Micro-Flameholders for Rayleigh-Taylor Combustion Mixing
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Solution Overview
Problem
Conventional combustors face challenges in achieving efficient interpenetration and mixing of reactants and combustion products, leading to suboptimal combustion efficiency and stability, especially under high acceleration conditions in engines like rotary ramjets, due to reliance on natural buoyancy or macro-scale aerodynamic flameholders which incur thermodynamic penalties.
Innovation Solution
The use of micro-flameholders within combustors to facilitate Rayleigh-Taylor instability, promoting interpenetration and mixing by creating transverse accelerations that induce large buoyancy forces, thereby enhancing RT-driven turbulence and reducing the need for macro-scale flameholders.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If macro-scale aerodynamic flameholders are used to maintain combustion, then flameholding performance is improved, but total pressure losses increase and thermodynamic efficiency decreases
Solution Approach 1:
The patent divides the continuous macro-scale flameholder into multiple discrete micro-flameholders arranged in an array. Each micro-flameholder is a small scale structure that individually stabilizes combustion, collectively providing flameholding performance comparable to macro-scale flameholders but with reduced flow blockage and pressure losses
Solution Approach 2:
The patent changes the scale parameter from macro to micro, transitioning from large continuous flameholder structures to small discrete micro-flameholder elements. This parameter change reduces the overall blockage ratio and flow resistance while maintaining combustion stability through the collective effect of multiple micro-structures
2Device complexity
If natural buoyancy is used for mixing reactants and combustion products, then device complexity is reduced, but mixing efficiency and combustion stability are insufficient under high acceleration conditions
Solution Approach 1:
The patent introduces dynamic elements including rotating or oscillating micro-flameholder structures that actively generate transverse accelerations. These dynamic motions create time-varying flow patterns and enhance mixing through inertial forces, allowing the system to maintain effective mixing under high acceleration conditions where static buoyancy mechanisms fail
Solution Approach 2:
The patent employs vibratory or oscillatory motion of micro-flameholders to generate transverse accelerations that drive Rayleigh-Taylor instability. This mechanical vibration creates periodic disturbances in the reactant-combustion product interface, enhancing mixing efficiency without requiring complex external actuation systems
3Productivity
If transverse acceleration is applied to enhance Rayleigh-Taylor instability, then interpenetration and mixing are improved, but device complexity and control requirements increase
Solution Approach 1:
The patent designs micro-flameholders that generate their own transverse accelerations through rotation or oscillation, making each element self-sufficient. The structures utilize the combustion process itself and available mechanical energy to produce the required accelerations, eliminating the need for external control systems while maintaining enhanced mixing and interpenetration
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 approach improves flameholding performance, expands blowout limits, increases combustion efficiency, and enhances thermodynamic efficiency with lower total pressure losses, allowing for stable combustion across a wider range of conditions without the penalties associated with macro-scale flameholders.
Implementation Method 1
The one or more micro-flameholders can be configured to facilitate or promote Rayleigh-Taylor instability in order to cause interpenetration of the reactants and the combustion products within the combustor
Implementation Method 2
creating transverse accelerations that induce large buoyancy forces, thereby enhancing RT-driven turbulence and reducing the need for macro-scale flameholders
Data Source
AI summary
Embodiments of the invention provide a system or a method for combusting reactants including a fuel and an oxidizer into combustion products in a combustor. A combustor can be configured to contain a flow of the reactants and the combustion products that extends in a first direction. The flow can be subject to acceleration in a second direction at least partly transverse to the first direction. One or more micro-flameholders can be disposed within the combustor at or upstream of a location at which the flow is subject to the acceleration in the second direction. The one or more micro-flameholders can be configured to facilitate or promote Rayleigh-Taylor instability to cause interpenetration of the reactants and the combustion products within the combustor.