Research on flow pulsation of aerospace ultra low viscosity gear micropump under trapped oil

In the water treatment and thermal control system of large spacecraft, liquid ammonia with ultra-low viscosity and easy to vaporize is often used. At present, the two-phase flow circuit driven by gear pump is widely used. Due to the latent heat transfer technology of phase change, the gear pump only needs to provide a small flow rate and a low head. It belongs to the category of micro magnetic gear pump in structure, and matches the flow coordination requirements of the circuit by stepless speed regulation. Even if the service characteristics are very high, the operation of the gear pump is very high Higher requirements are put forward for row characteristics, machining accuracy, average flow rate and pulsation quality.

Among them, the larger the average flow rate, the better the lightweight effect of the pump limited by high space launch cost; the better the pulsation quality, the smaller the flow pulsation coefficient, and the higher the service characteristics. In particular, the phenomenon of trapped oil should be alleviated as much as possible. At present, some research and achievements have been made on the ground gear pump. However, whether these results are fully applicable to the special requirements of aerospace ultra-low viscosity gear micropumps, especially the requirements of ultra-high service characteristics, are rarely reported in the relevant literature. In view of this, the purpose of this paper is to study the flow mean value and pulsation coefficient of aerospace ultra-low viscosity gear micro pump under trapped oil, so as to clarify its flow characteristics and achieve high performance requirements.

The results show that: (1) the axial gap is the most important factor for the symmetrical arrangement of double unloading grooves, and the quality of flow pulsation is hardly affected by simply increasing the unloading area to relieve the trapped oil pressure;

(2) the axial gap should be determined by the actual machining and assembling accuracy, and the stepped gap can meet the different requirements of trapped oil unloading and reducing axial leakage;

(3) the influence of tooth profile parameters is different, in which small modulus and large number of teeth can improve the mean value and pulse.