Gas Turbine Combustor with Segmented Fuel Injection for Low-Load Stability
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Solution Overview
Problem
Conventional gas turbines at high pressure ratios face challenges in maintaining stable combustion and preventing unburned fuel during low-load or speed-increasing states, where the fuel-air mixture becomes excessively lean, leading to deteriorated flame holding properties and increased unburned fuel occurrence.
Innovation Solution
A combustor design featuring internal and external swirler rings with divided fluid passages and strategically positioned fuel injection holes, along with distinct fuel supply means, ensures fuel is injected at appropriate concentrations to maintain flame stability, even at low loads, by limiting fuel injection to specific regions and using blocking members to inhibit fluid outflow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the fuel-air ratio is reduced to decrease NOx emissions, then environmental performance is improved, but flame holding properties deteriorate and unburned fuel increases during low-load operation
Solution Approach 1:
The combustor is divided into multiple independent combustion regions (first through fourth regions) with separate fuel injection systems. This segmentation allows different fuel-air ratios to be maintained in different zones, enabling low NOx emissions in most regions while preserving flame holding in specific regions during low-load operation.
Solution Approach 2:
Different fuel injection holes are designed with different diameters to create local variations in fuel concentration. Specifically, fuel injection holes facing the first and second combustion regions have larger diameters than those facing the third and fourth regions, allowing higher fuel concentration in inner regions for stable flame holding while maintaining lean combustion in outer regions for low NOx emissions.
2Loss of energy
If the total fuel supply is reduced during low-load operation, then fuel efficiency is improved, but combustion stability deteriorates and unburned fuel occurs
Solution Approach 1:
The fuel supply system is segmented into multiple independent channels controlling different combustion regions. During low-load operation, fuel is selectively supplied to specific regions (first and second regions with larger injection holes) while reducing or stopping supply to other regions, maintaining combustion stability with minimal total fuel consumption.
Solution Approach 2:
The system changes the distribution parameters of fuel supply across different regions rather than uniformly reducing total fuel supply. By adjusting which regions receive fuel and at what concentration, the system maintains stable combustion in critical regions while minimizing overall fuel consumption.
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 effectively suppresses unburned fuel occurrence and enhances flame holding performance by maintaining fuel concentrations above the flammability limit, even at low loads, ensuring stable combustion and improved efficiency.
Implementation Method 1
an internal swirler comprising a cylindrical internal swirler ring disposed concentrically with respect to a central axis of the inner tube, and a plurality of internal swirler vanes provided on an outer peripheral surface of the internal swirler ring, and an external swirler comprising a cylindrical external swirler ring disposed on an outer peripheral side of the internal swirler vanes and concentrically with respect to the internal swirler ring, and a plurality of external swirler vanes provided on an outer peripheral surface of the external swirler ring
Implementation Method 2
a fuel injection hole for injecting fuel into the internal divisional fluid passages is formed in a vane surface of each of the internal swirler vanes, and a fuel injection hole for injecting fuel into the external divisional fluid passages is formed in a vane surface of each of the external swirler vanes
Implementation Method 3
In the interior of an inner tube 15 of the combustor 10, fuel supplied from fuel nozzles 16 and compressed air are mixed and burned. A combustion gas produced by combustion is passed through a transition pipe 17
Data Source
AI summary
In a combustor, divisional fluid passages of a first group, and divisional fluid passages of a second group are present on an inner peripheral side, and divisional fluid passages are also present on an outer peripheral side, and swirl air flows are gushed from the divisional fluid passages. When the total amount of fuel supplied to the combustor is small as in a speed increasing state or in a low load state, fuel is injected only into the divisional fluid passages of the first group. Since a fuel injection region is limited to a position on the inner peripheral side, particularly, a specific position, the concentration of a fuel gas comprising a mixture of fuel and air is lean, but is higher than a flammability limit concentration, even when the total amount of fuel is small.