Centrifugal Compressor Impeller Trailing Edge for High-Flow Efficiency
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Solution Overview
Problem
Existing centrifugal compressor impellers face issues with efficiency decrease on the high flow rate side due to separation on the shroud side and increased cutting time due to complex trailing edge shapes.
Innovation Solution
The impeller design features a trailing edge with a convex shape and larger outer diameter at the shroud-side end compared to the hub-side end, along with linear pressure and suction surfaces, allowing for line cutting and reduced separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the trailing edge has a linear shape connecting shroud-side end and hub-side end, then the cutting work time is reduced, but separation occurs on the shroud side on the high flow rate side and efficiency decreases
Solution Approach 1:
The trailing edge is designed with different local geometries: a convex curved portion at the shroud-side end and a linear portion connecting to the hub-side end. This local differentiation allows the convex portion to prevent flow separation and maintain efficiency, while the linear portion enables efficient cutting, thus resolving the contradiction between cutting time and efficiency
Solution Approach 2:
The trailing edge incorporates a convex curved portion at the shroud-side end instead of a purely linear shape. This curvature is specifically designed to prevent flow separation on the shroud side during high flow rate operation, thereby maintaining efficiency while the overall trailing edge still allows for relatively simple manufacturing
2Loss of energy
If the trailing edge includes a curved convex portion, then the possibility of separation on the shroud side is reduced, but point cutting with a tip of a cutting tool is required which increases cutting time
Solution Approach 1:
The trailing edge is segmented into two distinct portions: a convex curved portion at the shroud-side end for preventing flow separation, and a linear portion connecting to the hub-side end for enabling efficient line cutting. This segmentation allows each portion to optimize its function without requiring complex point cutting throughout the entire trailing edge
Solution Approach 2:
Instead of making the entire trailing edge convex (which would require time-consuming point cutting), the convex shape is applied only to the necessary shroud-side portion where flow separation occurs. The remaining portion uses a simpler linear geometry that allows for faster line cutting, thus achieving the necessary flow control with minimal additional manufacturing time
3Stress or pressure
If the outer diameter of the impeller is increased to increase peripheral speed, then the pressure ratio increases, but mountability is adversely affected and fatigue failure may occur
Solution Approach 1:
The impeller adopts an asymmetric outer diameter configuration where the shroud-side outer diameter is larger than the hub-side outer diameter. This asymmetric design allows the impeller to achieve the necessary pressure ratio through the larger shroud-side diameter while maintaining compact overall dimensions for improved mountability and reduced fatigue stress
Data Source
AI summary
An impeller of a centrifugal compressor includes: a plurality of blades each of which has a leading edge, a trailing edge, a pressure surface and a suction surface extending between the leading edge and the trailing edge, and a shroud-side end and a hub-side end defining the pressure surface and the suction surface together with the leading edge and the trailing edge. The pressure surface and the suction surface are each configured such that a blade element connecting the shroud-side end and the hub-side end is linear. The trailing edge is configured such that an outer diameter at the shroud-side end is larger than an outer diameter at the hub-side end, the trailing edge having a convex shape with respect to an imaginary straight line connecting the shroud-side end and the hub-side end in the trailing edge.