Pneumatic Flow Modulator for Gas Turbine Nozzle Air Control
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Solution Overview
Problem
Conventional gas turbine combustion systems face difficulties in meeting emissions limits when a fuel nozzle is turned off, as air flow through the inactive nozzle quenches the reactions in other operating nozzles, preventing complete CO burnout.
Innovation Solution
A pneumatically actuated flow modulator with a fixed outer tube and a movable inner tube, featuring a bellows system and control valve, is used to selectively align or misalign apertures, controlling air flow into the fuel nozzle to prevent cold-air quenching and maintain burner tube velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a fuel nozzle is turned off to reduce fuel consumption, then fuel efficiency is improved, but air flow through the inactive nozzle quenches the reactions in other operating nozzles, preventing complete CO burnout and increasing emissions
Solution Approach 1:
The patent extracts the air flow path from the fuel nozzle system by introducing a separate damper device that can independently control air flow through turned-off nozzles. This allows the air flow to be removed from the combustion system when nozzles are inactive, preventing quenching effects while maintaining the fuel savings from reduced nozzle operation.
Solution Approach 2:
The damper acts as an intermediary component between the air supply and the fuel nozzle. It mediates the air flow by providing a controllable restriction that can be adjusted based on nozzle operation status, thereby preventing harmful quenching effects without interfering with the primary fuel combustion function.
2Ease of operation
If air flow through inactive fuel nozzles is allowed, then simple nozzle shutdown is achieved, but flame stability deteriorates due to cold-air quenching of reactions in operating nozzles
Solution Approach 1:
The system performs preliminary action by adjusting the damper position before or concurrent with nozzle shutdown. This pre-adjustment of air flow restriction prevents cold-air quenching from occurring, thereby maintaining flame stability in operating nozzles while enabling simple nozzle shutdown operation.
Solution Approach 2:
The system incorporates feedback mechanisms that monitor combustion conditions and adjust damper positions accordingly. This feedback control ensures that air flow through inactive nozzles is restricted when needed to maintain flame stability, while allowing simple shutdown operation when combustion is not affected.
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 flow modulator effectively reduces cold-air quenching and maintains flame stability in fueled nozzles during turndown operations, enabling compliance with emissions limits and extending the operating range of gas turbines.
Implementation Method 1
pneumatically displacing a movable inner tube within a fixed outer tube
Data Source
AI summary
A flow modulator for a fuel nozzle, including: a fixed outer tube, the fixed outer tube including a set of apertures; a movable inner tube concentrically positioned within the fixed outer tube, the movable inner tube including a set of apertures; and a pneumatically actuated component for displacing the movable inner tube within the fixed outer tube to selectively align the set of apertures of the fixed outer tube with the set of apertures of the movable inner tube.