Enhancing the mixing characteristics of multi-hydrogen jets in scramjet engines through the implementation of fuel injection strategies and vortex generator positioning

Abstract

Fuel injection strategies and vortex generators (VGs) play vital roles in effectively managing temperature distribution within the combustion chamber of scramjet engines. By optimizing the fuel injection mechanism and strategically positioning VGs, the efficiency of fuel/air mixing can be significantly improved. In this study, k-epsilon turbulence model used to accurately capture shock waves. The operating Mach number was maintained at 2.0 through the use of a pressure far-field inlet. The investigation focused on three different fuel injection mechanisms: backward-facing, transverse, and forward-facing, while also examining the mixing capabilities of VGs located at varying distances from the inlet. Detailed analysis was conducted to understand the impact of these factors. Backward flow injection was found to promote efficient mixing and reduce the risk of flame blowout. Furthermore, optimizing the injection location proved instrumental in enhancing fuel and air mixing efficiency, leading to higher Mach numbers and improved combustion efficiency. However, it is important to avoid excessively high Mach numbers as they can induce flame instability and blowout. Among the different injection methods, multiple port injection demonstrated the highest Mach numbers, while backward-facing injection yielded the lowest. Multiple port injection also achieved high static pressure. Introducing VGs into the system significantly increased static pressure, and optimal fuel injection and VGs location resulted in stable combustion, improved combustion efficiency, and minimized unburned fuel. The injection method and the presence of VGs greatly influenced turbulence kinetic energy. Notably, VGs located at distances of 81 mm and 31 mm from the inlet produced the highest turbulence intensity for forward-facing injection and transverse fuel injection, respectively.