US-12624707-B2 - Fluid compressor having blow-by flow for journal bearing cooling

Abstract

An electric motor-powered centrifugal compressor having serially connected low- and high-pressure stages includes journal bearings for the shaft of the compressor, the journal bearings being contained in a motor housing that defines a motor cavity enclosing the electric motor. A labyrinth seal is arranged between the high-pressure compressor wheel and the adjacent journal bearing. The labyrinth seal allows a metered flow of fluid, constituting a fraction of the main fluid flow, to pass the labyrinth seal and flow through the journal bearing into the motor cavity for cooling the journal bearing.

Inventors

• Vijaysarathy Anbazhagan
• Darius Mehta
• Gururaj JK
• Suryakant Gupta
• Kosuvari Vamsikrishna Reddy
• Aniket Santoshwar

Assignees

• Garrett Transportation I Inc.

Dates

Publication Date

20260512

Application Date

20240125

Claims (17)

1. 1 . A compressor, comprising: a high-pressure compressor comprising a shaft, a centrifugal high-pressure compressor wheel affixed to one end of the shaft, and a high-pressure compressor housing enclosing the high-pressure compressor wheel; a motor housing affixed to the high-pressure compressor housing and containing a high-pressure journal bearing for the shaft; a labyrinth seal disposed between the high-pressure compressor wheel and the high-pressure journal bearing; an electric motor contained in a motor cavity of the motor housing; a journal bearing cooling flow path extending axially past the labyrinth seal and through the high-pressure journal bearing into the motor cavity; and wherein the labyrinth s meters blow-by flow of compressed fluid, and wherein said blow-by flow passes the high-pressure journal bearing into the motor cavity to cool the journal bearing.
2. 2 . The compressor of claim 1 , further comprising a low-pressure compressor in series with the high-pressure compressor.
3. 3 . The compressor of claim 2 , further comprising an interstage cooler arranged between the low-pressure compressor and the high-pressure compressor.
4. 4 . The compressor of claim 1 , wherein the motor cavity includes an outlet conduit configured to recirculate the blow-by flow from the motor cavity back to an inlet of the low-pressure compressor.
5. 5 . The compressor of claim 1 , wherein the labyrinth seal is configured to meter the blow-by flow at a rate less than 5% of the main flow exiting the high-pressure compressor wheel.
6. 6 . The compressor of claim 1 , further comprising a temperature sensor disposed adjacent the high-pressure journal bearing and configured to monitor bearing temperature as the blow-by flow cools the bearing.
7. 7 . The compressor of claim 1 , further comprising an intercooler arranged between the low-pressure compressor and the high-pressure compressor, the intercooler configured to reduce the temperature of the blow-by flow entering the journal bearing.
8. 8 . The compressor of claim 1 , wherein the motor cavity is configured such that the blow-by flow, after passing through the high-pressure journal bearing, impinges on end windings of the motor to cool the motor windings.
9. 9 . A method for providing cooling flow in a high-pressure compressor of a compressor, the high-pressure compressor comprising a shaft, a centrifugal high-pressure compressor wheel affixed to one end of the shaft, and a high-pressure compressor housing enclosing the high-pressure compressor wheel, the compressor further comprising a motor housing affixed to the high-pressure compressor housing, the motor housing defining a motor cavity and containing a high-pressure journal bearing for the shaft, the method comprising: operating the high-pressure compressor to compress a fluid; producing a metered cooling flow by bleeding and metering a fraction of the fluid from an exit of the high-pressure compressor stage using a labyrinth seal disposed between the high-pressure compressor wheel and the high-pressure journal bearing; and passing the metered cooling flow through the high-pressure journal bearing and into the motor cavity, and wherein the labyrinth seal meters a blow-by flow of compressed fluid, and wherein said blow, by flow passes through the high-pressure journal bearing into the motor cavity to cool the journal bearing.
10. 10 . The method of claim 9 , wherein the compressor comprises a two-stage compressor having a low-pressure compressor arranged in series with the high-pressure compressor, the method further comprising: operating the low-pressure compressor to the fluid; and cooling the fluid discharged from the low-pressure compressor prior to the fluid entering the high-pressure compressor.
11. 11 . The method of claim 9 , further comprising discharging the blow-by flow from the motor cavity and recirculating the discharged flow to an inlet of a low-pressure compressor stage.
12. 12 . The method of claim 9 , wherein the labyrinth seal meters the blow-by flow at a mass flow rate less than 5% of the high-pressure compressor discharge flow.
13. 13 . The method of claim 9 , further comprising sensing a temperature of the high-pressure journal bearing and controlling the blow-by flow in response to the sensed temperature.
14. 14 . The method of claim 9 , further comprising intercooling fluid discharged from a low-pressure compressor prior to entry into the high-pressure compressor, thereby reducing the temperature of the blow-by flow cooling the journal bearing.
15. 15 . The method of claim 9 , further comprising directing the blow-by flow, after passage through the journal bearing, to cool end windings of the motor.
16. 16 . The method of claim 9 , wherein the blow-by flow and a motor cooling flow are combined within the motor cavity and exhausted through a common outlet.
17. 17 . The method of claim 9 , further comprising metering the blow-by flow by varying a clearance of the labyrinth seal.

