Seal Integrity Testing for Gas Turbine Bearing Cavities
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Solution Overview
Problem
Existing methods for testing the seals in gas turbine engine bearing cavities are inadequate for evaluating relatively small air leakages in cavities with small volumes, as they are not designed to handle the specific leakage characteristics of these engines.
Innovation Solution
A method involving a sealed test tank with a pressure differential is used to evaluate seal integrity by measuring the time it takes for pressure to balance between the tank and the cavity, with the test tank's internal volume calculated based on the leakage area and ambient conditions, and comparing this time to a predetermined reference time to assess the seal's integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If known seal testing methods are used, then they work for relatively small air leakages or large volume cavities, but they are ineffective for small volume cavities with relatively large acceptable air leakages
Solution Approach 1:
The patent changes the testing parameters by creating a pressure differential between the test tank and bearing cavity, and by carefully selecting the test tank volume to be sufficiently large to amplify the pressure change signal from small leakages. This allows the same testing methodology to effectively detect leakages across different cavity size and leakage rate scenarios.
Solution Approach 2:
The patent introduces an intermediary test tank with a specifically designed volume that acts as a signal amplifier. The test tank serves as a mediator between the small bearing cavity and the measurement system, converting small leakage flows into measurable pressure changes that can be accurately detected regardless of the original cavity size.
2Volume of stationary object
If the test tank volume is too small, then the testing setup is compact, but the pressure change signal from leakage is too weak to measure accurately
Solution Approach 1:
The patent determines the optimal test tank volume by analyzing the relationship between tank volume, leakage rate, and pressure change signal strength. By selecting a tank volume that satisfies V ≥ (A_leak × √(Tamb × Rgas) × δtime) / k, the system ensures the pressure change signal is sufficiently strong for accurate measurement while maintaining reasonable system compactness.
Solution Approach 2:
The patent employs an excessively large test tank volume relative to the bearing cavity volume, ensuring that the pressure change signal from even small leakages is amplified enough for accurate detection. This excessive action guarantees measurement precision at the cost of increased system size.
3Measurement precision
If the test tank volume is too large, then the pressure change signal is strong for accurate measurement, but the testing setup becomes cumbersome
Solution Approach 1:
The patent establishes a mathematical relationship that defines the minimum required test tank volume based on leakage area, ambient temperature, gas constant, and time measurement accuracy. This parameter optimization allows the system to achieve adequate measurement precision with the smallest necessary tank size, avoiding unnecessary system complexity.
Solution Approach 2:
The patent uses a volume ratio Rv between 10 and 53, representing a partial action approach where the test tank volume is sufficiently large to ensure accurate measurement but not excessively large to create unnecessary complexity. This optimized range balances measurement accuracy with system compactness.
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
This method effectively evaluates the sealing integrity of gas turbine engine seals by providing a reliable and accurate assessment of leakage rates, ensuring the seal meets design parameters, even in small volume cavities.
Implementation Method 1
generating a pressure differential between the test tank and the cavity by creating an initial test pressure within the test tank that is different than the ambient pressure
Data Source
AI summary
The method for testing the integrity of a seal of a cavity in an engine includes providing a sealed test tank external to the cavity, the test tank having an internal volume that is particularly selected, as described herein. A pressure differential is generated between the test tank and the cavity, by creating an initial test pressure within the test tank that is different than an ambient pressure inside the cavity. Gas flow between the test tank and the cavity is then permitted, and a change in pressure within the test tank is measured, as is a test time required for the pressure inside the test tank to reach a reference pressure. The measured test time is compared with a predetermined reference time, and the integrity of the seal may be confirmed when the test time is greater than or equal to the reference time.