Turbine Casing Inner Member Flow Separation Control
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Solution Overview
Problem
The radial expansion of the inner peripheral surface of a turbine casing can lead to fluid flow separation, resulting in efficiency losses and performance deterioration, as the fluid flow cannot keep up with the expansion, causing separation and loss.
Innovation Solution
A turbine design featuring an inner peripheral member with an extraction port and a discharge port, both annular in shape, where the discharge port has a smaller cross-sectional area than the extraction port, to manage the fluid flow and reduce separation by utilizing the Coanda effect to guide the flow back onto the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the inner peripheral surface of the casing is expanded radially outward toward the downstream side, then the output of the turbine is improved, but fluid flow separation occurs leading to performance deterioration
Solution Approach 1:
The inner peripheral surface is divided into multiple expansion sections with different expansion rates. The upstream section has a larger expansion rate to increase output, while the downstream section has a smaller expansion rate to prevent flow separation. This segmentation allows the casing to simultaneously achieve high power output and maintain fluid flow attachment.
Solution Approach 2:
Different sections of the inner peripheral surface are given different local expansion characteristics. The upstream portion allows aggressive expansion for performance improvement, while the downstream portion uses gentle expansion to maintain flow stability. This local differentiation resolves the contradiction between maximizing output and preventing separation loss.
2Length of stationary object
If the inner peripheral surface of the casing is excessively expanded radially, then the radial expansion is increased, but flow separation occurs due to fluid inability to keep up with expansion
Solution Approach 1:
The expansion profile is segmented into multiple zones with progressively different expansion rates. This allows the inner peripheral surface to achieve excessive radial expansion where needed while maintaining flow attachment in critical regions through controlled expansion sections.
Solution Approach 2:
The expansion rate is made dynamic along the flow direction, transitioning from high expansion rates upstream to low expansion rates downstream. This dynamic variation in expansion characteristics allows the system to accommodate large overall expansion while preventing flow separation at critical locations.
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 design enhances turbine performance by reducing efficiency losses and preventing fluid separation, allowing for larger radial expansion without performance degradation, and promotes the Coanda effect to maintain flow adherence to the surface.
Implementation Method 1
manage the fluid flow and reduce separation by utilizing the Coanda effect to guide the flow back onto the surface
Data Source
AI summary
A turbine includes a rotor including a rotation shaft that rotates around an axis and a blade row formed on an outer surface of the rotation shaft; a casing, which covers the rotor, has a casing inner surface being expanded radially outward approaching a downstream side of the casing in a direction of the axis; and an inner member body formed to line the casing inner surface of the casing such that an extraction port is formed between an upstream side end of the inner member body and the casing inner surface. A discharge port is formed between a downstream side end of the inner peripheral member body and the casing inner peripheral surface. The extraction port and the discharge port are formed in an annular shape centered on the axis. A flow path cross-sectional area of the discharge port is smaller than that of the extraction port.