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The effects of the spray impinging part on the in-cylinder airflow were numerically analyzed in the combustion chamber of the impinging diffusion direct injection diesel engine using KIVA-3 code. KIVA-3 code was enhanced to cater the impinging part as an internal obstacle by adopting the virtual droplet method, which is relatively easy to implement. Numerical result shows that the turbulence generation is promoted by the impinging part and is transformed by the squish flow into the piston cavity. The secondary flow is generated beneath the impinging part as well. The secondary flow area increases as the distance between top surface of the impinging part and bottom surface of the cylinder cover increases.

The new type of Diesel combustion engine has been developed. The new Idea Incorporates an impingement part in the central piston cavity. The fuel jet is injected against the impingement part, spreads and form fuel-air mixture. Single hole fuel injection nozzle is used and the relatively low opening pressure is needed. Intake air swirl is not needed. The re-entrant type combustion chamber is employed to get a relatively strong squish speed. Experimental with single cylinder 4 stroke prototype test engine showed that the brake mean effective pressure was 0.82 MPa and the maximum net specific fuel consumption was 220 g/kW.h. The NOx and smoke emissions was reduced compared with the conventional DI Diesel engine. The authors have developed a new type of Direct Injection Stratified Charge SI engine called “Direct Fuel Injection Impingement Diffusion Stratified Charge System” (hereafter called OSKA).

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.

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.

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 new idea incorporates an impinging part in the central piston cavity. A relatively low injection pressure, lower than that of a conventional IDI Diesel engine, and a single hole fuel nozzle are used. The fuel spray is injected against the impinging part, spreads and forms a fuel-air mixture. Since a comparatively rich fuel-air mixture always stays around the impinging part and ignition is accomplished near the center of the mixture, steady, instantaneous and high-speed combustion is possible. As the fuel-air mixture is formed mostly in the cavity, there is little fuel in the squish area. Therefore, it is possible to prevent end-gas knocking, and in spite of the use of spark ignition, to employ a higher compression ratio than that of the conventional premixed SI engine. Experiments with a single cylinder prototype (4-stroke cycle) engine with gasoline fuel showed that the maximum BMEP was 1.0 MPa and the maximum brake thermal efficiency was 37.7 % (217 g/kW.h).