Compressor interstage throttle, and method of operating therof
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Solution Overview
Problem
Centrifugal compressors in HVACR systems face challenges in efficiently controlling the flowrate of working fluid between stages, leading to suboptimal compression and energy efficiency due to the lack of effective interstage throttling mechanisms.
Innovation Solution
An interstage throttle system comprising a flow guide plate with radially inward channels, a throttle ring with teeth, and linkage assemblies connecting the throttle ring to a drive ring, allowing axial movement between retracted and extended positions to adjust the channel cross-sectional area, thereby controlling the flowrate of the working fluid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If no interstage throttling mechanism is used, then the structure is simple, but the flowrate control between stages is inefficient leading to suboptimal compression and energy efficiency
Solution Approach 1:
The throttle mechanism is segmented into multiple independent components: a throttle ring with teeth, a drive ring, and linkage assemblies. This segmentation allows each component to perform a specific function (flow control, actuation, motion conversion) while maintaining overall system manageability and effectiveness.
Solution Approach 2:
The throttle ring is designed to be movable rather than fixed, allowing it to dynamically adjust the channel cross-sectional area by rotating between retracted and extended positions. This dynamic adjustment enables precise flowrate control to optimize compression efficiency across varying operating conditions.
2Measurement precision
If the throttle ring is positioned in the extended position with teeth blocking channels, then the flowrate control is precise, but the pressure loss increases
Solution Approach 1:
The throttle ring teeth partially block the channels rather than completely obstructing them, even in the extended position. This partial blocking provides sufficient flowrate control precision while minimizing pressure loss by maintaining adequate flow passage area.
Solution Approach 2:
The throttle ring can dynamically adjust its position between retracted and extended states, allowing the system to optimize the balance between flowrate control precision and pressure loss based on real-time operating conditions.
3Adaptability or versatility
If the throttle ring rotates more than 5 degrees, then the flowrate adjustment range is larger, but the mechanical stability and sealing deteriorate
Solution Approach 1:
The linkage assemblies are specifically designed to convert rotational motion into precise axial movement, restricting the throttle ring rotation to less than 5 degrees. This localized motion control maintains mechanical stability and sealing while achieving sufficient flowrate adjustment range through the axial displacement of the throttle ring.
Solution Approach 2:
The linkage assemblies act as intermediaries between the drive ring and throttle ring, transforming the actuation motion into controlled axial movement of the throttle ring. This intermediary mechanism enables adequate flowrate adjustment while preventing excessive rotation that would compromise stability.
Data Source
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AI summary
An interstage throttle for a centrifugal compressor includes a flow guide plate, a throttle ring, a drive ring, and linkage assemblies. The flow guide plate includes guide vanes that form channels that direct working fluid in between stages of the compressor. The linkage assemblies connect the drive ring to the throttle ring such that rotation of the drive ring moves the throttle ring in an axial direction. Teeth of the throttle ring partially block the channels when the throttle ring is in an extended position. A method of operating a centrifugal compressor includes directing the working fluid discharged from the first stage to a second stage via channels in a interstage throttle. A centrifugal compressor includes a first stage with a first impeller, a second stage with a second impeller, and an interstage throttle fluidly connecting the first stage to the second stage.