Rocket Engine Nozzle Shutter for Reliable Ignition
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Solution Overview
Problem
Existing liquid propellant rocket engines face challenges in sealing the nozzle throat during ignition without increasing mass or cost, and in allowing multiple successful ignitions while maintaining a favorable length-to-diameter ratio in the combustion chamber.
Innovation Solution
A liquid propellant rocket engine with a selective closing device featuring an axisymmetric shutter member downstream of the nozzle neck, an axial control rod, and centering members with a specific diameter-to-length ratio, which automatically opens when pressure rises, eliminating the need for a control system and allowing complete closure of the nozzle neck.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a shutter is disposed upstream of the throat of the nozzle with a control system, then the nozzle neck can be sealed during ignition, but the volume of the combustion chamber increases and the length/diameter ratio becomes unfavorable
Solution Approach 1:
The shutter is inverted from the conventional upstream position to a downstream position behind the throat. This inversion allows the shutter to seal the nozzle neck from the rear, eliminating the need for a long guide structure in the combustion chamber and maintaining a favorable length/diameter ratio while preserving sealing capability
Solution Approach 2:
The shutter is designed with a specific geometry (discoidal shape with peripheral sealing elements) that allows it to seal the nozzle neck in a different dimensional arrangement - by blocking the flow path from the downstream side rather than from the upstream side, thus reducing the required combustion chamber volume
2Ease of operation
If a control system with locking in the open position is used, then the shutter can be maintained in the open position during operation, but the mass and manufacturing cost increase
Solution Approach 1:
The shutter system is designed to be self-regulating through its geometry and positioning. The shutter automatically moves to the closed position when combustion pressure exceeds a predetermined threshold and returns to the open position when pressure decreases, eliminating the need for external control systems, locking mechanisms, and actuators, thus reducing mass and manufacturing cost
Solution Approach 2:
The shutter's position is dynamically adjusted based on the combustion pressure parameter. When pressure exceeds a predetermined value, the shutter closes; when pressure drops below this value, the shutter opens. This parameter-based control eliminates the need for complex control systems while maintaining proper operation
3Device complexity
If an axisymmetric central core is disposed downstream of the throat, then the nozzle structure is simplified, but the core has a fixed position and cannot allow the nozzle neck to be closed
Solution Approach 1:
The shutter is designed as a movable component rather than a fixed structure. It can dynamically change position between closed and open states based on combustion pressure conditions, allowing the nozzle neck to be sealed when needed while maintaining a simple overall structure. The shutter is guided by two short centering members that allow axial movement while maintaining positioning
4Reliability
If a movable rod with shutter is used to close the nozzle neck, then sealing is achieved, but the flow in the combustion chamber is significantly disturbed
Solution Approach 1:
The shutter is designed with localized sealing elements (peripheral sealing lips or annular sealing surfaces) that concentrate the sealing function at specific locations rather than blocking the entire flow path. This localized approach allows sealing of the nozzle neck while minimizing disturbance to the overall combustion flow pattern
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 solution ensures reliable multiple ignitions without mass or cost increases, prevents pressure blockage, minimizes flow disturbance, and reduces mass and manufacturing costs by enabling automatic opening and closing of the nozzle neck.
Implementation Method 1
The system for returning the control rod to the closed position may comprise a calibrated spring
Implementation Method 2
The rise in pressure inside the combustion chamber induces a natural opening of the shutter at a predetermined pressure
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The engine has an annular type liquid-propellant injector device (8) injecting liquid-propellant into an upstream plate (51) of a combustion chamber (5). A selective shutter device shuts a nozzle throat (3). The shutter device has an axial control rod (7) to control an axially-symmetrical nose-cone shaped shutter unit (1). A short centering device (4) is placed in the chamber at the vicinity of the throat and at an upstream of the throat for centering the control rod. A rated spring (2) returns the rod to a closed position, where the chamber and the shutter unit are made of composite material.