Research On The Effects Of Fuel Injection To The Combustion Process In Direct-Injection Natural Gas Engine By Diesel Ignition

Diesel ignition natural gas direct injection technology as the latest natural gas engine technology,in addition to the traditional advantages of natural gas engines,it can also make up for its lack of power and volumetric efficiency loss and other issues,it becomes the focus of current research in the field.For diesel ignition direct injection natural gas engine,diesel and natural gas pilot injection process has an important impact on the engine's combustion process and emissions.And presently home and abroad study about ignition diesel and natural gas injection cylinder mixture formation and combustion process is still relatively small.Therefore,this article studied the influence of ignition diesel and gas-cylinder injection mixture formation and combustion processes,as well as emissions of NO generated by the simulation method,which lay a foundation for further study.During engine operation,the concentration of the mixture,the proportion of diesel fuel ignition and diesel pilot injection time and gas injection duration,and location of the injection holes,the diameter of the orifice size and orifice between angle will have important impacts on the mixture formation and combustion.In order to study the effect law of diesel ignition direct injection natural gas engine fuel injection to mixture formation and combustion processes,the paper established the diesel ignited natural gas engine simulation system using FIRE software,Under the case: the engine speed is2100r/min,full load conditions,the excess air ratio of 1.7,diesel and natural gas injection interval of 5°CA,the proportion of diesel fuel ignition amount of 5%.Simulated ignite diesel injection duration and nozzle diameter,gas injection hole angle and injection duration simulation four factors,Made an in-depth analysis about the formation of the mixed gas cylinder concentration distribution,in-cylinder flow field,an in-cylinder combustion temperature and pressure,heat characteristics,and NO generation.The results show that,while maintaining a certain amount of ignition of diesel injection,with the ignition diesel injection duration of the extension,the injection speed from the ignition of diesel fuel injection period 0.5°CA of 274m/s down to the injection duration period 65m/s on 2°CA.the Maximum drop of cylinder temperature and pressure peak were 2.6%,7.5%;With the ignition diesel nozzle diameter becomes larger,the fuel injection rate from the spray orifice diameter of 0.15 mm case of 234m/s,down to a diameter of 0.25 mm orifice 90.5m/s,the maximum of temperature and pressure peak in the cylinder decline were 2.8%,6.9%.And the concentration of NO with the ignition diesel nozzle diameter increases gradually reduced;the in-cylinder combustion temperature and pressure peak up to the highest when Gas injection hole angle is 130°,By contrast,the maximum in-cylinder temperature and pressure at the other angle value decreased 8.6%,8.2%,from the combustion duration gas injection hole angle of 45°CA on 130° under extended to 103°CA on 150°,maximum extension is 58°CA.the amount of in-cylinder NO generation up to the maximum at 130°,with the spray hole angle changes,the amount decrease;With the extension of the natural gas injection period,thefuel injection rate is decreased from a maximum 318m/s.on 4°CA time to 288.7m/s on10°CA,compared to the injection duration of 4°CA,the maximum decrease of the cylinder temperature and pressure peak,combustion heat release rate peak were 5.5%,13.8%,35.3%,The maximum lag of Temperature Peak up to 4°CA.With the extension of the natural gas injection period,the total amount of generated NO decreased.