Enhancing Combustion Characteristics in Cavity-Based Scramjet Combustors Using Diamond-Shaped Dual Struts

Scramjet propulsion systems are capable of space launches and provide excellent and efficient hypersonic flight; however, in supersonic conditions, they encounter difficulties with fuel mixing, ignition, and stable combustion, thus necessitating a thorough understanding of the underlying fluid dynamics and thermodynamic processes. To better understand the performance of a scramjet combustor, the following research examines a diamond-shaped dual strut design, the spacing between these struts, and a comparison between single and dual struts with the impacts of hydrogen-air-fueled combustion mechanisms. Furthermore, the study creates a rectangular hollow on both walls, 120 mm from the intake, and alters the lower wall angle to 3 degrees, matching the upper wall angle to the study for any changes. The combustion flow field of a typical strut-based scramjet combustor is simulated computationally using the two-dimensional coupled implicit Reynolds-averaged Navier-Stokes equations, the shear-stress transport k-ω turbulence model, and the finite-rate/eddy-dissipation reaction models for Mach numbers 2, 2.5, and 3 on ANSYS fluent. The experimental shadowgraph, velocity, and temperature measurements that are publicly available have been used to validate the numerical technique. Grid independence has been examined using the Grid Convergence Index (GCI) method, which keeps the Y+ value less than 1. The data obtained demonstrated that a dual strut with a cavity has a substantial impact on the creation of vortices, separation, and recirculation areas and gives an increase in both mixing and efficiency. When compared to a single diamond-shaped strut, the dual strut with a diamond shape has stronger and multiple shock reflections, which results in a wider recirculation region and vorticity generation. The length of the recirculation region filling the entire cavity boosts the minimal spacing's combustion efficiency when the flame stabilizes. In the hydrogen-air-fueled process, both expansion and shock waves coexist, with expansion waves developing before the typical shock wave. The waves are forced out of the combustor with a subsonic flow when injection pressure and temperature are increased from a shock wave to a normal wave.