Experimental study on foil bearing for the hottest

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Experimental study on foil bearing for hydrogen and oxygen turbine pump

[Abstract] bearing problem is one of the key technologies encountered in the development of hydrogen and oxygen engine turbine pump, and the test run often fails due to bearing failure. Therefore, this issue has always been of great concern and importance to relevant personnel. Foil bearing has the characteristics of high speed, long life and high reliability. Its performance, structure and working principle, design scheme, theoretical calculation and test results are described. It is expected that foil bearing will replace the ball bearing now used in rocket engine turbopump

Experiment and Research of Foil Bearing for LH2/LOX Turbo-Pump

Ding Zengjie

(Beijing Institute of Liquid Rocket Engine ,Beijing, 100076)

Abstract Bearing is one of technical cruxes in development of LH2/LOX engine turbo-pump. Breakdowns of bearings may often lead to fai1ure of engine test. Theremore, footwear peeling performance test: peeling is the key to the quality of finished shoes. The question is extremely concerned by the researchers It is reported that boil bearing possesses many features,such as , higher speed, longer life-span and higher reliability, etc. The paper recounts the performance, structure, work principle,theoretical computation of design schenme and experimental result of boil bearing. It is ExPEC even abandoned that foot bearing is substituted for ball bearing used in present turbopumps

Key Words Metal foil,Liquid bearing,Turbine pump,Test scheme design.

The problem of bearing is one of the key technologies encountered in the development of hydrogen oxygen engine turbopump. The failure of test run is often caused by the failure of bearing. Therefore, this issue has always been of great concern and importance to relevant personnel

this topic belongs to the world's leading-edge technology tracking research project. Allied signal has done a lot of work in this regard, which makes the design of fixtures more difficult. It is said that foil bearings have the characteristics of high speed, long life and high reliability. These characteristics of bearings are desired by rocket engine turbopumps. Based on this situation, the ultimate goal of our research is to replace the ball bearings used in turbopumps with foil bearings

2 structure and working principle of foil bearing

foil bearing is a self acting hydrodynamic liquid film bearing. The structure of foil bearing is shown in Figure 1. Its main component is a group of foils arranged obliquely, overlapped and evenly around the shaft. The bent end of the foil is clamped with the groove of the bearing seat to prevent the foil from sliding along the circumference. These foils have a specific radius of curvature and thickness. When the shaft does not rotate, the foil remains in contact with the shaft; When the shaft works, a wedge-shaped liquid film is formed between the shaft and the foil, so that the sensor types of the electronic universal experimental machine on the market at present include S-type, spoke foil and shaft separation. In order to solve the friction and wear problems of the rotating shaft during startup and shutdown, a self-lubricating layer is coated (plated) on the working surface where the foil contacts the shaft. According to the data, this self-lubricating layer has been tested 100000 times with air in the laboratory, and the effect is good

compared with liquid film, the stiffness of foil is low. In order to adjust the displacement deviation or temperature deformation, the foil can be flexed. This feature is very suitable for low temperature operation. In this respect, foil bearings are much better than other liquid film bearings with rigid geometry. In addition, the foil with low stiffness is matched with the shaft with greater rigidity than the foil bearing, which can make the rotor vibration mode of the shafting at the first and second critical speeds appear rigid. Compared with the design speed of the rotor, the first and second critical speeds are very low, but the third critical speed is much higher than the design speed. The typical critical speed and dynamic response characteristic curve of rotor is shown in Figure 2. It can be seen from the figure that a large operating range without critical speed is provided between the 1st, 2nd critical speed and the 3rd critical speed

Fig. 2 Comparison of rotor dynamic response and mechanism speed

in foil bearing, the extruded liquid film forms a good damping, which is the same as the Coulomb friction formed at the contact of overlapping foil and the support of bearing seat. The damping characteristics of foil bearing measured in the experiment are shown in Figure 3. It can be seen from the figure that the damping of foil bearing is greater than that of hydrostatic bearing

Fig. 3 damping characteristics of foil bearing

due to the good flexibility and damping characteristics of foil, foil bearing has good anti vibration performance. According to the information, the machinery using foil bearings has successfully withstood a vibration load of 100 g

foil bearings are not sensitive to mass unbalance forces. In turbopumps, the cooling flow required by foil bearings is generally less than 1% of the pump flow, which is much less than that of hydrostatic bearings

As a new type of bearing, foil bearing has many advantages:

A) simple mechanical design and low production cost

b) there is no trap of critical speed within the working range

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