A-Variant Design of Hypersonic Ludwieg Tube Wind Tunnel

Abstract

To improve the operation efficiency of conventional Ludwieg tube tunnel, a fast-acting valve is usually deployed between the storage tube and Laval nozzle in order to separate the high- and low-pressure air. However, the disturbance produced by the fast-acting valve as well as the nonuniform heating of storage tube affects the flow quality of the hypersonic Ludwieg tube. Stimulated by the motivation of overcoming the mentioned problems, the feasibility of a novel configuration of hypersonic Ludwieg tube is explored in this research. Upon this study, we introduced an additional Laval nozzle and settling chamber to the conventional Ludwieg tube tunnel, while the cross-section area of the main Laval nozzle is smaller than that of the introduced Laval nozzle. To begin with, the flow evolution along the dual-throat Ludwieg tube was analyzed theoretically; subsequently, numerical simulations were conducted to study the starting process of the dual-throat Ludwieg tube tunnel, and emphasis was placed on the influence of different throat area ratios and settling chamber lengths upon the startup time of wind tunnel. Lastly, the flowfield of the dual-throat Ludwieg tunnel was characterized by measuring the Mach number distribution and pitot pressure fluctuation in the test section as well as the pressures along the overall tunnel. The results show that this novel configuration of Ludwieg tube is applicable and it offers the opportunity for flow quality improvement for conventional Ludwieg tubes with small penalty of reducing the tunnel’s efficient running time.