Dual Fuel Gas Turbine Pilot Nozzle Recirculation Stabilization
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Solution Overview
Problem
Conventional dual fuel systems in gas turbine engines face challenges in achieving adequate air-fuel mixing and low NOx emissions, particularly due to difficulties in igniting fuel near the wall area where most air is injected, leading to inefficient combustion.
Innovation Solution
A pilot nozzle design with an inner air circuit, gaseous and liquid fuel circuits, and a shroud that stabilizes a pilot re-circulation zone, featuring a swirling inner air circuit, converging outer air circuit, and co-axial fuel circuits, along with an ignition device and floating seal, to enhance fuel-air mixing and ignition efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If fuel is injected near the wall area where most air is injected, then fuel-air mixing should be improved, but ignition becomes difficult due to lack of quiescent zone
Solution Approach 1:
The nozzle is divided into distinct functional zones: an inner quiescent zone for reliable ignition and an outer mixing zone for fuel-air mixing. This segmentation allows each zone to perform its specific function optimally without interference from the other.
Solution Approach 2:
A recirculation zone acts as an intermediary region between the inner quiescent zone and outer mixing zone. This recirculation zone provides a transition area that maintains stable combustion while enabling fuel-air mixing, resolving the conflict between ignition reliability and mixing efficiency.
2Object-generated harmful factors
If fuel staging is used to achieve better mixing and low NOx combustion, then emissions are reduced, but the system complexity increases
Solution Approach 1:
The fuel injection system is segmented into multiple stages with different injection timings and locations. This allows progressive fuel-air mixing and combustion phasing that reduces peak temperatures and NOx emissions while maintaining a relatively simple overall nozzle structure.
Solution Approach 2:
Fuel is injected in stages with preliminary fuel injection occurring first to establish a baseline combustion, followed by additional fuel injection. This preliminary action allows for controlled mixing and temperature management that reduces NOx formation.
3Stability of the object's composition
If a shroud is added to stabilize the pilot re-circulation zone, then combustion stability is improved, but the device complexity increases
Solution Approach 1:
The shroud acts as an intermediary structure that defines and stabilizes the recirculation zone without significantly complicating the overall nozzle design. It provides a boundary that maintains stable combustion while integrating smoothly with the existing nozzle architecture.
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 design achieves more stable pilot flames, efficient light-off, improved fuel-air mixing, and reduced emissions by creating a quiescent zone for ignition and stabilizing larger flames, while being adaptable for retrofitting into existing engines.
Implementation Method 1
The inner air circuit can be a swirling air circuit
Implementation Method 2
The shroud is configured to stabilize a pilot re-circulation zone downstream from outlets of the inner and outer air circuits and the liquid and gaseous fuel circuits
Implementation Method 3
dual fuel injectors within the gas turbine engines operate to mix air and fuel together for combustion
Data Source
AI summary
A pilot nozzle for a dual fuel turbine engine includes an inner air circuit, a gaseous fuel circuit radially outward from the inner air circuit, a liquid fuel circuit radially outward from the inner air circuit, an outer air circuit radially outward from the liquid fuel circuit and the gaseous fuel circuit, and a shroud radially outward from the outer air circuit. The shroud is configured to stabilize a pilot re-circulation zone downstream from outlets of the inner and outer air circuits and the liquid and gaseous fuel circuits.