Abstract
The shaft mechanical face seal in a high-speed turbopump of a liquid rocket engine often operates under extremely harsh conditions. For example, a low-temperature and low-viscosity fluid (such as liquid oxygen or liquid hydrogen) is used as a lubricant. The performance of the seal rings, especially the friction and wear behavior, directly determines whether the seal functions normal. In this study, the friction and wear behavior of several ring materials are tested using a pin-on-disk tribo-tester, and the wear morphology of the ring is investigated. The friction coefficients (COFs) and mass-wear rates under dry-friction and water-lubricated conditions, which are used to simulate low-viscosity conditions, are obtained. The results show that at a pressure-velocity (PV) value of 2.4 MPa·(m/s), the COF between the copper graphite (stator) and copper-chrome alloy disk (rotor) is low (with a value of 0.18) under the dry-friction conditions, and the 5-min wear mass of the copper graphite is approximately 2 mg. Under the water-lubricated conditions, compared with other materials (such as copper-chrome alloy, S07 steel, alumina ceramic coating, and nickel-based calcium fluoride), the S07 steel with a diamond-like carbon film is preferred for use in a high-speed turbopump under extreme conditions. The results of this study can provide theoretical and experimental guidance in the design of mechanical face seals in liquid rocket engines.
Highlights
Because the high-speed turbopump in a liquid rocket engine operates under extreme operating conditions, the shaft mechanical face seal in the turbopump is often made of a metal rotor and a graphite ring as the stator, which includes copper graphite rings [1, 2]
Five materials for mechanical face-seal pairs (S07 steel, alumina ceramic coating, diamond-like carbon (DLC) film, copper–chromium alloy, and nickel-based calcium fluoride) are proposed, and their friction and wear behavior are investigated under dry-friction and water-lubricated conditions
The PV values under the dry-friction and water-lubricated conditions are different because the actual engineering conditions of the mechanical seal in the liquid rocket engine are considered
Summary
Because the high-speed turbopump in a liquid rocket engine operates under extreme operating conditions, the shaft mechanical face seal in the turbopump is often made of a metal rotor and a graphite ring as the stator, which includes copper graphite rings [1, 2]. Studies on the performance of this type of mechanical seals under such harsh conditions require gradual transition and development from the poor lubrication of lowviscosity fluid tests (such as in dry friction and waterlubricated conditions) to low-temperature liquidnitrogen simulation, and to actual liquidoxygen or liquid-hydrogen experiments. Five materials for mechanical face-seal pairs (S07 steel, alumina ceramic coating, diamond-like carbon (DLC) film, copper–chromium alloy, and nickel-based calcium fluoride) are proposed, and their friction and wear behavior are investigated under dry-friction and water-lubricated conditions. The results provide both theoretical and experimental guidance for the design of mechanical face seals in a liquid rocket engine
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