Dual-Shutter Spiral Valve for Screw Compressor Leakage Control
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Solution Overview
Problem
The adiabatic efficiency of screw air compressors is reduced due to gas leakage around the spiral valve shutter, leading to wasted work and inlet gas preheating by hot gas and oil leakage.
Innovation Solution
A spiral valve with a second shutter is introduced to trap gas in the bypass chamber, independently controlled from the first shutter, with angled and orthogonal edges to enhance sealing, reducing the need for increased valve diameter and shutter overlap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single shutter is used to control bypass ports, then the device complexity is low, but gas leakage around the shutter reduces adiabatic efficiency
Solution Approach 1:
The single shutter is divided into two independent shutters: a first shutter that opens/closes bypass ports and a second shutter that opens/closes the inlet transfer duct. This segmentation allows each shutter to be optimized for its specific function, reducing gas leakage paths while maintaining manageable complexity through modular design
Solution Approach 2:
The second shutter acts as an intermediary component that specifically controls the inlet transfer duct, preventing hot gas and oil from leaking directly into the inlet. This intermediary shutter blocks the leakage path without requiring fundamental redesign of the entire valve system
2Loss of energy
If shutter overlap is increased to reduce leakage, then sealing improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
By segmenting the shutter system into two independent components with distinct functions, each shutter can be manufactured with standard tolerances and simple geometries. The first shutter focuses on bypass port sealing while the second shutter focuses on inlet transfer duct sealing, avoiding the need for complex increased overlap designs
Solution Approach 2:
Each shutter is designed with specific local sealing characteristics appropriate to its function: the first shutter has sealing surfaces matched to bypass ports while the second shutter has sealing surfaces matched to the inlet transfer duct. This localized optimization achieves effective sealing without requiring uniform increases in overlap across the entire valve
3Loss of energy
If valve diameter is increased to reduce leakage, then sealing improves, but the compression length and overall compressor size increase
Solution Approach 1:
The leakage control function is segmented between two shutters positioned at different locations along the compression chamber. The first shutter addresses bypass port leakage while the second shutter addresses inlet transfer duct leakage. This distribution allows effective sealing without requiring a single large valve diameter, preserving the compression length
Solution Approach 2:
Instead of increasing the valve diameter in one dimension, the solution adds a second shutter in a different spatial dimension (positioned to control the inlet transfer duct separately). This dimensional approach to leakage control achieves comprehensive sealing without compromising the compression chamber dimensions
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A spiral valve and a screw compressor having a compressor housing and the spiral valve are provided. The spiral valve includes an actuator module having an electric motor and a gearbox mechanically coupled to the electric motor to transmit a torque from the electric motor, and a spiral valve body coupled to the gearbox to rotate in response to the transmitted torque from the electric motor. The spiral valve body has a first shutter positioned to open and close one or more of a plurality of bypass ports formed in the compressor housing based on a rotational position of the second shutter, a second shutter positioned to progressively open and close a compressor inlet transfer duct formed in the compressor housing based on a rotation position of second shutter, and a gap formed between the first and second shutters.