Unloading device for HVAC compressor with mixed and radial compression
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Solution Overview
Problem
Refrigerant compressors in HVAC chiller systems face challenges with surge and choke points, limiting their operating range and efficiency, especially at high and low capacities.
Innovation Solution
The refrigerant compressor incorporates a mixed compression stage with both axial and radial flow components and a passive unloading feature, including a channel system that fluidly couples to the main flow path upstream and downstream of the vanes, allowing for flow redirection to prevent surge and choke conditions, thereby extending the operating range without active components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional centrifugal compressor design is used, then the structure is simple, but the operating range is limited due to surge and choke points
Solution Approach 1:
The compressor flow path is segmented into multiple regions using guide vanes and splitter vanes. The guide vanes divide the incoming flow into multiple streams, while splitter vanes further segment the flow between blade rows. This segmentation allows different portions of the flow to be controlled independently, preventing surge and choke conditions across the entire operating range without requiring complex active control systems.
Solution Approach 2:
Guide vanes and splitter vanes act as intermediary elements between the impeller blades and the refrigerant flow. These stationary vanes pre-condition the flow before it enters the blade rows and redirect flow after compression, serving as mediators that prevent adverse flow interactions without requiring complex active control mechanisms. The vanes create a passive flow control system that extends the operating range.
2Adaptability or versatility
If active control components are added to prevent surge and choke, then the operating range extends, but the device complexity and cost increase
Solution Approach 1:
The compressor design uses self-service flow control where the guide vanes and splitter vanes automatically adjust flow distribution based on operating conditions without requiring external control systems. The geometric configuration of these vanes creates inherent flow control that adapts to different capacity conditions, allowing the compressor to serve its own flow control needs without additional actuators, sensors, or control electronics.
Solution Approach 2:
The invention changes the geometric parameters of the flow path through carefully designed guide vane and splitter vane configurations. By optimizing vane angles, spacing, and positions, the flow distribution and pressure distribution are altered to prevent surge and choke conditions across a wide operating range. This geometric parameter optimization provides passive adaptability without complex control systems.
3Productivity
If the compressor operates at high or low capacity extremes, then the operating range is充分利用, but surge and choke points reduce efficiency
Solution Approach 1:
The guide vanes perform preliminary flow conditioning before the refrigerant enters the impeller blade rows. By pre-distributing the flow uniformly and at appropriate angles, the guide vanes prevent the development of unstable flow patterns that lead to surge at low capacity and choke at high capacity. This preliminary flow preparation maintains efficient operation across the entire capacity range.
Solution Approach 2:
The splitter vanes create periodic flow division between adjacent blade rows, establishing a repeating flow pattern that stabilizes the compression process. This periodic flow distribution prevents the buildup of pressure fluctuations that cause surge and choke conditions, maintaining steady efficient operation whether the compressor is running at high or low capacity.
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 configuration enhances the compressor's operating range and efficiency by preventing surge and choke points, allowing it to operate effectively at both high and low capacities without active control, resulting in a more compact and efficient design.
Implementation Method 1
A channel outside the main flow path... fluidly couples the channel to the main flow path upstream of the vanes, and a second orifice fluidly couples the channel to the main flow path downstream of leading edges of the vanes
Data Source
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AI summary
A refrigerant compressor according to an exemplary aspect of the present disclosure includes, among other things, an impeller arranged in a main flow path and including a plurality of vanes. The impeller is configured to rotate about an axis. A channel is outside the main flow path. A first orifice fluidly couples the channel to the main flow path upstream of the vanes, and a second orifice fluidly couples the channel to the main flow path downstream of leading edges of the vanes.