Centrifugal Compressor Impeller Blade Angle Distribution
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Solution Overview
Problem
Centrifugal compressors face challenges in increasing peripheral speed without compromising the structural integrity of the impeller cover due to increased centrifugal force, which leads to deformation and stress on the cover.
Innovation Solution
The impeller design incorporates a unique blade angle distribution, with a maximum blade angle difference between the disc-side and cover-side blades, enhancing stiffness without increasing weight, and a connection member to distribute stress effectively, thereby reducing deformation and stress on the cover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rotational speed of the impeller is increased to achieve larger capacity and smaller dimension, then the peripheral speed increases, but the centrifugal force acting on the cover increases causing deformation and stress
Solution Approach 1:
The blade angle is designed to vary locally along the blade length, with a larger angle at the disc-side end portion and a smaller angle at the cover-side end portion. This local variation in blade geometry creates differential stiffness distribution that counteracts centrifugal force effects on the cover without requiring increased cover thickness.
Solution Approach 2:
The invention addresses the cover deformation problem by introducing a new design dimension - the blade angle distribution along the blade length - rather than simply increasing cover thickness in the radial direction. This transforms the solution from a one-dimensional thickness increase to a multi-dimensional geometric optimization.
2Strength
If the wall thickness of the inner peripheral portion of the cover is increased to prepare for increased centrifugal force, then the stiffness of the inner peripheral portion increases, but the weight increases making it more susceptible to centrifugal force
Solution Approach 1:
Instead of uniformly increasing cover thickness, the invention applies local quality by varying the blade angle specifically at different portions of the blade. The disc-side end portion has a larger blade angle for stiffness, while the cover-side end portion has a smaller angle, creating localized structural optimization without adding overall weight.
Solution Approach 2:
The invention changes the geometric parameter of the blade angle along the blade length rather than changing the material parameter of cover thickness. This parameter change in blade geometry provides the necessary stiffness to counteract centrifugal force effects without increasing the weight of the moving impeller.
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 effectively suppresses cover deformation and circumferential stress, allowing for higher peripheral speeds and larger capacity with smaller dimensions in centrifugal compressors.
Implementation Method 1
Increasing the rotational speed of the impeller increases centrifugal force acting on the impeller
Data Source
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AI summary
The impeller of a rotating machine according to at least one embodiment of the present discloser is provided with: a disc; a cover disposed on an opposite side of a radial passage from the disc in an axial direction; and a blade disposed between the disc and the cover. In a dimensionless position along a camber line of the blade when the position of a leading edge of the blade is defined as 0 and the position of a trailing edge of the blade is defined as 1, a position where an angle difference between a first blade angle at a disc-side end portion of the blade and a second blade angle at a cover-side end portion of the blade is maximum is in a range of 0.5 or more and 1 or less. The first blade angle is -10 degrees or more and 0 degrees or less at the position where the angle difference is maximum.