Staged Pilot Fuel Injector for Gas Turbine Low Power Atomization
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Solution Overview
Problem
Conventional staged fuel injectors for gas turbine engines face challenges in providing thermally efficient, low emissions operation over a wide range of conditions, particularly during low power operation, where fuel distribution and atomization are inadequate, leading to issues like coking and inefficient startup due to insufficient air pressure for fuel atomization.
Innovation Solution
The design incorporates a dual pilot fuel circuit system with primary and secondary pilot fuel passages that feed into a common prefilming chamber, allowing for varying flow characteristics and improved fuel distribution, which enhances atomization and reduces emissions by optimizing staging pressure ratios and fuel distribution at low power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional staged fuel injectors are used with single pilot fuel circuit, then device complexity is reduced, but fuel distribution and atomization are inadequate at low power levels leading to coking and inefficient operation
Solution Approach 1:
The pilot fuel circuit is segmented into primary and secondary circuits with separate passages leading to different regions of the prefilming chamber. This segmentation allows independent control of fuel flow to different zones, improving fuel distribution and atomization quality at low power levels while maintaining manageable device complexity through modular circuit design
Solution Approach 2:
Different regions of the prefilming chamber receive fuel with different characteristics from the primary and secondary pilot circuits. The primary circuit supplies fuel to one region while the secondary circuit supplies another region, creating local quality variations that optimize combustion at different power levels and prevent coking in specific zones
2Reliability
If compressor discharge air pressure is used for fuel atomization, then atomization is achieved at high power levels, but insufficient air pressure at low power levels prevents proper atomization and causes fuel pooling
Solution Approach 1:
The fuel delivery system is segmented into multiple circuits that can operate independently at different power levels. The dual pilot circuits are designed to provide adequate fuel flow and atomization at low power levels when compressor discharge air pressure is insufficient, while the main circuit activates at higher power levels when adequate air pressure is available
Solution Approach 2:
The system dynamically transitions between different circuit configurations based on operating conditions. At low power levels, the dual pilot circuits are activated to provide reliable atomization with available air pressure. As power levels increase and air pressure becomes sufficient, the system transitions to utilizing the main fuel circuit, creating a dynamic adaptation to varying operational requirements
3Reliability
If single fuel circuit is active at low power levels, then device operation is simplified, but stagnant fuel in inactive circuits causes coking and reduces injector life
Solution Approach 1:
The fuel injector incorporates multiple independent fuel circuits (primary pilot, secondary pilot, and main circuits) that can be selectively activated. This segmentation allows the system to keep multiple circuits active or partially active at low power levels, preventing fuel stagnation and coking in any single circuit while extending injector life
Solution Approach 2:
Each fuel circuit is designed with multi-functionality to serve different operational requirements. The primary and secondary pilot circuits can serve as both pilot fuel sources and as active fuel delivery paths at low power levels, preventing stagnation. This universal design allows flexible circuit management to maintain fuel flow and prevent coking across various operating conditions
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 configuration improves fuel atomization and distribution, reducing emissions and extending injector life by maintaining efficient operation across a broader power range while minimizing fuel pooling and coking, and enabling reliable engine startup without the need for costly auxiliary systems.
Implementation Method 1
enabling rapid mixing with air at lean fuel-to-air ratios
Implementation Method 2
staged combustion, pollutant emissions can be reduced by providing a more thoroughly mixed fuel-air mixture prior to combustion wherein the fuel-to-air ratio is below the stoichiometric level
Implementation Method 3
Lean burning results in lower flame temperatures than would occur with stoichiometric burning. Since the production of NOX is a strong function of temperature, a reduced flame temperature results in lower levels of NOX
Data Source
AI summary
An injector includes a main nozzle body defining a central axis and having a main fuel circuit. A pilot nozzle body is mounted inboard of the main nozzle body. The pilot nozzle body includes a pilot air circuit on the central axis with fuel circuitry radially outboard of the pilot air circuit for delivering fuel to a fuel outlet in a downstream portion of the pilot nozzle body. The fuel circuitry includes a primary pilot fuel circuit configured and adapted to deliver fuel to the fuel outlet and a secondary pilot fuel circuit configured and adapted to deliver fuel to the same fuel outlet.