Pilot Injector Fuel Shifting in Axial Staged Combustor
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Solution Overview
Problem
Lean-staged liquid-fuelled aero-engine combustors in gas turbine engines are prone to combustion instabilities due to heat release concentration and weak flame holding, particularly in radial-staged designs where all fuel is injected at the front-end, leading to dilution by main stage air affecting pilot stage fuel-air ratios.
Innovation Solution
A pilot fuel injector with a swirler and nozzle featuring dual sub-circuits for fuel injection, where the first sub-circuit injects fuel upstream with apertures oriented counter to the swirler direction and the second sub-circuit injects downstream with apertures oriented co-swirl with the swirler direction, controlled by a fuel injection controller to optimize flame configuration and stabilize combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If all fuel is injected at the front-end of the combustor into different radial zones (radial staging), then the combustor can provide lean-staged combustion with low emissions, but combustion instabilities occur due to heat release concentration and weak flame holding
Solution Approach 1:
The fuel injection system is segmented into multiple axial stages (front-end radial staging and rear-end axial staging) with different injection patterns. The front-end injectors perform radial staging for low emissions, while rear-end injectors provide axial staging for combustion stability, combining the benefits of both approaches.
Solution Approach 2:
Different injection strategies are applied to different spatial zones within the combustor. Front-end injectors use radial staging optimized for emission control, while rear-end injectors use axial staging optimized for flame holding and stability, creating locally optimized combustion zones.
2Object-generated harmful factors
If main stage air is introduced to dilute the pilot stage fuel-air ratio in radial-staged lean combustors, then emissions are reduced, but flame holding capability weakens leading to combustion instabilities
Solution Approach 1:
The combustion process is segmented into pilot stage and main stage with spatially separated fuel injection zones. The pilot stage operates with a richer mixture for reliable flame holding, while the main stage provides dilution for emission control, avoiding the conflict between dilution and flame holding.
Solution Approach 2:
The pilot flame acts as an intermediary between the main stage air and the combustion process. It provides a stable ignition source that can sustain combustion even when main stage air dilutes the overall fuel-air ratio, enabling both low emissions and reliable flame holding.
3Object-generated harmful factors
If heat release is concentrated in the front of the combustor (radial staging), then emissions are reduced, but combustion instabilities are triggered
Solution Approach 1:
Heat release is segmented axially into front-end and rear-end zones with different injection patterns. The front-end radial staging provides low emissions, while the rear-end axial staging distributes heat release to stabilize combustion, preventing instabilities from concentrated heat release.
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 dual injection strategy enhances fuel-air mixing for low NOx and particulate emissions, mitigates combustion instabilities, and optimizes flame configuration within the combustion chamber, improving engine performance across power operations.
Implementation Method 1
The nozzle includes a primary fuel circuit configured to atomize fuel dispensed therethrough
Implementation Method 2
The swirler dispenses air in a swirler direction
Implementation Method 3
combustion chamber of the combustor
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A pilot fuel injector (338) for a combustor of a gas turbine engine includes a swirler (346) having an exit (346a) into a combustion chamber of the combustor and a nozzle (348) located within the swirler (346). The nozzle (348) includes a primary fuel circuit (360) configured to atomize fuel dispensed therethrough and a secondary fuel circuit (362) having a first sub-circuit (364) having at least one injection aperture a first injection depth (D1) from the exit of the swirler and a second sub-circuit (366) having at least one second injection aperture located at a second injection depth (D2) from the exit (346a) of the swirler (346), wherein the first injection depth (D1) is greater than the second injection depth (D2).