Combustor Air Chamber Prevents Back-flow in Low BTU Gas Turbines
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Solution Overview
Problem
Gas turbines face challenges in stabilizing combustion when operating on low BTU gases like blast furnace gas or coal gasification gas due to their low flame temperature and high nitrogen content, requiring additional pilot fuels and complex purge air systems to prevent back-flow and ensure stability, which increases costs and operational complexity.
Innovation Solution
A combustor and burner configuration that covers the gas nozzle jet holes with air flow during pilot fuel burning and supplies low BTU gas without air mixing during combustion, eliminating the need for a purge air system and ensuring stable mono-fuel operation by using a dual-perforated plate design with an air chamber to manage gas flow and prevent back-flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the opening area of the gas jet hole is excessively increased to ensure volumetric fuel flow of low BTU gas, then the fuel flow is improved, but high temperature combustion gas may back-flow from high-pressure side combustor to low-pressure side combustor
Solution Approach 1:
Air flow is introduced as an intermediary substance that fills the gas jet hole during pilot fuel burning, preventing combustion gas back-flow while allowing low BTU gas to flow through the same hole during combustion operation. The air chamber acts as a mediator to control the flow state of the jet hole dynamically.
Solution Approach 2:
The system dynamically changes the flow state of the gas jet hole based on operational mode. During pilot fuel burning, the jet hole is covered by air flow. During low BTU gas combustion, the jet hole opens to allow gas flow. This dynamic switching prevents back-flow during pilot operation while maintaining fuel flow during combustion.
2Object-affected harmful factors
If a purge air system is installed to prevent back-flow of combustion gas, then back-flow is prevented, but device complexity and cost increase
Solution Approach 1:
The air chamber and air flow system serve multiple functions: they provide atomizing air for fuel atomization, prevent combustion gas back-flow during pilot fuel burning, and enable dynamic control of the gas jet hole opening. This multi-functionality eliminates the need for a separate purge air system.
Solution Approach 2:
The existing air supply system for fuel atomization is utilized to also prevent back-flow and control jet hole opening. The system uses its own resources (air flow) to achieve additional functions, eliminating the need for external purge air equipment.
3Temperature
If cooling air is supplied across the gas flow passage to cool the fuel nozzle surface, then the nozzle is cooled, but combustion stability may be impaired
Solution Approach 1:
The cooling function is segmented and applied only to specific areas where heat accumulation occurs, rather than cooling the entire gas flow passage. The air chamber structure provides localized cooling to the fuel nozzle surface while maintaining combustion stability in the combustion chamber.
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 prevents high-temperature combustion gas back-flow and maintains combustion stability during both pilot fuel and low BTU gas operations, eliminating the need for a purge air system and enhancing operational efficiency and cost-effectiveness.
Implementation Method 1
a jet hole of a gas nozzle is covered by air flow to prevent the back-flow of combustion gas
Implementation Method 2
it is supplied to a combustion chamber without being mixed with air, so that even low BTU gas can stably be burned through diffusion combustion
Implementation Method 3
Contraction flow at air flow inlets and turbulence due to abrupt expansion at air flow outlets are used to rapidly mix the fuel with air in a short distance
Implementation Method 4
turbulence due to abrupt expansion at air flow outlets are used to rapidly mix the fuel with air
Data Source
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AI summary
A combustor 3 is provided that can ensure combustion stability even if being operated on low BTU gas 61a; 61b without the necessity of any equipment for preventing backflow of fuel gas during operation on pilot fuel 51. The combustor 3 includes: a first perforated plate 316 disposed upstream of a combustion chamber 12, the first perforated plate 316 having a plurality of nozzle holes 331, 332 and air holes 340; a second perforated plate 315 disposed on the upstream side of the first perforated plate 316; and a plurality of gas nozzles 320 each of which is inserted into a corresponding one of the nozzle holes 331, 332. The gas nozzle 320 has a leading end located inside the corresponding one of the nozzle holes 331, 332. Each of the gas nozzles 331, 332 includes: a jet hole portion 357 having a diameter smaller than that of a gas jet hole of the gas nozzle 320 and opposed to the combustion chamber 12 side; and a passage portion 358 designed to form an air passage on the outer circumference of the leading end portion of the gas nozzle 320. An air chamber 400 communicating the air passage 358 with the air hole 340 is defined between the first perforated plate 316 and the second perforated plate 315.