Interstage capacity control valve with side stream flow distribution and flow regulation for multi-stage centrifugal compressors
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Solution Overview
Problem
Multi-stage centrifugal compressors face instability and reduced efficiency due to low-momentum zones and adverse pressure gradients at partial load conditions, leading to narrower operating ranges and maintenance challenges with rotatable vane designs.
Innovation Solution
An interstage capacity control valve that regulates side stream flow by extending and retracting through a side stream injection port, increasing flow velocity and avoiding stagnant areas, while reducing maintenance complexity and bypass gas compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If rotatable return vanes are used to control interstage flow at partial load conditions, then flow direction can be adjusted, but low-momentum zones and adverse pressure gradients are created that reduce compressor stability and efficiency
Solution Approach 1:
The patent replaces static rotatable vanes with a dynamic axial piston mechanism that moves linearly along the axis of the capacity control valve. This linear motion dynamically adjusts the valve opening area to control side stream flow rate, eliminating the adverse pressure gradients and low-momentum zones created by rotatable vanes while maintaining adaptability across different load conditions
Solution Approach 2:
The invention extracts the flow control function from the rotatable return vanes and relocates it to a dedicated capacity control valve with axial piston mechanism. This separation allows the return vanes to focus on flow direction control while the capacity control valve independently manages flow rate, preventing the interaction problems that caused stability issues
2Ease of operation
If rotatable vane designs are used for capacity control, then flow regulation is achieved, but maintenance complexity increases due to the mechanical complexity of rotatable mechanisms
Solution Approach 1:
The patent replaces the complex rotatable vane mechanism with a simpler axial piston linear motion system. The piston moves only along the valve axis without rotation, reducing mechanical complexity and maintenance requirements while maintaining precise flow regulation capability through controlled piston displacement
Solution Approach 2:
Instead of rotating vanes to control flow, the invention inverts the approach by using linear axial motion of a piston to control valve opening area. This inversion of the control mechanism from rotational to linear motion simplifies the mechanical design and reduces maintenance complexity
3Power
If side stream flow is added at high-pressure areas, then compression efficiency is maintained, but bypass gases are compressed and cycled leading to reduced system efficiency
Solution Approach 1:
The patent applies local quality by selectively injecting side stream flow at a specific location (low-pressure area) rather than uniformly throughout the system. The capacity control valve with axial piston mechanism precisely controls where and how much side stream is injected, allowing bypass gases to be introduced at the optimal location to avoid unnecessary compression and energy loss
4Device complexity
If fixed flow injection is used in multi-stage compressors, then system simplicity is maintained, but operating range is narrowed and efficiency is reduced at partial load conditions
Solution Approach 1:
The invention introduces dynamics to the previously fixed system by implementing an axial piston that can move along the valve axis to dynamically adjust the opening area. This allows the side stream flow rate to be varied continuously, expanding the operating range and maintaining efficiency across both full and partial load conditions while adding minimal complexity to the overall system
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
Improves compressor stability and efficiency at both full and partial load conditions by effectively managing side stream flow and reducing maintenance issues related to rotatable vane designs.
Implementation Method 1
The interstage capacity control valve increases the velocity of the interstage flow where the side stream is added, avoiding stagnant areas of flow
Implementation Method 2
The capacity control valve is configured to be extended through the side stream injection port between an open position where the side stream of the fluid can flow through the side stream injection port and a closed position where the capacity control valve obstructs flow of the side stream of the fluid through the side stream injection port
Data Source
AI summary
Centrifugal compressors can incorporate a side stream flow of intermediate pressure vapor between stages of that compressor. The side stream flow can be controlled by a side stream injection port controlled by a capacity control valve that has a curved surface facing a flow of refrigerant from the first stage to the second stage. The capacity control valve can allow or obstruct flow through the side stream injection port. The capacity control valve can extend and retract in a direction substantially perpendicular to the direction of flow from the first stage impeller to the second stage impeller. The side stream injection port and the capacity control valve can be ring-shaped. The side stream injection port and the capacity control valve can allow at least some of the side stream to be introduced on a side of the capacity control valve opposite the curved surface.