Based on the conjugate heat transfer numerical simulation method，the wall temperature distribution of single expansion after⁃body of a high stealth unmanned aerial vehicle （UAV） was studied.The problem of excessive mesh caused by large area and thin thickness of skin and side plate structure was solved by using thin⁃walled layer mesh.A high⁃precision calculation model was constructed，and the relevant calculation and analysis was completed.The main conclusions were made as follows：although the traditional single fluid calculation can obtain similar temperature distribution，the temperature value was much higher，and the maximum difference can be more than 50 K；the results of conjugate heat transfer calculation were more practical，and could furthermore obtain the temperature gradient distribution in the structure，providing a guidance for thermal stress analysis and structural design；comparing the effects of different metal materials under the same flow conditions，the wall temperature extreme value of a high temperature resistant alloy was about 30 K higher than that of metal steel，and the temperature difference between the upper and lower walls was larger and the gradient was higher.The temperature gradient extreme values of longitudinal ribs of the two materials were 120 K/cm and 65 K/cm，respectively.

The numerical simulation technology of thermochemical non⁃equilibrium flow was established for aircraft hypersonic flight environment，the reliability of the calculation method was verified，and the influence law of high temperature real gas effect on plasma sheath and electromagnetic parameters in plasma was analyzed.The results showed:the numerical calculation results of aircraft peak plasma density on wall central line were in agreement with flight test results，as for the collision frequency，along the stagnation line，the two⁃temperature model and the Park reaction model had the same influence trend on the plasma collision frequency；for the relative dielectric constant，near the shock wave，the real part of other areas of the flow field was close to 1，and the imaginary part gradually increased along the stagnation line；The influence trend of the two⁃temperature model and the Park reaction model on the real and imaginary parts of the relative dielectric constant were consistent.

In order to predict the hysteresis characteristics of finger seal accurately,minimum hysteresis representing hysteresis characteristics of finger seal was proposed.Then minimum hysteresis mathematical calculation method was established,the correction coefficient of model was determined and verified by experiments.The influence rules of the structure and working condition parameters of finger seals on the hysteresis characteristics were studied and obtained based on the modified calculation model.Results showed that the maximum error between the numerical calculation of leakage characteristics considering the hysteresis effect based on modified calculation model and the test results was 7.64%,and the conclusion of model was reliable.The degree of influence of various structural parameters on the hysteresis characteristics of finger seal was in descending order: thickness of each finger laminate,finger repeat angle,arc radius of the finger beam arcs centers,diameter of the finger base circle,width of the interstice between fingers,and arc radius of finger beam.The results provide a theoretical basis and basis for further research on the influence of hysteresis on the finger seal leakage characteristics and the optimal design of finger seal structure.

Based on the nonlinear harmonic method and the acoustic analogy model，the influence of different rear rotor diameters on the aerodynamic and acoustic characteristics of the counter⁃rotating propeller was studied.First，the reliability of the numerical calculation method was verified by the wind tunnel test results of a single propeller.Subsequently，six counter⁃rotating propeller models with different rear rotor diameters were studied for a counter⁃rotating propeller.It was found that the clipping of the diameter of the rear rotor of the counter⁃rotating propeller could reduce the pull coefficient and power coefficient of the rear propeller，but the effect on the efficiency was not obvious.As the diameter of the rear rotor decreased，the noise of the front rotor at the blade passing frequency changed little，but the higher order noise changed more.When the diameter of the rear rotor was reduced by 0.25 times of the diameter，the noise of the blade passing frequency of the rear rotor was reduced by about 9 dB.The clipping of the diameter of the rear rotor can not only reduce the noise of the rear rotor，but also reduce the noise of the front rotor to a certain extent.By clipping the blades，the aerodynamic noise of the counter⁃rotating propeller was reduced by 5~6 dB.The reduction of the diameter of the rear rotor weakened the tip vortex interference and wake interference of the counter⁃rotating propeller，and also mitigated the potential flow field interference between the front and rear blades，which in turn reduced the noise radiation of the counter⁃rotating propeller.