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Authors have experimented the effects of cooling water temperature on the particulate emission characteristics from a high speed DI diesel engines. A single cylinder small high speed DI diesel engine is operated under various engine speed and load conditions. Cooling water temperature is varied from 313 K (40 °C) to 363 K (90 °C). Particulate is collected using a single stage full size dilution tunnel. Dry soot and SOF emissions are measured, as well as total particulate. SOF increases when the cooling water temperature decreases, as well as HC increases. SOF also increases as load decreases. This suggests that the SOF emits at the cold starting and warming up periods. This also suggests that the SOF can be reduced by increasing cooling water temperature. IT IS IMPORTANT TO CLARIFY the effects of cooling water temperature on the particulate emission.

This paper is concerned with the formation of Particulate Matter (PM) in direct-injection (DI) diesel engines. A system featuring an electromagnetically actuated sampling valve was used for sampling of gas directly from the combustion chamber. The concentrations of total particulate matter (TPM) and of its two components, the Soluble Organic Fractions (SOF) and the Insoluble Fractions (ISF), were determined at different locations in the combustion chamber at different sampling times (different crank angles). High concentrations of SOF were found at sampling positions along the spray flame axis. The concentrations of SOF and ISF were higher at sampling positions close to the wall than away from the wall. The results suggest that SOF formation is significantly affected by wall quenching. Also, the PM concentrations were much higher in the combustion chamber than in the exhaust.

This paper presents a fundamental study on the mixture formation process in a direct injection stratified charge (DISC) engine. Helium is injected intermittently and impinged on a wall to clarify the unsteady wall impinging jet. Instantaneous concentration and pressure distributions are obtained by using fast-response concentration and pressure probes, respectively. The jet tip rolls up after the impingement on the wall, consequently the volume of an unsteady wall impinging jet becomes larger than that of a steady wall impinging jet. Wall impingement increases air entrainment, which could promote faster combustion in DISC engines.

The mixture formation process plays an important role on combustion in the direct injection stratified charge engine. A new mixture formation technology named OSKA has been developed for direct injection stratified charge SI engines. The OSKA process has the potential to yield better fuel economy and cleaner emissions. However, the mixture formation process has not been clarified completely, and detailed studies of the mixture formation process with the OSKA technology are needed. As a fundamental study on the OSKA mixture formation, time and space resolved distribution is obtained on concentration and on pressure in the unsteady gas jet, which discharges with constant injection pressure into a quiescent atmosphere and impinges on a projection placed on a wall.

In the small high speed DI diesel engines, wall quenching plays an important role on the particulate formation process. In order to clarify the particulate formation process, authors have analyzed the deposit on the combustion chamber wall, which are the results of the wall quenching. Deposit is sampled at 22 locations on the combustion chamber wall. On the wall of the piston cavity, dry and SOF deposits generate. The deposit quantity is the highest on the side surface of the cavity, but SOF ratio is the smallest in the cavity.

As a fundamental work on Direct Injection Impinging Diffusion Combustion Engine, fuel spray was injected momentary into a pressured CO2 gas and impinged onto a projection on a wall. Instantaneous photograph was taken and analyzed to clarify the spray characteristics. Nozzle opening pressure was varied to clarify its effects on spray characteristics. Nozzle needle was cut to form two pairs of flats on needle surface instead of its cylindrical one. The effect of this needle shape was also studied. Opening pressure of injection nozzle has produced very little effect on the spray tip penetration. Spray thickness is larger when needle opening pressure of injection nozzle is high. Spray tip penetration and spray thickness have become large when widths across flats is narrow.

This study is concerned with development of a new type of Diesel engine by impingement of fuel jet. The impinging part is installed on the cylinder head (OSKA-DH), against which the fuel jet is injected to spread and form fuel-air mixture. As a fundamental study on the mixture formation process, the observation of the impinged fuel jet was studied by using a pressurized vessel. High-speed combustion photographs of the OSKA and DI Diesel engine were also taken by using the experimental transparent engine. A single cylinder 4 stroke cycle prototype OSKA-DH engine (ø 118 x 108 mm) was developed. Pintle type single hole fuel injector is used and relatively low opening pressure of 15.3 MPa is employed. The re-entrant type combustion chamber and relatively high compression ratio of 20.4: 1 are employed. Experiments with a single cylinder proto-type engine showed that the lower NOx and smoke emissions compared with the conventional DI diesel engine.

