Studies on Improvement of Combustion with an Accumulation-Type Fuel Injection System

点击翻译按钮获取中文摘要

In the present studies, a new accumulation-type fuel injection system was developed to control the injection pressure independently of engine speed. The injection characteristics and the effects on combustion characteristics in a direct-injection type diesel engine were investigated and the following were made clear.(1) The accumulation-type fuel injection system could be applied for relatively small-sized, high-speed diesel engines by controlling injection beginning and end with different valves.(2) It was possible to control the fuel quantity injected with almost same way as Bosch type injection system by using the plunger helix for injection end control.(3) It was possible to predict the pressure fluctuations in that system, using the similar calculation method as Bosch type injection systems.(4) Application of the new system for a test engine verified that exhaust smoke density could be sharply reduced by keeping high injection pressure even at low engine speed, and specific fuel consumption at retarded injection timing could be also improved.Moreover combustion tests and photographic observations were carried out to clarify the effect of injection pressure on the combustion characteristics of fuel spray. From the series of tests, the influences of the fuel injection pressure, the surrounding air pressure, the temperature and the swirl flow on the ignition delay were charified. And the factors affecting a period of initial stage of spray combustion were shown by introducing a new coefficient of heat release rate of spray combustion.