Search

For the horizontal take-off hypersonic cruise aircraft, research on the combined design method of multi-section was carried out, the main design parameters of different sections were analyzed, the parametric design model of the flight path was established, and the characteristics of the typical flight path were studied. On this basis, the calculation of sample points was carried out, and a prediction model of aircraft range and flight time based on the design parameters of the four main flight sections was established based on the neural network method. The genetic algorithm is used to optimize the flight path of the prediction model with the range as the objective function. The research results show that the neural network prediction model based on the parametric design of the trajectory can predict random sample points better than the trajectory model For the prediction of random sample points, compared with the calculation results of the trajectory model, the maximum errors of the flight range and flight time are within 0.82% and 0.45%. The prediction model is optimized with the flight range as the objective function, and the relative error between the optimal range and the trajectory model under the corresponding section parameters is less than 0.2%, which shows that the model established in this paper can better predict the range and flight time according to the section design parameters. Parametric modeling and neural network optimization are feasible methods for aircraft trajectory design and section parameter optimization.

Aiming at the problem of self-excited oscillation in a supersonic inlet, the oscillation suppression of parallel cavities in a shock system is studied. Based on the shock dynamic model, the theoretical calculation model of parallel cavity under dynamic shock is established, and the effects of cavity volume and oscillation frequency on shock oscillation flow field parameters are analyzed. On this basis, an integrated numerical model including cavity and inlet and outflow fields is established, and the effects of cavity on the inlet flow field parameter distribution and parameter oscillation are compared by using unsteady numerical calculation algorithm. The theoretical calculation results show that the parallel cavity can reduce the amplitude of flow field pressure oscillation, and increasing the cavity volume is beneficial to suppress parameter oscillation. The unsteady numerical calculation of three groups of working conditions shows that the cavity changes the amplitude of parameter oscillation, and the high amplitude frequency point also decreases compared to the model without cavity. Through the alternating change of pressure between the channel and cavity during the movement of the shock wave, the cavity gas filling and overflow dampen the shock wave forward and pressure change of the mainstream, so as to suppress the self-excited oscillation.

According to the requirements of a wide speed range, a variable-geometry supersonic inlet with inner surface adjustment is studied. The basic design model of the inlet is established, and the influence of profile adjustment on the resisting back pressure ability and inlet performance boundary are analyzed using a theoretical method. Based on the numerical simulation method, the flow field simulation is carried out, and the flow field parameter distribution and performance of the adjustment inlet are studied in comparison with the fixed-geometry scheme. The results show that the starting Mach number is not changed for two inlet schemes because they have the same profile during low-speed flight. The fixed-geometry inlet has insufficient compression on the incoming flow, and the resisting back pressure ability decreases significantly during high-speed flight. The compression ratio and the compression wave system can be easily changed at the same time through the adjustment of the inner profile for the adjustable inlet during high-speed flight. Both the theoretical analysis and numerical simulation show that the resisting back pressure ability and performance are significantly improved after the adjustment. As such, the adjustment method in this paper can fundamentally solve the problem of the insufficient compression of the wide-range working inlet during high-speed flight, and the method can be easily realized.

With a focus on the shock oscillation phenomenon of a supersonic inlet at a high Mach number, the influence of isolator overflow on shock oscillation is studied in this paper. The shock wave dynamic model with overflow was established by the theoretical method, and the integrated numerical model of internal flow and external flow in the inlet was established too. The theoretical analysis of rate of overflow and overflow position on the flow field is carried out, and the changes of flow field parameters are studied by numerical simulation under different overflow positions. The results showed that both increasing the rate of overflow and setting the overflow gap close to the shock front were beneficial to reducing the flow parameters’ oscillation. In the viscous flow field, the overflow gap restricted the forward development of the local separation region of the shock train system, thus constraining the shock wave movement process, which could significantly reduce the parameter oscillation. In model C with two groups of overflow gaps, pressure oscillations of sampling point PU8 and PL8 were reduced to 29.81% and 30.56% relative to without overflow, and the corresponding rate of overflow was within 3.6%, which indicated that the appropriate overflow gap setting could effectively suppress the self-excited oscillation in the inlet.