喷油特性对F-T煤制油压力振荡影响规律研究

Study on the Influence of Fuel Injection Characteristics on F-T Fischer-Tropsch Fuel Pressure Oscillation

为了减小燃烧噪声,确定影响柴油机高频压力振荡的关键因素,在某型电控高压共轨柴油发动机上燃用的清洁代用燃料Fischer-Tropsch(F-T)煤制油,选取柴油机典型运行工况,研究不同喷油特性条件下柴油机燃烧压力振荡的时域和频域特性。结果表明:推后主喷提前角和提前预喷提前角会使放热率降低,压力振荡幅值减小,气缸压力级也有明显减小的趋势;减小预喷油量会使压力升高率和放热率降低,气缸声压级减小,压力振荡现象减缓,使燃烧更加柔和;提高喷射压力,会使喷油速率增大,燃油雾化效果增强,混合气放热率提升,放热率曲线也随之上升,气缸声压级增大,发动机缸内燃烧压力振荡幅值增大。喷射压力是影响压力振荡的最显著的参数,喷射压力从85MPa上升至115MPa时,压力振荡幅值增加一倍以上;预喷油量对F-T煤制油发动机的燃烧压力振荡影响不显著;同时压力振荡的产生与放热率的变化呈现出较强的相关性。

In order to reduce the combustion noise and determine the key factors that affect the high-frequency pressure oscilla-tion of the diesel engine,a clean alternative fuel Fischer-Tropsch(FT)coal-to-liquid is used in a certain type of electronically controlled high-pressure common rail diesel engine,and the typical operating conditions of the diesel engine are selected.The time-domain and frequency-domain characteristics of diesel engine combustion pressure oscillations under different injection characteristics are studied.The results show that the advance angle of the main injection after the push and the advance angle of the pre-injection will reduce the heat release rate,the pressure oscillation amplitude will decrease,and the cylinder pressure level will also significantly decrease;reducing the pre-injection amount will increase the pressure The rate and heat release rate are re-duced,the sound pressure level of the cylinder is reduced,the pressure oscillation phenomenon is slowed down,and the combus-tion is softer.Increasing the injection pressure will increase the fuel injection rate,increase the fuel atomization effect,and in-crease the heat release rate of the mixture.The heat rate curve also rises,the sound pressure level of the cylinder increases,and the oscillation amplitude of the combustion pressure in the engine cylinder increases.The injection pressure is the most significant pa-rameter that affects the pressure oscillation.When the injection pressure rises from 85MPa to 115MPa,the amplitude of the pres-sure oscillation more than doubles;the amount of pre-injection has no significant effect on the combustion pressure oscillation of the FT coal-to-liquid engine;at the same time,the generation of pressure oscillation and the change of heat release rate show a strong correlation.