Mutsumi Kanda

Application of a New Combustion Concept to Direct Injection Gasoline Engine

A direct injection (DI) gasoline engine having a new stratified charge combustion system has been developed. This new combustion process (NCP) was achieved by a fan-shaped fuel spray and a combustion chamber with a shell-shaped cavity in the piston. Compared with the current Toyota D-4 engine, wider engine operating area with stratified combustion and higher output performance were obtained without a swirl control valve (SCV) and a helical port. This report presents the results of combustion analyses to optimize fuel spray characteristics and piston cavity shapes. Two factors were found to be important for achieving stable stratified combustion. The first is to create a ball-shaped uniform mixture cloud in the vicinity of the spark plug. The optimum ball-shaped mixture cloud is produced with a fuel spray having early breakup characteristics and uniform distribution, and a suitable side wall shape in the piston cavity to avoid the dispersion of the mixture. The second factor is to reduce the over-lean area in the piston cavity. A compact shell-shaped cavity was designed for this purpose. The resulting flame propagation improves combustion stability. The effect of tumble motion was also investigated. The best combustion characteristics were obtained at weak tumble motion condition. Measurement results of incylinder flow by LDV showed that the fan-shaped fuel spray produces sufficient turbulence strength without extra intake air flow systems. The application of the NCP to an actual 3L in-line 6 DI gasoline engine showed that in addition to satisfying Japanese regulations which start in from 2000, a fuel economy gain of more than 20% was obtained. INTRODUCTION Increasing the fuel economy of automotive engines is very important for saving energy and improving the global environment. DI gasoline engines which are able to achieve both better fuel economy and output power simultaneously, have been considered for many years as a possible solution for these problems [1-3]. MITSUBISHI was the first to introduce gasoline DI engines in the market in1996, and Toyota launched the D-4 engine later in the same year [4]. The main features of the D-4 stratified charge combustion system are: 1. Piston with involute shaped concave combustion chamber; 2. High pressure swirl fuel injector; 3. Intake system with a helical port and a swirl control valve (SCV). This combustion system achieves a wide range of stratified combustion, but the output power is partially deteriorated by the helical port at high speed conditions. We have been conducting research and development of a new combustion system jointly with Toyota Central R&D Labs,Inc. to improve the previous system. This joint R&D resulted in a new combustion process (NCP), which realizes both wider range of stratified combustion and excellent homogeneous combustion without an extra intake air flow controlling system. This paper discusses the required characteristics of the fuel spray and piston cavity shapes that are the main elements of the NCP, and also presents the performance characteristics of an actual engine in which the NCP was utilized.

Analysis of cycle-by-cycle variation in a direct injection gasoline engine using a laser-induced fluorescence technique

Abstract To analyse the cycle-by-cycle variation of combustion in a direct injection gasoline engine equipped with a fan-shape spray nozzle and operated with exhaust gas recirculation (EGR), the fuel mixture distribution was measured at a time of spark and during the combustion period by the laser-induced fluorescence (LIF) technique. It was found that in the case of advanced or retarded injection timing, the initial combustion period tends to extend and the indicated mean effective pressure (i.m.e.p.) becomes low when lean mixtures appear at the spark position and at the spark timing. This suggests that the cycle-by-cycle variation of combustion under these conditions is dominated by the fuel concentration at the spark position and spark timing. In contrast to this, for the best injection timing, which allows the lowest cycle-by-cycle variation, the i.m.e.p. fluctuation is affected not by the initial combustion period but by the main combustion period. The observation of LIF images revealed that the i.m.e.p. fluctuation at this condition is strongly correlated to the unburned mixture quantity at the side area of the piston cavity during the latter half of the combustion period. It was shown by a computational fluid dynamics (CFD) calculation that the combination of a uniform spray pattern and a compact cavity shape is effective to reduce the over-lean mixture region in the edge of the piston cavity, which is responsible for the cycle-by-cycle variation of combustion at the condition of best-tuned injection timing.

Development of instrument for measurement of fuel-air ratio in vicinity of spark plug : application to DI gasoline engine

Abstract An instrument to measure time-resolved fuel–air ratio in the vicinity of a spark plug was developed. Properties of absorption and scattering at the wavelengths of visible and infrared rays were utilized to determine the fuel–air ratio in the mixture including liquid and vaporized fuel. The measurement error of the instrument was within 10% as a result of comparison between the overall and the measured fuel–air ratio at the vicinity of the spark plug under the inlet port injection, which forms a relatively homogeneous mixture. The instrument was applied to a direct injection gasoline engine and the mixture formation process was clarified.

Development of Instrument for Measurement of Fuel-Air Ratio in the Vicinity of Spark Plug. Application to DI Gasoline Engines.

An instrument to measure time-resolved fuel-air ratios in the vicinity of a spark plug was developed. Absorption and scattering at the wavelengths of visible and infrared rays were utilized to determine the fuel-air ratios in the mixture including liquid and vaporized fuel. The measurement error of the instrument was estimated within 10% from comparison between the overall and the measured fuel-air ratios at the vicinity of the spark plug with inlet port injection which froms homogeneous mixture. The instrument was applied to direct injection gasoline engines and the mixture formation process was discussed.