Variable Guide Vane Centrifugal Compressor Surge Margin
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Solution Overview
Problem
Conventional centrifugal compressors face challenges with narrow stable operation ranges due to increased intake-air resistance and reduced choke flow rates caused by fixed guide vanes and center nose cones, which limit the compressor's operation range.
Innovation Solution
A centrifugal compressor design featuring guide vanes on the housing's inner circumferential side without a center nose cone, with a variable inclination angle mechanism to control the swirl flow, reducing surge flow rates while maintaining choke flow rates, and incorporating a recirculation flow path to enhance surge margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If guide vanes are provided to swirl intake air and increase surge margin, then surge margin is improved, but intake-air resistance increases and choke flow rate decreases
Solution Approach 1:
The flow path is segmented into two separate channels: a guide vane flow path that generates swirl flow to improve surge margin, and a center flow path that allows air to pass through without guide vanes to minimize resistance and maintain choke flow rate. This segmentation allows each path to serve its specific function without compromising the other.
Solution Approach 2:
Different regions of the intake air flow are given different properties: the peripheral region uses guide vanes to create swirl flow for surge prevention, while the central region maintains straight flow with minimal resistance. This local differentiation allows simultaneous optimization of both surge margin and choke flow rate.
2Reliability
If fixed guide vanes are used to stabilize compressor operation, then surge margin is improved, but operation range is limited due to fixed inclination angle
Solution Approach 1:
The guide vanes are made movable with adjustable inclination angles rather than fixed, allowing the compressor to adapt to different operating conditions. The guide-vane moving mechanism enables real-time adjustment of vane angles to optimize performance across varying flow rates and surge conditions, thereby expanding the operational range while maintaining surge margin.
3Ease of operation
If center nose cone is positioned in central space to direct air flow, then flow direction is controlled, but intake-air resistance increases and choke flow is reduced
Solution Approach 1:
The center nose cone is completely removed from the design, eliminating the source of unnecessary resistance in the central flow path. Instead of using a nose cone to direct flow, the invention relies on the natural flow patterns and guide vanes positioned at the periphery to control air direction, thereby maintaining choke flow rate while still achieving proper flow direction control.
4Reliability
If recirculation flow path is provided to recirculate intake gas, then surge margin is improved, but device complexity increases
Solution Approach 1:
The recirculation flow path is merged with the existing housing structure by forming it as an integrated component of the housing rather than adding separate external components. This integration allows the recirculation function to be achieved while minimizing additional structural complexity and maintaining compact design.
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
The design improves surge margin and maintains choke flow rates by reducing intake-air resistance and allowing adjustable guide vane angles, thereby expanding the compressor's operation range without increasing air resistance.
Implementation Method 1
a plurality of guide vanes disposed in a circumferential direction along an inner circumferential wall of the housing between the intake-air inlet and the impeller wheel and configured to swirl the intake gas flowing in from the intake-air inlet around the rotational axis
Implementation Method 2
a recirculation flow path configured to recirculate a part of the intake gas introduced into the impeller wheel
Implementation Method 3
an impeller wheel disposed inside the housing rotatably around the rotational axis, and configured to compress intake gas which flows in from the intake-air inlet
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
An object is to position guide vanes for generating swirl flow at a housing inner circumferential side in front of an impeller wheel to improve a surge margin and to restrict decrease in a choke flow rate, while making the inclination angle of the guide vanes variable. A centrifugal compressor 19 includes a compressor housing 15, an impeller wheel 7 which compresses intake gas from an intake-air inlet 23, a plurality of guide vanes 63 disposed circumferentially along an inner circumferential wall of the intake-air channel 21 between the intake-air inlet 23 and the impeller wheel 7 to swirl the intake gas around the rotational axis, a central intake-air flow path 71 formed at an inner side of the guide vanes 63 to allow the intake gas to flow to the impeller wheel without passing through the guide vanes 63, and a guide-vane moving mechanism 73 which simultaneously changes the inclination angle of the guide vanes 63.