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Engine parameters such as the start of injection (SOI) timing, the level of charge dilution via exhaust gas re-circulation (EGR), intake temperature, injection pressure and engine coolant temperature were varied. Furthermore, the level of swirl and the diameter of the injector nozzle holes were also varied in order to determine and quantify the sources of UHC. ...Low temperature combustion is a promising way to reach low NOx emissions in Diesel engines but one of its drawbacks, in comparison to conventional Diesel combustion is the drastic increase of Unburned Hydrocarbons (UHC). ...In this study, the sources of UHC of a low temperature combustion system were investigated in both a standard, all-metal single-cylinder Diesel engine and an equivalent optically-accessible engine.

This study deals with a comparative Life Cycle Analysis of Natural Gas, diesel oil and gasoline fuels looking at the French and the European situation. For the “Tank to Wheel” study, new data for vehicle emissions have been used based on a French medium-class sedan vehicle, both measured and modeled. ...Local pollutant have a lower impact in the Natural Gas pathway than in the gasoline or diesel oil pathways. The relative contribution of upstream (well to tank) and downstream (tank to wheel) parts depends on the pathway.

Latest emissions standards impose very low NOx and particle emissions that have led to new Diesel combustion operating conditions, such as low temperature combustion (LTC). The principle of LTC is based on enhancing air fuel mixing and reducing combustion temperature, reducing raw nitrogen oxides (NOx) and particle emissions. ...The principle of LTC is based on enhancing air fuel mixing and reducing combustion temperature, reducing raw nitrogen oxides (NOx) and particle emissions. However, new difficulties have arisen. ...At the same time, lower combustion temperature and reduced oxygen concentration increases hydrocarbon (HC) and carbon oxide (CO) emissions, which can be problematic at low load.

The impact of sulfates stored on the catalyst surface during low temperature running phases and removed during high temperature running phases has also been outlined. ...More specifically, the following evaluations are being performed at regular intervals (around 20 000 km): Regulated gaseous pollutant emissions on NEDC cycle (New European Driving Cycle) Particulate emissions, by mass measurement on NEDC but also by particle number and size measurement with SMPS (Scanning Mobility Particle Sizer) technique on NEDC and on unconventional steady-state running points.

This methodology uses different fuels and analysis tools to assess the HC sources. Oil and water are heated to follow the thermal behavior of a multi cylinder engine. A fast prototyping system is used to control the engine.

Gasoline exhaust injection led to less HC slip than diesel fuels. Temperature dynamics resulting from injection steps showed taught that the shorter the hydrocarbons (within the tested fuels), the slower the response. ...These differences can be caught by simple models, leading to interesting opportunities for the model-based control of the DPF inlet temperature during active regenerations.

If these changes in the engine tunes are not enough, the gap between exhaust gas temperature at the output of the engine and the regeneration temperature of the particulate trap may be filled by a catalytic combustion of post injected hydrocarbons. ...Nevertheless, with light-duty vehicles and their low level of exhaust gas temperature, it may be necessary to facilitate or force the regeneration. The objective of this work is to give an overview of the possibilities offered by the engine management system to increase significantly exhaust gas temperatures. ...The objective of this work is to give an overview of the possibilities offered by the engine management system to increase significantly exhaust gas temperatures. Thus, different engine tunes, through injection timing, boost pressure or EGR rate, may be sufficient to ensure safe regeneration of the trap.

These data have further been compared to those obtained from an engine test bench, in running conditions representative of the entire operating range of the engine. 15 operating points have been chosen, considering the air mass flow and the exhaust temperature, and tested with different NH3/NOx ratios. Steady-state as well as transient conditions have been studied, showing the influence of three main parameters on the reductant storage characteristics: exhaust temperature, NO2/NOx ratio, and air mass flow. ...Steady-state as well as transient conditions have been studied, showing the influence of three main parameters on the reductant storage characteristics: exhaust temperature, NO2/NOx ratio, and air mass flow. It has also been shown that the reducing agent release strongly depends on the current exhaust conditions, but also on the way it has been stored.

This model consists firstly in reducing the analytical data to a single (i.e. pure) pseudo-component characterized by its molecular weight, critical pressure and temperature, and acentric factor. For a gasoline fuel, the required analytical data are those provided by gas chromatography. ...For a Diesel fuel, the required data are a true boiling point (TBP) distillation curve and the fuel density at a single temperature. This model provides a valuable tool for studying the effects of fuel physical properties upon the behavior of a vaporizing spray in a chamber, as well as upon direct injection gasoline and Diesel engines using the multidimensional (3D) KMB code.

