Studies on principles of long-running shot tunnel driven by opposite compression piston drivers

The theoretical basis of the long-running shot tunnel driven by opposite compres-sion pistons is laid.The long-running shot tunnel driven by opposite compression pistons can provide long-lasting high enthalpy and high pressure experimental gas flow,which is a new idea to build long-running hypersonic tunnels.The operation principles of the long-running shot tun-nel driven by opposite compression pistons are analyzed by theoretical simplification and computa-tional fluid dynamics to validate its feasibility.In theoretical analysis,based on the uniform flow field assumption,the test time and the time histories of pressure and temperature are presented with the consideration of the specific heat at constant pressure changing with temperature.The operation of the tunnel is simulated numerically by commercial code Fluent.The results indicate that the pressure of the experimental gas can be kept nearly constant with pressure stabilizer by extruding for about 25 microseconds,that is consistent with theoretical analysis results.Because of the compression of the opposite pistons,the temperature of the flow field is non-uniform and the temperature fluctuation amplitude is less than 180K.This is a notable problem of long-run-ning shot tunnel driven by opposite compression pistons that needs to be resolved.