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In this study, the effects of fuel properties, aromatics content and 90% distillation temperature T90, on flame temperature and soot formation were studied using a rapid compression machine (RCM). Aromatics content and T90 distillation temperature were parameters isolated from influence of each other, and from cetane number. A fuel spray was injected in the RCM combustion chamber by a single nozzle hole. The ignition and combustion processes of diesel spray were observed by a high-speed direct photography. Flame temperature and KL factor (which indicates the soot concentration), were analyzed by the two-color method. The rate of heat release was analyzed from indicated diagrams. The fuels with aromatics content showed higher flame temperature. The fuel with highest T90 distillation temperature showed highest flame temperature.

In this study, effects of nozzle hole diameter and EGR ratio on flame temperature (indication of NO formation) and KL value (indication of soot formation) were investigated. Combustion of a single diesel fuel spray in the cylinder of a rapid compression machine (RCM) was analyzed. Three nozzles with different hole diameter were used corresponding to present, near term and long term heavy duty diesel engine specifications. EGR was simulated through 2%vol. CO2 addition to the inlet air and by increase of in-cylinder surrounding gas temperature. Various types of fuels were used in this. The ignition and combustion processes of diesel fuel spray were observed by a high-speed direct photography and by indicated pressure diagrams. Flame temperature and KL factor were analyzed by a two-color method. With larger nozzle hole diameters there are larger high temperature areas. With smaller nozzle hole diameters there is more soot formed. Introduction of 2% vol.

The characteristics of auto-ignition of DME/Air mixture in Homogeneous Charge Compression Ignition (HCCI) engine were investigated by numerical calculation with elementary reactions and experiment. Calculations were carried out using Di-Methyl Ether (DME) elementary reactions at 0 dimension and adiabatic condition. DME is paid attention as the alternative fuel of next generation because of its possibility to take the place of conventional fossil fuels. DME has good characteristics of auto-ignition and combustion with low flame temperature, and makes no soot because of its molecular structure. In autoignition process, DME shows two-stage combustion, heat release with low temperature reaction (LTR) and high temperature reaction (HTR). This characteristic is similar to higher hydrocarbons such as gasoline in auto-ignition process. In this study, analysis of HCCI combustion of DME/Air mixture was carried out by using numerical calculation and comparing with experimental results.

The thermal efficiency of a spark-ignition (SI) engine must be improved to reduce both environmental load and fuel consumption. Although lean SI engine operation can strongly improve thermal efficiency relative to that of stoichiometric SI operation, the cycle-to-cycle variation (CCV) of combustion increases with the air dilution level. Combustion CCV is caused by CCVs of many factors, such as EGR, spark energy, air-fuel ratio, and in-cylinder flow structure related to engine speed. This study focuses on flow structures, especially the influence of a tumble structure on flow fluctuation intensity near ignition timing. We measured the flow field at the vertical center cross section of an optically accessible high-tumble flow engine using time-resolved particle image velocimetry. There are many factors considered to be sources of CCV, we analyzed three factors: the intake jet distribution, distribution of vortex core position and trajectory of the fluid particle near the spark plug.

High pressure fuel injection and a micro-hole nozzle were used with a rapid compression machine to study soot and nitrogen oxide reduction by creating a uniform and lean fuel distribution in the combustion chamber. The rapid compression machine was optically accessible, which allowed high-speed photography and subsequent two-color flame temperature and soot concentration measurements to be made. In addition, band spectrum radical luminescence images were also observed.

Reduction of particulate emissions from diesel engine is an important theme from the view point of air pollution. Experiments were carried out using a four-stroke single cylinder direct-injection diesel engine. A new method to measure diesel particulates has been developed. Particulates were sampled with a freezing method just behind an exhaust valve and examined through a scanning electron microscope. Shape and structure of particulates and the size distributions are measured under wide operating conditions obtained with above method. The total mass of particulate emissions was measured using a dilution tunnel sampling system. The heat release processes were analyzed using indicator diagrams and the relation between burning condition and particulate emissions were discussed, after systematic experiments under constant revolution speed of 2000 r/min for several load and injection timing conditions.

The concept of oxygen enriched charging (OEC) was exploratively examined as a means of reducing particulate emissions from a direct injection (DI) diesel engine. A single cylinder DI engine was operated with intake gas oxygen concentrations of 21% to 29%, under a constant engine speed of 40 Hz, and several load conditions. It was found that OEC reduces particulate emissions from a DI diesel engine for all operating conditions tested. Insoluble particulate is especially suppressed by OEC at high load conditions. Oxygen enriched charging has little effect on particulate size distribution at high loads when the mass fraction of extractables is low. Fuel consumption, at constant injection timing, is improved a little by OEC. Emissions of NOx increase exponentially with increasing oxygen concentration. Ignition delay is decreased by OEC and this allows injection timing to be retarded to reduce NOx emissions without increasing the specific fuel consumption.