Stepped-Ridge Grommets for Gas Turbine Dilution Hole Cooling

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Solution Overview

Problem

Combustor temperatures in gas turbine engines exceed the melting point of the combustor liner, causing damage to dilution holes and surrounding components due to hot spots and localized hot gas entrainment.

Innovation Solution

The implementation of grommets with annular or elliptical geometries and internal cooling features, such as ridges with steps, trenches, and fillets, to direct cooling flow circumferentially or radially, mitigating hot gas entrainment and oxidation at dilution holes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If dilution holes are used to minimize emissions and promote mixing, then combustion efficiency is improved, but local hot spots and hot gas entrainment occur causing damage to the dilution holes and combustor liner

Engineering Contradiction:

Improvedurability of dilution holesVSAvoidhot spots and hot gas entrainment

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by introducing cooling features (ridges with steps, trenches, and fillets) at specific locations within the dilution hole structure. These features create localized cooling zones that target the specific areas experiencing hot spots and hot gas entrainment, rather than uniformly cooling the entire combustor. The cooling flow is directed specifically at the dilution hole openings and surrounding areas where thermal damage occurs.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses cooling flow as an intermediary substance to protect the dilution holes from thermal damage. The cooling flow acts as a mediator between the hot combustion gases and the dilution hole structure, absorbing excess heat and preventing direct thermal contact that would cause damage. This intermediary cooling layer shields the dilution holes from the harmful thermal environment.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Power

If combustor temperatures are increased to improve combustion, then energy output is improved, but temperatures exceed the melting point of the combustor liner causing damage

Engineering Contradiction:

Improvecombustion energy outputVSAvoidcombustor liner temperature

Core Design Contradiction:

PowerVSTemperature

Solution Approach 1:

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the thermal parameters of the dilution hole structure by introducing cooling flow that modifies the temperature distribution. The cooling features alter the local temperature field, creating a temperature gradient that protects the combustor liner from exceeding its melting point while maintaining the high overall combustion temperatures needed for energy output.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If cooling features are added to protect dilution holes, then thermal protection is improved, but device complexity increases

Engineering Contradiction:

Improvethermal protection of dilution holesVSAvoidgrommet structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the cooling features directly into the grommet structure that defines the dilution holes. Rather than adding separate cooling systems, the cooling channels, ridges with steps, trenches, and fillets are integrated into the existing grommet component. This consolidation provides thermal protection while minimizing the increase in device complexity by using a single integrated component.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The grommet structure serves multiple functions: it defines the dilution hole geometry, provides structural support, and incorporates cooling features for thermal protection. By making the grommet multi-functional, the patent avoids adding separate dedicated cooling components, thereby reducing the overall complexity increase while achieving improved thermal protection.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enhances thermal protection and durability of dilution holes by reducing local temperatures and preventing premature oxidation, thereby extending the operational life of combustor components.

Implementation Method 1

the outlet is configured to direct a cooling flow circumferentially along the fillet and fill the ridge with the cooling flow

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS12460818B2Dilution holes with ridge feature for gas turbine engines

Publication Date: 2025.11.04 RTX CORP

AI summary

A grommet may define a dilution hole in a combustor panel. The grommet may comprise a ridge having a stepped geometry formed about an inner diameter of the grommet, the ridge comprising a passage. The passage may comprise an outlet. The ridge may further comprise a fillet about the inner diameter of the grommet, wherein the outlet is configured to direct a cooling flow circumferentially along the fillet and fill the ridge with the cooling flow.