Screw Compressor Slide Piston Assembly for Variable Volume Ratio
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Solution Overview
Problem
Screw compressors in vapor compression systems, such as HVACR, typically operate at maximum efficiency only at full load, leading to inefficiencies and overpressurization at part load conditions due to their fixed volume ratio design.
Innovation Solution
Converting a fixed volume ratio screw compressor into a variable volume ratio compressor by incorporating a slide piston assembly that selectively connects intermediate outlets to the discharge outlet, allowing for adjustment of the compression ratio based on discharge pressure, thereby reducing overcompression and enhancing part load efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed volume ratio screw compressor is used, then the compressor structure is simple and easy to manufacture, but the compressor operates inefficiently at part load conditions due to overpressurization
Solution Approach 1:
The patent converts a fixed volume ratio compressor into a variable volume ratio compressor by making the discharge location dynamic. A slide piston assembly is introduced that can selectively connect different intermediate outlets to the discharge outlet based on operating conditions, allowing the compression ratio to vary with load requirements and eliminating overpressurization at part load
2Loss of energy
If a variable volume ratio mechanism is incorporated, then part load efficiency increases by reducing overcompression, but device complexity increases
Solution Approach 1:
The compression chamber is segmented into multiple intermediate outlets along its length, each capable of being selectively connected to the discharge outlet. The slide piston assembly segments the discharge path, allowing different portions of the compressed fluid to be discharged at different stages of compression based on system needs
Solution Approach 2:
The slide piston assembly acts as an intermediary mechanism between the compression chamber and discharge outlet. It mediates the connection between intermediate outlets and the discharge outlet, enabling variable volume ratio operation without requiring complete redesign of the compressor architecture
3Use of energy by moving object
If the compressor operates at full load only, then maximum efficiency is achieved, but the system lacks adaptability to varying load conditions
Solution Approach 1:
The patent changes the operational parameters of the compressor by enabling variable volume ratio through the slide piston assembly. This allows the compression ratio to be adjusted as a variable parameter based on discharge pressure and load conditions, rather than being fixed, thereby maintaining efficiency across different operating points
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 modification results in a 10-14 percent increase in part load efficiency by reducing overcompression, allowing the compressor to operate more effectively across a range of load conditions.
Implementation Method 1
The one or more outlets are selectively fluidly connectable to the discharge outlet based on a discharge pressure of the screw compressor
Implementation Method 2
a compression mechanism that compresses the working fluid
Data Source
AI summary
A screw compressor is disclosed. The screw compressor includes a suction inlet that receives a working fluid to be compressed; a compression mechanism fluidly connected to the suction inlet that compresses the working fluid; a discharge outlet fluidly connected to the compression mechanism that outputs the working fluid following compression by the compression mechanism; wherein the compression mechanism fluidly communicates with one or more outlets disposed at an intermediate location between the suction inlet and the discharge outlet, the one or more outlets being selectively fluidly connectable to the discharge outlet such that the working fluid can be provided from the one or more outlets to the discharge outlet.