Study On The Difference Of High Enthalpy Flow Field Between Flight And Ground And The Parameter Simulation Method In Arc-heated Wind Tunnel

In order to achieve safe flight and successfully carry out the tasks,the thermal protection system of a hypersonic vehicle is a key that must be solved in the design process.The arc-heated wind tunnel is an indispensable facility to screen the thermal protection materials,optimize the thermal protection structure,and guide the design of the thermal protection system of aircraft.Due to the increasing variety of aircraft trajectories and configurations,the thermal environment is more complex than previous aircraft,so the requirements for the effectiveness of the test simulation parameter and the test efficiency are constantly improving.In this paper,the numerical method for thermal-chemical nonequilibrium flow under flight and ground test conditions was established,and its verification was presented using typical cases.The flight-ground difference of high enthalpy flowfield and the test parameter simulation method in the arc-heated wind tunnel were investigated,the effectiveness of test simulation was explored,which is helpful to guide the test design,reduce the number of test debugging and running cost,shorten the development cycle.The flowfield in the semi-elliptical nozzle and test section was simulated and compared,and the influence of test parameters on the flow state was found.The influence of nozzle size on the heat flux distribution was studied,and the optimized route of semi-elliptical nozzle was proposed to improve the simulation ability of arc-heated wind tunnel for large-scale thermal assessment test.The test flowfield of stagnation point model with conical nozzle was simulated.The flight-ground difference of flowfield parameters and surface heat flux and the range of simulation parameters were obtained with different nozzle sizes under the limited power.The mechanism of the difference and the amelioration way of improving the effectiveness of simulation parameters were described.The difference of high enthalpy flowfield around a leading edge model was investigated.It is found that the difference of oxygen atom mass fraction near the wall between flight and ground is obvious,so that it is difficult to simulate in the ground test.For the test conditions of reentry body model,there is an approximate linear relationship between the stagnation point pressure and the chamber pressure,while the stagnation point heat flux is approximately linear with the enthalpy.It is necessary to increase the enthalpy in the ground test if the incoming velocity of flight condition is to be simulated,so it is difficult to simulate the high flight velocity.However,it is relatively easy to simulate the dynamic pressure of flight conditions.This thesis consists of seven chapters.Firstly,the research background,research significance,research status and research content were introduced.Then,the numerical method and its verification were presented in detail.Based on the numerical method,the flowfield in the semi-elliptical nozzle and around the stagnation point model,leading edge model and reentry body model were simulated,and parameter simulation method of thermal assessment test were investigated respectively.Finally,the summary and outlook are given,which summarize the research work,progresses,the existing problems and look forward to the future work.