Impeller Baffle Ribs for Gas Turbine Pressure Sealing
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Solution Overview
Problem
The pressure at the impeller backface and tip of gas turbine engines is often too low, despite the presence of an impeller baffle, which can lead to insufficient pressurization of the engine air system and oil leakage from bearing cavities.
Innovation Solution
An improved impeller baffle design with radially disposed ribs and air slots is introduced, which slows down the swirling air behind the impeller backface, increasing air pressure and enhancing the sealing efficacy of carbon seals by reducing air velocity and increasing pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If an impeller baffle is disposed downstream of the impeller backface to act as a diffuser, then the air pressure is locally increased, but the pressure at the impeller backface tip remains too low
Solution Approach 1:
The impeller baffle is segmented with multiple radially disposed ribs extending into the airspace. These ribs divide the airflow path and create multiple diffuser passages, allowing more effective distribution of the diffusing action across the entire baffle surface, including the previously problematic tip region.
Solution Approach 2:
The ribs are strategically positioned at specific radial locations and angles to create localized diffuser passages where pressure buildup is most needed. This localizes the diffusing effect to critical areas, particularly near the impeller backface tip, rather than applying a uniform structure throughout.
2Stress or pressure
If the impeller backface air is used to pressurize the engine air system and bearing cavities, then the P3 Bleed Air System is driven, but insufficient pressure causes oil leakage from bearing housings
Solution Approach 1:
The ribs create preliminary diffusing action that opposes the harmful swirling flow before it can reach the bearing cavity region. By introducing counter-swirling flow patterns through the rib structures, the design prevents the low-pressure condition that would otherwise cause seal failure and oil leakage.
3Stress or pressure
If the impeller baffle slows the impeller backface air to increase pressure, then local pressure increases, but the swirling velocity is not sufficiently diminished
Solution Approach 1:
The ribs extend in the radial dimension into the airflow path, creating three-dimensional diffuser passages that effectively interact with the swirling flow. This radial extension adds a new dimensional element to the diffusing process, enhancing the conversion of rotational kinetic energy to pressure more effectively than a flat baffle surface alone.
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 improved impeller baffle effectively increases air pressure at the impeller backface, preventing oil leaks from bearing housings and improving the sealing efficiency of carbon seals, thus maintaining sufficient pressure for the engine air system.
Implementation Method 1
An impeller baffle can be disposed downstream of the impeller backface and can act as a diffuser, slowing the impeller backface air to locally increase the air pressure
Implementation Method 2
slowing the impeller backface air to locally increase the air pressure
Implementation Method 3
the impeller baffle diminishes the velocity of air swirling behind an impeller backface to thereby increase air pressure to improve the efficacy of the carbon seal to thus prevent bearing oil leak
Data Source
Figure 1
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AI summary
A gas turbine engine includes a high-pressure compressor (22) having an impeller (40) and an impeller baffle (50) having a generally annular body (52), the impeller baffle (50) spaced apart from a back face (42) of an impeller (40) to create an airspace therebetween, the airspace communicating between an impeller exit and an apparatus to be pressurized, the impeller baffle (50) including a plurality of generally radially-disposed ribs (56) extending into the airspace for diminishing the velocity of air swirling in the airspace.