Rocket Injector Resonator Damping Acoustic Instability
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Solution Overview
Problem
Existing injector devices for rocket engines face challenges in minimizing or eliminating acoustic pressure fluctuations in combustion chambers, which can lead to mechanical or thermal failures due to high-frequency thermoacoustic combustion instabilities, and current damping solutions like baffles and resonators are complex, inefficient, and difficult to design and test effectively.
Innovation Solution
The proposed injector device connects resonator elements directly to injection elements via fluid channels, ensuring identical conditions and allowing for efficient damping of pressure fluctuations across various operating states, eliminating the need for resonators in the combustion chamber wall and simplifying the design and production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If baffles are inserted into the combustion chamber to dampen transverse eigenmodes, then combustion instability is reduced, but the device complexity increases and longitudinal eigenmodes remain unaffected
Solution Approach 1:
The combustion chamber acoustic field is segmented into transverse and longitudinal eigenmodes, with different damping strategies applied to each. Baffles address transverse modes while resonator elements specifically target longitudinal modes, allowing independent optimization for each mode type without interfering with the other.
Solution Approach 2:
Resonator elements are introduced as intermediary components that specifically mediate the damping of longitudinal eigenmodes. These resonators act as acoustic intermediaries between the injection elements and the combustion chamber, providing targeted damping without requiring direct modification of the combustion chamber structure.
2Reliability
If resonators are installed in the combustion chamber wall, then longitudinal eigenmodes can be damped, but the manufacturing complexity and cooling channel routing become significantly more complex
Solution Approach 1:
The resonator elements are extracted from the combustion chamber wall and relocated to the injector device. This extraction eliminates the need to route cooling channels around resonators embedded in the combustion chamber, simplifying both the manufacturing of the combustion chamber and the cooling system design.
Solution Approach 2:
Instead of modifying the combustion chamber wall with resonators, the damping function is copied to the injector device. The resonator elements are replicated in the injector structure, maintaining the acoustic damping function while avoiding the manufacturing complexities of integrating resonators into the combustion chamber wall.
3Reliability
If the speed of sound in resonators is unknown due to uncertain gas composition and temperature, then resonator design becomes difficult, but extensive testing and simulations are required
Solution Approach 1:
The resonator elements are positioned within the injector device where they are exposed to the same fluid conditions as the injection elements. This self-service arrangement ensures that the resonators automatically experience identical gas composition and temperature conditions, eliminating the need for separate characterization and extensive testing.
Solution Approach 2:
By relocating resonators to the injector device, the operating parameters (temperature, pressure, gas composition) of the resonators are changed to match those of the injection elements. This parameter alignment simplifies the design process since the resonator performance can be directly correlated with the injection element operating conditions without requiring separate parameter characterization.
4Reliability
If resonators are designed for a specific combustion chamber mode at a defined operating point, then damping is effective at that point, but the resonators are not adapted during engine startup or shutdown
Solution Approach 1:
The resonator elements are merged with the injection elements into a single integrated injector device. This merging ensures that both components experience identical operating conditions and fluid properties throughout the entire operating range, allowing the resonators to automatically adapt to changing conditions during startup, shutdown, and steady-state operation.
Solution Approach 2:
The resonator elements are designed to dynamically respond to changing operating conditions by being positioned within the injector device where they experience real-time variations in temperature, pressure, and gas composition. This dynamic positioning allows the resonators to automatically adjust their damping characteristics across the full operating range without requiring separate adaptation 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 approach effectively minimizes acoustic pressure fluctuations, prevents flame oscillations, and allows for a more straightforward design and retrofitting of existing combustion chambers, reducing the complexity and cost of simulations and testing while ensuring consistent performance across different operating conditions.
Implementation Method 1
at least one first resonator element is assigned to the at least one first injection element and/or wherein at least one second resonator element is assigned to the at least one second injection element and wherein the at least one first resonator element is tuned to a natural frequency of the assigned at least one first injection element and/or that the at least one second resonator element is tuned to a natural frequency of the assigned at least one second injection element
Implementation Method 2
acoustic natural vibrations are damped in at least one first injection element and/or wherein acoustic natural vibrations are damped in at least one second injection element
Data Source
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AI summary
The invention relates to an injector device for an engine device for introducing a fluid fuel, in particular a liquid fuel, and a fluid oxidant, in particular a liquid oxidant, into a combustion chamber of the engine device, which injector device defines a longitudinal axis and comprises at least one first injection element, which is in the form of a first fluid channel for fluidically connecting a first collecting chamber for the fluid fuel and the combustion chamber, and at least one second injection element, which is in the form of a second fluid channel for fluidically connecting a second collecting chamber for the fluid oxidant and the combustion chamber. According to the invention, in order to improve the injector device in such a way that the amplification of acoustic pressure fluctuations in a combustion chamber is minimized or completely avoided, at least one first resonator element is associated with the at least one first injection element and/or at least one second resonator element is associated with the at least one second injection element and the at least one first resonator element is matched to a natural frequency of the associated at least one first injection element and/or the at least one second resonator element is matched to a natural frequency of the associated at least one second injection element. The invention also relates to an engine device, in particular for an air- and/or spacecraft, which engine device comprises a combustion chamber, the combustion chamber having a nozzle and an injection device arranged opposite the nozzle.