Acoustically Stable Combustion Chamber Design
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Solution Overview
Problem
Conventional combustion chambers for rocket engines face challenges in achieving acoustic stability at full-scale due to the complex interplay of acoustic modes and energy transfer, leading to instability and increased development costs and time, as small-scale models often fail to replicate the stability characteristics of larger systems.
Innovation Solution
A combustion chamber design with a diverging geometry and optimized injector configuration that shapes resonant acoustic modes to decouple them from driving mechanisms at the head portion and enhance coupling with damping mechanisms at the aft portion, using computer simulations to predetermine stability and performance levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If small-scale combustion chamber models are used for design and testing, then development cost and time are reduced, but the stability characteristics cannot be replicated in full-scale implementations
Solution Approach 1:
The patent applies parameter changes by modifying the combustion chamber geometry parameters, specifically the divergence angle of the aft portion, to optimize acoustic stability. By adjusting geometric parameters and using computerized simulations to predict stability characteristics, the design enables scaling from small models to full-scale implementations while maintaining acoustic stability, thus resolving the contradiction between development time and reliability.
2Ease of manufacture
If conventional combustion chamber geometries are used, then manufacturing is simpler, but acoustic instability occurs due to uncoupled resonant modes and driving mechanisms
Solution Approach 1:
The patent applies local quality by creating a diverging geometry in the aft portion of the combustion chamber, where the divergence angle is specifically optimized to enhance coupling between resonant acoustic modes and damping mechanisms. This localized geometric modification, rather than changing the entire chamber geometry, achieves acoustic stability while maintaining manufacturing feasibility, resolving the contradiction between ease of manufacture and reliability.
3Reliability
If full-scale combustion chamber testing is performed to verify acoustic stability, then reliability is improved, but development cost and time increase significantly
Solution Approach 1:
The patent applies preliminary action by using computerized simulations to predict acoustic stability characteristics before physical testing. The simulations allow for preliminary verification of stability properties, enabling designers to identify and correct potential issues before full-scale testing, thus reducing the time and cost associated with iterative physical testing while maintaining reliability verification.
4Reliability
If the combustion chamber geometry is modified to enhance acoustic damping, then stability is improved, but the complexity of the design increases
Solution Approach 1:
The patent applies segmentation by dividing the combustion chamber into distinct geometric sections with specific functions: a converging head portion for efficient combustion and a diverging aft portion for acoustic stability. This segmentation allows each section to be optimized independently, achieving acoustic stability through the aft portion's divergence angle while keeping the overall design relatively simple and manufacturable, thus resolving the contradiction between reliability and device complexity.
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 results in a scalable, acoustically stable combustion chamber that maintains stability across different scales, reducing the complexity and cost of full-scale model development by effectively decoupling acoustic modes from energy sources, thereby enhancing overall stability and performance.
Implementation Method 1
the geometry is predetermined to shape resonant acoustic modes to diminish coupling between the resonant acoustic modes and driving mechanisms at a head portion of the combustion chamber and to enhance coupling between the resonant acoustic modes and damping mechanisms at an aft portion of the combustion chamber
Implementation Method 2
a configuration of the injector ports alters a speed of sound profile of the combustion to draw resonant acoustic modes towards the aft portion of the combustion chamber where a speed of sound is configured to be lower relative to the head portion where a speed of sound is configured to be higher
Data Source
AI summary
An apparatus and/or system for an acoustically stable combustion chamber includes a combustion chamber with a geometry predetermined to shape resonant acoustic modes. The geometry diminishes coupling between resonant acoustic modes and driving mechanisms at a head portion and enhances coupling between resonant acoustic modes and damping mechanisms at an aft portion while meeting a predetermined stability level. The geometry diverges radially outward in an aftward direction at a divergence angle (AD) relative to a longitudinal axis, a diameter at the diverging portion is greater than at the injector end. An injector coupled at the head portion includes injector ports in a coplanar arrangement. The configuration of the injector ports alters the speed of sound profile of the combustion, drawing resonant acoustic modes towards the aft portion where the speed of sound is lower. Methods for simulating, designing, and using the acoustically stable combustion chamber are disclosed.