Computational Uncertainty Quantification of Thermal Radiation in Supersonic Combustion Chambers.

Abstract

The scramjet engine is an air-breathing jet propulsion system for hypersonic vehicles. Currently, the scramjet exists at an experimental development stage, with numerous physical phenomena necessary for the prediction of flight behavior still uncharacterized. Thermal radiation is predicted to significantly affect the thermal management of scramjet engines, but it is difficult to completely characterize through measurements in experiments and, therefore, requires the use of computational modeling.

Two scramjet engines, the HyShot-II and HIFiRE-2 combustors, are simulated with radiative heat transfer approaches using the Ray Tracing and Discrete Ordinates Methods. The computational predictions characterize the thermal radiative heat transfer of the scramjet engines, and the numerical simulations are, themselves, characterized for the uncertainties in their predictions. Radiative wall heating and flow cooling are studied as the direct effects of thermal radiative heat transfer.

The realistic variation in the predictions of thermal radiation, known as computational uncertainty, is effected by a lack of numerical modeling convergence and numerical modeling truncations, as well as by a lack of knowledge of the scramjet flowfield parameters, spectral modeling parameters, and radiative boundary conditions. The factors of uncertainty are quantified in individual as well as ensemble investigations of the radiative heat flux uncertainty.

Experimental measurements of thermal radiation within a scramjet allow for a direct comparison to the computational predictions. The measurements are conducted for the HIFiRE-2 scramjet using a series of photodetectors whose fields of view can be directly modeled with a Ray Tracing approach. The comparison between experimental measurement and computational predictions has a partial agreement, giving support to the validity of the computational predictions.