Method For Estimating The Aerodynamic Performance Of Scramjet Propulsion Flowpath

In order to meet the demand of rapid performance evaluation of scramjet during scheme selection and preliminary design stage,the method for estimating the aerodynamic performance of scramjet propulsion flowpath was studied.The domestic and foreign research status of method for scramjet performance calculation was studied at first,and the deficiencies was analyzed.After that,the traditional CFD method was accused of too much amount of calculation,which cannot meet the requirements of rapid performance evaluation of scramjet under current computing power.Then the thermodynamic analysis of the working process of scramjet and its parts was carried out.Based on subsystems' performance,the mathematical model of calculating sectional parameters in scramjet was established.Given enough design variables,this method can calculate the aerodynamic parameters of key section,based on which the overall performance of a scramjet can be figured out.According to this method,the performance calculation program of scramjet flowpath was developed.The flow field and phenomena of three cases of the combustion system in two modes were analyzed,and the definition of inner section was determined.Under the assumption of quasi-one-dimension theory,the governing equations of generalized one-dimensional steady flow under two flow states(with and without separation)were derived.Then the solution of these equations in the case of constant specific heat and variable specific heat was studied,and the solution program was written to work out the onedimensional flow field.The comparison between the calculated results and the experimental results showed that the method can effectively calculate and evaluate the performance of scramjet combustion system.Then,based on the governing equations of generalized one-dimensional flow,a method for calculating the parameters along scramjet combustor on the basis of experimental pressure data was proposed.At last,the specific thrust,specific impulse,specific fuel consumption,thermal efficiency,propulsion efficiency and overall efficiency was selected to judge the performance of the engine.After that,the flow characteristics of scramjet under typical design and working conditions were calculated using the program we developed.Then,the influence of chief design parameters on scramjet performance is studied by means of parametric analysis,and the reason was figured out.