Rectangular Hypersonic Inlet Research Articles

Prediction dynamic model of shock train with complex background waves

Oblique shock waves are unavoidable in a rectangular hypersonic inlet, leading to a non-uniform flow field. While a significant body of the literature exists regarding the shock train modeling in a uniform incoming flow condition, few efforts have focused on the shock train behavior considering the influence of the shock wave boundary layer interactions. A low-order dynamic model of the shock train has been constructed with the help of the free interaction theory and a 1-D analysis approach. Experimental and numerical investigations have been carried out to evaluate the low-order model. The results show that the model has the capability of qualitatively analyzing the shock train behavior. In the cases with incident shocks, the rapid forward movement of the shock train has been observed by experiment. Besides this phenomenon was also modeled using the low-order model. Schlieren images show that when the shock train approaches the interaction zone, its behavior is characterized by oscillation and then follows a rapid forward movement with a linear increasing backpressure at 2.7 Ma. This phenomenon is analyzed theoretically based on the free interaction theory. Meanwhile with the help of the direct numerical simulation results from some existing studies, the flow structures in the interaction region and the following boundary layer also provide the evidence.

Unstart Process of a Rectangular Hypersonic Inlet at Different Mach Numbers

A rectangular hypersonic inlet is tested at the low-speed mode ( 5), the design mode ( 6), and the overspeed mode ( 7) to enrich the understanding of hypersonic-inlet unstart. A flow plug is placed at the duct exit to simulate the combustion-induced high pressure and initiate the inlet unstart. High-speed schlieren imaging and time-resolved pressure measurements are used simultaneously to record the unsteady-flow structures and surface pressures of the unstart process. The results indicate that the unstart processes are basically the same for the low-speed mode and the design mode. An unstart phenomenon dominated by the ramp-side flow separation, which exhibits violent fluctuations along the entire duct with a low frequency, is observed at these two operating modes. While operating at the overspeed mode, the strong shear layer, induced by the Mach reflection of the coalesced external oblique shock, divides the internal flow into two parts. The cowl side is filled by fully subsonic flow after the compression of the detached normal shock, and the ramp side mainly contains supersonic flow downstream of the shear-layer-induced oblique shock. Therefore, a real-time adjustment of the detached cowl shock to the downstream high pressure is formed, keeping the entire flowfield of the inlet from oscillation in a much wider range of throttling ratio. With a further increase of the throttling ratio, an oscillation dominated by the cowl-side reversed flow occurs. The oscillation phenomenon exhibits relatively gentle fluctuations, and the characteristic frequencies are mainly determined by the shock train in front of the throat section.

Variable geometry cowl sidewall for improving rectangular hypersonic inlet performance

A variable geometry cowl sidewall control technique is implemented in a generic rectangular hypersonic inlet in this study, in effort to improve inlet performance under both on-design and off-design conditions. Wind tunnel tests and numerical simulations were conducted to investigate the feasibility of the control mechanism, as well as to acquire corresponding inlet flow details. Steady-state pressure distribution was recorded and schlieren photos were obtained simultaneously in the experiment to thoroughly evaluate inlet performance. Combined numerical-experimental results indicate that the variable geometry technique generally enhances inlet performance by two mechanisms. First, the increased cowl sidewall sweepback (CSS) expands the inlet flow spillage window, thus effectively restarting the inlet from an unstart status. The large sweepback cowl sidewall decreases the transverse pressure gradient of the started inlet in the cowl entrance region, compared to an unstart inlet. Second, for a started inlet, decreasing CSS significantly raises mass flux, while slightly lowering total pressure recovery. Smaller CSS, which is preferable for inlet performance improvement, primarily suppresses spillage on the edge of the inlet ramp around the cowl entrance.

Oscillatory Flows of Rectangular Hypersonic Inlet UnstartCaused by Downstream Mass-Flow Choking

Oscillatory Flows of Rectangular Hypersonic Inlet UnstartCaused by Downstream Mass-Flow Choking

Simulating Hypersonic Magnetofluid-Dynamic Compression in Rectangular Inlet

The combined effects of an electromagnetic perturbation and viscous-inviscid interaction generate a high-pressure plateau near the hypersonic leading edge surface. The surface pressure induced by magnetofluid-dynamic interaction emulates a movable leading edge strake. This phenomenon has been verified in experimental research, which shows that a direct current surface discharge becomes a virtual compression ramp for flow control. More recently, investigation has extended to a rectangular hypersonic inlet. The present analysis solves the magnetofluid-dynamic equations using weakly ionized gas models, including the formulation based on the drift-diffusion theory. The numerical simulation provides a detailed description of the intriguing magnetofluid-dynamic interacting flowfield. After validation by experimental measurements, the computed results quantify the effectiveness of a magnetofluid-dynamic compression for a hypersonic inlet. Applying a plasma generation power input to a direct current surface discharge of 7.87 W per square centimeter of electrode area, the interaction produces an 11.7% higher compression of a constant cross-section inlet.