排气压力对发动机性能的影响研究

Research on Influence of Exhaust Pressure on Diesel Engine Performance

在一台3.8L涡轮增压中冷4缸柴油机上通过试验研究了排气压力对柴油机燃烧和性能的影响。试验中拆除了原机增压器及中冷器,通过自制压力调节装置直接控制柴油机进、排气压力。试验结果表明:排气压力对柴油机缸内压力的影响较小,最高燃烧压力及相位变化不明显;空气质量流量与排气压力具有一定的线性关系,排气压力每增加10kPa,空气质量流量减少约1.2~2.0kg/h,减小百分比为0.4%~0.7%;柴油机排气温度与排气压力具有一定的线性关系,排气压力每增加10kPa,排气温度增加约4.0~4.7℃;排气压力增加使柴油机的动力性和经济性恶化,排气压力每增加10kPa,转矩减小约2.3~3.1N·m,减小百分比为1.0%~1.9%,比油耗增加约2.8~7.1g/(kW·h),增加百分比为1.4%~3.3%。仿真计算表明:排气压力增加使泵气过程负功增加,排气压力每增加10kPa,泵气过程平均指示压力减小约9.8~10.7kPa,减小百分比约13%。

An experimental study was carried out o n a 4-cylinder turbocharged an d inter-cooled diesel engine with 3. 8 L displacement to reveal the influence of exhaust pressure on the engine performances. During the engine tests, the turbocharger of the engine was removed, and the intake and exhaust pressures of the engine were controlled directly by a self-made pressure control system. Experimental results show that the exhaust pressure has little influence on the cylinder pressure and maximum combustion pressure changes with crankshaft angle. The air mass flow rate has a certain linear relationship with exhaust pressure T h e air m a s s flow rate will be decreased b y1. 2-2. 0 kg/h, accounting for 0. 4： % -0. 7% of the original value, when the exhaust pressure increases b y 10 kPa. There is a linear relationship between the exhaust temperature and exhaust pressure. The exhaust temperature will be increased by 4. 0 -4. 7 ℃ when the exhaust pressure increases by 10 kPa. Increasing exhaust pressure makes the engine power and fuel economy seriously deteriorated resulting in decrease in brake torque by 2. 3 -3. 1 N · m , accounting for 1. 0% -1. 9% of the original value and increase in brake specific fuel consumption b y 2. 8 - 7. 1 g/（kW·h） , accounting for 1. 4% -3. 3% of the original value, when the exhaust pressure increases b y 10 kPa. Simulations show that an increase in exhaust pressure makes the pumping loss increased so that the indicated mean effective pressure will be decreased by 9. 8-10. 7 kPa, accounting for about 13% of the original value, when the exhaust pressure increases by 10 kPa.