Rotating Machine Impeller Cover Thickness Distribution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rotating machines, such as centrifugal compressors, face challenges in increasing peripheral speed due to deformation caused by increased centrifugal force, which leads to reduced fastening forces and potential contact issues with diaphragms.
Innovation Solution
The impeller design includes a disc with a recess and protruding portions, along with a cover having varying thicknesses, to distribute centrifugal forces effectively, reducing deformation and maintaining fastening forces, thereby allowing for increased peripheral speed without excessive weight or stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the rotational speed of the impeller is increased to increase peripheral speed, then the peripheral speed increases, but the centrifugal force increases causing impeller deformation and reduced fastening force
Solution Approach 1:
The cover is designed with non-uniform thickness distribution, having a maximum thickness at the radially inner end and a minimum thickness at the radially outer end. This local variation in thickness allows the cover to have greater strength where centrifugal forces are highest (near the center) while reducing weight at the outer periphery, thereby maintaining fastening force during high-speed rotation
Solution Approach 2:
The patent optimizes the thickness ratio parameter (minimum thickness to maximum thickness ratio between 0.2 and 0.6) to balance structural strength and weight. By changing this geometric parameter, the cover can withstand high centrifugal forces at high rotational speeds while minimizing the increase in centrifugal force that would otherwise reduce fastening force
2Speed
If the rotational speed of the impeller is increased to increase peripheral speed, then the peripheral speed increases, but deformation of the impeller occurs due to increased centrifugal force
Solution Approach 1:
The cover features localized thickness variation with maximum thickness at the radially inner end where deformation stresses are concentrated. This local reinforcement prevents deformation in the critical region while allowing the outer regions to be thinner, enabling high-speed operation without excessive deformation
Solution Approach 2:
The thicker portion of the cover at the radially inner end acts as a counterweight that balances the centrifugal forces acting on the impeller. This counterbalancing effect reduces net deformation forces, allowing the impeller to maintain its shape at higher rotational speeds
3Strength
If the thickness of the cover is increased to reduce deformation, then the strength increases, but the weight increases causing higher centrifugal force
Solution Approach 1:
Instead of uniformly increasing cover thickness, the patent applies thickness variation locally - maximum thickness at the radially inner end where strength is most needed, and minimum thickness at the radially outer end where weight reduction is most beneficial. This selective reinforcement achieves the required strength-to-weight ratio
Solution Approach 2:
The patent transitions from considering only radial thickness to optimizing the three-dimensional thickness distribution across the cover. By varying thickness in both radial and axial dimensions, the design achieves optimal strength and weight characteristics that cannot be obtained with uniform thickness
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 the reduction in fastening force and reduces circumferential stress, enabling higher peripheral speeds while minimizing weight and local stress, thus enhancing the efficiency and cost-effectiveness of rotating machines.
Implementation Method 1
increasing the rotational speed of the impeller increases the centrifugal force acting on the impeller, which causes an undesired phenomenon due to deformation of the impeller
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An impeller of a rotating machine according to at least one embodiment includes: 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. A back surface of the disc has a recess extending in a circumferential direction in a radial range where the blade is disposed.