Analysis and Control of Combustion Instabilities in Rocket Engines

Sound is the transmission of energy that is produced when two particles or objects undergo collision. It is one of the forms in which energy modulates and travels in a medium. Vibration is a phenomenon in which an object of mass executes a periodic oscillatory displacement when certain energy is transferred to it. Combustion is a chemical reaction in which a lot of molecules collide. Combustion instabilities occur in a reacting flow. It is a physical phenomenon. Combustion instabilities have mostly been studied in a particular flow but they also occur in real life. Real engines often feature specific unstable modes such as azimuthal instabilities in gas turbines or transverse modes in rocket chambers. Eddy simulation has been the major tool to study this type of instabilities so far but recently it has been proved to be insufficient to completely understand the complex nature of these instabilities [3]. These instabilities involve large Reynolds number, high pressure, densities in real engines. Combustion instabilities can occur at any part of the rocket propulsion system like nozzle, combustion chamber, injectors, feed systems and lines. Theory plays an important role in understanding and analysing these instabilities and the amount of damage they can cause to a particular object. In this paper we will look at different types or modes of combustion instabilities and active and passive ways to control them in real situations.