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

在目前的研究中，开发了一种新的蓄能式燃油喷射系统，以独立于发动机转速来控制喷油压力。对直喷式柴油机的喷油特性及其对燃烧特性的影响进行了研究，得出以下结论：(1)蓄能式喷油系统可以通过不同的阀门控制喷油开始和喷油结束，从而适用于相对较小的高速柴油机。(2)通过柱塞螺旋线控制喷油结束，可以几乎以与博世喷油系统相同的方式控制喷油量。(3)可以预测该系统的压力波动。(4)在一台试验发动机上的应用验证了在低转速下保持高喷油压力可以显著降低排气烟度，并且可以提高延迟喷油时刻的燃油消耗率。此外，通过燃烧试验和摄影观察，阐明了喷油压力对燃油喷雾燃烧特性的影响。通过一系列试验，分析了燃油喷射压力、周围空气压力、温度和涡流流量对点火延迟期的影响。并通过引入新的喷雾燃烧放热率系数，揭示了影响喷雾燃烧初期阶段的因素。

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.