Study on Cryogenic Hybrid Journal Bearings for Rocket Thrbopumps

动静压混合轴承是一种兼具静压轴承和动压轴承特点的动静压滑动轴承。混合动力轴承的主要优点是设计尺寸小，承载能力好，准无限寿命(没有观察到的磨损)，并使用工艺液进行润滑。在未来可重复使用运载火箭(RLV)的低温火箭发动机中，通过用动静压轴承替代低温涡轮泵中的自润滑球轴承，可以显著提高涡轮泵的寿命，并且可以广泛地延长涡轮泵转速的固有限制，而机械部件的寿命是一个关键问题。为此，开展了低温动静压轴承的试验研究，根据常规计算方法得到的分析结果，设计了转速高达12万转/分的试验动静压轴承。TES…More t轴承的直径为60 mm，L/D=0.42，游隙/半径=0.001，有9个凹槽。旋转试验是利用日本宇宙航空研究开发机构Kakuda推进研究中心的滑动轴承试验台进行的。向测试轴承提供液氮，压力约为5兆帕。对小孔直径为0.51 mm的轴承的试验结果表明，自激振动的幅度比同步振动大几倍，是由于液氮空化流动引起的气锤不稳定引起的。然而，小孔直径为0.80 mm的轴承可以在高达50,000 rpm的转速下运行，没有任何自激振动。试验结果与基于试验条件的动静压系数数值预测结果的对比表明，流体旋转引起的大耦合刚度系数引起的失稳被认为是在50000转/分以上的转速下开始产生的。因此，基于上述数值预测，设计并制造了一种具有更高动静压性能的新型动静压轴承。较少

A hybrid bearing is a fluid-film journal bearing with characteristics of both hydrostatic and hydrodynamic bearings. The main advantage of hybrid bearings are small design size, good load capacity, a quasi-unlimited life (no observed wear), and the use of the process fluid for lubrication. By replacement of the self-lubricating ball bearings in the cryogenic turbopumps by the hybrid bearings, a significantly higher lifetime can be obtained and the inherent limitation of the rotational speed of the turbopumps can be widely extended in cryogenic rocket engines for future reusable launch vehicles (RLVs), where the lifetime of mechanical components is a critical issue. Therefore, experimental study on cryogenic hybrid bearings was carried out to develop the high performance hybrid bearings forcryogenic turbopumps.Test hybrid bearings were designed to operate at a rotational speed of up to 120,000 rpm based on the analytical results obtained from the conventional calculation method. The tes … More t bearing has a 60 mm diameter with L/D = 0.42, clearance/radius = 0.001, and 9 recesses. Rotating tests were carried out using the journal bearing test apparatus in Kakuda propulsion research center of JAXA. Liquid nitrogen is supplied to the test bearing with a pressure of about 5 MPa. Test results for the bearing with a 0.51 mm orifice diameter show that the self-excited vibration having a several times larger amplitude than that of the synchronous vibration was induced by pneumatic hammer instability due to cavitating flow of liquid nitrogen. However, the bearing with a 0.80 mm orifice diameter can be operated at the rotational speed of up to 50,000 rpm without any self-excited vibration. Comparison between the test results and the numerical predictions of rotordynamic coefficients based on the test conditions shows that instability induced by large cross-coupled stiffness coefficients due to fluid rotation is considered to onset at the rotational speed over 50,000 rpm.Therefore, a new hybrid bearing with a higher rotordynamic performance has been designed and manufactured based on the numerical predictions described above. Less