Description

BACKGROUND OF THE INVENTION This application relates generally to turbomachinery, and relates more particularly to high-pressure compressors of the centrifugal type. High-pressure compressors are used in a variety of applications, such as industrial air compressors, fuel cell compressors, refrigerant compressors, and the like. Typically, multi-stage arrangements are employed in order to achieve the required high pressure ratio. A common architecture, for example, is a serially connected pair of serial two-stage compressors, yielding a four-stage compression process. The journal bearing adjacent the stage-4 compressor is at particular risk of overheating because of the relatively low levels of cooling flow typically available in such compressors, combined with the relatively high temperature of the fluid within the stage-4 compressor. SUMMARY OF THE DISCLOSURE The present disclosure describes embodiments of compressors defining a journal bearing cooling flow path that facilitates effective cooling of the journal bearing via blow-by flow. In accordance with one embodiment described herein, a compressor comprises: a high-pressure compressor comprising a shaft, a centrifugal high-pressure compressor wheel affixed to one end of the shaft, and a high-pressure compressor housing enclosing the high-pressure compressor wheel;a motor housing affixed to the high-pressure compressor housing and containing a high-pressure journal bearing for the shaft;a labyrinth seal disposed between the high-pressure compressor wheel and the high-pressure journal bearing;an electric motor contained in a motor cavity of the motor housing; anda journal bearing cooling flow path extending axially past the labyrinth seal and through the high-pressure journal bearing into the motor cavity. The side of the labyrinth seal closer to the high-pressure compressor wheel is in fluid communication with the high-pressure fluid at the exit of the wheel. A fraction of such high-pressure fluid (i.e., the “bleed portion”) flows radially inwardly along the back disk of the wheel into the space adjacent to the labyrinth seal. The pressure on the opposite side of the labyrinth seal closer to the motor cavity is relatively lower in pressure, and the bleed portion of the fluid, also referred to herein as the “blow-by flow,” passes through the labyrinth seal. The labyrinth seal is effectively a metering device that governs the flow split between the blow-by flow and the main flow of fluid exiting the high-pressure compressor wheel. After passing through the labyrinth seal, the blow-by flow proceeds through the high-pressure journal bearing into the motor cavity, thereby cooling the journal bearing. In one embodiment, the compressor further comprises a low-pressure compressor in series with the high-pressure compressor, and an interstage cooler arranged between the low-pressure compressor and the high-pressure compressor. Cooling of the fluid coming out of the low-pressure compressor prior to entering the high-pressure compressor is effective to further improve the cooling of the high-pressure journal bearing. The invention also provides a method for providing cooling flow in a high-pressure compressor of a compressor, the high-pressure compressor comprising a shaft, a centrifugal high-pressure compressor wheel affixed to one end of the shaft, and a high-pressure compressor housing enclosing the high-pressure compressor wheel, the compressor further comprising a motor housing affixed to the high-pressure compressor housing, the motor housing defining a motor cavity and containing a high-pressure journal bearing for the shaft. The method comprises: operating the high-pressure compressor to compress a fluid;producing a metered cooling flow by bleeding and metering a fraction of the fluid from an exit of the high-pressure compressor stage using a labyrinth seal disposed between the high-pressure compressor wheel and the high-pressure journal bearing; andpassing the metered cooling flow through the high-pressure journal bearing and into the motor cavity. The compressor can comprise a two-stage compressor having a low-pressure compressor arranged in series with the high-pressure compressor. The method accordingly can further comprise: operating the low-pressure compressor to the fluid; andcooling the fluid discharged from the low-pressure compressor prior to the fluid entering the high-pressure compressor. BRIEF DESCRIPTION OF THE DRAWINGS Having described the present disclosure in general terms, reference will now be made to the accompanying drawing(s), which are not necessarily drawn to scale, and wherein: FIG. 1 is an axial end view of an electric motor-powered compressor in accordance with one embodiment of the invention; FIG. 2 is a cross-sectional view along line 2-2 in FIG. 1; FIG. 3 is a magnified view of a portion of FIG. 2, showing details of the cooling flow path for the high-pressure journal bearing; and FIG. 4 is a schematic view of a system employing