Combustion Chamber Wall Dilution Hole Positioning for Hot Spot Prevention

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Solution Overview

Problem

The existing combustion chambers in turbomachinery often experience hot spots on the walls due to the relative positioning of dilution holes and multiperforation orifices, leading to mechanical strength and lifespan issues without effectively managing temperature distribution and emissions.

Innovation Solution

The dilution holes are repositioned such that the smallest diameter holes are aligned axially with the primary holes, and large diameter holes are placed equidistantly between them, with multiperforation orifices positioned closer to the small diameter dilution holes to enhance cooling and prevent hot spots.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If dilution holes are positioned downstream of primary holes with larger spacing, then cooling effectiveness is improved, but hot spots appear on chamber walls reducing mechanical strength

Engineering Contradiction:

Improvewall temperature distributionVSAvoidmechanical strength of chamber walls

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

The patent applies local quality by differentiating the positioning of dilution holes based on their diameter. Small diameter dilution holes are aligned axially with primary holes to provide localized cooling in specific zones, while large diameter dilution holes are positioned downstream to provide broader cooling coverage. This differentiated local positioning prevents hot spots and maintains uniform wall temperature distribution, thereby preserving mechanical strength.

Inventive Principle:

Principle #3Local quality

2Productivity

If dilution holes are positioned closer to primary holes, then combustion efficiency is improved, but wall cooling effectiveness is reduced

Engineering Contradiction:

Improvecombustion efficiencyVSAvoidwall temperature

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The patent resolves this contradiction by applying local quality through differentiated positioning strategies. Small diameter dilution holes are aligned with primary holes to maintain combustion efficiency in the primary zone, while large diameter dilution holes are positioned downstream to provide effective wall cooling. This spatial differentiation allows each zone to optimize its function without compromising the other.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the dilution hole population into two groups based on diameter size and positions them differently along the axial direction. This segmentation allows the system to simultaneously achieve good combustion efficiency (through small holes aligned with primary holes) and effective wall cooling (through large holes positioned downstream), resolving the contradiction between these two requirements.

Inventive Principle:

Principle #1Segmentation

3Ease of manufacture

If uniform dilution hole distribution is used, then manufacturing simplicity is maintained, but temperature uniformity at chamber outlet is reduced

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidtemperature uniformity at outlet

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The patent applies local quality by creating non-uniform distribution patterns where small diameter dilution holes are aligned with primary holes and large diameter dilution holes are positioned downstream. This localized differentiation improves temperature uniformity at the chamber outlet while maintaining reasonable manufacturing simplicity through systematic positioning rules rather than completely arbitrary arrangements.

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 arrangement effectively avoids hot spots on the chamber walls, maintaining mechanical strength and combustion efficiency while ensuring uniform temperature distribution and minimizing emissions.

Implementation Method 1

Different cooling technologies exist, such as forced convection where cooling is ensured by the circulation of air from the compressor around the chamber

Methodology Applied

Scientific EffectForced convection: Forced Convection

Implementation Method 2

cooling by air film where one interposes between the walls of the chamber and the gases a film of fresh air from the compressor

Methodology Applied

Scientific EffectAir film cooling: Thermal Insulation

Implementation Method 3

The walls are then cooled both by convection inside the orifices and by film since this air then licks the internal face of the walls

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 4

The dilution air cools the gases resulting from the combustion as well as the walls of the chamber

Methodology Applied

Scientific EffectHeat exchange: Heat Exchanger

Data Source

PatentEP2053311B1Combustion chamber walls with optimised dilution and cooling, combustion chamber and turbomachine equipped with same

Publication Date: 2016.04.06 SAFRAN AIRCRAFT ENGINES SAS

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Figure 2
Figure 3~4

AI summary

The invention relates to the field of turbomachinery and concerns a combustion chamber (4) for which the supply of dilution air and cooling air is optimized. The invention relates more particularly to an optimization of the position of the dilution holes (30a, 30b) present on the walls (7a, 7b) of the combustion chamber.