Retracting Running Gap for Compressor Blade Tip Stability

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Solution Overview

Problem

Fluid flow machines, such as blowers, compressors, and fans, face limitations in aerodynamic loadability and efficiency due to boundary layer growth and separation at the rotor and stator blade tip areas, leading to re-flow phenomena and instability, particularly with existing casing treatments that compromise efficiency and occupy significant space.

Innovation Solution

The implementation of a fluid flow machine design where the running gap at the blade tip retracts into the main flow path confinement, guided by a peripheral device with straight or cambered profiles, reducing leakage flow and re-flow instability while maintaining efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If conventional casing treatments (slots, chambers, grooves) are used to stabilize boundary layer flow, then stability is improved, but efficiency is reduced and space is consumed

Engineering Contradiction:

Improveboundary layer stabilityVSAvoidefficiency loss

Core Design Contradiction:

Stability of the object's compositionVSLoss of energy

Solution Approach 1:

The invention extracts the harmful boundary layer by introducing a running gap between the blade tip and casing, allowing the separated boundary layer to be removed from the main flow path. This eliminates the need for conventional stabilizing structures while maintaining flow stability through passive gap-induced boundary layer control.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention transitions from two-dimensional planar casing treatments (slots and grooves in the casing wall) to a three-dimensional running gap structure that extends axially into the flow path. This dimensional change allows the boundary layer to be managed in the axial direction rather than requiring complex wall treatments.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Stability of the object's composition

If conventional casing treatments are used to control boundary layer, then stability is improved, but device complexity and space occupation increase

Engineering Contradiction:

Improveboundary layer stabilityVSAvoidcasing treatment complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The invention removes the need for complex casing treatments by extracting the boundary layer control function into a simple running gap structure. The gap itself, rather than complex wall features, becomes the primary mechanism for boundary layer management, significantly simplifying the overall device design.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of trying to stabilize the boundary layer through complex wall treatments, the invention inverts the approach by allowing the boundary layer to separate and be carried away through the running gap. This passive removal strategy replaces active stabilization mechanisms.

Inventive Principle:

Principle #13The other way round (Inversion)

3Loss of energy

If running gap is used to reduce boundary layer effects, then efficiency is improved, but re-flow instability occurs at higher loads

Engineering Contradiction:

ImproveefficiencyVSAvoidflow stability

Core Design Contradiction:

Loss of energyVSStability of the object's composition

Solution Approach 1:

The invention applies preliminary action by pre-separating the boundary layer through the running gap before it can cause harmful effects in the main flow path. The gap acts as a pre-conditioning structure that prepares the flow by removing low-momentum boundary layer fluid, preventing subsequent re-flow instability at higher operating loads.

Inventive Principle:

Principle #10Preliminary action

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 aerodynamic loadability, reduces component weight and parts by over 20%, and achieves a specific fuel consumption reduction of up to 0.5% in high-pressure compressors, while maintaining or improving efficiency.

Implementation Method 1

The aerodynamic loadability and the efficiency of fluid flow machines such as blowers, compressors, pumps and fans, is limited in particular by the growth and the separation of boundary layers in the rotor and stator blade tip area near the casing or the hub wall, respectively.

Methodology Applied

Scientific EffectBoundary layer: Boundary Layer

Implementation Method 2

Methodology Applied

Scientific EffectFlow separation: Flow Separation

Data Source

PatentUS8690523B2Fluid flow machine with running gap retraction

Publication Date: 2014.04.08 ROLLS ROYCE DEUT LTD & CO KG

AI summary

A fluid flow machine includes a main flow path which is confined by a hub (3) and a casing (1) and in which at least one row of blades (5) is arranged, with a blade end with gap being provided on the blade row, with the blade end and the main flow path confinement performing a rotary movement relative to each other in a vicinity of the blade end, with at least part of the running gap (11) retracted radially from the main flow path confinement into the main flow path, with the running gap (11) at the retractions no longer being confined by the main flow path confinement, but by a peripheral guiding device (10) passed by the main flow and firmly connected to the main flow path confinement and having a row of profiles (12).