Recent advances in fuel transport and fuel-air mixing processes in supersonic combustor for scramjet applications: A review

Abstract

Scramjet combustion technology faces many challenges because of supersonic flight, including air-fuel mixing, combustion stabilization, and aerothermodynamic stresses. Numerous researchers have tried a number of fuel injection systems, including strut injection, ramp injection, wall injection, and cavity injection, to address these problems. This study does a thorough analysis of the variables affecting the combustion performance, mixing efficiency, and total pressure loss within the combustion chamber of the scramjet engine. It focuses on aforementioned fuel injection techniques and how their geometry and position affect mixing and combustion efficiencies as well as overall pressure loss characteristics in the scramjet combustor. Furthermore, the latest developments in cavity-based injectors, including multiple cavities, cavity rear wall expansion strategy, and cavity dual fuel injection schemes, and strut-based injectors, including bumpy struts, blunting of the strut’s leading edge, strut plus wall injection, and double-nozzle strut, are reviewed. Based on observations, it is discovered that ramp in a strut-based combustor causes a delay in ignition and higher flame temperatures, which leads to a marginal increase in total pressure loss. On the other hand, compared to a single strut, multiple struts can improve combustion efficiency and mixing by facilitating the mixing of oxidizer and fuel by creating more vortexes, shock waves, and a wider recirculation zone. Positive aft cavity height and aft wall angle are important factors in cavity rear wall expansion technique that improve mixing efficiency.