Retractable Igniter Pintle Injector for Stable Rocket Combustion
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Solution Overview
Problem
Rocket engines experience unpredictable imperfections in propellant mixing and combustion, leading to unstable combustion and limited throttling and restart capabilities due to complex injector designs, which restrict their performance across various flight regimes and environmental conditions.
Innovation Solution
A novel pintle injector design with a retractable concentric igniter and improved flow control sleeve that allows for full face shutoff and efficient radial spoke jet spray, ensuring stable combustion and throttleability by maintaining uniform flame front and recirculation patterns through symmetrical hot gas ignition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional shower spray type injectors are used, then multiple jets of fuel and oxidizer can be sprayed across the combustion chamber surface, but unstable combustion and uneven flame front propagation occur leading to limited throttling and restart capability
Solution Approach 1:
The patent extracts the ignition function from the main injector body by incorporating a separate, retractable igniter that can be inserted into the combustion chamber only when needed. This separation allows the injector to focus on stable propellant delivery while the igniter provides reliable ignition on demand, resolving the contradiction between injection coverage and combustion stability.
Solution Approach 2:
The igniter is designed to be retractable and movable, transitioning between retracted and extended positions. This dynamic capability allows the system to adapt between normal operation (igniter retracted) and ignition mode (igniter extended), enabling reliable restart capability and deep throttling while maintaining stable combustion during operation.
2Adaptability or versatility
If deep throttling and restart capability are implemented, then flexible operation across all power levels is achieved, but complex injector designs with multiple components increase device complexity
Solution Approach 1:
The patent merges the igniter and injector into a single integrated assembly where the igniter is housed within the injector body and shares common structural elements. This integration allows deep throttling and restart capability to be achieved without proportionally increasing device complexity, as the igniter utilizes the injector's existing mounting structure and sealing mechanisms.
Solution Approach 2:
The injector assembly serves multiple functions: propellant injection during normal operation, combustion stabilization, and ignition during restart. The retractable igniter adds ignition capability without requiring a completely separate system, making the overall device more versatile while minimizing additional complexity through multi-functionality.
3Device complexity
If conventional injectors are used without face shutoff capability, then simpler design is maintained, but dribble volume and unstable combustion occur at low power levels
Solution Approach 1:
The flow control sleeve is designed to be movable, allowing it to transition between partial opening (normal flow) and full closing (face shutoff) positions. This dynamic capability enables the injector to achieve complete face shutoff and eliminate dribble volume at low power levels, ensuring stable combustion without requiring overly complex additional components.
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 high combustion efficiency, scalability, and deep throttling capabilities, enabling stable thrust across all power levels and environmental conditions, while reducing engine size, mass, and manufacturing costs through simplified components and additive manufacturing.
Implementation Method 1
symmetrical jets of hot gas radiating from the centerline of the pintle injector to ignite the surrounding spray of fuel-oxidizer mixture
Implementation Method 2
A spark plug centered in the end of the igniter head
Implementation Method 3
The collision, or impinging of the fuel from behind on the oxidizer flow would produce a conical pattern concentric with the pintle
Data Source
AI summary
A rocket engine pintle injector with optimized spray pattern and with integrated igniter design for providing construction simplicity, throttleable thrust, stop/start/restart capability, optimized operational combustion, and improved ignition combustion stability. A user can start, throttle, and stop the engine by moving the internal concentric injector sleeve forward and backward to cause the fuel/oxidizer to spray out of the pintle head at different flow rates. The concentric igniter can be deployed so that the hot gasses or spark produced are radially projected into the spray of fuel/oxidizer surrounding the igniter. Once the fuel/oxidizer spray has been ignited, the igniter is stopped and retracted to protect the device from the heat of the combustion chamber and is ready for redeployment and restart of the engine as needed. Thus, a versatile, fully integrated, and scalable device can be used to start, throttle, stop, and restart any size rocket engine during any mission phase from launch to return from space.