The ignition of gas turbine engines at high altitude

One important requirement that a gas turbine engine has to fulfil is its altitude relight capability. Relighting this kind of engine at high altitude is more challenging than at sea level because of adverse temperature and pressure conditions. Furthermore the combustion efficiency is very low due to the poor fuel atomization quality, leading to slow shaft acceleration rates. This work deals with the most important subjects that can interest the ignition, in particular at high altitude. All the processes, parts of the engine and phenomena connected to the ignition are described, starting from a description of the most important engine’s components, till atomization, evaporation and ignition process, with also some digressions about fuel properties and different kind of atomizers and igniters. In the last chapter a simplified analysis is developed, trying to give an idea about what happen in the primary zone of the combustion chamber, in order to to build a box of conditions that allow the ignition of a gas turbine engine at any altitude, and so at any pressure and temperature conditions. The results are then compared with results found by Ballal and Lefebvre in his work about the influence of flow parameters on minimum ignition energy.