Variable Airflow Gas Turbine Combustor for LDI Stability
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Solution Overview
Problem
Conventional gas turbine engines with lean direct injection (LDI) combustion struggle with reduced combustion efficiency and stability at low fuel air ratios, limiting their operational range and increasing NOx emissions.
Innovation Solution
An annular combustor with selectively adjustable primary and dilution air admission nozzle geometries, allowing for varying airflow to match power demand, optimizing fuel air ratios across an extended range by adjusting nozzle areas to maximize or minimize airflow based on power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional LDI combustion is used with fixed airflow geometry, then combustion efficiency is maintained at high power demand, but combustion stability deteriorates at low fuel air ratios
Solution Approach 1:
The patent applies dynamics by making the primary combustion air admission nozzle geometry selectively adjustable. The nozzle flow area can be changed from a first geometry (maximum area) at high power demand to a second geometry (reduced area) at low power demand. This dynamic adjustment allows the system to adapt to varying operating conditions, maintaining both combustion efficiency and stability across the full power range.
2Object-generated harmful factors
If excess air is injected into the forward region to suppress NOx formation, then NOx emissions are reduced, but combustion stability deteriorates at low fuel air ratios
Solution Approach 1:
The patent applies parameter changes by selectively adjusting the nozzle flow area geometry based on power demand. At low power demand, the nozzle flow area is reduced to provide a more favorable fuel-air ratio for stable combustion, while still maintaining fuel-lean overall conditions to suppress NOx. This dynamic parameter adjustment resolves the contradiction between NOx suppression and combustion stability.
3Device complexity
If fixed nozzle geometry is used, then device complexity is minimized, but adaptability to different power demands is limited
Solution Approach 1:
The patent applies dynamics by implementing selectively adjustable nozzle flow area geometry. The system can transition between different nozzle geometries (first geometry for high power demand, second geometry for low power demand), enabling adaptation to various operational conditions while maintaining reasonable structural complexity through the use of adjustable mechanisms.
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 solution enables stable and efficient LDI combustion over a wide power demand range, reducing NOx formation by maintaining fuel-lean conditions and optimizing combustion efficiency, thereby improving engine performance and emissions control.
Implementation Method 1
The swirlers impart a swirl to primary combustion air entering the forward end of the combustion chamber at the bulkhead to provide rapid mixing of the fuel and combustion air
Implementation Method 2
Each primary combustion air admission nozzle has a selectively variable flow area geometry for varying the flow of primary combustion air admitted into the combustion chamber
Implementation Method 3
Each dilution air admission hole has a selectively variable flow area geometry for varying the flow of dilution air admitted into the combustion chamber
Implementation Method 4
The LDI combustion strategy recognizes that the conditions for NOx formation are most favorable at elevated combustion flame temperatures, i.e. when the fuel-air ratio is at or near stoichiometric
Implementation Method 5
more than the stoichiometric amount of air required for combustion of the fuel is injected into the forward region of the combustion chamber and rapidly mixed with the fuel to combust via a fuel-lean, as opposed to fuel-rich, process
Data Source
Figure 1~3
Figure 2
Figure 4~5
AI summary
An annular combustor and a method for operating a gas turbine engine over a power demand range facilitate combustion in a lean direct ignition (LDI) mode over an extended range of operating fuel air ratios. The flow primary combustion air admitted into the primary combustion zone is varied in response to power demand from a maximum air flow rate of high power demand to a minimum flow air rate of low power demand, while the flow of dilution air into a quench zone downstream of the primary combustion zone is increased from a minimum air flow rate at high power demand to a maximum air flow rate at low power demand.