Starting Process of a Double-Throat Ludwieg Tube Tunnel and the Extension of Its Effective Running Time

The Ludwieg tube wind tunnel serves as a crucial testing ground for fundamental studies of hypersonic aerodynamics. However, the quick-opening valve-started hypersonic Ludwieg tube wind tunnel has been affected by the quick-opening valve for a long time, resulting in different types of flow disturbance modes. The double-throat aerodynamic configuration can effectively eliminate the disturbance source of the upstream components of the quick-opening valve-started hypersonic Ludwieg tube wind tunnel, but it will lead to a significant reduction in the effective running time of the wind tunnel. In order to solve this problem, the unsteady numerical simulation was used to study the start-up characteristics of the hypersonic Ludwieg tube wind tunnel with double-throat aerodynamic configuration. Then, a fusion design was carried out for the first nozzle expansion section and the stable section. The effects of different combinations of expansion angles and stable sections on the start-up time and flow field quality of the wind tunnel were studied. The results show that the effective running time of the hypersonic Ludwieg tube wind tunnel with double-throat aerodynamic configuration can be increased by nearly 20% by using the combined design of reducing the expansion angle, and the static flow field quality in the downstream experimental section is almost unaffected, which effectively improves the experimental ability of the wind tunnel. At the same time, compared with the larger expansion angle combination, the smaller expansion angle design can reduce the total pressure loss by about 10%.