可变进气对船用柴油机性能影响的试验研究

Experimental Research on the Influence of Variable Intake on the Performance of a Marine Diesel Engine

为了探究可变进气系统对船用柴油机性能的影响,在一台配备进气可变配气和进气旁通阀的船用中速柴油机上开展试验研究。分别在可变配气机构处于强米勒正时和弱米勒正时,进气旁通阀处于开启和关闭状态下开展船用柴油机螺旋桨特性试验。试验结果表明:采用弱米勒正时可降低燃油消耗率,但是最高燃烧压力和NOx比排放增加,燃油消耗率降低幅度随负荷升高而减小,最高燃烧压力和NOx比排放增加幅度随负荷升高而增加,弱米勒正时对低负荷优化效果更明显。受到最高燃烧压力限制,高负荷必须采用强米勒正时。弱米勒正时角度从20°增加到30°,燃油消耗率基本不变,最高燃烧压力和NOx比排放进一步增加,对于试验柴油机而言,20°弱米勒正时配置更优。开启进气旁通阀可以提高中低负荷增压压力,降低燃油消耗率、排温和烟度。在超低负荷及高负荷时开启进气旁通阀效果与中低负荷相反。在25%及50%负荷下应用可变进气技术,燃油消耗率分别降低6.0%和2.9%、烟度分别降低61.6%和59.7%。合理的可变进气系统控制策略可有效优化船用柴油机性能。

In order to explore the influence of variable intake system on the performance of a marine diesel engine,experimental study was carried out on a marine medium-speed diesel engine equipped with variable intake valve and charge air bypass valve.The propeller characteristics of marine diesel engine were tested when the variable valve distribution was in strong/weak Miller timing and the charge air bypass valve was in open/closed state.Test results show that using weak Miller timing can reduce fuel consumption,but the maximum combustion pressure and NO_(x) emission increase.The reduction of fuel consumption decreases with the increase of load,and the increase of maximum combustion pressure and NO_(x) emission rises with the increase of load,indicating that weak Miller timing has better effect for low load optimization.Limited by maximum combustion pressure,strong Miller timing must be used at high load.When weak Miller timing angle is increased from 20°to 30°,the fuel consumption is basically unchanged,and the maximum combustion pressure and NO_(x) emission are further increased.For the experimental engine,20°weak Miller timing is better.When charge air bypass valve is open,charge air pressure is increased at medium and low load,and fuel consumption rate,exhaust temperature,and smoke number are decreased.At ultra-low load and the high load,the effect of opening charge air bypass valve is opposite to that of medium and low load.Adopting variable intake technology at 25% and 50% load,fuel consumption rate is reduced by 6.0% and 2.9%,respectively,while smoke number is decreased by 61.6% and 59.7%,respectively.Using reasonable control strategy of variable intake system can effectively optimize the performance of marine diesel engine.