Multi-Stage Centrifugal Compressor With Variable Diffusers for Surge Control
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Solution Overview
Problem
Multi-stage centrifugal compressors face challenges in achieving high pressure ratios and efficient operation at part-load conditions, particularly in heat pump systems, where existing technologies rely on variable speed and fixed diffusers, limiting their capacity control and surge characteristics.
Innovation Solution
A heat pump system incorporating a centrifugal compressor with two impellers in series, each with variable geometry diffusers, and a flow reversing device to manage refrigerant flow, enabling a high pressure ratio of at least 10:1 and improved surge characteristics through adjustable diffuser geometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-stage centrifugal compressors use fixed vaneless diffusers with variable speed control, then the compressor can operate at variable capacities, but the surge characteristics deteriorate at part-load conditions
Solution Approach 1:
The patent applies the dynamics principle by implementing variable geometry diffusers that can change their geometric configuration dynamically. The diffuser vanes are made adjustable rather than fixed, allowing the diffuser angle and area to be optimized for different operating conditions. This dynamic adjustment capability enables the compressor to maintain stable operation and avoid surge at part-load conditions while preserving capacity control flexibility.
2Adaptability or versatility
If single-stage compressors use variable frequency drive for capacity control, then capacity regulation is improved, but the pressure ratio capability deteriorates for high pressure ratio applications
Solution Approach 1:
The patent applies the segmentation principle by dividing the compression process into multiple stages. Instead of relying on a single-stage impeller to achieve high pressure ratio, the system uses two or more impellers arranged in series, each contributing to the overall pressure increase. This multi-stage configuration enables the compressor to achieve high pressure ratios (suitable for heat pump applications) while maintaining the benefits of variable frequency drive control for capacity regulation.
3Stress or pressure
If multi-stage compressors are designed for high pressure ratio, then the pressure capability is improved, but the complexity of the system increases
Solution Approach 1:
The patent applies the merging principle by integrating multiple functional elements into a unified multi-stage compressor design. The system combines multiple impellers, variable geometry diffusers, and capacity control mechanisms into a single coordinated system. By merging these elements and optimizing their interaction, the patent achieves high pressure ratio capability while managing system complexity through integrated design rather than separate components.
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 system achieves efficient capacity control and enhanced surge characteristics at part-load conditions, ensuring reliable operation in high pressure ratio applications like heat pumps and air-cooled chillers.
Implementation Method 1
a pump portion for sucking fluid medium into the compressor and least three spaced wall members with convoluted fins positioned therebetween that direct the incoming fluid medium radially outwardly while accelerating the velocity of the medium
Implementation Method 2
a first diffuser arranged at the first stage outlet, and the first diffuser is a variable geometry diffuser
Data Source
Figure 1~4
AI summary
A heat pump system includes a refrigerant circuit. First and second heat exchangers are arranged in the refrigerant circuit. A flow reversing device selectively changes a direction of flow in the refrigerant circuit between the first and second heat exchangers. A centrifugal compressor is arranged in the fluid circuit and has first and second impellers arranged in series relative to one another to provide a desired compressor pressure ratio. In one example, the centrifugal compressor mounts the first and second impellers on opposing ends of a shaft. The first and second impellers respectively include first and second stage inlets and outlets. One example desired compressor pressure ratio of at least 10:1 corresponds to a second stage outlet pressure to a first stage inlet pressure. A first diffuser is arranged at the first stage outlet, and the first diffuser is a variable geometry diffuser.