Study of an internally mixed liquid injector for active control of atomization process

This thesis describes an experimental and theoretical investigation of an internally mixed air assisted liquid injector. The primary objective of this research was to develop a liquid atomizer to actively control the atomization process for wide range of operating conditions of airborne gas turbine engines. An extensive experimental investigation of the developed internally mixed injector was carried out. The effects of atomizing air flow rate, liquid supply pressure, back pressure and injector geometry on the injector's performance were studied. The results showed that the atomization can be controlled by simultaneously varying the liquid supply pressure and the atomizing air flow rate. The results also showed that the range of obtainable droplet sizes does not change with the increase in the back pressure. The atomization improved with a decrease in the air injection area and an increase in the injector's length. In support of the experimental investigation, a theoretical study was carried out to model the two-phase flow through the injector and the atomization process. Its objective was to develop capabilities for predicting the dependence of injector's performance upon its design parameters and operating conditions. Fundamental conservation equations, along with appropriate boundary conditions, were used to model the two-phase air-liquid flow inside the injector and a critical Weber number criterion was used to describe the droplet formation process. The model predictions were compared with the experimental data and they were found to be in good qualitative agreement.