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Spray formations of three injection directions against swirl have been investigated by means of 3D numerical calculation, in-cylinder measurement, and engine performances tests. A direct injection type engine which has a single hole nozzle and a spark plug, has been operated, and three injection directions; a forward (same) direction, a reverse one, and a right-angled (central) one against a swirl direction, have been selected. Three types of intake port, futhermore, have been selected owing to create three types of in-cylinder flow, low swirl, middle swirl, and high swirl. Spray formations in 3D cylinder flow have been investigated by using a ‘KIVA’ code. Initial conditions of in-cylinder flow are based on data which have been measured in three dimensional by a LDV system under a motoring operation. Analysis results of spray formations by numerical calculations can explain well data of engine performance tests qualitatively, and some interesting results have been obtained.

The new combustion method in DISC engine has been developed. It has a double structure combustion chamber characterized as ‘Caldera’. The chamber is constructed by a center cavity for the purpose of forming a stable mixture around a spark plug electrode, and by an outer cavity which has a role of a main chamber. This method makes possible a perfect un-throttling operation, and a fuel consumption equal to a diesel engine is achieved. With regard to an out-put of DISC engine, a stoichmetric combustion and a high torque are achieved by controling a fuel injection timing with an electro-magnetic injection system device. With regard to emission regulations, a heavy EGR include residual gas decreases greatly NOx and HC emissions simultaneously, and which suggests a possibility to achieve LEV/ULEV regulations.

The study of the phenomena of in-cylinder flow, spray and combustion by measurement and calculation has been vigorously pursued, because thermal efficiency and emissions of the D. I. diesel engine are influenced by them. To investigate the effects of in-cylinder flow on spray and combustion, the D. I. diesel engine simulation model has been developed. This model is composed of in-cylinder flow, spray and combustion models. In the spray model, spray non-uniformity is considered, and physical and chemical processes are considered in the combustion model. The effects of swirl, number of nozzle holes, injection pressure and squish area on thermal efficiency and emissions have been investigated, and the existence of optimum values of these parameters against thermal efficiency have been predicted and these predictions have been verified by measurement.

Combustion in spark ignition engines is strongly affected by characteristics of in-cylinder flow. The role of in-cylinder flow on combustion becomes more important under lower temperature conditions which are made by, for example, Millor cycle engines whose power is controlled by inlet valve open and close timings (1)*. In this study, influences of early and late Inlet valve close timings have been investigated by means of an engine simulation model which is based on the entrainment model, and by means of in-cylinder flow measurements using the Hot Wire Method. Inlet valve open and close timings can be varied from 150°BBDC to 170°ABDC (in case of close timings), changing a phase between a cam shaft and a crank shaft through a gear. An early close and a late close cycles are then gotten. In case of early or late valve closed timings, decreases of magnitude of gas flow velocity and temperature have been made sure by measurements as well as by calculations.