Research On Integrated Cryogenic Propellant Management Scheme

Integrated Vehicle Fluids（IVF）reveals an innovative technology adapting to long duration spaceflight of LOx/LH₂ upper stages.By combining H₂/O₂ propellant and boiloff with internal combustion engine（ICE）technology,IVF can integrate functions of tank pressurization,attitude control and power generation into one compact system,eliminating the conventional helium pressurization subsystem,hydrazine attitude control subsystem and large batteries power subsystem,which reduces LOx/LH₂ upper stages mass and adaptes to missions days or weeks on orbit.Thus,it’s of great significance to carry out IVF research.Integrated cryogenic propellant management（ICPM）scheme for the LOx/LH₂ upper stage with missions days on orbit is proposed based on IVF concept.Installed on the LOx/LH₂upper stage,ICPM system can provides functions of tank pressurization,attitude control and power generation by utilizing H₂ boiloff and O₂ propellant.According to the methodology of modularization modeling and simulation,ICPM system is divided into the GH₂ compressor,LO₂ piston pump,H₂/O₂ internal combustion engine,generator,battery,H₂/O₂ gas bottles,pipes,heat exchangers,GH₂/GO₂ thrusters and valves,etc..Models of these components are established using AMESim and integrated into ICPM system simulation model.Working process of ICPM system during the trans-lunar mission is simulated.ICPM components working mode and parameters variation law are studied,and components working characteristics get analyzed.Calculation result of LOx/LH₂ upper stage propulsion system mass shows that ICPM scheme has an advantage in LOx/LH₂ upper stage propulsion system mass compared with the conventional propulsion scheme.PI speed regulating strategy is proposed under the phenomenon that H₂/O₂ ICE parameters change dramatically when H₂/O₂ ICE working condition changes.H₂/O₂ ICE system simulation model is constrcuted using AMESim and dynamic characteristics when H₂/O₂ ICE working condition changes are simulated.Result shows that PI speed regulating strategy offers an effective control strategy for H₂/O₂ ICE with the capability of parameters wide range adjustment and rapid response.PI controller parameters such as k_p and k_ihave significant impacts on H₂/O₂ ICE dynamic characteristics.Genetic algorithm is used to optimize ICPM components parameters such as GH₂compressor flow rate,H₂/O₂ gas bottles upper pressure limit and volume,with LOx/LH₂upper stage propulsion system mass as the optimization objective.Result shows that genetic algorithm provides an effective method for components parameters design to obtain the optimal solution of components parameters quickly and optimize the LOx/LH₂ upper stage propulsion system mass.