Flow delivery system for seals

Abstract

A turbo machine includes a housing having a bearing compartment for receiving lubrication. The housing also provides a buffer compartment for receiving air, for example, compressor bleed air. A turbine shaft is supported within the housing on a bearing for rotation relative to the housing. The bearing is arranged within the bearing compartment. A seal is arranged between the turbine shaft and the housing and separates the bearing and buffer compartments. The seal includes opposing lubrication and air sides that are respectively exposed to the bearing and buffer compartments. The buffer tube is fluidly connected to a body of the buffer compartment. A buffer tube introduces flow generally tangential to an inner surface of the body for generating a swirl within the body. The buffer tube includes a velocity control device such a venturi arranged at an exit of the tube to control the velocity of the flow entering the body. An orifice plate is arranged upstream from the venturi to control the flow to a desired flow rate. The swirling flow within the body at the desired flow rate and velocity provides a uniform pressure gradient at idle having a large enough pressure magnitude to create the desired pressure differential across the seal. The increased pressure in the buffer compartment in the vicinity of the seal prevents leakage of lubricant past the seal at idle.