Study On Starting Characteristics Of Supersonic Inlet

Integral solid propellant ducted rocket has the advantages such as high speed, long working hours, simple structure, strong maneuverability, etc, which make it become one of the most important development direction of the future advanced missile power systems. Inlet is the part that be the core of integral solid propellant ducted rocket. The inlet starting performance determines the reliable working range of the engine. Therefore,determining the inlet starting characteristic is very important.The flight test that the certain type of domestic ramjet failed in 2014, the reason is that the back pressure was too large during the transition. The start performance and effect of inlet entrance closure have become one of the bottlenecks restricting the development of integral solid ramjet technology. The paper was based on the practical engineering application, carried out numerical simulation research to study the start characteristics of two-dimensional mixed-compression supersonic inlets with 90°configuration at the venter of the missile respectively from the transition and the back pressure.Based on integrated missile/inlet model, the flow field characteristics of two-dimensional mixed-compression supersonic inlets with 90° configuration at the venter of the missile was investigated by numerical simulation. Results indicate: With increasing back pressure, the terminal shocks gradually move to the upstream. Within range of suitable back pressure, the terminal shocks can be stabilized at the convergence channels of the inlet, which means the inlet exist stable subcritical condition.Secondly, this paper studied inlet on the back pressure characteristic under different working conditions, and fitted an estimate formula of the ultimate back pressure ratio.Results indicate: The back pressure characteristic of the inlet associated with the inlettotal pressure and total pressure recovery coefficient and the mass flow ratio. With the increasing of the free stream Mach number, the free flow total pressure and mass flow ratio improves, back pressure characteristic enhances. In α=-2o ~ 8o range, with the increasing of angle of attack, the inlet total pressure recovery coefficient and mass flow ratio increases, the back pressure characteristic enhances. In the case of sideslip, leeward side inlet performance is superior to the windward side inlet. Within the scope of β=0o~8o, with the increasing of yaw angle, both sides of the inlet performance parameters have different change trend, leeward side inlet total pressure recovery coefficient and discharge coefficient increase at first and then decrease; while the windward side of the total pressure recovery coefficient and discharge coefficient keep decreasing, and the back pressure characteristic declines. When the windward side of the inlet works in unstarting state, if the back pressure can’t quickly reduce, leeward side inlet will turn into unstarting state.The primary focus of the third part in this paper is on restart characteristics of two-dimensional mixed-compression supersonic inlet under different working conditions.Results indicate: The total pressure of air is the main factor that determines the restart performance. The restarting back pressure becomes higher while the free stream Mach number or the angle of attack goes bigger. When α ≥ 2o, the missile interference is relatively weak, so the restarting back pressure basically remains unchanged. In the case of sideslip, the restarting back pressure of two inlets is not synchronized. The interference on leeward side inlet is weak, and the restarting back pressure doesn’t change with yaw angle. For windward side inlet, when β≤2o, the interference of missile is weak, and the restarting back pressure is close to the leeward side; when β≥4o, with the increasing of yaw angle, the missile interference enhances, and the restarting back pressure reduces,the wind inlet side restarting obviously lags behind the leeward side.At the last part of this paper,the effect of inlet entrance closure and port cover opening process on start performance was investigated. Results indicate: The entrance closure can decrease the starting Mach number from Ma=2.31 to Ma=2.29. When theinlet entrance closure opened and port cover closed, the inlet flow field presents periodic oscillation, the frequency is similar with acoustic modal frequencies, and the pressure peak become higher while the location goes deeper. The open moment of port cover has great influence on the inlet starting performance, opening the port cover during inflation is more conducive to inlet starting.