二冲程点燃式直喷煤油发动机冷起动控制策略

针对某二冲程点燃式空气辅助缸内直喷煤油发动机,设计了冷起动控制策略.利用自主研发的电控单元,在4℃环境下通过试验验证了该策略正确性,并在14℃左右环境下研究了关键参数对冷起动性能影响,结果表明:点火提前角对起动阶段后期影响较大,起动成功后点火提前角为上止点前40°时暖机效果最好.采用饱和点火能量策略,冷起动性能最好,暖机平均转速最高,转速波动最小；起动喷油脉宽修正系数大于25时有利于改善起动阶段动力性,转速增加率大,起动喷油脉宽修正系数在25至45间冷起动过程基本一致.上止点前40°~60°的喷气结束角有利于冷起动成功,适度提前喷气结束角可加快暖机过程.油气间隔直接影响油气雾化效果,6ms油气间隔冷起动性能最佳,其作用主要体现在拖动和起动阶段. 

Cold start control strategy of a two-stroke direct injection spark-ignited kerosene engine

The cold start control strategy was designed for a two stroke spark ignited kerosene engine with air assisted direct injection. With the use of self developed electronic control unit, bench tests were carried out to verify the accuracy of the control strategy under 4℃ ambient temperature, and the effects of the key control parameters on cold start performance were researched under about 14℃ ambient temperature. The experimental results showed that, the ignition advance angle had effects on late stage of starting process; after the successful starting, ignition advance angle with 40° before top dead center was most beneficial to accelerate the warm up process. When applying the saturated ignition energy strategy, the cold start performance was the best, the average engine speed of warm up process raised to the maximum level, and the related engine speed fluctuation reached to the minimum value. The fuel enrichment factor bigger than 25 improved the dynamic performance of starting process, whose speed raising rate was increased, but the variations of cold start process were almost consistent when continuing to increase the fuel enrichment factor from 25 to 45. The air injection timing angle from 40° to 60° before top dead center was helpful to successful cold start; moderately advancing air injection timing angle at warm up condition can accelerate the warm up process. The fuel to air injection delay had direct influence on the fuel air mixture process, which may affect the motor dragging and starting process, and rapidly realize the best successful cold start when the fuel to air injection delay was about 6ms.