Centrifugal Compressor Casing Treatment for Surge Restriction
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Solution Overview
Problem
Current centrifugal compressors face limitations in their operating range due to surging caused by fluid backflow, which restricts their functionality, and existing casing treatments only partially address this issue.
Innovation Solution
The compressor design includes a casing with a tongue at the boundary between the discharge port and annular flow passage, featuring a downstream slot that pulsates along the circumferential direction, with the most downstream point positioned within a specific range to effectively recirculate fluid and enhance surging restriction, and an inner wall cylinder body that can be rotated to optimize the slot's position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a slot is formed along the entire circumference of the casing wall surface near the upstream end of the impeller, then fluid recirculation is achieved and surging is restricted, but the operating range cannot be further expanded
Solution Approach 1:
The invention changes the slot configuration from a full circumferential slot to a localized slot with specific angular positioning (within -150° to +30° relative to the tongue). This local quality change optimizes fluid recirculation at critical positions while avoiding adverse effects from circumferential slots, thereby improving surging restriction without limiting operating range expansion
Solution Approach 2:
The invention introduces an inner wall cylinder body that can rotate about the rotary shaft to dynamically adjust the slot's rotational position. This dynamic adjustment capability allows optimization of slot positioning for different operating conditions, enabling both improved surging restriction and expanded operating range
2Ease of manufacture
If the downstream slot position is fixed in the casing, then manufacturing is simplified, but adequate slot positioning for optimal surging restriction cannot be easily achieved
Solution Approach 1:
The inner wall cylinder body is designed to rotate relative to the casing, transforming the fixed slot positioning problem into a dynamic adjustment problem. This allows the slot to be positioned at optimal angles for different operating conditions without requiring complex precision manufacturing of the casing itself
Solution Approach 2:
The slot positioning function is segmented from the casing structure and transferred to the rotatable inner wall cylinder body. This segmentation allows independent optimization of slot positioning without complicating the overall casing manufacturing process
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 significantly expands the operating range of the centrifugal compressor by improving the surging restriction effect, allowing for more efficient operation and increased performance by effectively managing pressure distribution and fluid recirculation.
Implementation Method 1
fluid partially recirculates from a high-pressure portion locally generated in the impeller when flow volume is small to the upstream side from the impeller, so that surging is restricted
Implementation Method 2
an impeller that rotates at high speed, and a casing that houses the impeller while forming a scroll flow passage around the impeller
Data Source
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AI summary
A centrifugal compressor includes an impeller, a casing, an impeller housing portion for housing the impeller, an inlet port provided coaxially with the impeller, an annular flow passage provided so as to surround the impeller, a discharge port communicated with the annular flow passage, an annular chamber provided around the inlet port, a downstream slot communicating a downstream end of the annular chamber with the impeller housing portion, and an upstream slot communicating an upstream end of the annular chamber with the inlet port. The downstream slot draws a one-cycle curved line that pulsates in an axial direction of the inlet port with a predetermined amplitude. A most upstream point on a center line of the downstream slot is located at an upstream end portion of the impeller blades when seen along a direction perpendicular to a direction of a rotary shaft of the impeller. According to the centrifugal compressor, it becomes possible to expand its operating range by improving a surging restriction effect brought by more effective casing treatment.