Compressor Inner Casing Air Extraction for Leak Flow Control
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Solution Overview
Problem
In gas turbines, static pressure recovery in the diffuser leads to leak flows through recesses, causing losses as the leak flow merges with the primary flow.
Innovation Solution
A compressor design with an outlet guide vane and inner shrouds, featuring an air extraction hole in the inner casing to guide leak flows into an air extraction cavity, reducing the likelihood of leak flows reaching the upstream side and enhancing diffuser performance by suppressing swirling components and boundary layer development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a diffuser is provided to expand the flow path cross-sectional area for static pressure recovery, then the static pressure recovery is improved, but a leak flow occurs from the downstream side toward the upstream side through the recesses
Solution Approach 1:
The harmful leak flow is extracted and diverted from the recesses into a dedicated leak flow passage that leads to the air extraction cavity. This separates the leak flow from the primary flow path, preventing it from merging back into the main flow and causing energy loss, while allowing the diffuser to maintain its pressure recovery function
Solution Approach 2:
The air extraction cavity acts as an intermediary space that receives leak flow from the recesses through the leak flow passage and directs it through the air extraction hole. This intermediary structure provides a controlled path for the leak flow, preventing it from adversely affecting the primary flow while maintaining the diffuser's pressure recovery capability
2Productivity
If outlet guide vanes with inner shrouds are provided in the diffuser flow path, then the diffuser performance is improved, but recesses are formed on the inner casing for accommodating the shrouds which enable leak flow
Solution Approach 1:
The leak flow path is extracted from the recesses by providing a dedicated leak flow passage that diverts the leak flow into the air extraction cavity. This allows the recesses to continue accommodating the inner shrouds for outlet guide vanes while preventing the harmful effect of leak flow merging into the primary flow
Solution Approach 2:
The leak flow that would normally cause energy loss is converted into a beneficial flow by directing it through the air extraction cavity and out through the air extraction hole. This transforms the harmful leak flow into a controlled extraction flow that removes swirling components and boundary layer development, thereby improving overall compressor performance
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 configuration reduces losses by minimizing leak flows and improving compressor performance through increased static pressure recovery and expanded diffuser cross-sectional area.
Implementation Method 1
The diffuser is configured to expand a flow path cross-sectional area toward the downstream side. As a result, the flow velocity of a high-pressure fluid flowing into the diffuser is reduced, and the static pressure is recovered.
Implementation Method 2
An air extraction hole is formed through the inner casing in the radial direction, in a portion, in the recesses, on the downstream side in the axial direction. This configuration reduces losses by minimizing leak flows and improving compressor performance through increased static pressure recovery
Data Source
AI summary
A compressor includes a rotor including a plurality of disks, a shaft portion connected on a downstream side of the disks; and rotor blade rows fixed to the plurality of disks; a stator including a compressor casing; and a plurality of stator vane rows each provided between corresponding adjacent ones of the rotor blade rows; an outlet guide vane including blade main bodies disposed at an interval in a circumferential direction on the downstream side of the disk located most downstream, and inner shrouds connecting the blade main bodies in the circumferential direction, on an inner side in a radial direction; and an inner casing disposed on the downstream side of the disk located most downstream with a gap between the disk and the inner casing. The inner casing includes an outer peripheral wall surface having recesses accommodating the inner shrouds and forming, together with an inside surface of the compressor casing, a diffuser on the downstream side of the recesses, and an inner peripheral wall surface forming an air extraction cavity. An air extraction hole is formed in a portion, in the recesses, on the downstream side.