Passive Variable-Flow Liquid Rocket Injector for Deep Throttling
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Solution Overview
Problem
Deep throttling of liquid rocket engines poses challenges in minimizing pressure drop across the injector while avoiding coupling between the feed system and the thrust chamber.
Innovation Solution
A rocket combustion chamber injector with a passively varying flow area, comprising a housing, poppet, spring, and bellows, that adjusts the annular flow area based on propellant flow velocity to maintain a targeted pressure drop ratio across a range of flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If the flow area of the injector is reduced to minimize pressure drop during deep throttling, then the pressure drop across the injector decreases, but coupling between the feed system and the thrust chamber increases
Solution Approach 1:
The patent employs a poppet that can dynamically adjust its position to vary the flow area of the injector. During deep throttling, the poppet moves to reduce the flow area and minimize pressure drop, while during normal operation, it opens to maintain proper coupling characteristics. This dynamic adjustment allows the system to adapt to different operating conditions and resolve the contradiction between minimizing pressure drop and avoiding coupling.
Solution Approach 2:
The invention changes the flow area parameter of the injector by moving the poppet between different positions. This parameter change enables the injector to maintain optimal performance across a wide range of throttling conditions, specifically addressing the contradiction by reducing flow area during deep throttling to minimize pressure drop while preventing excessive coupling.
2Productivity
If the flow area is increased to allow higher flow rates, then productivity increases, but pressure drop across the injector increases
Solution Approach 1:
The poppet mechanism dynamically adjusts the flow area based on operating conditions. When higher flow rates are required, the poppet moves to increase the flow area, allowing productivity to increase. The system automatically balances this against the pressure drop increase, optimizing performance for the current operating point.
3Device complexity
If a fixed flow area injector is used, then device complexity is reduced, but adaptability to different flow rates and pressure conditions deteriorates
Solution Approach 1:
The patent introduces a dynamic element (the movable poppet) that allows the injector to adapt to different flow rates and pressure conditions. While this increases device complexity compared to a fixed injector, it provides significant adaptability benefits, enabling the injector to maintain optimal performance across a wide range of operating conditions including deep throttling.
Solution Approach 2:
The poppet mechanism is designed to automatically adjust the flow area in response to changing operating conditions without requiring external control systems. The injector essentially regulates itself, adapting to different flow rates and pressure conditions through the passive movement of the poppet, thereby providing adaptability while minimizing the complexity of control systems.
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 injector effectively maintains a pressure drop ratio within a target range of 15% to 25% across varying flow rates, minimizing pressure drop and preventing coupling between the injector and thrust chamber, thus optimizing engine performance.
Implementation Method 1
propellant flowing along the propellant flow path around the variable outer width portion applies a first axial force on the distal end of the poppet
Implementation Method 2
The spring is coupled to the proximal end of the poppet within the housing and is configured to apply a second axial force on the proximal end of the poppet
Implementation Method 3
the bellows comprises a plurality of openings through which propellant is configured to be transmitted to dampen movement of the poppet along the longitudinal axis
Data Source
AI summary
A variable flow area injector for a liquid rocket engine. The injector has a poppet with a variable outer width portion and a housing with a variable inner width portion. An annular flow path is defined between the variable width portions. Increased throttling of the engine passively increases the annular flow area of the injector by forcing the poppet in a distal direction. Decreased throttling allows a restoring spring to move the poppet in a proximal direction to decrease the annular flow area. A bellows can be included to dampen movement of the poppet. The bellows may be in a propellant-filled cavity separate from the main propellant flow path and have a series of openings through which the separate propellant flows.