Experimental Study On Combustion Characteristics Of A Surrogate Fuel Of RP-3 Kerosene

The actual combustion in an aero engine is difficult to be measured directly through experiments.The numerical simulation is used to analyze the combustion process and flow field structure,to study the interaction between turbulence and combustion reaction dynamics,and to predict the generation of emissions in the actual combustor.However,the composition of aviation kerosene is complex,which cause great difficulties to describe the combustion reaction of all components.An effective solution is to develop a surrogate fuel containing simple components and to obtain the corresponding chemical reaction mechanism.The following work has been done in this paper to develop a new five-component alternative fuel for RP-3 kerosene and to obtain its laminar combustion characteristics:The main physical properties of RP-3 kerosene were tested.Average molecular weight,ratio of hydrogen-carbon,cetane number and low calorific value are selected as the main selection criterions through the comprehensive consideration of the physical and chemical characteristics of aviation kerosene.The components of the five-component surrogate fuel were preliminarily determined according to the selection criterions,and the optimal component distribution ratio is obtained by optimizing calculation.Finally,a new five-component surrogate fuel comprising 14% n-decane,10% n-dodecane,30% iso-cetane,36% methylcyclohexane and 10% toluene is proposed.The laminar combustion characteristics of n-decane,n-dodecane,iso-cetane,methylcyclohexane and toluene were tested in a constant volume combustion chamber.The experimental results show that the flame development characteristics of single-component fuel are greatly influenced by equivalent ratio,and with the increase of equivalent ratio the laminar burning velocity of single-component fuel increases initially and then decreases gradually.The laminar burning velocity decreases with the increase of initial temperature or the decrease of initial pressure.In addition,the effect of equivalent ratio on flame stability is obvious: with the increase of equivalent ratio,the length of Markstein length decreases gradually,and the flame becomes unstable.The initial temperature has obscure effect on combustion stability.At different equivalent ratios,the effect of the initial pressure on the Markstein length is different.The laminar combustion characteristics of five-components surrogate fuel were tested in a constant volume combustion chamber.The experimental results show that the laminar burning velocity of the five-component surrogate fuel increases initially and then decreases gradually with the increase of equivalent ratio from 0.8 to 1.5.The laminar burning velocity at different initial temperatures is intersected between the equivalent ratio of 1.3-1.4 under the influence of the difference sensitivity of combustion characteristics of each component on the temperature.The laminar burning velocity and the corresponding equivalent ratio aredecreased by increasing the pressure.The Markstein length decreases with the increase of equivalent ratio,while the combustion stability changes accordingly.The effect of the initial temperature on the combustion stability is not obvious.Different from five single-component fuel,the Markstein length of mixture decreases monotonously with the increase of pressure,and the trend become more obvious with the increase of equivalent ratio.The laminar burning velocity of five-component mixture is compared with RP-3kerosene.The results are in good agreement and show that the five-component surrogate fuel can be use to accurately predict the combustion characteristics of RP-3 kerosene.