Mixed-Radial HVAC Compressor Layout for Wider Surge-Free Operation
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Solution Overview
Problem
Refrigerant compressors in HVAC chiller systems face inefficiencies due to limited operating range and compactness, particularly in mixed and radial compression stages, leading to surging issues at lower capacities.
Innovation Solution
A refrigerant compressor design featuring a mixed compression stage with inclined fluid flow and a radial compression stage, utilizing an array of static diffuser vanes and an impeller to transition axial to radial flow, with a 180-degree turn in the refrigerant flow path and deswirl vanes for efficient energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a mixed compression stage with inclined fluid flow is used, then the compressor operating range is enhanced, but the device complexity increases
Solution Approach 1:
The compression process is divided into two distinct stages: a mixed compression stage with inclined fluid flow (less than 45 degrees from axial) and a radial compression stage. This segmentation allows each stage to be optimized for specific operating conditions, expanding the overall operating range while managing complexity through functional division.
Solution Approach 2:
The compressor design incorporates variable geometry elements including curved outer and inner walls with inflection points that smoothly transition between parallel sections. The mixed compression stage uses inclined blade angles that vary along the flow path, allowing the compression characteristics to adapt dynamically across different operating points, thereby enhancing operating range.
2Volume of moving object
If the compressor size is reduced for compactness, then the volume decreases, but surging issues occur at lower capacities
Solution Approach 1:
The radial compression stage is positioned downstream of the mixed compression stage within the same housing, with the impeller nested within the compressor casing. The diffuser vanes are arranged concentrically around the mixed compression stage outlet, creating a compact nested arrangement that reduces overall volume while maintaining adequate flow paths to prevent surging at lower capacities.
Solution Approach 2:
The design transitions from a purely axial flow path to a mixed flow path with inclined angles, then to a radial flow path in the second stage. This dimensional change in flow direction allows the compressor to maintain stable operation at lower capacities by utilizing radial compression characteristics that are less prone to surging, while keeping the overall volume compact through efficient spatial arrangement.
3Use of energy by moving object
If static diffuser vanes are added between compression stages, then energy transfer efficiency improves, but device complexity increases
Solution Approach 1:
An array of static diffuser vanes is positioned between the mixed compression stage and the radial compression stage to act as an intermediary element. These vanes gradually convert the kinetic energy from the mixed compression stage into pressure energy, improving overall energy transfer efficiency. The vanes are strategically arranged to minimize flow separation and maximize diffusion efficiency without requiring complex active control 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
The design enhances compressor compactness and operating range, preventing surging at lower capacities while maintaining efficiency, offering a balance between size and performance.
Implementation Method 1
a first compression stage arranged in a main refrigerant flow path. The first compression stage is a mixed compression stage having both axial and radial components
Implementation Method 2
the second compression stage includes an impeller configured to turn a substantial axial flow to a substantial radial flow
Implementation Method 3
an array of static diffuser vanes is arranged in the main refrigerant flow path between the first compression stage and the second compression stage
Implementation Method 4
deswirl vanes are arranged within the main refrigerant flow path downstream of the cross-over bend and upstream of the second compression stage
Data Source
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AI summary
A refrigerant compressor according to an exemplary aspect of the present disclosure includes, among other things, a first compression stage arranged in a main refrigerant flow path. The first compression stage is a mixed compression stage having both axial and radial components. The compressor further includes a second compression stage arranged in the main refrigerant flow path downstream of the first compression stage. The second compression stage is a radial compression stage.