to understand ignition phenomena and the so-called “combustion recession” that is observed in experiments. Experimentally, it is often difficult to discriminate between formaldehyde and other species such as poly-aromatic hydrocarbons, which is why a selective excitation approach is used in this work. Simultaneous high-speed imaging of the chemically-excited hydroxyl radical (OH*) is used to improve indication of flame location and second stage ignition. During experiments in a constant-volume vessel, two 0.5-ms injections of n-dodecane, separated by 0.5-ms dwell time, are injected into a 900-K ambient. The global flame development is characterized based on high-speed diagnostics, followed by an investigation into the spatial distribution of formaldehyde at four different times after start-of-injection (aSOI). Results show significant influence of the first injection on characteristics of the second. Ignition delay and lift-off location of the second injection are prominently reduced, while flame penetration is greatly enhanced by the wake of the first…
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Experimental and Numerical Analyses of Liquid and Spray Penetration under Heavy-Duty Diesel Engine Conditions

SAE International Journal of Fuels and Lubricants

Eindhoven University of Technology-Noud Maes, Nico Dam, Bart Somers
FPT Industrial-Gilles Hardy
  • Journal Article
  • 2016-01-0861
Published 2016-04-05 by SAE International in United States
The modeling of fuel sprays under well-characterized conditions relevant for heavy-duty Diesel engine applications, allows for detailed analyses of individual phenomena aimed at improving emission formation and fuel consumption. However, the complexity of a reacting fuel spray under heavy-duty conditions currently prohibits direct simulation. Using a systematic approach, we extrapolate available spray models to the desired conditions without inclusion of chemical reactions. For validation, experimental techniques are utilized to characterize inert sprays of n-dodecane in a high-pressure, high-temperature (900 K) constant volume vessel with full optical access. The liquid fuel spray is studied using high-speed diffused back-illumination for conditions with different densities (22.8 and 40 kg/m3) and injection pressures (150, 80 and 160 MPa), using a 0.205-mm orifice diameter nozzle. High-speed Schlieren imaging is used to analyze the influence of these boundary conditions on the spray penetration. Simulations of the fuel spray are performed using a dedicated computational mesh with refinements at the known location of the jet to capture the smallest scales of interest. Using a blob injection model refined with a primary atomization…
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Ignition Sensitivity Study of Partially Premixed Combustion by Using Shadowgraphy and OH* Chemiluminescence Methods

Eindhoven University of Technology-Mohammad Izadi Najafabadi, Nico Dam, Bart Somers
Lund University-Bengt Johansson
Published 2016-04-05 by SAE International in United States
Partially Premixed Combustion (PPC) is a promising combustion concept for future IC engines. However, controllability of PPC is still a challenge and needs more investigation. The scope of the present study is to investigate the ignition sensitivity of PPC to the injection timing at different injection pressures. To better understand this, high-speed shadowgraphy is used to visualize fuel injection and evaporation at different Start of Injections (SOI). Spray penetration and injection targeting are derived from shadowgraphy movies. OH* chemiluminescence is used to comprehensively study the stratification level of combustion which is helpful for interpretation of ignition sensitivity behavior. Shadowgraphy results confirm that SOI strongly affects the spray penetration and evaporation of fuel. However, spray penetration and ignition sensitivity are barely affected by the injection pressure. There is a critical SOI range, in which a significant amount of fuel is trapped in the crevice volume. Injection in this critical range has a negative influence on the combustion efficiency and ignition sensitivity. Impingement of liquid fuel on the piston crown advances the combustion phasing by providing higher…
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