Radially Staged RQL Combustor Premixing for Low Emissions
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Solution Overview
Problem
Conventional RQL combustors face challenges in achieving low emissions, good flame stability, and multifuel compatibility, particularly with low BTU gases, while maintaining durability and cost-effectiveness, due to issues with flame temperature control, fuel nozzle design, and mixedness of fuel-air mixtures.
Innovation Solution
A radially staged RQL combustor with tangential fuel-air premix chambers, featuring a toroidal primary combustion zone, elongated tubular premix chambers, and a secondary combustion zone, which ensures homogeneous fuel-air mixing, reduces stagnation areas, and incorporates ceramic materials to prevent coke formation, allowing for low-pressure fuel injection and efficient combustion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional RQL combustors use liquid or gaseous fuels with continuous flame, then combustion efficiency is improved, but flame temperature control becomes difficult leading to high emissions
Solution Approach 1:
The combustor is divided into multiple zones with different functions: a primary combustion zone for efficient burning, a secondary zone for temperature control, and a dilution zone for emissions reduction. This segmentation allows each zone to optimize its function while collectively achieving both high efficiency and low emissions
Solution Approach 2:
The invention changes the combustion parameters by using a premixed fuel-air mixture with specific equivalence ratios in different zones, controlling flame temperature to remain within the 2400-2800°F range. This parameter control enables simultaneous achievement of low CO/UHC and low NOx emissions
2Object-generated harmful factors
If variable geometry means are incorporated to control flame temperature, then emissions are reduced, but device complexity and maintenance cost increase
Solution Approach 1:
The fuel and air are premixed before entering the combustion zone, establishing the correct equivalence ratio in advance. This preliminary mixing action eliminates the need for complex variable geometry controls during operation, as the mixture composition is already optimized for the desired flame temperature range
Solution Approach 2:
The invention uses simple, fixed geometry combustor components rather than expensive variable geometry mechanisms. The design accepts that the combustor structure is relatively simple and non-adjustable, relying instead on precise fuel-air mixing ratios to achieve emissions control
3Object-generated harmful factors
If large quantities of engine air are admitted at the upstream end, then primary-zone temperature is lowered reducing NOx, but flame stability deteriorates
Solution Approach 1:
Air is introduced in staged quantities at different locations: primary air for combustion support at the upstream end, and secondary air for temperature control downstream. This segmentation ensures flame stability is maintained in the primary zone while NOx is controlled in the secondary zone
Solution Approach 2:
Different regions of the combustor have different air-fuel ratios optimized for their specific functions. The primary combustion zone maintains a richer mixture for stability, while the secondary and dilution zones use leaner mixtures for temperature control and emissions reduction
4Stability of the object's composition
If fuel nozzle assemblies are positioned in the forward end with tangential direction, then flame dispersion and stability are improved, but premix homogeneity becomes difficult to achieve
Solution Approach 1:
Fuel and air are mixed in a dedicated premixing section before entering the combustion zone. This preliminary mixing action ensures homogeneity is achieved before combustion begins, allowing the tangential nozzle positioning to focus on flame stability without compromising mixedness
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 solution achieves low emissions, high durability, and good flame stability across various power settings and engine speeds, enabling efficient combustion of multiple fuels, including low BTU gases, with reduced costs and complexity.
Implementation Method 1
tangential fuel-air premix chambers, featuring a toroidal primary combustion zone... ensures homogeneous fuel-air mixing
Implementation Method 2
RQL combustors have been in use for years... internal combustion energy means for a gas turbine engine
Data Source
AI summary
An improved fuel air premix chamber for a gas turbine engine. An integral heat exchange structure is used to cools the premix chamber outer wall, preheating the compressor air supply as it passes into an inner central longitudinal premix tube and preheating also the fuel and F/A mixture for an improved mix, low emissions combustion and low differential combustor pressure. The F/A premix flow thru the central longitudinal tubes and yields an exiting spouting velocity into the primary combustion zone for swirl/circumferential flow combustion yielding flame stability.