An Investigation By The Sketal Chemical Kinetics Model About The Effect Of Nitric Oxide With The Toluene Reference Fuel On HCCI Combustion

Homogeneous charge compression ignition(HCCI) engine has big challenges of the coverage of the load and speed rang in the HCCI engine, the control of its ignition delay and combustion rate, and the working range. To overcome these difficulties and achieve effective control of HCCI combustion process, researchers have conducted a lot of researches and searched some ways, and the exhaust gas recirculation(EGR) is the most important among these technologies. The EGR gases mainly include of CO, NO and unburned hydrocarbons, which are very active in HCCI combustion. These active EGR gases reflect the chemical effect in the HCCI combustion. In this paper, NO as a very important component is chosen for research target.With the deep study of gasoline surrogate mixture, Toluene reference fuel(TRF) is widely applied in the gasoline surrogate mixture as the ternary fraction, which has solved the problem of the nonlinear with the octane number of gasoline. It can capture the features of antiknock performance with the change of working condition of engine and also describe the fuel properties in low temperature combustion process.Based on the availability of nitric oxide(NO) and TRF as the research object, the HCCI combustion is controlled by chemical reaction kinetics of fuel. So this article is mainly focused on chemical kinetics model of NO and TRF. By comparing the research achievements of NO and TRF, the correct mechanisms were chose and the reaction path and the key reactions of NO on each TRF component through the sensitivity analysis and reaction path analysis. After analysis, it was found that the new transformation pathes are generated after the addition of NO. It also was known that the reaction paths between n-heptane and NO is similar with the reaction paths between iso-octane and NO, while it is different with the reaction paths between toluene and NO. The key reactions of NO on each TRF component are the reactions(NO+OH(+M)=HONO(+M) and HO2+NO=NO2+OH). NO has a promoted effect on iso-octane and toluene and the effect was instended with the higher mole fraction fo NO. But the effect of NO on n-heptane is different from that on iso-octane and toluene. For n-heptane, the ignition delay times advance with the increase of NO when the NO concentration is low, but if the concentration of NO is high enough, the ignition times will keep constant and even delay. Through the reaction path analysis, the effect of NO n-heptane is depended on the performance of the reaction(NO+OH(+M)=HONO(+M)).On the above analysis, the skeletal mechanism of TRF-NO was built, consisting of 80 species and 184 reactions. By comparisons of TRF- NO sketal and detail mechanism with experimental value, TRF branch of TRF-NO sketal mechanism can discribe well the ignition delay time and the pressure trace in shock tube and HCCI engine. TRF- NO sketal mechanism can also discribe well the ignition delay time in the HCCI engine with the concentration change of NO.