Variable Geometry Diffuser Mechanism for Compressor Surge Control
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Solution Overview
Problem
Centrifugal compressors in HVAC systems face issues with rotating stall and surge due to unsteady fluid flow, leading to noise, vibration, and efficiency reduction, particularly when operating at low fluid flow rates.
Innovation Solution
A variable geometry diffuser mechanism with a movable diffuser ring that adjusts the diffuser gap to stabilize fluid flow by varying the geometry of the diffuser at the impeller exit, using bearing assemblies to restrict radial and axial movements of the drive ring, optimizing space for high specific speed impellers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional diffuser mechanism is used, then the diffuser can be simple in structure, but it cannot effectively control airflow separation and maintain performance across varying operating conditions
Solution Approach 1:
The patent applies the dynamics principle by making the diffuser vane geometry adjustable during operation. The diffuser mechanism transitions from a fixed geometry to a variable geometry system where vanes can be repositioned to different angles, allowing the diffuser to adapt to varying operating conditions and maintain optimal performance across different airflow rates.
Solution Approach 2:
The patent applies segmentation by dividing the diffuser into multiple adjustable vanes rather than using a single fixed structure. This segmentation allows independent control of each vane, enabling precise control over airflow separation and providing adaptability while keeping each individual vane relatively simple in design.
2Reliability
If the diffuser is designed for high adaptability with variable geometry, then it can control airflow separation effectively, but the mechanism becomes more complex
Solution Approach 1:
The patent employs an intermediary mechanism (actuator system) that mediates between the control input and the diffuser vanes. This intermediary allows automated or controlled adjustment of vane positions, improving airflow separation control reliability while managing the complexity through a systematic approach rather than direct manual adjustment.
3Productivity
If a fixed geometry diffuser is used, then the mechanism is simple, but it cannot optimize performance across different operating conditions
Solution Approach 1:
The patent applies parameter changes by varying the geometric parameters of the diffuser vanes (specifically the angle of the diffuser walls) according to the square law relationship with airflow rate. This allows the diffuser to optimize its performance efficiency across different operating conditions by dynamically adjusting its geometric parameters rather than remaining fixed.
Data Source
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AI summary
A diffuser system for a centrifugal compressor is provided.. The diffuser system includes a nozzle base plate (206) that defines a diffuser gap (212), support blocks (216, 246), and a drive ring (220) rotatable relative to the support blocks. The drive ring includes cam tracks (224, 242) and bearing assemblies (226, 234) positioned proximate an outer circumference of the drive ring. The diffuser system further includes drive pins (214) extending through the support blocks and the nozzle base plate. The first end of each drive pin includes a cam follower (218) mounted into a cam track on the drive ring. The second end of each drive pin is coupled to a diffuser ring (208). Rotation of the drive ring causes axial movement of the drive pins by movement of the cam followers in the cam tracks. This results in movement of the diffuser ring to control fluid flow through the diffuser gap.