Wall quenching plays a vital role on particulate formation. A single cylinder engine test has been carried out to clarify the effects of wall quenching on particulate emission. A completely warmed up engine is fired in variety of operating period under various engine load, and then stopped immediately. Deposits are collected from 25 positions on the combustion chamber wall. Area basis concentration of deposit is obtained at each position. Soluble organic fractions (SOF) extracted from deposit are analyzed with gel permeation chromatograph (GPC). Results show the correlation between SOF in exhaust particulate and in deposit. Deposit concentration is highest on the spray axis impinging region of piston cavity wall. GPC pattern of the SOF in deposit indicates that higher molecular weight composition generates as a result of polymerization of fuel where the main jet region of the spray impinges.

This study is concerned with development of a new type of diesel engine using the fuel jet impingement (OSKA-DH). Simultaneous reduction of the NOx and smoke emission were demonstrated with single cylinder prototype OSKA-DH engine. As a fundamental study on the mixture formation process, the observation of impinged fuel spray was studied by using a pressurized constant volume vessel. The high-speed combustion photographs of both re-entrant and open type combustion chamber were also taken by using the experimental transparent engine. From the observation of pressurized vessel and high-speed combustion photographs, the mixture formation and combustion was strongly affected by the squish flow velocity. The short ignition delay and faster combustion were observed by the re-entrant type combustion chamber because of high squish speed.

In order to clarify the mixture formation process of the direct injection gas engine, helium gas was injected into a quiescent atmosphere. The time- and space-resolved velocity, pressure and concentration distributions were measured in the free unsteady gas jet and in the wall impinging unsteady gas jet. They were also obtained for the unsteady gas jet impinging onto a projection on a wall to enhance mixture formation. Empirical equations for the unsteady free jet were obtained, and the mixture formation mechanism of the wall impinging unsteady gas jet were clarified. The unsteady gas jet impinging onto the projection on a wall entrains much more air than the unsteady wall impinging jet.

A new mixture formation and combustion process for reducing both emissions and fuel consumption has been developed, where the fuel impinges onto the impinging surface and spreads into the free space, named the OSKA process. A single cylinder engine particulate emission test was conducted with full flow dilution tunnel. The OSKA process shows lower TPM (total particulate matter) emission than the conventional DI diesel at the corresponding operating condition. ISF(insoluble fractions) and SOF(soluble organic fraction) are lower than DI diesel's. Correlation between SOF and THC of OSKA engine is, however different from that of conventional DI diesel. OSKA emits lower THC than conventional DI diesel does at the same SOF emission. This is because the wall quenching effect is smaller in OSKA than in conventional DI diesel. A NEW MIXTURE FORMATION and combustion technology, impinging diffusion one named OSKA, has been developed by the authors.

The OSKA-DH diesel engine employed a unique system (hereafter called OSKA system) which is composed of a single-hole fuel injector, an impinging disk and a re-entrant type combustion chamber. This study is concerned with the combustion observation of both OSKA-DH diesel engine and conventional DI diesel engine by the high-speed photography and video system. This video system enables us to take combustion photographs under the warm-up condition of the engine. From the observation of those photographs, the OSKA-DH engine shows the shorter ignition delay compared with a DI diesel engine and the combustion flame of OSKA-DH diesel engine are concentrated in the center of the combustion chamber and a relatively monotonous flame intensity are observed. THE AUTHORS HAVE DEVELOPED a new type of Direct Injection Stratified Charge Engine called “Direct Fuel Injection Impingement Diffusion Stratified Charge System” (hereafter called OSKA System).

The effect of intake oxygen concentration on both the flame temperature and emission of NOx and particulates from a direct injection diesel engine is reported. Nitrogen oxide emissions from a direct injection diesel engine was correlated with calculated stoichiometric flame temperature, yielding -143,000 cal/mole for the overall activation energy for the processes involved. It was found that when In (EIP) was plotted against the inverse of flame temperature at a range in load between 0% to 100% the values of In(EIP) are linear. Analyzing the slope gave a constant apparent activation energy. But the correlation of In(EIP) with flame temperature at 110% load shows smaller activation energy than that at lower load conditions.