加注系统是装备有液体推进剂的火箭、导弹地面设备的重要组成部分。其核心部件是航天加注泵，用以输送液体，然而当其发生故障，就可能造成加注任务的推迟甚至失败。由于应用于航天领域，所以对航天加注泵的空间尺度、运行质量、稳定性与可靠性有着非常高的要求。因此不仅需要对航天加注泵进行地面实验，还需要对加注泵进行微重力下的数值模拟，研究在微重力下的水力性能与空化性能。然而在微重力情况下，不仅仅只是质量力的改变，还有表面力（尤其是液体的表面张力）和浸润角的变化，这些因素都可能使得航天加注泵内空化发生显著的改变。本文基于流体机械基本理论，采用液体动压悬浮技术以及叶轮与电机一体化的概念，对航天加注泵进行了水力设计和结构设计，并完成了样机的试制。为了精确地开展航天加注泵的性能试验，设计并搭建了航天加注泵综合测试实验系统。该系统包括测试系统、采集系统、控制系统，等。该试验系统美观、紧凑，操作简单，能满足航天加注泵水力性能和空化性能的精确测试，实验精度可达0.15%。利用此试验台对本文设计的航天加注泵进行了水力性能与空化性能的实验。实验结果表明，研制出的航天加注泵满足设计要求，并且运行平稳，稳定性高。为考虑微重力环境下表面张力的影响，本文引入了level-set方法，并考虑了液体与流道壁面的接触角对空化发展的影响。采用RANS模型和基于均质混合流假设的空化模型来计算航天加注泵的内部流动。本文对航天加注泵进行了水力性能与空化性能的数值模拟，并与实验数据进行了对比。结果表明：与常规数值方法相比，采用level-set方法对水力性能预测的影响不明显，但对空化性能预测却有显著的影响，可更为精确地模拟泵的内部流动；航天加注泵在微重力下的扬程略高于常重力下的扬程；在常重力与微重力下，空化都是在叶片吸力面靠近进口前缘处初生，而后向下流的叶片间流道发展。对比两种情况下的空泡体积大小和NPSHr，可以发现微重力下的空化性能优于常规重力下的空化性能。原因是由于表面张力延缓了空化的初生。本文基于流体机械基本理论，液体动压悬浮技术，磁耦合技术，叶轮与电机一体的概念，对航天加注泵的过流部件进行了设计，并完成了样机的试制。为了精确地开展该泵的性能试验，设计并搭建了航天加注泵综合测试实验系统。该系统包括测试系统、采集系统、控制系统的设计。该试验台美观，紧凑，操作简单，能满足航天加注泵水力性能和空化性能的测试。利用此试验台对本文设计的航天加注泵进行了
The fueling system is one of the most significant parts of the rocket and missile ground equipment which uses liquid propellant. The core component of the filling system is the mini pump. Once the pump is out of work, it would result in delay or failure of the refueling task. It has a very high demand for its space size, stability, quality and reliability because of its application in the field of space. So it is necessary to not only take an experiment on the ground, but also to simulate under microgravity condition to study the hydraulic performance and cavitation performance. under microgravity condition, however, not only the mass force, but also the surface force (especially the surface tension of the liquid) and attach angle will change, leading cavitation performance making a significant variation.Based on the basic theory of the fluid machinery, and the hydrodynamic suspension technology, magnetic coupling technology, concept of combined impeller with motor rotor, the hydraulic design for the flow passage components of the mini pump was built. Further, to conduct the experiment successfully, the mini pump test bench is designed, including the design of test system, acquisition system and control system. The test bench is compact and easy to operate, and it can meet the need of the hydraulic and cavitation performance test, while the accuracy can reach 0.03%. The hydraulic and cavitation performance is measured through the test bench, which shows the mini pump meets the design requirements as well as stable operation, compact structure and high stability.To consider the influence of surface tension, the level-set method is introduced in this paper.The cavitating flow inside the mini pump is numerically simulated by using RANS method and a homogeneous cavitation model. For better accuracy, the attach angle on the flow passage wall is also introduced to figureout the effect of surface tension on cavitation development under microgravity operation condition. The hydraulic and cavitation performance of the mini pump are simulated and through the comparison of the simulation data and the experimental data, it shows that using level-set method has no obvious influence on the hydraulic performance, but it has a significant influence on the cavitation performance and the vortex on suction surface is also more obvious by using the method. The numerical results indicated that the mini pump impeller head operating under the microgravity condition was a little higher than that under the conventional gravity condition. However, the difference of the hydraulic efficiency under two different gravity conditions was negligible. For both gravity conditions, cavitation inception occurs along the vane suction surface near the leading edge, and the cavity inside the pump expands toward the downstream of the blade-to-blade flow passage. If the cavity size and NPSHr are considered, cavitation performance under the microgravity condition is better than that under the constant gravity condition. The reason is that the surface tension will delay the cavitation inception and accelerate the process of cavitation.
