掺水燃烧对STC柴油机燃烧和排放特性的影响

Effect of Water Mixed Combustion on Combustion and Emission Characteristics of STC Diesel Engine

文章对采用相继增压(STC)技术的TBD234V6型柴油机在25%P_(e0)和75%P_(e0)工况下的燃烧和排放特性进行研究,分析不同比例的掺水乳化油对缸内压力、缸内温度场、燃烧放热率、NO和Soot浓度场的影响,并通过灰色决策理论确定最佳掺水率。模拟结果表明:随着掺水率的升高,相比原机,STC柴油机在25%P_(e0)工况下缸内压力先升高后降低,在75%P_(e0)工况下最高缸压逐渐下降;在25%P_(e0)和75%P_(e0)工况下,STC柴油机的燃烧放热率均滞后,折合油耗率呈下降趋势,缸内高温分布区域逐渐缩小,NO和Soot生成质量分数下降。通过灰色决策优化评估分析,计算得出25%P_(e0)和75%P_(e0)工况下最佳掺水率分别为20%和15%。在高负荷下掺水率过高,STC柴油机的动力加速性能减弱,故掺水率不宜过高。

The combustion and emission characteristics of TBD234 V6 diesel engine with sequential supercharging(STC)technology under 25%P_(e0) and 75%P_(e0) conditions are studied in this paper.The effects of different proportions of water emulsified oil on cylinder pressure,cylinder temperature field,combustion heat release rate,no and soot concentration field are analyzed.The simulation results show that with the increase of water mixing rate,compared with the original engine,the cylinder pressure of STC diesel engine first increases and then decreases under 25%P_(e0) working condition,and the maximum cylinder pressure gradually decreases under 75%P_(e0) working condition;Under 25%P_(e0) and 75%P_(e0) operating conditions,the combustion heat release rate of STC diesel engines lags behind,and the equivalent fuel consumption rate shows a downward trend.The high temperature distribution area in the cylinder gradually shrinks,and the mass fraction of NO and Soot produced decreases.Through gray decision optimization evaluation analysis,it is calculated that the optimal water mixing rate under 25%P_(e0) and 75%P_(e0) working conditions is 20%and 15%,respectively.If the water mixing rate is too high under high load,the power acceleration performance of the STC diesel engine will be weakened,so the water mixing rate should not be too high.