Cooling rocket nozzle extensions with supersonic gas injection

Rocket exhaust is extremely hot, often reaching temperatures of over 3,000 degrees Celsius. These extreme temperatures require extensive cooling support to maintain components all the way from the combustion chamber to the outer edge of the nozzle extension. In the outer region of the nozzle extension, the thrust gas is moving at supersonic speeds, limiting and complicating cooling options.

Peter and Kloker developed a numerical simulation of supersonic thrust gas in the rocket nozzle extension regime and studied the effects of film cooling on the system. They hope industry engineers will use their simulations to design next-generation rocket nozzles.

“Detailed insights into the fluid dynamics and thermodynamic fields are required to improve design tools for advanced rocket engines,” said author Johannes Peter. “Specialists in turbulence modeling are now working to improve their models using our data.”

The nozzle extension environment is challenging due to the large surface area of the material and the supersonic flow rate of the thrust gas. Existing cooling methods, such as regenerative cooling and liquid film cooling, are either unable to provide sufficient cooling or result in an unacceptable loss of efficiency.

The researchers instead examined gaseous film cooling and simulated a case where laminar supersonic helium gas is injected at the boundary layer and interacts with the turbulent supersonic thrust gas. They plan to continue this line of research.

“Additional physics will be incorporated into the simulations: a more complex wall shape and its surface quality, a refined injection slot geometry, as well as flow- and cooling-film control techniques like liners or plasma actuators to stabilize the cooling film for its better persistence,” said author Markus Kloker.

Source: “Direct numerical simulation of supersonic turbulent flow with film cooling by wall-parallel blowing,” by Johannes M. F. Peter and Markus J. Kloker, Physics of Fluids (2022). The article can be accessed at https://doi.org/10.1063/5.0080049 .