Abstract:To improve the ordered characteristic of external gear pump with liquid ammonia medium for the purpose of better matching dynamic performance of mechanically pumped two-phase loop (MPTL) in large spacecraft, based on the pump’s required characteristic by MPTL and the precise calculation of volume efficiency are researched. From the output characteristic such as flux and volume efficiency, the ordered characteristic of revolving speed was derived; finally, the related sample calculation and sensitivity analysis were carried on. All results show that volume efficiency of the gear pump with liquid ammonia medium is generally low; the output flux is positive linearity with revolving speed and negative linearity with pressure difference, and negative inverse linearity with viscosity of working medium. The volume efficiency is negative linearity with the ratio of pressure difference to revolving speed, so it is suitable for high speed and light load condition; the ordered revolving speed is positive linearity with required flux of MPTL and negative linearity of required pressure difference of MPTL and negative inverse linearity with viscosity of working medium, so it is suitable for the approximately fixed ratio condition of pressure difference to revolving speed; the ordered revolving speed is more sensitive to required pressure difference than required flux when medium viscosity is less than 0004 19 Pa·s, otherwise, the ordered revolving speed is more sensitive to required flux than required pressure difference. So a previous theoretical basis is provided for further research and development for the external gear pump with liquid ammonia medium used by MPTL of spacecraft.
