Variable-Flow Rocket Engine Injector for Deep-Throttle Pressure Control
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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, a poppet, a spring, and a bellows, which adjusts the annular flow area based on propellant flow velocity to maintain a target 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 is minimized, but coupling between the feed system and the thrust chamber occurs
Solution Approach 1:
The injector employs a movable poppet that dynamically adjusts the flow area based on operating conditions. During deep throttling, the poppet position changes to increase the flow area, preventing excessive pressure drop that would cause feed system-thrust chamber coupling. This dynamic adaptation allows the injector to maintain optimal performance across varying throttle levels.
Solution Approach 2:
The injector changes the flow area parameter in response to varying flow rates. The variable outer width portion of the poppet, when moved to different positions, alters the annular flow area to maintain a target pressure drop ratio (15-25%) across the injector, thereby preventing coupling while adapting to different operating conditions.
2Reliability
If the flow area of the injector is increased to avoid coupling between feed system and thrust chamber during deep throttling, then coupling is avoided, but the pressure drop across the injector increases
Solution Approach 1:
The movable poppet provides dynamic control of the flow area, allowing the system to adapt to different operating conditions. During deep throttling, the poppet adjusts its position to increase the flow area just enough to prevent coupling, while minimizing the pressure drop increase. This dynamic adjustment optimizes the balance between avoiding coupling and maintaining acceptable pressure drop.
Solution Approach 2:
The injector design incorporates feedback mechanisms where the propellant flow characteristics influence the poppet position. The variable flow area responds to changes in flow rate and pressure conditions, automatically adjusting to maintain the target pressure drop ratio and prevent coupling without requiring external control systems.
3Device complexity
If a fixed flow area injector is used, then the structure is simple, but it cannot maintain controlled pressure drop ratio across a range of flow rates during deep throttling
Solution Approach 1:
The injector incorporates a movable poppet with variable outer width that can adjust its position along the longitudinal axis, transforming a fixed-structure injector into a dynamic flow control device. This allows the flow area to vary with operating conditions while maintaining a relatively simple overall structure, achieving adaptability without excessive complexity.
Solution Approach 2:
The poppet is designed with a variable outer width portion that creates an annular flow area between itself and the housing. This segmentation of the flow path allows independent control of the flow area through poppet displacement, enabling pressure drop control across varying flow rates while maintaining structural simplicity.
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 solution effectively minimizes pressure drop and avoids coupling between the injector system and the thrust chamber, enabling deep throttling with a controlled pressure drop ratio of 15% to 25% across varying flow rates.
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.