电控系统转速计算对燃烧循环变动的影响研究

The Influence of Electronic Control System Speed Calculation on Cycle-to-cycle Variation

在电控单缸柴油机上进行了燃烧循环变动试验研究,分析试验结果得知,单缸柴油机循环间喷油持续期存在变动,主要原因是电控系统瞬时转速的波动导致喷油驱动信号变动。通过分析现有电控系统转速计算方法存在的不足,提出两种采用循环间平均转速代替两齿间瞬时转速来计算喷油持续期的方法,一种是优化转速滤波因子β并确定其最优值,另一种是曲轴缺齿位置(缺齿后为排气上止点)计数来计算转速。经验证,提出的方法可以精确计算循环平均转速,使各个循环的喷油持续期趋于稳定,有效地降低燃烧循环变动。

The cycle-to-cycle variation test was carried on an economically controlled single-cylinder diesel engine and it was found that the injection duration varied from cycle to cycle. Through further analysis, it was known that the vibration was caused by the instant speed fluctuation of electronic control system. Analyzing the shortage of existed speed calculating method, two methods of calculating injection duration with the cycle average speed instead of instant speed between two teeth were put forward. One method was to optimize the speed filter factor β and determine its optimal value, and the other method was to record MCU＇counter value when the crank rotated to the gap. Through the validation, the proposed methods can calculate the cycle average speed accurately and make the injection duration more stable, which reduce the cycle-to-cycle variation effectively.