两级相继增压对柴油机低负荷性能影响的试验研究

Effects of Two-stage Sequential Turbocharging on Diesel Engine Low Load Performance

为综合提升陆用与船舶柴油机中低转速工况动力性、经济性和排放性能,搭建发动机性能试验台架,分别从增压系统性能、柴油机燃烧和整机性能三个方面,对比研究了低压级增压、高压级增压、两级增压和两级相继增压四种增压方式对某型柴油机的性能影响。研究结果表明:柴油机运行在推进特性中低转速工况下,与其他增压模式相比,两级相继增压模式能显著提高进气流量,而不引起增压压力的大幅度增加,缸内最高燃烧压力远离极限值,因此可适当增加喷油量,实现中低转速工况较高的扭矩输出;在高温富氧燃烧条件下虽然NO_(x)排放略有增加,但两级相继增压模式通过排气能量的合理利用,获得了泵气功的收益和燃油消耗率的降低;在推进特性30%负荷下,与低压级增压相比,两级相继增压泵气平均有效压力提升0.0193 MPa,燃油消耗率降低4.9 g/(kW·h),经分析得出两级相继增压为柴油机在低负荷工况下最优的增压模式方案。

In order to comprehensively improve the power,economy and emission performance of land and marine diesel engine under low and medium speed conditions,the engine performance test bench was built.From three aspects of supercharging system,combustion and overall performance,the effects of four supercharging modes on the performance of diesel engine were compared,including low-pressure stage supercharging,high-pressure stage supercharging,two-stage supercharging and two-stage sequential turbocharging.The results show that,compared with other supercharging modes,the two-stage sequential turbocharging mode can significantly increase the intake air flow without causing a significant increase of supercharging pressure and the in-cylinder maximum combustion pressure is far away from the limit when diesel engine operates during propulsion at low and medium speed.Therefore,the appropriate increase of injection amount is feasible to achieve a higher torque output under the low and medium speed conditions.Although the NO_(x) emission increases slightly under high temperature and oxygen-enriched combustion condition,the two-stage sequential turbocharging mode obtains the benefit of pump work and the reduction of specific fuel consumption through the reasonable utilization of exhaust energy.Compared with the low-pressure stage supercharging,the pumping mean effective pressure of two-stage sequential turbocharging increases by 0.0193 MPa and the fuel consumption rate reduces by 4.9 g/(kW·h)under 30%load of propulsion characteristic.Accordingly,two-stage sequential turbocharging is the optimal supercharging matching scheme with low load conditions of diesel engine.