Study of the effect of particles on the two-phase flow field and radiation in aluminized rocket engine plumes
Creators: name:  M.G. DE GIORGI 
name:   A.M. TOSCANO 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: PROPULSION PHYSICS
SOLID ROCKET MOTOR

description: In a typical rocket motor the propellant is burned in the combustion chamber, after the combustion products pass through a convergent-divergent nozzle where with a rapid expansion the exhaust jet is formed. The exhaust gases of rockets leave the nozzle outlet at very high temperatures, knowledge of thermal produced emissions is a crucial aspect during the design and the tests of the rocket motors. The thermal radiation signature produced by rocket engine exhaust plumes is a challenging phenomenon to analyze. The thermal emissions is affected by several characteristics, such as: motor type; propellant type, liquid or solid; additives in each propellant; burn time; rocket geometry and furthermore results to be influenced by other causes such as the trajectory of the rocket, the atmosphere conditions, the models used for the calculation of gas and particles radiative properties. In this paper, a signature analysis procedure was developed to understand the spectral characteristics of exhaust plumes in detail. Hence a detailed description of radiative particles properties as well as the measurement of the exhaust plume temperature and its distribution are important, because radiative heat transfer leads to a rise of the rocket surface temperature by several hundred degrees, resulting in a deterioration of the rocket base. Moreover, the rocket plume plays an important role in the operation of target detection, tracking, classification and identification. The rocket thermal radiation is in visible, infrared and ultraviolet regions. The infrared radiation mostly is given by the gas radiation of the some combustion products as CO2 and H2O, and the continuous spectral radiation of smoke solid micro particles. As a matter of fact in the solid rocket motor propellant generally there are additives such as boron and aluminum. The Al2O3 particles in the exhaust plume produce emission spectra in ultraviolet band due to the high temperature that reaches values in the range 2000-3000K. Moreover the high temperature iron oxide particles also emit in the ultraviolet spectrum. Finally the unburned fuels in the exhaust plume generate high concentrations of C, N, and H, among which the chemical reactions produce a large number of free photons, and the chemiluminescence participated by these free photons will also produce ultraviolet radiation [1]. To study the exhaust plume leaving the nozzle outlet, it is necessary to simulate compressible flow through and beyond rocket engine nozzle. For this purpose, commercial computational fluid dynamics software, ANSYS Fluent 2020 CFD, is used. The turbulent flow of the high speed combustion jet is described with the axisymmetric form of the Navier Stokes equation coupled with the turbulence model k - ?, solved with a pressure-based solver formulation with second-order weighted upwind central spatial discretization. Substantial efforts have been directed to studying the effects of afterburning reactions on IR signatures and predicting how different parameters of the propellant components affect the spectral radiation signature of the exhaust plume.