Dual-Threshold Fuel Injectors for Turbomachine Re-Ignition

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Solution Overview

Problem

The re-ignition of turbomachine combustion chambers during flight is challenging due to low pressures, low temperatures, and fuel viscosity variations at altitude, with existing solutions struggling to achieve a homogeneous fuel distribution and limit temperature heterogeneities.

Innovation Solution

A combustion chamber design featuring fuel injectors of two types, where the first type is closer to the spark plug with a lower opening threshold for its mobile sealing member than the second type, facilitating re-ignition by reducing fuel drop size and improving air-fuel mixture homogeneity through differential pressure management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the opening threshold of the sealing member of all injectors is lowered to facilitate re-ignition, then re-ignition is improved, but the impact on the fuel supply system increases significantly

Engineering Contradiction:

Improvere-ignition capabilityVSAvoidimpact on fuel supply system

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by differentiating the opening thresholds of sealing members based on injector location. Injectors closer to the spark plug (first type) have a lower opening threshold than those farther away (second type). This localized differentiation optimizes re-ignition capability near the spark plug while maintaining normal operation for other injectors, thus improving reliability without excessively impacting the entire fuel supply system.

Inventive Principle:

Principle #3Local quality

2Reliability

If the opening threshold of the sealing member is lowered to reduce fuel drop size, then re-ignition is facilitated, but fuel distribution homogeneity deteriorates

Engineering Contradiction:

Improvere-ignition capabilityVSAvoidfuel distribution homogeneity

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent implements local quality by assigning different opening thresholds to sealing members based on their position relative to the spark plug. The first type of injector (closer to spark plug) has a lower threshold to produce smaller drops for reliable re-ignition, while the second type (farther away) maintains a higher threshold to ensure proper fuel distribution and mixing in other regions of the combustion chamber.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the injector population into two distinct types based on their location and function. This segmentation allows each type to be optimized independently: first type injectors prioritize drop size reduction for re-ignition, while second type injectors maintain parameters for homogeneous fuel distribution throughout the combustion chamber.

Inventive Principle:

Principle #1Segmentation

3Reliability

If injectors of the first type generate a cloud with greater spray cone angle, then re-ignition is facilitated, but temperature heterogeneities in the combustion chamber increase

Engineering Contradiction:

Improvere-ignition capabilityVSAvoidtemperature heterogeneities

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent applies local quality by configuring first type injectors (near spark plug) with larger spray cone angles to facilitate re-ignition in the critical zone near the spark plug, while second type injectors (farther away) use smaller spray cone angles to ensure proper air-fuel mixing and reduce temperature heterogeneities in the broader combustion chamber volume.

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 design enhances re-ignition of the combustion chamber during flight by ensuring a more uniform air-fuel mixture and reducing temperature heterogeneities, while minimizing the impact on the fuel supply system.

Implementation Method 1

The mobile sealing member is configured to open when the fuel pressure exceeds an opening threshold of the mobile sealing member

Methodology Applied

Scientific EffectPressure differential: Pressure Gradient

Implementation Method 2

The first elastic return means is configured to stress the mobile sealing member towards its closed position

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 3

The difference in pressure between the pressure of the fuel arriving in the injector of the first type and the pressure of the fuel exiting this injector tends to increase, which tends to reduce the size of the drops of the injected fuel

Methodology Applied

Scientific EffectPressure differential effect on droplet size: Pressure Gradient

Data Source

PatentUS11002196B2Combustion chamber comprising two types of injectors in which the sealing members have a different opening threshold

Publication Date: 2021.05.11 SAFRAN AIRCRAFT ENGINES SAS

AI summary

The invention relates to a combustion chamber for a turbomachine. The combustion chamber comprises at least one spark plug, at least one fuel injector of a first type of injector that is located facing the spark plug, and at least one fuel injector of a second type. Each fuel injector comprises a mobile sealing member that is configured to open when the fuel pressure exceeds an opening threshold. The opening threshold of the mobile sealing member of the injector of the first type is strictly less than the opening threshold of the mobile sealing member of the injector of the second type.