Junsu Shin

Numerical Investigation of a Model Scramjet Combustor Using DDES

Abstract Non-reactive flows moving through a model scramjet were investigated using a delayed detached eddy simulation (DDES), which is a hybrid scheme combining Reynolds averaged Navier-Stokes scheme and a large eddy simulation. The three dimensional Navier-Stokes equations were solved numerically on a structural grid using finite volume methods. An in-house was developed. This code used a monotonic upstream-centered scheme for conservation laws (MUSCL) with an advection upstream splitting method by pressure weight function (AUSMPW+) for space. In addition, a 4th order Runge-Kutta scheme was used with preconditioning for time integration. The geometries and boundary conditions of a scramjet combustor operated by DLR, a German aerospace center, were considered. The profiles of the lower wall pressure and axial velocity obtained from a time-averaged solution were compared with experimental results. Also, the mixing efficiency and total pressure recovery factor were provided in order to inspect the performance of the combustor.

Comparison of Hybrid RANS/LES Methods for Supersonic Combustion in a Model Scramjet Combustor

Numerical studies are carried out on the boundary layer behavior on a flat plate as well as on the non-reactive and reactive flows in a scramjet combustor to analyze the effects of various hybrid RANS/LES methods. Three hybrid RANS/LES methods are selected—an improved delayed detached eddy simulation, the l 2ω-detached eddy simulation, and the dynamic l 2ω-detached eddy simulation. The present method is based on the finite-volume approach on structured mesh, and the governing equations are treated using the Favre averaging approach. Inviscid fluxes are discretized using 5th order WENO schemes. Turbulent combustion is modeled as a level-set flamelet model. Based on the results from the flat plate and the non-reacting and reacting simulation, most of the hybrid RANS/LES methods show equivalent trends. However, dramatic differences are found in the calculations for the improved delayed detached eddy simulation and dynamic l 2ω-detached eddy simulation in terms of eddy capturing.

Study on Boron-bead Combustion Characteristics for High Energy Gas Generator

The combustion characteristics of Boron-beads to improve the energy density of gas generator has been investigated in accordance with diameter of beads and their composition. In this paper, electrically heated tungsten sheet and visualized furnace are applied to measure ignition temperature and burning time of bead respectively. The results proposes ignition temperature between 720~800 K and burning time proportional to bead diameter. Also a ignition delay of boron particle is detected through the temperature and radiation intensity measurements.

Effect of Particle Size and Velocity Ratio on the Flow Mixing Characteristics in the Secondary Combustor

In this study, the effect of velocity ratio and particle size on the flow mixing characteristics in the secondary combustor was investigated. Both PIV(Particle Image Velocimetry) technique and LES(Large Eddy Simulation) were applied. Two sizes of Polystyrene PIV seeding particle of 5 and 50 μm, and three velocity ratios of 5, 3, and 1.5 were considered. Results showed that the mixing of two air streams created reattachment and recirculation regions. The size of the recirculation region was decreased as the velocity ratio increased. For the larger particle cases, due to the increased momentum by the larger particles, the size of the recirculating regions were larger than that of the smaller particle cases and the effect of the velocity ratio was not as significant as in the smaller particle case.