Rocket Engine Injector With Choked-Flow Mixture Control
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Solution Overview
Problem
Existing rocket engine thrust control systems face challenges due to the nonlinearity and coupling of fluid-mechanical and thermodynamic processes, leading to feedbacks and oscillations, and are limited in control range and efficiency, especially in systems using separate control valves and variable area injectors.
Innovation Solution
An injector design that operates in a 'choked flow' state, where the throttle points are adjusted to ensure fluids flow at the speed of sound, decoupling mass flows from combustion chamber pressure, using a setting element to control the narrowest cross-section for both fuel and oxidant supplies, allowing precise control of total mass flow while maintaining constant mixture ratio and injection speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If separate control valves are used to throttle mass flows, then mass flow control is achieved, but the system becomes complex and limited in control range with power loss
Solution Approach 1:
The patent combines two separate control valves into a single integrated control element that simultaneously throttles both fuel and oxidant flows. This unified approach reduces system complexity while maintaining the ability to control mass flows, eliminating the need for separate valve mechanisms and reducing associated power losses and control limitations.
Solution Approach 2:
The single control element serves multiple functions by simultaneously controlling both fuel and oxidant mass flows, as well as adjusting injection speeds. This multi-functional design replaces the need for separate specialized valves for each function, simplifying the overall system while maintaining comprehensive control capabilities.
2Ease of operation
If variable area injector with axially displacing concentric conical surfaces is used, then injection speed control is achieved, but the injector geometry is complex and coupling between injection openings occurs
Solution Approach 1:
The patent divides the control function into separate adjustable elements for fuel and oxidant flows, allowing independent control of each injection opening while maintaining overall simplicity. This segmentation avoids the complex coupling inherent in concentric conical surface designs while preserving the ability to control injection speeds through geometric adjustments.
3Device complexity
If throttle points are not operated in cavitation range, then mass flow control is simplified, but mass flow becomes dependent on combustion chamber pressure causing feedbacks and oscillations
Solution Approach 1:
The patent operates the throttle points in the cavitation range, fundamentally changing the flow regime from pressure-dependent to geometry-dependent mass flow. This parameter change breaks the coupling between combustion chamber pressure and mass flow, eliminating feedbacks and oscillations while maintaining simple control through geometric adjustments of the throttle points.
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 design achieves stable combustion and simplified control by linearly varying mass flow and injection speeds through geometric adjustments, reducing nonlinearities and pressure dependencies, suitable for various propulsion systems including satellite control.
Implementation Method 1
the throttle points are configured such that, during operation, the fuel and the oxidant each flow through the narrowest cross-section of the throttle points at the speed of sound
Implementation Method 2
Systems which partially rely on the cavitation principle are also know; they are therefore partially pressure-decoupled
Data Source
AI summary
An injector for a rocket engine includes a base body in which a fuel supply and an oxidant supply are provided, and a setting element which, in cooperation with the base body, defines both a throttle point in the fuel supply and a throttle point in the oxidant supply, wherein the. The setting element is adjustable relative to the base body. The throttle points are configured such that, during operation, the fuel and the oxidant each flow through the narrowest cross-section of the throttle points at the speed of sound.