基于排气VVT的直喷汽油发动机性能试验研究

摘要

In order to understand the influence of exhaust variable valve timing (exhaust VVT) on engine power and fuel economy, a sweeping experiment was made on a natural aspirated GDI engine.The influence causing changes in engine power and fuel economy at different exhauste VVT phase angles was analzed based on the parameters of intake airflow, peak combustion temperature, indicated thermal effiency and pumping loss.The results show that delaying the exhaust VVT by 15° crank angle can enhence engine torque and intake airflow at full load and full speed, but its further delay will decrease the torque and increase the pumping loss.Using the exhaust VVT at the medium and high loads below 2400r/min can enhance the thermal effiency and reduce the pumping loss and fuel comsumtion.When the exhaust VVT is delayed by more than 15° crank angle , the fuel economy will become deteriorated at the medium and high loads over 2800r/min.%在一台自然吸气直喷汽油发动机上进行运行工况内的进、排气可变气门正时(VVT)相位扫点试验,根据不同排气VVT相位下的发动机动力性和燃油经济性,结合进气流量、最高燃烧温度、指示热效率和泵气损失等因素,分析了发动机性能变化的原因.研究结果表明,外特性工况排气VVT推迟15°曲轴转角时,进气量增加,动力性提高;继续推迟排气VVT相位,泵气损失增加,动力性降低.在转速低于2400r/min的中、高负荷区域,开启排气VVT使得指示热效率增大,泵气损失减少,发动机油耗降低;在排气VVT相位大于-15°曲轴转角、转速高于2800r/min的中、高负荷区域,发动机经济性变差.