Single Screw Compressor Slide Valve Capacity Control
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Solution Overview
Problem
Existing single screw compressors face inefficiencies at part-load operations due to the need for non-return valves and limited capacity control, especially when transitioning between loaded and unloaded states, which affects overall compressor efficiency and operational range.
Innovation Solution
A single screw compressor design featuring a slide with an additional outlet port and inlet port configuration that eliminates the need for non-return valves by providing a fully vented path for gas, allowing for asymmetric unloading and efficient capacity control through the use of two slides with distinct operational ranges, one for full load/unload and the other for partial loads, and an oil pathway that interrupts oil injection during part-load operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If non-return valves are used in conventional screw compressors, then gas flow direction is controlled, but churning losses increase and efficiency decreases at part-load operations
Solution Approach 1:
The invention removes non-return valves from the compressor system entirely. The slide mechanism with selectively positionable sealing elements directly controls gas flow paths, eliminating the need for separate non-return valve components and their associated energy losses.
Solution Approach 2:
The slide mechanism performs multiple functions: it controls capacity by positioning sealing elements, directs gas flow paths, and eliminates the need for non-return valves. This multi-functional design replaces several separate components with a single integrated mechanism.
2Adaptability or versatility
If conventional capacity control mechanisms are used, then compressor capacity is adjusted, but operational range is limited and part-load efficiency is reduced
Solution Approach 1:
The invention uses a dynamic slide mechanism that can be positioned continuously along the rotor circumference, enabling smooth capacity adjustment from 12% to 100% of full load. This dynamic positioning system provides fine-grained control compared to conventional discrete capacity steps.
Solution Approach 2:
The slide mechanism pre-positions sealing elements to control gas admission timing and duration before compression begins. By adjusting the axial position of sealing elements relative to rotor rotation, the system prepares the compression chambers at optimal moments for efficient part-load operation.
3Loss of substance
If oil injection is continuous, then lubrication is maintained, but refrigerant loss increases during part-load operation
Solution Approach 1:
The invention implements periodic oil injection that synchronizes with the compression cycle and load conditions. Oil injection is activated only when compression is occurring and deactivated during unloading phases, reducing refrigerant-oil mixing and refrigerant loss while maintaining necessary lubrication.
Solution Approach 2:
The system automatically adjusts oil injection based on compression chamber activity. When sealing elements block compression chambers during unloading, oil injection is self-regulated to stop, eliminating the need for external control systems and preventing unnecessary refrigerant loss.
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 design enhances efficiency by eliminating the need for non-return valves, reducing churning losses, and allowing for a wider operational range from 12% to 100% capacity, achieving improved performance at part-load conditions and reducing refrigerant loss, thus matching the efficiency of variable speed compressors.
Implementation Method 1
axial movement of the slides opens or closes ports in the compressor casing to achieve changes in the capacity and the volume ratio
Implementation Method 2
Continued rotation causes the teeth of the gate rotors 110, 115 to progress along the flutes 105 causing a reduction in volume and thus an increase in pressure
Implementation Method 3
an oil pathway that interrupts oil injection during part-load operation
Data Source
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AI summary
A single screw compressor is arranged to vent the flutes of its main rotor at all times, without having to provide a check valve in the discharge port of the main rotor casing. An additional outlet port in the casing vents gas from the discharge ends of the flutes into the body of a slide instead of to the discharge port. The vented gas is guided to an exit port of the slide, from where it can reach either the discharge port or the bypass port of the casing at all times during use of the compressor and under all loading conditions. The design of the slide further allows the use of an offset ° ' discharge port in the casing, in relation to the main rotor. This means that pressure acting through the discharge port in use of the compressor tends to press the slide against another structure than the main rotor, for instance a bearing housing, giving better support to the slide. The slide also provides an improved oil delivery arrangement