Variable-speed multi-stage refrigerant centrifugal compressor with diffusers
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Solution Overview
Problem
Existing multi-stage centrifugal compressors face challenges in maintaining surge-free operation at low capacity conditions and achieving efficient capacity control without relying on variable inlet guide vanes, which limits their efficiency and stability.
Innovation Solution
A refrigerant centrifugal compressor design featuring a two-stage configuration with a variable geometry diffuser downstream of the first stage impeller and a fixed diffuser downstream of the second stage impeller, eliminating the need for variable inlet guide vanes by using a movable-wall variable-geometry diffuser and a fixed-wall rotatable-vane diffuser to regulate flow and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable inlet guide vanes are used for capacity control, then the compressor can operate at low capacity conditions, but the compressor efficiency deteriorates and surge characteristics worsen at part-load conditions
Solution Approach 1:
The patent applies the dynamics principle by implementing a variable-geometry diffuser that can dynamically adjust its geometry (throat area and passage shape) in response to operating conditions. This allows the diffuser to adapt to varying flow rates and maintain optimal flow characteristics across the operating range, eliminating surge at part-load conditions while maintaining efficiency without requiring variable inlet guide vanes.
2Adaptability or versatility
If variable inlet guide vanes are used for capacity control, then the compressor can regulate capacity during various operating conditions, but the compressor efficiency deteriorates by 4-7%
Solution Approach 1:
The variable-geometry diffuser dynamically adjusts its throat area and passage geometry based on operating conditions, optimizing flow characteristics at each operating point. This dynamic adaptation eliminates the energy losses associated with fixed geometry or inlet guide vane adjustments, maintaining high efficiency across the full capacity range.
Solution Approach 2:
The patent changes the geometric parameters of the diffuser (throat area, passage cross-section, vane angles) to optimize performance at different operating conditions. By adjusting these parameters, the diffuser maintains efficient flow patterns and pressure recovery across varying capacity conditions without the energy penalties of traditional inlet guide vane systems.
3Device complexity
If fixed vaneless diffusers are used in multi-stage centrifugal compressors, then the structure is simple, but the surge characteristics deteriorate at part-load operating conditions
Solution Approach 1:
The patent transitions from fixed to variable geometry in the diffuser, allowing it to adapt its shape and throat area based on operating conditions. This dynamic capability significantly improves surge characteristics at part-load conditions while maintaining a relatively simple overall structure through the use of movable walls and actuation mechanisms.
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 enhances compressor efficiency by 4-7% and improves surge characteristics at part-load conditions, providing better off-design efficiency and stability compared to traditional rotatable inlet guide vane arrangements.
Implementation Method 1
a variable geometry diffuser downstream of the first stage impeller
Implementation Method 2
centrifugal compressor having first and second compressor stages with a variable geometry diffuser and a fixed diffuser respectively arranged downstream from the first and second stage impellers
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A refrigeration system includes a chiller having a refrigerant loop. A compressor is part of and in fluid communication with the refrigerant loop. The compressor has two stages, one with a variable geometry diffuser and one with a fixed geometry diffuser.