The flow in a low-powered arc gas heater com- bined with a supersonic nozzle of throat diameter less than 1 mm is quite complicated and difficult to describe in quan- titative detail. Experiments on arc-heated superso...The flow in a low-powered arc gas heater com- bined with a supersonic nozzle of throat diameter less than 1 mm is quite complicated and difficult to describe in quan- titative detail. Experiments on arc-heated supersonic jet thrusters of monatomic gases argon and helium have been carried out and their performance measured. The flow charac- teristics are analyzed with the help of numerical simulation. Results show that the viscous effect is the most important factor causing the large difference between ideal and real performance. A large outer section of the exit flow is slow- moving. This is especially pronounced in helium, where 70 % of the exit area of the nozzle might be in subsonic flow. Fric- tion forces can be much larger than the net thrust, reaching several times higher in helium, resulting in very low efficien- cies. Other factors causing the differences between ideal and real flow include： complex flow in the throat region, electric arc extending to the nozzle expansion section, heat transfer to the inlet gas and from the hot plasma, and environmen- tal pressure in the vacuum chamber. It is recognized that the ordinary concepts of supersonic nozzle flow must be greatly modified when dealing with such complicated situations. The general concepts presented in this paper could be helpful in guiding the design and operation of this equipment.展开更多
In this paper exit.bend angle(tea-pot effect)has been analysed theoretically based on thebasic)aw of hydromechanics.It was proved that it is the transverse shear stress that causes exitbend angle while the bending dir...In this paper exit.bend angle(tea-pot effect)has been analysed theoretically based on thebasic)aw of hydromechanics.It was proved that it is the transverse shear stress that causes exitbend angle while the bending direction is along with the resultant force of the shear stresses andthe magnitude of the exit angle is directly proportional to the resultant force.The equation re·lating exit bend angle with the resultant force was set up and experiment verification of theequation was carried out with rational agreement to theoretical results.展开更多
The suppression of the aerodynamic noise in the cavity has a great significance to solve relevant puzzles of weapon bays. Acoustic field of the standard cavity model is simulated by using the computational fluid dynam...The suppression of the aerodynamic noise in the cavity has a great significance to solve relevant puzzles of weapon bays. Acoustic field of the standard cavity model is simulated by using the computational fluid dynamics technology based on scale-adaptive simulation （SAS） model. The results obtained by the proposed method in this paper show reasonable agreement with experiments. On the basis of this, effect of different jet flow rates on the time-averaged variables, turbulent kinetic energy, root mean square （RMS） of sound pressure, sound sources distribution and the pulsating pressure distribution in the cavity is studied. The analysis shows that the jet flow has great influence on the cavity flow field and the distribution of pulsating pressure RMS by changing the morphology of the shear layer. The most obvious of these measures is spout4 configuration, the influence mainly in the form of reducing the pulsating pressure of the whole cavity and changing the sound pressure level in the far field. The results show that different jet flow rates have different control effects on pulsating pressure in the cavity and sound pressure level in the far field. Furthermore, the jet flow rates and the suppression effect on the pulsating pressure have no linear relation.展开更多
基金supported by the National Natural Science Foundation of China(Grants 50836007,11475239,10921062,and 11275021)
文摘The flow in a low-powered arc gas heater com- bined with a supersonic nozzle of throat diameter less than 1 mm is quite complicated and difficult to describe in quan- titative detail. Experiments on arc-heated supersonic jet thrusters of monatomic gases argon and helium have been carried out and their performance measured. The flow charac- teristics are analyzed with the help of numerical simulation. Results show that the viscous effect is the most important factor causing the large difference between ideal and real performance. A large outer section of the exit flow is slow- moving. This is especially pronounced in helium, where 70 % of the exit area of the nozzle might be in subsonic flow. Fric- tion forces can be much larger than the net thrust, reaching several times higher in helium, resulting in very low efficien- cies. Other factors causing the differences between ideal and real flow include： complex flow in the throat region, electric arc extending to the nozzle expansion section, heat transfer to the inlet gas and from the hot plasma, and environmen- tal pressure in the vacuum chamber. It is recognized that the ordinary concepts of supersonic nozzle flow must be greatly modified when dealing with such complicated situations. The general concepts presented in this paper could be helpful in guiding the design and operation of this equipment.
文摘In this paper exit.bend angle(tea-pot effect)has been analysed theoretically based on thebasic)aw of hydromechanics.It was proved that it is the transverse shear stress that causes exitbend angle while the bending direction is along with the resultant force of the shear stresses andthe magnitude of the exit angle is directly proportional to the resultant force.The equation re·lating exit bend angle with the resultant force was set up and experiment verification of theequation was carried out with rational agreement to theoretical results.
文摘The suppression of the aerodynamic noise in the cavity has a great significance to solve relevant puzzles of weapon bays. Acoustic field of the standard cavity model is simulated by using the computational fluid dynamics technology based on scale-adaptive simulation （SAS） model. The results obtained by the proposed method in this paper show reasonable agreement with experiments. On the basis of this, effect of different jet flow rates on the time-averaged variables, turbulent kinetic energy, root mean square （RMS） of sound pressure, sound sources distribution and the pulsating pressure distribution in the cavity is studied. The analysis shows that the jet flow has great influence on the cavity flow field and the distribution of pulsating pressure RMS by changing the morphology of the shear layer. The most obvious of these measures is spout4 configuration, the influence mainly in the form of reducing the pulsating pressure of the whole cavity and changing the sound pressure level in the far field. The results show that different jet flow rates have different control effects on pulsating pressure in the cavity and sound pressure level in the far field. Furthermore, the jet flow rates and the suppression effect on the pulsating pressure have no linear relation.
