Influence Of Key Design Parameters Of Pre-chamber Jet Ignition Device On Combustion Process Of Gasoline Engine

Energy is the cornerstone of a country’s development.The increasingly severe shortage of petroleum resources and environmental pollution in the country have put increasing pressure on passenger vehicles to save energy and reduce emissions.In order to reduce greenhouse gas and pollutant emissions,more and more new technologies are used in gasoline engines.Compared with the traditional spark plug ignition method,the pre-chamber jet ignition system has great potential in increasing the ignition energy,speeding up the flame propagation speed,and increasing the combustion rate of the mixture in the cylinder,making it possible for the engine to use a high compression ratio without knocking.Thus,the thermal efficiency of the gasoline engine can be effectively improved.In this paper,a steady-state bench test is carried out on a four-cylinder supercharged direct-injection gasoline engine to explore the influence of the precombustion chamber structural parameters(nozzle diameter,volume)on the combustion process of the mixture in the gasoline engine,and determine the precombustion chamber jet ignition.The optimal design of the system.In addition,the differences in combustion characteristics,performance and emission characteristics of pre-chamber jet ignition and spark plug ignition under different loads of gasoline engine were compared and analyzed in detail.The main research contents and conclusions are as follows:In order to explore the influence of the structure of the pre-combustion chamber on the combustion characteristics in the cylinder,and to ensure that the rest of the structure of the pre-combustion chamber remains unchanged,schemes with different nozzle diameters(0.7mm/0.9mm/1.1mm)are designed.The process has a significant impact.If the aperture is too small,the 50% combustion position will be delayed and the peak pressure will decrease due to the restriction of throttling,and the combustion will deteriorate obviously with the increase of intake pressure;if the aperture is too large,the jet intensity will be weakened,resulting in a significant decrease in the combustion rate in the cylinder;the aperture is The 0.9mm pre-combustion chamber can maximize the speed of jet flame propagation and ignite the main cylinder mixture faster.The 50% combustion position is significantly advanced,the 10-90% combustion duration is the shortest,the peak pressure is significantly increased,and the combustion heat is released.Fastest.On the basis of determining the diameter of the nozzle hole to be 0.9mm,different pre-chamber volume(0.52 m L/0.63 m L/0.74 m L)schemes were designed.The results show that the larger pre-chamber volume(0.63 m L/0.74 m L)in-cylinder combustion exothermic process is slower;the smaller volume(0.52 m L)pre-chamber ignition scheme 50% combustion point is more forward,with higher explosion pressure and faster combustion heat release rates.Therefore,it is concluded that the pre-combustion chamber with a pore size of 0.9 mm and a volume of 0.52 m L is an ideal design scheme.After determining the design scheme of the pre-chamber,the effects of jet ignition and spark plug ignition on the combustion characteristics,performance and emission characteristics of the gasoline engine were compared and analyzed.The research results show that the pre-chamber jet ignition is similar to the spark plug ignition combustion heat release process at low load;compared with the spark plug ignition,the pre-chamber jet ignition and the spark plug ignition at medium and high loads have an advanced combustion phase,a faster combustion heat release rate,and a corresponding increase in the maximum explosion pressure(Maximum increase of19.7%),lower fuel consumption(up to 5% reduction),higher effective thermal efficiency(maximum increase of 1.7%),and the performance improvement is more obvious as the load increases.The pre-chamber jet ignition combustion duration was shortened at all loads.The HC and NOx emissions of the pre-chamber jet ignition system are slightly higher,and the CO emissions are similar to those of spark plug ignition.In this paper,an ideal pre-combustion chamber design scheme is developed,and the influence of the pre-combustion chamber structural parameters on the combustion characteristics,economic performance and emission characteristics of gasoline engines is revealed.The research results have reference significance for the research and application of the pre-chamber jet ignition device in gasoline engines.