Multi-Lobed Cooling Holes for Low-Separation Turbine Film Cooling

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Solution Overview

Problem

Gas turbine engine components face challenges in efficiently managing high gas path temperatures, leading to increased cooling loads and reduced service life due to the inefficiencies in existing cooling techniques, particularly in the hot sections of the compressor, combustor, and turbine.

Innovation Solution

The development of multi-lobed cooling holes with specific inlet, metering, and diffusing section geometries, formed using techniques such as laser drilling, particle beam machining, fluid-jet guided laser machining, and mechanical machining, to enhance cooling efficiency and reduce flow separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional cooling holes are used in gas turbine engine components, then cooling flow can be provided to hot sections, but cooling efficiency is reduced and flow separation occurs

Engineering Contradiction:

Improveservice lifeVSAvoidcooling efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The cooling hole is divided into multiple lobes (typically three) in the diffusing section, which segments the cooling flow into multiple streams. This segmentation improves cooling efficiency by reducing flow separation and enhancing heat transfer at the component surface, directly addressing the technical contradiction between cooling efficiency and service life.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The cooling hole features different geometries in different sections: a circular inlet section for uniform flow distribution, a metering section for flow control, and a multi-lobed diffusing section for enhanced heat transfer. This local variation in geometry optimizes cooling performance at each stage, resolving the contradiction between cooling efficiency and flow separation.

Inventive Principle:

Principle #3Local quality

2Temperature

If cooling flow is increased to improve cooling efficiency, then heat transfer improves, but engine efficiency is reduced due to higher cooling loads

Engineering Contradiction:

Improveheat transferVSAvoidengine efficiency

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

By segmenting the cooling flow into multiple lobes, the heat transfer efficiency is enhanced, allowing better cooling performance with reduced total cooling flow. This reduces the energy penalty on engine efficiency while maintaining effective heat transfer from the hot gas path.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The multi-lobed geometry changes the flow parameters in the diffusing section, creating multiple jets that improve heat transfer coefficients. This allows achieving the same cooling effect with lower cooling flow rates, thereby maintaining engine efficiency.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If multi-lobed cooling holes are formed using advanced machining techniques, then cooling efficiency improves, but manufacturing complexity increases

Engineering Contradiction:

Improvecooling efficiencyVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The inlet and metering sections are formed first using laser drilling or particle beam machining, creating a precise circular opening. Subsequently, the multi-lobed diffusing section is formed by mechanical machining or additional laser processing. This preliminary formation of the basic geometry simplifies the overall manufacturing process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Laser drilling and particle beam machining are used to form the inlet and metering sections, replacing traditional mechanical drilling. This substitution enables precise geometry formation and facilitates the subsequent creation of the multi-lobed diffusing section with reduced manufacturing complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The multi-lobed cooling holes improve the spread of cooling fluid, minimize flow separation, and increase coverage on gas turbine engine components, thereby reducing the need for cooling flow and maintaining engine efficiency while extending service life.

Implementation Method 1

laser drilling

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Implementation Method 2

particle beam machining

Methodology Applied

Scientific EffectParticle beam machining: Ion Beam

Implementation Method 3

fluid-jet guided laser machining

Methodology Applied

Scientific EffectFluid-jet guided laser machining: Laser Ablation

Data Source

PatentUS11371386B2Manufacturing methods for multi-lobed cooling holes

Publication Date: 2022.06.28 RTX CORP

AI summary

A method for producing a diffusion cooling hole extending between a wall having a first wall surface and a second wall surface includes forming a cooling hole inlet at the first wall surface, forming a cooling hole outlet at the second wall surface, forming a metering section downstream from the inlet and forming a multi-lobed diffusing section between the metering section and the outlet. The inlet, outlet, metering section and multi-lobed diffusing section are formed by laser drilling, particle beam machining, fluid jet guided laser machining, mechanical machining, masking and combinations thereof.