Variable Volume Ratio Control in Screw Compressors
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Solution Overview
Problem
Screw compressors face inefficiencies due to fixed volume ratios that do not adapt to varying load conditions or ambient temperatures, leading to over or under compression and resulting system losses.
Innovation Solution
A compressor system with a control mechanism that adjusts the volume ratio by using a valve to bypass vapor, controlled by solenoid valves and a microprocessor, allowing for step changes in volume ratio to match changing pressure conditions, thereby optimizing efficiency at part-load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed volume ratio compressor is used, then the compressor can be optimized for specific suction and discharge conditions, but the compressor efficiency deteriorates when operating conditions vary from the design point
Solution Approach 1:
The patent applies the dynamics principle by making the volume ratio adjustable rather than fixed. A variable volume ratio mechanism is implemented that allows the compressor to change its volume ratio dynamically based on operating conditions. This enables the compressor to maintain optimal efficiency across varying suction and discharge pressure conditions, resolving the contradiction between being optimized for specific conditions and adapting to varying conditions.
2Power
If the volume ratio is increased to match high discharge pressure, then compression efficiency improves at high load, but overcompression occurs at part load causing system losses
Solution Approach 1:
The variable volume ratio mechanism allows the compressor to dynamically adjust its volume ratio based on the discharge pressure and load conditions. At high load with high discharge pressure, the volume ratio is increased to maintain compression efficiency. At part load with lower discharge pressure, the volume ratio is reduced to prevent overcompression and the associated energy losses. This dynamic adjustment resolves the contradiction between maintaining high compression efficiency and avoiding overcompression losses.
3Power
If the volume ratio is decreased to match low discharge pressure, then part load efficiency improves, but undercompression occurs at full load causing system losses
Solution Approach 1:
The variable volume ratio mechanism enables the compressor to adjust its volume ratio according to operating conditions. When operating at part load with low discharge pressure, the volume ratio is decreased to match the system conditions and improve compression efficiency. When operating at full load with high discharge pressure, the volume ratio is increased to prevent undercompression and associated energy losses. This dynamic adaptation resolves the contradiction between part load efficiency and full load performance.
4Adaptability or versatility
If a variable volume ratio mechanism is implemented, then compressor efficiency across varying conditions improves, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex mechanical variable volume ratio mechanisms with a simpler control system. Instead of using elaborate mechanical devices to continuously vary the volume ratio, the invention employs a control mechanism that adjusts the volume ratio based on sensed operating conditions. This substitution reduces device complexity while maintaining the ability to adapt to varying compression conditions.
Solution Approach 2:
The variable volume ratio mechanism is designed to automatically adjust based on sensed discharge pressure and load conditions without requiring complex external control systems. The compressor self-regulates its volume ratio in response to changing operating conditions, reducing the need for complex control mechanisms and associated complexity.
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 system improves energy efficiency and matches the compressor's volume ratio to system pressures, reducing system losses and maintaining optimal performance across varying load conditions.
Implementation Method 1
The compressor further includes at least one solenoid valve and a controller. The at least one solenoid valve is positioned to control a flow of fluid to the valve and the flow of fluid to the valve determines the position of the valve.
Implementation Method 2
The compression mechanism is positioned to receive vapor from the intake passage and provide compressed vapor to the discharge passage.
Data Source
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AI summary
A system and method for controlling the volume ratio of a compressor is provided. The system can use a port (88) or ports in a rotor cylinder to bypass vapor from the compression chamber to the discharge passage of the compressor. A control valve (90) can be used to open or close the port or ports to obtain different volume ratios in the compressor. The control valve (90) can be moved or adjusted by one or more valves that control a flow of fluid to the valve. A control algorithm can be used to control the one or more valves to move the control valve to obtain different volume ratios from the compressor. The control algorithm can control the one or more valves in response to operating parameters associated with the compressor.