Low-Temperature Reforming Products coupling Spark Plug on Gasoline Compression Ignition and Combustion Characteristics under Low-Load Condition

Gasoline compression combustion engine has the advantages of low emission and high efficiency, which is very promising for research, but it is difficult to apply under low-load conditions. Gasoline has the characteristics of low reactivity; in the case of low thermodynamic state in the cylinder, the fire delay period of the fuel is longer, and the combustion phase is relatively lagging, which will lead to the increase of combustion cycle fluctuations, and even difficult to ignite and other adverse combustion phenomena. In order to improve the combustion stability of Gasoline Compression Ignition (GCI) engine under low-load condition and expand the limit of low-load combustion boundary, gasoline was reformed without catalyst under the boundary condition of reforming temperature of 488 K and reforming equivalent ratio of 8, and the concentration of reformed product was measured by a gas detection device. Subsequently, the coupling of the reformed product and spark plug with GCI engine under low-load condition was investigated to analyze the effect on engine combustion and emission. The results showed that the initial combustion timing of the low-load GCI engine was late, but the addition of reformed products could advance the combustion phase, shorten the combustion duration, reduce single-cycle NOx emission, and improve the small-load operation characteristics of GCI engine. Coupled spark plug ignition on the basis of adding reformed products could further improve the problem of combustion stability under low-load GCI engine. And the optimization effect became more obvious as the ignition position of the spark plug moves down. However, spark plug ignition would cause local high temperature areas, resulting in an increase in NOx emission.