M.Sc Thesis

M.Sc StudentGordana Roni
SubjectHigh Altitude Ignition Process in Small Jet Engine
DepartmentDepartment of Aerospace Engineering
Supervisor PROFESSOR EMERITUS Yeshayahou Levy


Manned and unmanned flight vehicles that are propelled by small gas turbine engines are limited in their flight altitude mainly by the low air density and the low temperature of the air that exists at high altitude. The present work is concerned with solutions for the ignition problem in small gas turbine engines using vaporizers. The solution that was implemented consisted of two types of sprayers: “Air Blast” and “Air Assist”. The mechanism that was developed, included design and manufacturing several accessories that assists to investigate the effect of the spray form and drop size distribution. Quantitative measurements of the droplet’s diameter performed using PDA (Phase Doppler Analyzer) facility, while investigating the influencing factors. Within the controlled parameters inside the combustion chamber it was found that the “assisting air” has a paramount influence on the size of the drops. The effect of pre-heating and also the measurement distance from the vaporizer edge were investigated. The experimental testing was concluded with the system being integrated into a combustion chamber segment of an engine in order to investigate ignition possibility in practical fuel and air-flow conditions. The ignition process took only several milliseconds. The research helped to implement the theory while combining two different spraying methods unified as a common system. The design solution is not expected to affect the steady state operation of the combustor in the engine where fuel is vaporized using vaporizers. The system has potential for increasing reliability that is critical for the engine activity and for the mission success.