氩氧氛围下天然气发动机的燃烧特性研究

Research on Combustion Characteristics of Natural Gas Engine under Argon/Oxygen Atmosphere

为提高内燃机热效率,将发动机进气由空气替换为氩氧混合气,试验研究了过量氧气系数、氩气比例、点火正时对发动机指示热效率、平均指示压力(IMEP)及燃烧循环变动的影响。试验结果表明:在过量氧气系数为1时,直接用79%氩气比例的氩氧混合气代替空气可使发动机的指示热效率从36.9%提高到43.0%,平均指示压力从0.81 MPa提高到0.95 MPa,当过量氧气系数提高到1.1时,在79%氩气比例下发动机指示热效率最高达49.8%;相对于空气,氩氧混合气使得燃烧循环变动增大,燃烧相位循环变动减小,随着混合气变稀,燃烧循环变动和燃烧相位循环变动均增大,氩气比例增加可优化燃烧循环变动,而燃烧相位循环变动会增大。

In order to improve the thermal efficiency of the internal combustion engine,the engine intake charge is changed from air to argon-oxygen mixture,and tests are conducted to study the effects of excess oxygen coefficient,argon proportion,and ignition timing on the engine indicated thermal efficiency,IMEP and cyclic variation of combustion.The test results show that when the excess oxygen coefficient is 1,the indicated thermal efficiency of the engine can be increased from 36.9%to 43.0%and IMEP from 0.81 MPa to 0.95 MPa by directly replacing air with the argon-oxygen mixture with 79%argon proportion;When the excess oxygen coefficient is increased to 1.1,the indicated thermal efficiency of the engine is increased to 49.8%at 79%argon proportion.Compared with air,argon-oxygen mixture increases combustion cyclic variability,while combustion phase cyclic variability decreases;both combustion and combustion phase cyclic variability increase as mixture becomes leaner;combustion cyclic variability is optimized as argon proportion increases,while combustion phase cyclic variability increases.