Tangential Buffer Tube Swirl for Turbo Machine Seal Leakage
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Solution Overview
Problem
Carbon seals in turbo machines experience lubricant leakage at idle conditions due to inadequate pressure differential across the seals, caused by uneven pressure distribution in the buffer compartment, which is insufficient at idle operation.
Innovation Solution
A buffer tube introduces air flow tangentially into the buffer compartment, using a venturi and orifice plate to control velocity and flow rate, generating a uniform radial pressure gradient that increases pressure at the seal's periphery, preventing lubricant leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If compressor bleed air flows into the buffer compartment body in a direction normal to a tangential plane, then the flow enters the body directly, but this creates a stagnation area and uneven pressure distribution along the cylindrical wall, resulting in inadequate pressure at idle conditions
Solution Approach 1:
The patent inverts the conventional flow entry direction by introducing air flow tangentially to the cylindrical wall rather than normally to a tangential plane. This inversion eliminates the stagnation area and creates a uniform pressure distribution pattern, resolving the contradiction between flow entry speed and pressure distribution uniformity.
2Reliability
If the pressure in the buffer compartment is increased to prevent lubricant leakage at idle, then the seal effectiveness improves, but the existing flow introduction method creates uneven pressure distribution that undermines this pressure increase
Solution Approach 1:
The patent applies inverted flow introduction by entering air flow tangentially to the cylindrical wall, which creates a uniform pressure distribution pattern. This ensures that when pressure is increased to prevent lubricant leakage, the pressure is evenly distributed across the seal, maintaining seal effectiveness without creating localized high-pressure zones that would cause uneven sealing.
3Stress or pressure
If a buffer tube introduces flow tangentially to generate a swirl and uniform radial pressure gradient, then the pressure distribution becomes uniform and seal effectiveness improves, but the system complexity increases with additional flow control devices
Solution Approach 1:
The patent utilizes pneumatic principles by introducing air flow tangentially to generate a swirl and uniform radial pressure gradient through the buffer tube. This pneumatic approach achieves uniform pressure distribution without requiring complex mechanical flow control mechanisms, as the swirl flow naturally creates the desired pressure pattern.
Solution Approach 2:
The patent changes the flow parameters by controlling the flow rate and velocity through the buffer tube to generate the desired swirl and pressure gradient. By adjusting these parameters, the system achieves uniform pressure distribution while keeping the overall system design relatively simple, avoiding the need for multiple complex flow control devices.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution ensures a sufficient pressure differential across the carbon seals at idle conditions, effectively preventing lubricant leakage by creating a uniform radial pressure gradient within the buffer compartment.
Implementation Method 1
The buffer tube introduces flow generally tangential to an inner surface of the body for generating a swirl within the buffer compartment
Implementation Method 2
The swirling flow within the body at the desired flow rate and velocity generates a uniform radial pressure gradient
Implementation Method 3
The buffer tube includes a velocity control device such as a venturi arranged at an exit of the tube to control the velocity of the flow entering the body
Implementation Method 4
A flow control device such as an orifice plate is arranged upstream of the venturi to control the flow to a desired flow rate
Data Source
AI summary
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.