Film Cooling (Rocketry)
Script error: No such module "Draft topics".
Script error: No such module "AfC topic".
Film cooling is a crucial technique in rocket engines to protect components, such as the combustion chamber and nozzle, from the intense heat generated during propellant combustion. This method involves circulating the coolant through channels or tubes in the engine structure and expelling it through small openings in the component's surfaces to absorb and dissipate heat effectively. This forms a protective film, reducing temperatures and preventing structural damage.
Film Cooling Mechanism[edit]
Film cooling is a dynamic process where the coolant, fuel or oxidizer, in either liquid or gaseous form, is injected along the inside walls of the combustion chamber and nozzle.
This injection creates a protective boundary layer, acting as insulation against the hot gases produced during combustion. The coolant, typically extra fuel, flows along the chamber walls, forming a thin film coating that absorbs and carries away heat, preventing damage to the engine walls.[1]
In film cooling, a higher concentration of fuel or oxidizer is strategically injected around the outer perimeter of the injector face. This creates an unreacted fuel layer along the chamber walls, acting as a heat-absorbing film. Holes can also be drilled into regeneratively cooled walls to allow controlled amounts of liquid fuel to leak in, addressing hotspots such as the throat of the engine.
Using fuel as a coolant, especially with carbon-based fuels like RP-1, has an additional side effect. It creates a carbon layer, or coking, along the walls. In engines like Merlin, SpaceX deliberately runs the gas generator very fuel-rich to prevent turbine meltdown. This process produces a dark and sooty exhaust, and while it's not ideal for injectors and cooling holes, the soot on the walls acts as an extra thermal shield.[2]
Use of turbine exhaust gas[edit]
In certain cases, cooler turbine exhaust gas is employed for film cooling in specific engine sections.
Several open-cycle rocket engines have turbine exhaust gas delivered to the nozzle for film cooling, including the F1 engine and J2 engine, the LE5 engine and Vulcain 2.
It facilitates temperature regulation in specific engine sections, ensuring that critical areas maintain lower temperatures. This enhances the engine's overall thermal management.[3]
Combined with regenerative cooling[edit]
Film cooling is frequently used alongside regenerative cooling. Regenerative cooling involves circulating the fuel around the combustion chamber and nozzle walls before it is injected into the combustion process.
Both are often used together in rocket engines to optimize the cooling process, by providing an additional layer of temperature control.
Regenerative cooling is used for cooling the chamber walls, throat and the first section of the nozzle, and for the inside of the engine, some film cooling is done. Film cooling with the gas generator exhaust at the nozzle extension is utilized when the regenerative cooling channels end.[4]
Cooling Efficiency[edit]
Film cooling efficiency is a critical parameter, defined as the ratio of the achieved wall temperature reduction to the maximum theoretically possible reduction. Researchers have developed theoretical film cooling models and methods for calculating cooling efficiencies from experimental data.
These models provide insights into the complex interaction between hot gas and coolant, contributing to a better understanding of film cooling behavior under various conditions.[5]
Experimental Studies[edit]
Recent experimental studies have focused on supersonic, tangential film cooling in the expansion part of nozzles with rocket-engine-like hot gas conditions.
These studies involve parametric investigations in conical nozzles and the development of new film cooling models. The aim is to provide a better understanding of film cooling behavior in conditions characterized by high stagnation temperatures and pressures.[6]
The utilization of film cooling represents a strategic engineering choice, showcasing the synergy between historical rocket designs and modern innovations in thermal control. This method stands as a testament to the industry's relentless pursuit of efficiency and reliability in propelling humanity toward the stars.
See also[edit]
References[edit]
- ↑ Wessels, Wessel (2022-04-04). "How Rocket Engines Stay Cool And Don't Melt". Headed For Space. Retrieved 2023-11-11.
- ↑ Percival, Claire (2022-01-13). "Engine Cooling - Why Rocket Engines Don't Melt". Everyday Astronaut. Retrieved 2023-11-11.
- ↑ Shine, S. R.; Nidhi, S. Shri (2018-03-01). "Review on film cooling of liquid rocket engines". Propulsion and Power Research. 7 (1): 1–18. Bibcode:2018PPR.....7....1S. doi:10.1016/j.jppr.2018.01.004. ISSN 2212-540X.
- ↑ Percival, Claire (2022-01-13). "Engine Cooling - Why Rocket Engines Don't Melt". Everyday Astronaut. Retrieved 2023-11-11.
- ↑ Ludescher, Sandra; Olivier, Herbert (2021), Adams, Nikolaus A.; Schröder, Wolfgang; Radespiel, Rolf; Haidn, Oskar J., eds., "Film Cooling in Rocket Nozzles", Future Space-Transport-System Components under High Thermal and Mechanical Loads: Results from the DFG Collaborative Research Center TRR40, Notes on Numerical Fluid Mechanics and Multidisciplinary Design, Cham: Springer International Publishing, pp. 65–78, doi:10.1007/978-3-030-53847-7_4, ISBN 978-3-030-53847-7, retrieved 2023-11-11
- ↑ Ludescher, Sandra; Olivier, Herbert (2021), Adams, Nikolaus A.; Schröder, Wolfgang; Radespiel, Rolf; Haidn, Oskar J., eds., "Film Cooling in Rocket Nozzles", Future Space-Transport-System Components under High Thermal and Mechanical Loads: Results from the DFG Collaborative Research Center TRR40, Notes on Numerical Fluid Mechanics and Multidisciplinary Design, Cham: Springer International Publishing, pp. 65–78, doi:10.1007/978-3-030-53847-7_4, ISBN 978-3-030-53847-7, retrieved 2023-11-11
This article "Film Cooling (Rocketry)" is from Wikipedia. The list of its authors can be seen in its historical and/or the page Edithistory:Film Cooling (Rocketry). Articles copied from Draft Namespace on Wikipedia could be seen on the Draft Namespace of Wikipedia and not main one.
