Atomizers are primarily used to convert bulk liquid into small droplets. The design of fuel atomizer influences the combustion efficiency and pollutant emissions from the combustors. In the present work, numerical simulations are performed to model the flow inside the simplex atomizer and primary break-up of the liquid stream using a fixed-grid based technique of Volume Of Fluid (VOF) method. Axisymmetric simulations are considered, as they prove to be effective and economical for such problems. The validated numerical method is used for evaluating different injector designs for better performance. Further, an experimental study is also carried out to highlight the change in spray characteristics for atomizers with different internal geometries. Experimental techniques like shadowgraphy using backlight or laser beam (for spray imaging) and Phase Doppler Interferometry (for measuring drop sizes) are used. Overall, the numerical model is used to understand the flow phenomena occurring inside the atomizer such as air core formation, whereas experimental study is primarily intended to highlight the effects of injector geometry on the resulting spray outside the orifice.

As a sequel to the extensive studies carried out with a simplex atomizer, a novel Turbo Swirl Atomizer (TSA) is developed which exhibits better performance than pressure swirl atomizers in many aspects. It is based on the concept of imparting tangential momentum and kinetic energy to the fluid (fuel in the combustor) using a rotating spindle, rather than by high pressure drop, as in conventional pressure based atomizers. The atomization behavior of the novel Turbo swirl atomizer has been thoroughly studied experimentally, especially at low injection pressures for which the performance of the pressure swirl atomizer is poor. With the development of the new atomizer, an attempt has been made to achieve small drop sizes in an energy efficient manner at low injection pressures. Also, an air-swirler is incorporated, which is co-annular to the rotating spindle, to induce swirling air in the combustion chamber. The main purpose of using swirler is to enhance the break-up of droplets which are originally formed by rotating spindle utilized in the TSA. With this configuration, very small drop sizes (of the order of 20 micron) are achieved even at low injection pressures of the order of 1 bar.