Research On Experimental Technologies For Inner Flowfield Of Scramjet And Their Applications

Hypersonic technology has become one of the most significant research fields of the world powers.And as the critical technology,the experimental technology has attracted more attentions of many institutions and researchers.From the development of hypersonic vehicles,a larger number of manpower,material and financial resources have been invested in the field of experiments.Direct-connect experiments have many advantages,such as less experimental cost,long-test duration,and reduced experimental complexity.Because of these advantages,direct-connect experiments have become the main methods in ground tests.So this paper starts from the direct-connect experiments and puts the focuses on the researches of the direct-connect measurement methods and the design methods of the direct-connect facility.The main content of this thesis includes the non-contact optical measurement method for the direct-connect experiments,the inverse design method of the direct-connect facilities for combustion,the design and starting characteristics of the direct-connect variable Mach number wind tunnel,the experiment of the inlet in wind tunnel and so on.Firstly,to solve the limitation of the commercial PIV post-processing algorithm and increase the accuracy of PIV,the paper thoroughly studies the PIV post-processing algorithms.Based on these studies,home-made software for PIV is developed using Matlab.From the verification of processing the synthetic and experimental images,the accuracy and reliability of the code have been attested.In addition,BOS experimental platform is set up to increase the test ability.And the density of Ma=1.9 nozzle under over-expanded condition has been measured by BOS,which attested the reliability of the BOS experimental platform.Secondly,for increasing the accuracy and spatial resolution of PIV post-processing algorithm,an adaptive algorithm that adopted the concept of spring force is proposed in this paper.The working principle of the adaptive processing method is to generate the spring force on the bias of the deviation between the ideal and actual distances of measurement points.Under artificial force,the sampling points are moved to the desirable places iteratively.And the ideal distances of measurement points are constructed based on the seeding density and the velocity information.From processing the synthetic images,it has been verified that the bias and random error can be reduced by 7.3% and 4.0% using the adaptive method,respectively.Then,from the distributions of the outliers,vorticity and continuity in the experimental verification,the robustness and reliability of the proposed method are attested again.At the same time,this thesis has got some achievement in the design of direct-connect facility.To solve the starting problem encountered in the traditional direct-connect facilities,a new configuration has been proposed,which expands the flow firstly and then forms the shock wave distortion.And for increasing the accuracy of the facility,two inverse design methods have been proposed.One method starts from the flow before the shock wave,the other starts from the shock wave directly.From the verification cases,the relative errors of Mach number at the exit and the pressure along the isolator wall are less than 2.1% and 5%,respectively.Furthermore,an integrated design method is studied,which can reduce the effect of manufacturing and assembly errors and the complexity of the design procedure.And then,a direct-connect variable Mach number wind tunnel is designed and built for the study of inlet.From the numerical simulation and the experimental calibration,the effectiveness and accuracy of the wind tunnel have been verified.Then,the starting procedures of the wind tunnel,including ideal and actual procedures,have been researched.Based on the studies,the characteristic total pressure curve of the wind tunnel inlet can be obtained.After that,the starting characteristics of the wind tunnel with inlet model are also studied.It is obtained that the wind tunnel would not start easily with medium blockage ratio.And once the wind tunnel does not start,the flow structure presents stable.Only the total pressure jumps,the wind tunnel can start again.From the result of unsteady numerical simulations,it can be concluded that the moving shock wave is the key factor for the re-start of the wind tunnel.Because,the moving shock wave can destroy the structure of the separation zone and then decrease the total pressure loss.At last,based on the flow characteristics of the direct-connect wind tunnel,the inlet experiments have been conducted in the variable Mach number wind tunnel.Compared with the inlet experiments at the fixed Mach number inflow,this experiment obtains the procedure of the inlet starting from unstarting to starting conditions.In other words,the experiment reproduces the flight procedure of the inlet in the actual situation and accumulates a large amount of data.Besides that,owing to the special configuration of the wind tunnel,two particular flow structures have been investigated in the experiments,named as inlet coupled unstarting and coupled starting conditions.Furthermore,the numerical simulation of the inlet under over-speeding process has been conducted.From the simulations result,it can be concluded that the starting process requires significantly less time.Besides,the pressure along the bottom wall agrees well with that obtained from the experiments,which can verify the effectiveness and reliability of CFD and experiments.