Numerical Simulation of Reactive Flows in Overexpanded Supersonic Nozzle with Film Cooling

Abstract

Reignition phenomena occurring in a supersonic nozzle flow may present a crucial safety issue for rocket propulsion systems. These phenomena concern mainly rocket engines which use H2gas (GH2) in the film cooling device, particularly when the nozzle operates under over expanded flow conditions at sea level or at low altitudes. Consequently, the induced wall thermal loads can lead to the nozzle geometry alteration, which in turn, leads to the appearance of strong side loads that may be detrimental to the rocket engine structural integrity. It is therefore necessary to understand both aerodynamic and chemical mechanisms that are at the origin of these processes. This paper is a numerical contribution which reports results from CFD analysis carried out for supersonic reactive flows in a planar nozzle cooled with GH2film. Like the experimental observations, CFD simulations showed their ability to highlight these phenomena for the same nozzle flow conditions. Induced thermal load are also analyzed in terms of cooling efficiency and the results already give an idea on their magnitude. It was also shown that slightly increasing the film injection pressure can avoid the reignition phenomena by moving the separation shock towards the nozzle exit section.

Numerical Study on Combustion and Atomization Characteristics of Coaxial Injectors for LOX/Methane Engine

“…Model. The governing equation is the three-dimensional Reynolds-averaged Navier-Stokes (RANS) equation in the Eulerian coordinate system, including continuity, momentum, and energy equations [27,28].…”

Propulsion and Thermodynamic Parameters of van der Waals Gases in Rocket Nozzles

“…where subscript "t" indicates the throat conditions. Replacing equations (11) and (13) into equation (14) yields the nozzle throat temperature:…”

“…Chamber conditions also can be affected by real gas behavior, such as equilibrium composition and temperature, reaction rates, and other combustion parameters, especially at high pressures [7,8]. Other pro-cesses can affect the performance of nozzles and propulsion parameters, such as viscous losses, chemical kinetics, heat transfer, boundary layer, flow separation, shock waves, twophase flow, and three-dimensional effects [9][10][11][12][13]. Correction factors are often used to estimate the performance of real nozzles; however, there is limited information about the effects of real gases and variable properties.…”