Spiral Grooves on Compressor Hub to Reduce Tip Leakage

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Solution Overview

Problem

Existing fluid flow machines, such as compressors and blowers, face limitations in aerodynamic load capacity and efficiency due to boundary layer growth and separation at rotor and stator blade tip areas, leading to instability and increased tip clearance leakage, especially at off-design conditions.

Innovation Solution

The implementation of spiral grooves on the rotating hub beneath cantilevered stators, which are angled relative to the axis and configured to add energy to the working fluid, minimizing leakage flow by creating an axial motion that pushes near-wall flow downstream and delays separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional casing treatments with circumferential grooves are used, then the structure is simple and easy to manufacture, but the aerodynamic load capacity and efficiency are limited due to boundary layer growth and separation

Engineering Contradiction:

Improveease of manufactureVSAvoidaerodynamic load capacity

Core Design Contradiction:

Ease of manufactureVSProductivity

Solution Approach 1:

The patent replaces conventional circumferential grooves with spiral grooves that follow a curved path around the hub. This curvature allows the groove to interact with the boundary layer in a more effective manner, creating a controlled separation pattern that reduces leakage flow and improves aerodynamic performance while maintaining manufacturing simplicity.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The invention transitions from two-dimensional circumferential grooves to three-dimensional spiral grooves that wrap around the hub in a helical pattern. This adds a third dimension (axial component) to the groove geometry, enabling better control over boundary layer development and leakage flow patterns across multiple blade rows.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If no particular hub treatment is applied, then the device complexity is low, but tip clearance leakage and flow separation increase at off-design conditions

Engineering Contradiction:

Improvedevice complexityVSAvoidoperability range

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The spiral grooves are designed to pre-condition the boundary layer before it reaches the blade tips at off-design conditions. By creating controlled separation zones within the grooves upstream, the treatment prevents harmful leakage flows and delays adverse pressure gradient effects, thereby extending the stable operating range without adding complex active control systems.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If spiral grooves are implemented on the rotating hub, then tip clearance leakage and flow separation are reduced, but the device complexity increases

Engineering Contradiction:

Improveoperability rangeVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The spiral grooves are strategically positioned only in specific regions where boundary layer separation is most problematic, rather than applying treatments across the entire hub surface. This localized approach targets the critical interaction zones between rotor and stator blades, achieving performance improvements with minimal additional complexity.

Inventive Principle:

Principle #3Local quality

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 operability and efficiency of gas turbine compressors by reducing tip clearance leakage and flow separation, improving the stable operating range and energy addition to the fluid flow, thereby optimizing compressor performance across varying operating conditions.

Implementation Method 1

The at least one spiral groove is configured to add energy to a working fluid in the flow path, and minimize a leakage flow that moves opposite the flow path

Methodology Applied

Scientific EffectAxial motion:

Implementation Method 2

the at least one spiral groove is configured to add energy to a working fluid in the flow path

Methodology Applied

Scientific EffectEnergy addition:

Implementation Method 3

minimize a leakage flow that moves opposite the flow path

Methodology Applied

Scientific EffectFlow separation delay: Flow Separation

Data Source

PatentUS11136895B2Spiraling grooves as a hub treatment for cantilevered stators in compressors

Publication Date: 2021.10.05 RTX CORP

AI summary

A casing treatment comprising a hub having a surface, the hub being rotatable about an axis within a casing of a gas turbine engine compressor, at least one spiral groove formed in the surface extending axially relative to the axis, a stator blade fixed to the casing, wherein a tip of the stator blade is proximate to the at least one spiral groove.