Screw Compressor Variable Volume Ratio via Suction Port Control
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Solution Overview
Problem
Screw compressors in vapor compression systems, such as HVACR systems, typically have a fixed volume ratio, leading to inefficiencies when operating at part load conditions, resulting in over pressurization and reduced reliability due to lubrication challenges at lower speeds.
Innovation Solution
A screw compressor with a variable volume ratio controlled by a valve assembly that modifies the suction port location in response to discharge pressure, allowing for a controllable volume ratio adjustment without varying the discharge port, which reduces leakage and discharge pulsation, and ensures adequate lubrication at lower speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a screw compressor operates at part load conditions with a fixed volume ratio, then the compressor structure is simple, but over pressurization occurs and reliability reduces due to lubrication challenges
Solution Approach 1:
The patent applies the dynamics principle by making the volume ratio variable instead of fixed. The valve assembly dynamically adjusts the suction port location based on operating conditions, allowing the compressor to adapt to part load conditions while maintaining reliable lubrication and preventing over pressurization.
Solution Approach 2:
The patent changes the parameter of volume ratio from fixed to variable. By adjusting the suction port location through the valve assembly, the volume ratio can be modified to match operating conditions, resolving the contradiction between simple structure and reliable operation at varying loads.
2Use of energy by moving object
If a screw compressor reduces operating speed to handle part load conditions, then energy consumption decreases, but lubrication issues arise and lifetime is reduced
Solution Approach 1:
Instead of reducing speed to handle part load conditions, the patent dynamically adjusts the volume ratio while maintaining adequate operating speed. This ensures continuous proper lubrication while still achieving energy savings through reduced capacity operation.
Solution Approach 2:
The patent changes the volume ratio parameter to match part load conditions rather than changing speed. This allows the compressor to operate at lower capacity with appropriate lubrication, extending lifetime while maintaining energy efficiency.
3Ease of manufacture
If a screw compressor uses a fixed volume ratio design, then manufacturing is simpler, but performance at part load conditions deteriorates
Solution Approach 1:
The patent segments the suction port control function into a separate valve assembly. This allows the main compressor body to remain relatively simple for manufacturing, while the additive valve assembly provides the variable volume ratio capability needed for improved part load performance.
4Reliability
If a screw compressor operates with higher minimum speed to ensure lubrication, then reliability improves, but energy consumption increases
Solution Approach 1:
The patent changes the volume ratio parameter to allow proper lubrication at lower operating speeds. By reducing the volume ratio through suction port adjustment, the compressor can maintain adequate speed for lubrication while consuming less energy at part load conditions.
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 solution enhances the reliability and efficiency of screw compressors by maintaining a higher minimum operating speed, reducing the risk of lubrication issues and extending the compressor's lifetime, while also improving performance at part load conditions.
Implementation Method 1
A volume ratio of a compressor, as used in this specification, is a ratio of a volume of working fluid at a start of a compression process to a volume of the working fluid at a start of discharging the working fluid
Data Source
AI summary
A screw compressor, method of operating, and refrigerant circuit are disclosed. The screw compressor includes a suction inlet that receives a working fluid to be compressed. A compression mechanism is fluidly connected to the suction inlet that compresses the working fluid. A discharge outlet is fluidly connected to the compression mechanism that outputs the working fluid following compression by the compression mechanism. A valve assembly is configured to vary a location at which the compression mechanism compresses the working fluid, the valve assembly being disposed to modify a suction location of the screw compressor.