ID 251

Spray characterisation of Heavy Fuel Oil (HFO) in spray flames and impact on Particulate Emissions

 

Abstract:

Heavy Fuel Oil (HFO) is extensively used as a fuel in industrial burners and marine engines. Heavier hydrocarbons present in HFO present challenges in terms of atomisation and combustion due to the very high viscosity, high boiling temperature and low H/C ratio. Poor atomisation results in incomplete droplet combustion leading to emission of soot particles and cenospheres. An experimental study is carried to investigate impact of spray characteristics of HFO spray on cenosphere formation. An experimental setup is built to inject a dilute HFO spray in a hot environment mimicking spray flame combustion. It is found that HFO spray characteristics considerably change in the combustion environment. It is challenging to image droplets using shadowgraphy in a high temperature environment due to higher thermal gradients. Hence, a novel technique is employed to image HFO droplets in a hot spray flame environment using the Laser Induced Fluorescence (LIF) technique. Using this technique, HFO spray characteristics are measured under co-flow temperatures ranging from 550°C to 1100°C. The increasing co-flow temperatures result in reduced viscosity of HFO liquid column thereby improving atomisation and generating finer HFO droplets. Particulate emissions were measured using Aerodynamics Particle Size spectroscopy. It was found that cenosphere emissions reduced from 11543 per cm3 to 5112 per cm3 with reduction in SMD. It was also observed that finer droplets result in complete combustion of HFO droplets and fewer droplets undergo droplet pyrolysis leading to reduced cenosphere emissions.