增压汽油机不同排气歧管长度下的压力波动特性

利用台架试验数据校准了增压直喷汽油机一维性能仿真模型,应用校准后的模型研究了低速(1 500r/min)全负荷工况不同排气歧管长度下排气阀口与涡轮机入口处的压力波动特性,并对压力波动形态与低速增压压力的建立、瞬态响应、缸内充气效率等的关联性进行了深入分析。研究结果表明:在现有排气歧管结构形式下,在低转速宜采用较短歧管,从而有望获得更高的增压压力和扭矩;相继工作的气缸不宜在涡轮机前共用一根排气总管,否则容易引起废气倒流,而且歧管越短倒流越严重;排气歧管中的压力波在传向涡轮机入口过程中被"均值化",不能充分应用排气压力波动效应来提高低速扭矩和改善增压延迟。

Fluctuation Characteristics of Exhaust Pressure Wave for Turbocharged Gasoline Engine with Different Manifold Lengths

The one-dimensional performance simulation model of turbocharged direct injection gasoline engine was calibrated with bench test data .With the calibrated model ,the pressure fluctuation characteristics at the exhaust valve port and turbine inlet were studied in full load at 1 500 r/min based on different exhaust manifold lengths ,and the relationships of pressure fluc-tuation with low speed boosting pressure build up ,transient response and in-cylinder volumetric efficiency were deeply ana-lyzed .The results show that higher boosting pressure and torque can be achieved by a short manifold at low speed .The se-quential working cylinders cannot share one exhaust pipe before turbine ,otherwise exhaust gas backflow may occur .Moreover , the shorter the manifold ,the more serious the backflow .The individual characteristic of pressure wave in exhaust manifold dis-appears in the process of moving to turbine inlet ,which makes it impossible to improve the low speed torque and turbocharging lag with wave fluctuation effect .