Liquid-Propellant Rocket Engines

Liquid propellants have been used for a long time in rocket engines due to their higher specific impulse. Subsequently, liquid-propellant rocket engines (LPREs) underwent significant improvements that outweigh the performance of typical solid-propellant rockets. The main components of a typical LPRE are thrust chamber, injector, igniter, combustion chamber, nozzle, propellant tank, propellant feed system, and cooling system. Based on single liquid or two liquids, LPRE can be broadly classified into two types: monopropellant rocket engine and bipropellant rocket engine. The droplet size range for rocket engines is higher as compared to aerogas turbine combustor. The chapter explores how different phases take place in the combustion chamber for two types of liquid propellants, namely, hypergolic and nonhypergolic. A smaller combustion chamber that uses less reactive propellant is less prone to the bulk mode of combustion instability. Based on physical changes, the methodologies of controlling combustion instabilities can be broadly divided into three categories: chemical, aerodynamic, and mechanical.