Analysis of the impact of translating cowl on hypersonic vehicle performance

For the power plant of hypersonic vehicle - scramjet, this work mainly studies the effects of the translating cowl of inlet on the static and dynamic performance of the hypersonic vehicle. The results indicate that the effects of the cowl on lift and drag can be negligible, while the effects of the cowl on thrust and pitching moment are significant. The cowl makes thrust-drag ratio bigger and the accelerated conditions corresponding angle of attack range larger. The cowl increases the degree of flexible deformation, but in total this effects can be negligible. For the balance states, the elevator deflection angle needed becomes bigger to offset the additional pitching moment; a smaller angle of attack and stoichiometrically normalized fuel equivalence ratio (FER) needed generate enough thrust to reach a certain speed and height, thereby the flight left margin considering viscous is expanded. The article also analyzes the effects of a translating cowl on open-loop poles and zeros of the typical transfer function of the linear model, and found the RHP unstable zeros was away from the imaginary axis, the flight control system bandwidth limit can be slightly widened. This article provides the basis theoretical study for further controller design of the hypersonic vehicle.