Pintle Injector Tip Active Cooling via Propellant Flow
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Solution Overview
Problem
Conventional pintle injector tips for coaxial rocket engines face limitations in convenience and reuse due to the need for ablative layers that erode and char, requiring frequent replacement, which complicates the use and maintenance of reusable rockets.
Innovation Solution
The design incorporates a pintle tip with a central chamber and a secondary chamber, featuring apertures of varying path lengths and shapes to facilitate active cooling of the downstream face, reducing the need for ablative layers by directing propellant flows to cool the tip during combustion, with a secondary chamber having a thicker sidewall and longer path lengths to enhance cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pintle injector tips use ablative surfaces to protect from heat damage, then the downstream face is protected from heat, but the ablative layer must be replaced frequently due to erosion and charring
Solution Approach 1:
The invention extracts the ablative layer from the pintle tip design, eliminating the need for frequent replacements. Instead of relying on consumable ablative materials, the patent uses active cooling channels that circulate propellant through the pintle tip to remove heat, allowing the metal tip to be reused without degradation from thermal exposure
Solution Approach 2:
The cooling system uses the propellant itself as the cooling medium, eliminating the need for separate cooling systems or replacement parts. The propellant flowing through the central passageway is directed through cooling channels in the pintle tip, allowing the working fluid to simultaneously serve both combustion and cooling functions
2Temperature
If conventional pintle tips are made from copper or nickel with ablative layers, then heat resistance is improved, but the complexity of replacement and maintenance increases
Solution Approach 1:
The invention replaces the mechanical/chemical protection system (ablative layers that erode and char) with a thermal management system using fluid circulation. The propellant flows through internal cooling channels, transferring heat away from the pintle tip through convection, eliminating the need for mechanical replacement of protective layers
Solution Approach 2:
The propellant serving as both the combustion fuel and the cooling medium simultaneously performs multiple functions. The same liquid oxygen or other oxidizing propellant that fuels the combustion reaction also circulates through the cooling channels to remove heat from the pintle tip, simplifying the overall system
3Productivity
If the pintle tip downstream face is exposed to substantial heat from combustion, then combustion efficiency is maintained, but the tip material degrades requiring frequent replacement
Solution Approach 1:
The cooling channels are strategically positioned within the pintle tip structure, with apertures located at specific locations on the downstream face. This creates localized cooling zones where propellant is directed to the hottest areas, providing targeted thermal management without interfering with the overall combustion process and maintaining combustion efficiency
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 configuration effectively reduces the heat load on the pintle tip, minimizing the need for ablative layers and improving the stability and longevity of the tip, allowing for more convenient reuse and reduced maintenance in rocket engines.
Implementation Method 1
the flow of primary propellant through the secondary chamber sidewall cools a downstream face of the end wall during combustion of the mixed propellants adjacent the downstream face of the end wall
Data Source
AI summary
A bi-propellant rocket engine may include a primary propellant flowing in a central passageway, a secondary propellant flowing in a secondary passageway generally coaxial with central passageway and a pintle tip having a central chamber sidewall coaxial with the primary passageway and surrounding a central chamber, the central chamber sidewall having a first plurality of apertures there through so that some of the primary propellant exits the central chamber transverse to the flow of the secondary propellant in the secondary passageway. The pintle tip may have a secondary chamber sidewall, substantially thicker than the primary chamber sidewall, surrounding a secondary chamber downstream of and in fluid communication with the primary chamber, the secondary chamber sidewall having a second plurality of apertures there through so that some of the primary propellant exits the secondary chamber transverse to the flow of the secondary propellant in the secondary passageway. The pintle tip may have an end wall generally traverse to the flow of the primary propellant in the central passageway and adjacent the secondary chamber sidewall so that the flow of primary propellant through the secondary chamber sidewall cools a downstream face of the end wall during combustion of the mixed propellants adjacent the downstream face of the end wall. The pintle tip may be used for mixing a first liquid with a second liquid.