进气歧管喷水对发动机燃烧性能的试验研究

Experimental Study on Effect of Intake Port Water Injection on Engine Combustion Performance

为研究进气歧管喷水技术对汽油发动机热效率的提升潜力,基于一台研究型单缸汽油发动机,采用试验的手段对比研究了不同的喷水比例、不同的负荷工况及不同的压缩比下进气歧管喷水对发动机燃烧性能的影响。结果表明,采用进气歧管喷水技术可有效降低发动机的爆震趋势,随着喷水比例的增加,CA50逐渐提前,燃料的滞燃期及燃烧持续期增加,同时伴随着传热损失逐渐增加。相比于无喷水(w/o PWI)的结果,喷水的引入虽然导致未燃损失增加,但有利于排气能量损失大幅降低,最终反应到经济性的表现为热效率随着喷水比例的增大呈先增加后降低的趋势,油耗率的表现同热效率的结果相反;此时最佳的净指示热效率(GITE)为43.1%,相比于w/o PWI的结果升高了2.5%;最佳的净指示油耗率(GISFC)为197.9 g/(kW·h),相比于w/o PWI的结果降低了11.8 g/(kW·h)。高负荷运用喷水技术将达到更显著的热效率改善及油耗改善效果;同时,喷水技术的引入使得发动机高压缩比的应用成为可能。

In order to study the potential improvement of intake port water injection(w PWI)technology on the thermal efficiency of gasoline engines,a research single cylinder gasoline engine was used to compare and study the effects of w PWI on the engine combustion performance under different spray ratios,load conditions,and compression ratios(CRs)through experimental means.The results show that the w PWI technology can effectively reduce the knock tendency of the engine.With the increasing of water injection ratio,the CA50 is gradually advanced,the ignition delay period and combustion duration are increased,and the heat transfer loss is gradually increased.Comparing with the result of no port water injection(w/o PWI),although the introduction of water injection leads to the increase in unburned loss,it is conducive to the substantial reduction of exhaust energy loss.The final economic performances of engine show that the thermal efficiency increases firstly and then decreases with the increasing of proportion of water injection,and the fuel consumption rate is opposite to that of the thermal efficiency.At this time,the best gross indicating thermal efficiency(GITE)is 43.1%,which is 2.5%percentage points higher than that of w/o PWI;The best gross indicated specific fuel consumption(GISFC)is 197.9 g/(kW·h),which is 11.8 g/(kW·h)lower than that of w/o PWI.The application of water injection technology at high load will achieve more significant improvement in thermal efficiency and fuel consumption.At the same time,the introduction of the water injection technology makes it possible to apply the high compression ratio(CR)on the engine.