Comparative Study of Spray of Different Liquids

Sprays can be defined as a dispersion of droplets with sufficient momentum to penetrate
the surrounding medium. Generally a spray is produced by using a nozzle which is
normally referred to as an atomizer and the surrounding medium is gaseous. Processes
utilizing droplets require enough momentum to transport the droplets to where they are
utilized or to provide mixing with the gas. Shape, pattern and some measure of droplet
sizes are the primary spray characteristics. The study of sprays of liquid fuels can be
hazardous and costly. However, by replacing the liquid fuel with non flammable liquids
such as water can reduce these problems. The objective of the project is to find whether
water has any similar characteristics with the selected liquid fuel or not. The studies
focus on two major components. Firstly, the study focuses on microscopic
characteristics such as droplet size and mean velocity. Spray characteristics of different
liquids (methanol, diesel and water) are analyzed by Laser Doppler Anemometry (LDA)
and Phase Doppler Anemometry (PDA). Laser Doppler Anemometry (LDA) systems are
used to measure droplet velocities of fluid sprays. Phase Doppler Anemometry (PDA)
systems are used to measure the droplet sizes of fluid sprays. A high speed camera is
used in the second part of the research in order to observe the structure of droplets,
measure the spray angles at nozzle exit and determine the droplets movement. Spray
angle variations are observed under different pressures for each fluid. From analysis of
the results, it is found that the water and diesel has similarity in Sauter Mean Diameter.
For both horizontal and vertical velocities, water and diesel did not have any similarity
in term of spray characteristics.