Design and experimental research of a sub-Newton N_(2)O monopropellant thruster with inner-heater

Nitrous oxide(N_(2)O)is a green propellant with excellent application prospects.A subNewton N_(2)O monopropellant thruster with inner-heater and a N_(2)O self-pressurization stable supply system with regenerative heat compensation are designed in this paper.The experimental research of the thruster is described,including measurements of preheating power,activation temperature,vacuum thrust,specific impulse,life-span and pulsed operation performance.By inserting the heater into the catalyst-bed,preheating efficiency of the heater is significantly improved compared to the thruster with outer-heater.Thus,the preheating power demand of the thruster is successfully reduced to around 10 W.The mean vacuum thrust of 322 mN is attained and the corresponding specific impulse reaches 162s at the mass flow rate of 0.2 g/s.Successful activation temperature of 523 K is achieved,and the activation performance of the thruster is affected by the loading factor.A long term hot-firing test longer than 12000 s is attained.The pulsed operation performance of the inner-preheating thruster is also studied by measuring chamber pressure.Impulses with different magnitudes are produced by adjusting the opening duration of the control valve.A minimum impulse of 81 mN·s is attained.Finally,the performance of the thruster is evaluated by comparison with other thrusters of the same type.The results indicate that the proposed thruster with inner-heater is superior in terms of preheating power,activation temperature and specific impulse performance.

Thermal-structural analysis of regeneratively-cooled thrust chamber wall in reusable LOX/Methane rocket engines

To predict the thermal and structural responses of the thrust chamber wall under cyclic work,a 3-D fluid-structural coupling computational methodology is developed.The thermal and mechanical loads are determined by a validated 3-D finite volume fluid-thermal coupling computational method.With the specified loads,the nonlinear thermal-structural finite element analysis is applied to obtaining the 3-D thermal and structural responses.The Chaboche nonlinear kinematic hardening model calibrated by experimental data is adopted to predict the cyclic plastic behavior of the inner wall.The methodology is further applied to the thrust chamber of LOX/Methane rocket engines.The results show that both the maximum temperature at hot run phase and the maximum circumferential residual strain of the inner wall appear at the convergent part of the chamber.Structural analysis for multiple work cycles reveals that the failure of the inner wall may be controlled by the low-cycle fatigue when the Chaboche model parameter c3= 0,and the damage caused by the thermal-mechanical ratcheting of the inner wall cannot be ignored when c3〉 0.The results of sensitivity analysis indicate that mechanical loads have a strong influence on the strains in the inner wall.