Theoretical model of driving force for variable geometry hypersonic inlet based on principle of virtual work

To enable hypersonic inlets to operate across a wide Mach number range, the geometric configuration of the inlet must be adjusted. The magnitude of the driving force required to actuate these geometric changes is fundamental to the design of the inlet adjustment mechanism. For this purpose, this paper proposes a calculation method for the driving force of hypersonic variable geometry inlets, which enables quick computation of the driving force. This provides a theoretical foundation and a practical computational approach for the design, experimentation, and application of variable geometry inlets. Initially, the principal configuration of a typical two-dimensional variable geometry inlet is proposed, and a simplified four-bar linkage model is derived. Utilizing the principle of virtual work, a rapid calculation method for calculating the connecting rod driving force is derived. The method determines equivalent driving forces and their points of application on each linkage element, calculated from the pressure distribution. This approach expedites the calculation of the required driving force for the four-bar linkage. This paper details a specific variable geometry inlet configuration. The developed method is then applied to calculate the driving force under varying back pressures and mechanical positions of the four-bar linkage. Increased backpressure, decreased connecting rod angle (β), and higher freestream Mach number all lead to a greater driving force. Moreover, this study proposes a dimensionless parameter termed the “driving force index,” noting its insensitivity to variations in β angle and freestream Mach number.