The spray is observed in a high pressure, high temperature cell that reproduces the thermodynamic conditions which exist in the combustion chamber of a Diesel engine during injection. ...The analysis of the combustion processes shows that in the case of double injections, the ignition of the second injection is promoted by the entrainment of high temperature gases originating from the combustion of the first injection. As a consequence, while for the conditions studied no soot are formed during the combustion of the first injection, the combustion of the second injection is more fuel rich and therefore forms PAH and soot. ...Also, for the operating conditions studied, it was found that when the dwell time is increased, the extension of the combustion of the first injection leads to the presence of low temperature intermediates closer to the injector nozzle at the timing of the second injection. As a result, those higher temperature gases are entrained faster in the second jet, provoking faster ignition, and stabilization of the flame closer to the nozzle.

Investigated conditions are the following: unburned gases temperature was varied from 300 to 600 K, pressures from 0.5 to 25 bar, and equivalence ratios range from 0.4 to 2.

Indeed, reduction of ambient temperature leads to penalties in fuel vaporization and auto ignition capabilities, even more at very low temperature (-20°C and below). ...Indeed, reduction of ambient temperature leads to penalties in fuel vaporization and auto ignition capabilities, even more at very low temperature (-20°C and below). In this paper, we present the work operated on an HSDI Common rail Diesel 4-cyl engine in three area: engine tests till very low temperature (down to -25°C); in cylinder imaging (videoscope) and CFD code development for cold start operation. ...In this paper, we present the work operated on an HSDI Common rail Diesel 4-cyl engine in three area: engine tests till very low temperature (down to -25°C); in cylinder imaging (videoscope) and CFD code development for cold start operation.

The CAI™ concept is based on the auto-ignition of a fuel mixture highly diluted with burnt gases in order to achieve high indicated efficiency and low pollutant emissions through low temperature combustion. Large amounts of burnt gases can be trapped in the cylinder by re-breathing them through the exhaust ports during the intake stroke. ...Not only does this interaction directly act on the mean in-cylinder conditions (temperature, dilution), but it can also induce some mixture stratification. As identified in part 1, the phasing and the duration of the second exhaust valve event have a very significant influence on combustion. ...Those results were related with the auto-ignition locations which were observed using direct visualisation of the combustion. 3D CFD results explained the origin of such mixture stratification and balanced the species stratification with the temperature stratification. The combination of both tools allowed the CFD results to be validated and provided complementary information on the combustion process.

Advanced soot characterization emphasized that HCCI soot is oxidized at a slower reaction rate than conventional soot, but with a lower temperature. This last characteristic could partially compensate the poor continuous regeneration effect due to low NO2 emission levels observed in HCCI combustion.

The CAI™ concept is founded on the auto-ignition of a highly diluted gasoline-based mixture in order to reach high indicated efficiency and low pollutant emissions through a low temperature combustion. Previous research works have demonstrated that the valve strategy is an efficient way to control the CAI™ combustion mode. ...Not only the valve strategy has an impact on the amount of trapped burnt gases and their temperature, but also different valve strategies can lead to equivalent mean in-cylinder conditions but clearly differentiated combustion timing or location.

Consequently, Diesel blends containing ethanol become highly flammable at a temperature around ambient temperature. This study proposes to improve the formulation of ethanol based diesel fuel in order to avoid flash point drawbacks.

Thus, concerning hardware configuration, glow plug and spray interaction appears to be the first order parameter and glow plug temperature shows a great influence on cold idle. Concerning calibration, the use of Pilot injection improves significantly cold operation (especially opacity and engine speed stability), by deeply modifying the fuel and temperature stratification in the combustion chamber. ...Concerning calibration, the use of Pilot injection improves significantly cold operation (especially opacity and engine speed stability), by deeply modifying the fuel and temperature stratification in the combustion chamber.

The sprays are observed in a high pressure, high temperature cell that reproduces the thermodynamic conditions which exist in the combustion chamber of a diesel engine during injection. ...Typical ambient temperature of 800K and ambient density of 25 kg/m3 are chosen. The air entrainment is studied with the PIV technique, giving access to the velocity fields in the surrounding air and/or in the interior of two neighboring jets.

The CAI™ concept is based on the auto-ignition of a fuel mixture highly diluted with burnt gases in order to achieve high indicated efficiency and low pollutant emissions through low temperature combustion. In a 4-stroke engine, large amounts of burnt gases can be trapped in the cylinder by re-breathing them through the exhaust ports during the intake stroke using a 2-step exhaust valve-lift profile. ...Furthermore, the operating points were analysed with a 0D code to investigate the mean in-cylinder conditions (species, pressure, temperature) and to help to understand the consequences of the valve actuation choices. The influence of the valve-lift profile characteristics on the combustion process and the engine efficiency are presented.

This combustion concept is based on the auto-ignition of an air-fuel-mixture highly diluted with hot burnt gases to achieve high indicated efficiency and low pollutant emissions through low temperature combustion. To minimize the costs of conversion of a standard spark-ignition engine into a CAI engine, the present study is restricted to a Port Fuel Injection engine with a cam-profile switching system and a cam phaser on both intake and exhaust sides. ...To complete the test bench data, the operating points are analyzed with system simulation to investigate the mean in-cylinder conditions (species and temperature) just before auto-ignition and to understand the consequences of the different strategies.