Study On The Ignition And Flame Propagation Property Of Light-Weight, Spark Ignition, Heavy Oil Aeroengine

Heavy oil is generally used in compression-ignition engine. However, that’s required higher compression ratio, more complex structure and larger weight. In order to ensure dynamic property under the premise of no increasing the weight, spark-ignition heavy oil engine is proposed. The related domestic researches on the small aviation piston engine are mostly built on the HS-700two-stroke gasoline engine, which is converted to spark-ignition by using the heavy oil. However, the studies on heavy oil ignition and the flame propagation are still rarely reported. In this paper, heavy oil spark-ignition and flame propagation are simulated by the commercial software FIRE, by which how different factors impact on the process of spark-ignition and flame propagation is analyzed.Firstly, the geometric and simulation model are built based on the constant volume bomb. The influences of initial combustion condition and the parameters of ignition system on the flame characteristics of uniform mixture heavy oil are studied in laminar flame. The results show that the ignition energy and plug gap are two main factors. Moreover, the minimum ignition energy under different initial condition is determined.Secondly, the geometric and simulation model are built based on the HS-700engine. Consequently, the influences of related initial condition on uniform mixture heavy oil are investigated. Variation of kernel growth rate, the ignition delay and ignition duration are analyzed under different initial conditions, such as mixture concentration, swirl ratio, temperature and ignition energy. Moreover, the minimum ignition energy is also determined.Lastly, comparing to gasoline, the heavy oil shows its different properties. The minimum ignition energy is larger than gasoline. The flame kernel growth rate and flame propagation speed are smaller than gasoline. Average in-cylinder pressure and instantaneous combustion rate of heavy oil engine are lower than gasoline.Since the study of spark ignition and flame propagation properties of heavy oil needs to be deeper researched, some significant results are put forward in this paper which can provide theoretical supporting for the development of the light-weight high-speed heavy oil aero engine.