| Design and build of a supersonic/hypersonic wind tunnel was studied in this paper. The working Mach number of this wind tunnel ranges from 2.5 to 7.0. In order to realize wide Mach numbers, a special "blowing-sucking" structure was adopted, and an electric storage heater was fixed in this system to prevent the air from condensing at high Mach number. The high pressure air is used as gas source while the wind tunnel working at hypersonic velocity. The low pressure condition downstream of wind tunnel is provided by a vacuum container instead of ejector. By setting different running parameters, this wind tunnel can partly simulate the atmosphere environment at the altitude of 20～30Km and can be used to study the structure of turbulence, Shockwave turbulent boundary layer interactions and the boundary layer's transition in supersonic/hypersonic flows.The wind tunnel runs by way of sucking/blowing-sucking for its wide Mach number range. While Mach number is 4.0, for its large mass flow ratio and low pressure ratio, the stablizing section is designed based on the theory of non-isoentropy flow, and the wind tunnel run by reducing the total pressure successfully. A new method of design supersonic/hypersonic nozzle was developed here. By using the method of characteristics from the turning contour back to the expansion contour, the flow qualities at the exit of the throat-changing nozzles are much better than that of classical approximate methods. The cost of the system has been cut down in a certain extent by optimum design of air source, vacuum system and heater system.In this paper, the trade-off among the security, the use of the wind tunnel and the techniques are solved. The whole system is sealled by different means, which makes the operation of the system be secure and convenient.The troubles of the reductor and the wind tunnel's start-up have been solved by right way. Finally, the calibrating experiments showed that the quality of the flow field met the requirement of the wind tunnel design. |
