Kenjiro Kamijo

Tribo-characteristics of self-lubricating ball bearings for the LE-7 liquid hydrogen rocket-turbopump

The tribo characteristics of self-lubricating 40-mm-bore ball bearings with a retainer of glass cloth-polytetrafluoroelhylene (PTFE) laminate, which has elliptical pockets with a large pocket clearance, were tested under thrust loads at speeds up to 50000 rpm, 2 million DN, in liquid hydrogen (LH2) and in liquid nitrogen (LN2). During testing, the bearing torque, outer-race temperature, and electric resistance between the inner and outer races were monitored to verify the formation and rupture of a PTFE transfer film. Testing showed that the bearings having the elliptical retainer pockets were superior to the conventional bearings with circular pockets. It was determined that at the maximum inner race spinning velocity of about 5 mls a PTFE transfer film could sustain the maximum Hertz stress, up to about 2000 N/mm2, in LH2, without severe film rupture resulting in bearing seizure. In LN2, the critical load capacity of PTFE transfer film with bearing seizure was about 2700 N/mm2. Presented as a Society of...

Experimental study on high-pressure gas seals for a liquid oxygen turbopump

An experimental study on high-pressure gas seals was carried out in order to investigate the feasibility of a liquid oxygen (LOX) turbopump rotating-shaft seal system for the LE-7 rocket engine of Japan. Floating-ring seals 50 millimeters in diameter were successfully operated under the following conditions: a maximum rotational speed of 25,000 rpm and a maximum sealed hydrogen gas pressure of about 15 MPa. The leakage rates obtained in the experiment were in good agreement with the analytical results obtained from the quasi-one-dimensional compressible flow equation. Observational results indicated that the housing sealing surface coated with rf (radio frequency)-sputtered molybdenum disulphide (MoS2) film was extremely effective in reducing the wear on the carbon sealing surfaces. A 100-millimeter-diameter double segmented hydrodynamic circumferential seal designed for a helium gas purge system was tested in order to investigate the wear process of the carbon segmented-rings. The seal was operated for a...

Improvements of Inducer Inlet Backflow Characteristics Using 3-D Inverse Design Method

The three-dimensional inverse design method was applied to improve the inlet backflow characteristics of highly loaded turbopump inducers for a liquid hydrogen rocket engine. Flow mechanisms, both for conventional and inverse design inducers, were investigated experimentally by flow field measurements and flow visualization, as well as numerically by the application CFD. The conventional inducer, which had been designed for the H-IIA rocket LE-7A engine turbopump, had a strong inlet backflow at the design point. Optimizing the blade loading distribution using the 3-D inverse design method and a CFD analysis eliminated this inlet backflow. Water model tests confirmed the elimination of inlet backflow in the inverse design inducers. However, it was confirmed that the suppressed inlet backflow tended to make cavitation occur in the blade passages and reduced suction performance. Cavitation visualization and FFT analysis of unstable phenomena were also performed in this study.

Rotor vibrations of turbopump due to cavitating flows in inducer

During the initial phase of the development of the LE7 liquid-oxygen turbopump, supersynchronous and subsynchronous shaft vibrations occurred. We experienced a very curious phenomenon, namely, that three types of shaft vibrations appeared in the tests of the turbopump under almost the same operating conditions. That is, only supersynchronous shaft vibration occurred, only subsynchronous shaft vibration occurred, or supersynchronous shaft vibration appeared just after subsynchronous vibration had disappeared concomitant with the decrease of inducer inlet pressure. First, it was clarified that the supersynchronous shaft vibration was caused by rotating cavitation which occurred in the inducer of the liquid oxygen main pump. However, considerable time was needed to identify the cause of the subsynchronous shaft vibration, because this vibration occurred under almost the same conditions as that which brought about the rotating cavitation. Finally, it was concluded that the subsynchronous shaft vibration was a cavitation-induced system oscillation, that is cavitation surge. In the present paper, we show how the subsynchronous shaft vibration was identified as cavitation surge. Some results of calculations will also be presented to explain the test results.

Development status of LE-7☆

Abstract A development program of LE-7, the first stage engine of the H-II launch vehicle, is now in a component development phase. This paper represents the results of the following tests: 1. (1) tests of the combustion devices (igniters, preburner, main chamber) 2. (2) tests of the fuel turbopump 3. (3) tests of the oxidizer turbopump.

Fatigue Strength of Rocket Pump Inducers

Various kinds of unsteady phenomena, such as cavitation surge, rotating cavitation, rotating stall, backflow cavitation, etc., have occurred in recent rocket pump inducers for booster engines because they are used under the condition of high head, high load and low suction pressure. Therefore, it is very important to estimate unsteady stress on the blades to obtain the required durability of an inducer. An analytical method to obtain fatigue life, which utilizes the results of water tests, is presented in this paper.

Preliminary Evaluation of Heat Exchanger for LACE

An experimental study on cooling the heat exchanger by liquid hydrogen was conducted to establish a method of estimating the heat exchanger performance for LACE. Based on the test results, an analytical method of estimating the liquefaction ratio, a!, and the hydrogen outlet temperature, THout of the heat exchanger is proposed to evaluate the performance of the heat exchanger. According to comparison of the specific impulse, Isp, obtained from this method of estimating a! and THout with that obtained by using the coolant-side temperature efficiencies, 4 L and r

Observation of Backflow and Prewhirl at Rocket Propellant Pump Inducer

=, in the liquefaction section and the precooler section of the heat exchanger, it was found that selecting the values of d L and r

Development history of liquid oxygen turbopumps for the LE-7 engine

c as performance indexes of the heat exchanger is one of the simplest and most effective ways for estimating the I,, value of the basic LACE. Based on this method of estimating the Isp value, the effect of the flight trajectory on the basic LACE performance was investigated. The results show that the I, value of the basic LACE has a low value iu the low flight Mach number range regardless of the difference of the flight trajectories. Therefore, the tank return feeding system using subcooled hydrogen is discussed as a way to improve the performance of the basic LACE. reulace the stored oxidizer for rocket engines by ut&ing the large cooling capacity of liquid hydrogen to liquefy atmospheric air. Moreover, LACE is greatly advantageous for application in RBCC engines because many engine components can be commonly used under both modes of operation, i.e., the LACE mode and the pure rocket mode. Various investigatorsg) have discussed typical LACE technology, namely, using liquid hydrogen to liquefy inlet air. The air liquefaction ratio ranges from 3.0 to 5.0, which is much lower than the stoichiometric ratio. As a result, the specific impulse of such a LACE is not significantly higher than that of a pure LH&02 rocket engine. Various methods4 to improve the performance of LACE have been discussed, for example, the use of slush hydrogen,) the use of a vortex-tube,5) the use of a high-pressure hydrogen-expansion liquefied engine,@ and so on. However, the key technologies needed to realize improvements have not been sufficiently investigated making it diflicult to, evaluate their feasibility, Therefore, it is necessary to clarify the required criteria for realizing the basic LACE.