Screw Compressor Control Slide Throttle Gap Design

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Solution Overview

Problem

Existing screw compressors face challenges in reliably transitioning control slides from a connected to a separated position along the slide channel, affecting the medium's flow and pressure management.

Innovation Solution

The control slides are designed with throttle gaps at their end regions, creating defined flow conditions by forming a first throttle gap with a smaller width than the gap between the end faces, allowing for controlled medium outflow and enabling a transition over a significant distance, with additional features like parallel wall surfaces and recessed inner surfaces to enhance sealing and movement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If control slides are transitioned from connected to separated position along the spool channel, then the volume ratio and compressor performance can be adjusted, but the transition reliability is insufficient starting from different connected positions

Engineering Contradiction:
Improvevolume ratio adjustmentVSAvoidtransition reliability
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

A first throttle gap is introduced as an intermediary flow path between the compression chamber and the space between control slides. This throttle gap, with its smaller gap width, acts as a mediator that ensures controlled and reliable medium flow during the transition from connected to separated position, regardless of the starting position. The throttle gap provides a defined flow condition that facilitates reliable transition.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Device complexity

If the gap between control slides is used for medium outflow, then the structure is simple, but the flow conditions are not well defined

Engineering Contradiction:
Improvestructure simplicityVSAvoidflow condition definition
Core Design Contradiction:
Device complexityVSManufacturing precision

Solution Approach 1:

The throttle gap is designed with a specifically smaller gap width compared to the gap between control slides. This local differentiation in gap width creates a dedicated region with controlled flow characteristics. The first throttle gap's smaller dimension provides well-defined flow conditions for medium outflow, while the larger gap between slides maintains structural simplicity.

Inventive Principle:
Principle #3Local quality

3Measurement precision

If the throttle gap path in displacement direction is increased, then the transition position can be realized over a significantly defined path, but the device complexity increases

Engineering Contradiction:
Improvetransition position definitionVSAvoidthrottle gap structure
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The throttle gap is formed by wall surfaces that extend in the displacement direction, creating a path-length dimension rather than just a simple transverse gap. By making the throttle gap path in the displacement direction greater than the gap width, the transition position can be realized over a significantly defined path. This dimensional approach provides precise position definition without requiring complex additional structures.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 ensures reliable and defined flow conditions for the medium, allowing for precise control of the volume ratio and compressor performance by maintaining consistent gap width and facilitating the transition between connected and separated positions.

Implementation Method 1

a first throttle gap with a gap width running transversely to the direction of displacement is formed in a first transition position following the connected position

Methodology Applied
Scientific EffectThrottling: Pressure Drop

Data Source

PatentEP3859159B1Screw compressor
Publication Date: 2024.03.27 BITZER KUEHLMASCHINENBAU GMBH
  • EP3859159B1 patent drawingFigure 1
  • EP3859159B1 patent drawingFigure 2
  • EP3859159B1 patent drawingFigure 3

AI summary

The invention relates to a screw compressor comprising a compressor housing with a screw rotor chamber arranged therein, two screw rotors arranged in the screw rotor chamber and each rotatably mounted on the compressor housing about a screw rotor axis, the screw contours interlocking, and two control slides arranged one behind the other in a slide channel of the compressor housing in a displacement direction parallel to the screw rotor axes and adjacent to both screw rotors with slide compression wall surfaces, which are movable in the displacement direction, wherein the first control slide and the second control slide are in a combined position with their end faces facing each other tightly sealing each other and are movable together in the displacement direction and can be positioned at a distance from each other in a separating position, forming an intermediate space.wherein the control valves form an inlet chamber at least in a transitional position between the compound position and the separation position, into which the medium to be compressed flows from one of the compression chambers by passing between the opposing end faces of the control valves, and wherein one of the control valves is provided with at least one outlet adjacent to the inlet chamber, through which the medium from the inlet chamber enters an outlet opening on the valve channel which overlaps with the outlet in this transitional position.