Методика раціонального формування поверхонь гальмування плоского надзвукового вхідного пристрою

Abstract

This article deals with methodological support for the design of effective supersonic flat external compression input devices. A concise analysis of the contribution of well-known scientists in the study of braking processes of supersonic flows of the working body in the system of sealing jumps is presented in the input devices. The proposed method of rational formation of the braking surfaces of a flat supersonic inlet device is based on the main provisions of the gas-hydraulic theory of sealing jump proposed by Rankin and Hugoniot. The main goal of this study is the development of a method of rational formation of braking surfaces of a supersonic flat input device of external compression according to the criterion of its efficiency, namely the maximum value of the coefficient of preservation of full pressure in sealing jumps. The choice of the value of the angle of inclination of the braking surfaces of the supersonic input device and the corresponding angles of inclination of the oblique jumps of the seal for a given calculated value of the number M consists in finding such values of the angles of inclination of the braking surfaces, at which the intensity of the oblique jumps of the seal is the same, under this condition the coefficient of preservation of full pressure is maximum. The mathematical formulation of the problem of determining the rational position of the braking surfaces of the supersonic flat input device of external compression is possible in the form of finding the angle of inclination of the first braking surface, which corresponds to the maximum value of the coefficient of preservation of full pressure for the determined value of the number M before the first oblique jump of the seal and at a constant intensity of the oblique jumps of the seal. This article outlines the main elements of the proposed methodology. Using the given methodology, a rational value of the angle of inclination of the first oblique jump of the seal was searched for the calculated value of the number M=2.5. In the supersonic input device operating at the specified design number M, three oblique sealing jumps and one direct-closing sealing jump are selected. The dependence of the full pressure preservation coefficient of oblique sealing jumps, direct jump, and total pressure preservation coefficient in the sealing jumps of the supersonic inlet device is obtained. It is shown that with an increase in the angle of inclination of the first braking surface and the corresponding values of the angles of inclination of the second and third braking surfaces, the coefficient of preservation of the full pressure of oblique jumps of the seal decreases, and that of direct jumps increases, which determines the presence of an extremum and makes it possible to determine the rational value of the angle of inclination of the first braking surface. This technique allows for any number of M before the first oblique jump of the seal to determine the rational values of the angles of inclination of the braking surfaces of the flat supersonic external compression input device.