8/12/2019 Articulo Hydrostatic Bearing JOSE ESCOBAR

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JOSE LUIS ESCOBAR_200028583

Hydrostatic Bearings for Cryogenic Rocket Engine Turbo pumpsJ. M. ReddecliffandJ. H. Vohr[+] Author AffiliationsJ. of Lubrication Tech.91(3), 557-575 (Jul 01, 1969) (19 pages)doi:10.1115/1.3554989History: Received

August 08, 1968; Online August 23, 2011

Abstract

This paper summarizes an analytic and experimental investigation of hydrostatic bearings for use in high-

pressure cryogenic rocket engine turbopumps. A hydrostatic bearing analysis was developed to predict

bearing steady-state and time-dependent (stability) performance. The analysis accounts for the effects of

turbulence, inertia, and compressibility in the fluid film. Bearing design charts were generated from the

analysis to permit rapid prediction of bearing performance and to aid in the selection of optimum bearing

configuration. Liquid hydrogen and liquid oxygen turbopump conceptual designs were prepared and the

designs were used to establish hydrostatic bearing size and performance requirements. The turbopump

designs included provision for operation when bearing supply pressure is insufficient to support the rotor.

Two bearing designs, one LH2 and one LO2 , were fabricated and tested in a test rig. Test bearing designs

met turbopump requirements and included the turbopump start-stop rotor support provision. Experimental

data for both test programs agreed well with steady-state predictions and the bearings were stable under all

conditions. Both test bearing designs were in excellent mechanical condition after testing, which included 10

simulated turbopump start-stop cycles.

A hydrostatic bearing is a mechanical device that uses nothing more than a thin film of fluid or

gas to support its load. Also known as afluid bearing,a hydrostatic bearing uses an externally

pressurized source of air, oil, or water to form a barrier film between the outer casing of the

bearing and the shaft it supports. The rotational speed of the shaft then maintains a high

pressure in the surrounding fluid which supports the shaft with very little friction. Hydrostatic

bearings are used in applications where high working loads, speeds, and precision

requirements demand bearings with a long service life, low noise, and minimal vibration. A

hydrostatic bearing delivers far superior performance in these areas and is far more cost

effective than conventional ball or roller bearings.

The device works by having a fluid pumped under pressure into the space between the device

or machine shaft and the outer casing of the bearing. The fluid enters the bearing through a

restrictive opening and is kept in the bearing cavity by seals. If some of the fluid should escape,

the gap between the shaft and the casing will decrease, causing the pressure in the fluid to

increase. This increase in pressure forces the surfaces apart again which makes the fluid

bearing largely self regulating and allows for very fine tolerance control.

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8/12/2019 Articulo Hydrostatic Bearing JOSE ESCOBAR

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When compared to ball or roller bearings, hydrostatic bearings are very simple in design,

manufacture, and operation. Conventional bearings require the precision machining of balls or

rollers and the inner and outer casings they run in. This is obviously expensive and time

consuming especially when the limited lifespan of these bearings is taken into account. Ball

and roller bearings also generate considerable amounts of noise and vibration which make

them undesirable for high precision use. A hydrostatic bearing runs with very little friction and

vibration and generates almost no noise. This makes it ideal for high precision applications

such as disk drives.

Hydrostatic bearings are also cheaper to maintain and have particularly long service lives. A

good example of this longevity is the hydrostatic bearing set installed in the Holtwood

hydroelectric plant in Pennsylvania. These bearings were installed in 1912 and have run

continuously ever since with no parts being replaced. The manufacturers calculate that the

bearings would have a maintenance free life span of approximately 1,300 years. These

bearings carry total loads in the region of 205 tons and are an excellent example of the

efficiency and long service life of the hydrostatic bearing.