Centrifugal Compressor Impeller Trailing Edge for Flow Separation Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In typical centrifugal compressors, the parallel trailing edge of the impeller blades leads to boundary layer development near the shroud and hub walls, resulting in slower radial flow speeds and increased risk of flow separation, which reduces efficiency and expands the operating range.
Innovation Solution
The impeller design features a trailing edge with a first decrease section and a first increase section in the meridian plane shape, which helps to uniformize the radial flow speed across the blade span, reducing the risk of flow separation and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the trailing edge of the blade is formed parallel to the axial direction, then the blade structure is simple, but boundary layers develop near the shroud and hub walls causing flow separation and stall
Solution Approach 1:
The trailing edge of the blade is designed with a curved surface instead of a flat parallel configuration. The curved trailing edge surface is configured to reduce the development of boundary layers near the shroud and hub walls, thereby preventing flow separation and stall while maintaining structural simplicity
Solution Approach 2:
The curved surface is specifically applied to the trailing edge portion of the blade, while the rest of the blade maintains its conventional structure. This localized modification targets the specific area where boundary layer separation occurs, improving flow stability without complicating the overall blade design
2Stress or pressure
If the outer diameter of the impeller is uniformly expanded from base end to tip end, then the centrifugal stress is reduced, but flow bias in the blade span direction cannot be suppressed
Solution Approach 1:
The impeller diameter is not uniformly expanded but is instead varied locally along the blade span. The diameter is smaller near the hub and larger near the tip, creating a non-uniform expansion that suppresses flow bias in the blade span direction while maintaining acceptable centrifugal stress distribution
Solution Approach 2:
The impeller diameter varies asymmetrically along the blade span, with different diameter values at different radial positions. This asymmetric configuration creates a more favorable flow distribution across the blade span, improving compressor efficiency while keeping centrifugal stress within acceptable limits
3Productivity
If the trailing edge is made curved to reduce flow separation, then efficiency is improved, but manufacturing complexity increases
Solution Approach 1:
The curved trailing edge surface is designed with a specific curvature radius that can be achieved through conventional machining operations. The curvature is optimized to reduce flow separation while remaining compatible with standard manufacturing processes, avoiding the need for complex or specialized manufacturing techniques
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 flow bias in the blade span direction, reduces loss due to separation, and enhances the operating range of the centrifugal compressor, resulting in a more efficient and wider-ranging compressor.
Implementation Method 1
boundary layers develop on a downstream side of the impeller in the vicinity of a wall surface on a shroud wall portion side facing a tip end of the blade and in the vicinity of a wall surface on a hub wall portion side
Implementation Method 2
a risk of an increase in loss due to separation of a flow in the vicinity of the wall surface on the shroud wall portion side and in the vicinity of the wall surface on the hub wall portion side
Data Source
AI summary
An impeller (10) of a centrifugal compressor (4) is provided with a hub (14) and a plurality of blades (16) provided at intervals in a circumferential direction of the impeller (10) on an outer peripheral surface of the hub (14). In a meridian plane shape of the blades (16), as the coordinate axes with the origin at a tip end (30s) of a trailing edge (30) of the blades (16), an X-axis connecting the tip end (30s) and a base end (30h) of the trailing edge (30) and a Y-axis orthogonal to the X-axis are defined. When a direction from the tip end (30s) toward the base end (30h) along the X-axis is defined as a positive direction of the X-axis and a direction toward the outside in a radial direction of the impeller (10) along the Y-axis is defined as a positive direction of the Y-axis, the trailing edge (30) in the meridian plane shape of the blades (16) includes a first decrease section (30a) extending so that the Y-coordinate decreases as the X-coordinate increases, and a first increase section (30b) positioned between the first decrease section (30a) and the base end (30h) and extending so that the Y-coordinate increases as the X-coordinate increases.