Research On Combustion Organizing Technology Of Scramjet In Wide Range Mach Number

The object of this research is to obtain the combustion organizing technology for scramjet working at flight Ma4-7conditions. Both experimental and numerical methods are employed to investigate the ignition and combustion performances at three typical inflow conditions.All the experiments are conducted in pulse combustion wind tunnel. The wind tunnel produces test inflow with hydrogen and oxygen-rich air combusting. The simulating parameters include total temperature, total pressure and Mach number. Three typical inflow conditions at scramjet isolator entry are chosen to represent the flow conditions in the range of flight Ma4-7, which are Ma2,2.6and3respectively. A high precision fuel supply system with multi scheduling for multi fuel supply pipelines is designed to meet the need of wind tunnel. Functions of the system include fuel supplying to scramjet model, air and hydrogen supplying to torch igniter and air supplying for throttling. All these functions are achieved very well.Room temperature ethylene is ignited reliably at Ma2condition. Seven igniting methods are investigated under this condition, including ethylene auto-igniting, torch igniting, air-throttling igniting, torch plus air-throttling igniting, torch plus pilot hydrogen igniting, air-throttling plus pilot hydrogen igniting, pilot hydrogen igniting. The experiments show that the last three methods can ignite ethylene reliably.Combustion characters with fueling at single injector and performances with fueling at multi injectors are investigated. Flame development processes of different injector are explored by high speed photograph. Lean and rich limits of ethylene equivalence ratio (ER) for these injectors are gained. A mathematic model is employed to analysis the relationship between ER and combustion pressure. Three indexes are used to evaluate combustion performance, including isolator undisturbed length, combustor thrust and fuel specific impulse.Pilot hydrogen can ignite ethylene at Ma2.6condition yet in experiments. However, whether ethylene can combust steady or not after hydrogen turning off depends on the quantity of ethylene. When fueling at upper wall only, the main combustion area occurs near upper wall which causes oxidizer cannot be comsued completely. When fueling at upper and lower walls simultaneously, the ethylene injected from lower wall can be ignited by flame anchored at upper wall. Then the flame at lower wall can improve combustion at upper wall inversely. So there is an interactive mechanism between upper and lower wall flame.Ethylene is ignited reliably by air-throttling at Ma3condition. Three parameters of air-throttling are investigated quantitatively, including throttling mass flux, ethylene equivalence ratio and throttling duration. The ignition time is used to evaluate the effect of throttling parameters. The relation curves between these parameters and ignition time are ploted respectively. Multiple unlinear regression method is used to establish a mathematic model of air-throttling ignition.The data got in these experiments are analysed comprehensively. Detailed insight is obtained to put forward a combustion organzing draft for scramjet working at a wide range of Mach number. This draft could be a reference for the engineering application.