Turbomachinery Casing Non-Uniform Gap Design
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Solution Overview
Problem
In turbomachinery, a gap between the rotor blade tip and the casing inner surface leads to leakage flow, affecting the flow field and performance, necessitating a narrow gap while avoiding contact due to deformation, which is challenging to manage during operation.
Innovation Solution
The turbomachinery features a non-uniform gap size along the circumferential direction of the impeller, with strategic adjustments in the casing's shape and alignment to offset deformation-induced changes, ensuring a uniform gap during operation and preventing contact, including elliptical casing edges and asymmetric designs to accommodate thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the gap between the rotor blade tip and casing inner surface is narrowed to reduce leakage flow, then the efficiency of the turbomachinery is improved, but the risk of contact between the rotor blade and casing due to deformation increases
Solution Approach 1:
The casing is designed with a predetermined deformed shape that anticipates and counteracts the thermal deformation occurring during operation. By pre-deforming the casing in the opposite direction of expected thermal expansion, the gap between the rotor blade tip and casing is maintained more uniformly, preventing contact while preserving the narrow gap needed for high efficiency
Solution Approach 2:
The invention changes the geometric parameters of the casing, specifically making the inner circumferential edge elliptical rather than circular. This parameter change creates a non-uniform gap distribution during stop that compensates for thermal deformation during rotation, allowing the gap to remain narrow without causing blade-casing contact
2Productivity
If the gap size is made uniform during operation, then leakage flow is minimized and efficiency is maximized, but the complexity of designing for thermal deformation increases
Solution Approach 1:
The casing is pre-formed with an elliptical inner circumferential edge and predetermined deformation characteristics before operation. This preliminary action ensures that when thermal deformation occurs during rotation, the gap distribution becomes uniform without requiring complex real-time adjustments or control systems
Solution Approach 2:
The invention introduces asymmetry by making the inner circumferential edge of the casing elliptical rather than circular. This asymmetric geometry creates a non-uniform gap during stop that precisely compensates for thermal deformation during operation, achieving uniform gap distribution through geometric design rather than complex mechanical or control systems
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 effectively narrows the operational gap, enhancing turbomachinery efficiency by minimizing leakage flow and preventing blade-casing contact, thus maintaining performance despite thermal and mechanical deformations.
Implementation Method 1
it is necessary to avoid contact of the rotor blade with the casing, even if deformation or the like of the rotor blade and the casing is caused by operating the turbomachinery
Data Source
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Figure 15
AI summary
A turbomachinery according to an embodiment includes an impeller including at least one blade, and a casing for housing the impeller rotatably. A size of a gap between a tip of the blade and an inner surface of the casing during a stop of the impeller is formed non-uniformly over a circumferential direction of the impeller.