PhD Defense by Hafiz M. Amin

Jan 31 2018 05:00 PM - Jan 31 2018 06:00 PM


Join Hafiz M. Amin as he presents his Ph.D. defense titled "Investigating Soot Morphology in Counterflow Flames at Elevated Pressures".

Time: 5:00 pm, Wednesday, 31 January 2018

Location: Building 5, lev. 5. Room 5209

Abstract

Practical combustion devices such as gas turbines and diesel engines operate at high pressures to increase their efficiency. Pressure significantly increases the overall soot yield. Morphology of these ultra-fine particles determines their airborne lifetime and their interaction with the human respiratory system. Therefore, investigating soot morphology at high pressure is of practical relevance.

In this work, a novel experimental setup has been designed and built to study the soot morphology at elevated pressures. The experimental setup consists of a pressure vessel, which can provide optical access from 10° to 165° for multi-angle light scattering, and a counterflow burner which produces laminar flames at elevated pressures.

In the first part of the study, N2-diluted ethylene/air and ethane air counterflow flames are stabilized from 2 to 5 atm. Two-angle light scattering and extinction technique have been used to study the effects of pressure on soot parameters. Path averaged soot volume fraction is found to be very sensitive to pressure and increased significantly from 2 to 5 atm. Primary particle size and aggregate size also increased with pressure.

Multi-angle light scattering is also performed and flames are investigated from 3 to 5 atm. Scattering to absorption ratio is calculated from multi-angle light scattering and extinction data. Scattering to absorption ratio increased with pressure whereas the number of primary particles in an aggregate decreased with increasing pressure.

In the next part of the study, Thermophoretic Sampling of soot is performed, in counterflow flames from 3 to 10 atm, followed by transmission electron microscopy. Mean primary particle size increased with pressure and these trends are consistent with our light scattering measurements. Fractal properties of soot aggregates are found to be insensitive to pressure.

2D diffused light line of sight attenuation (LOSA) and Laser Induced Incandescence (LII) are used to measure local soot volume fraction from 2 to 10 atm. Local soot volume fraction increased with pressure and soot concentration profiles showed good agreements when measured by both techniques. Experimental data obtained in this work is very helpful for the modelers for validating their codes and predicting the soot formation in pressurized flames.

Bio

Hafiz completed his B.Sc in Mechanical Engineering from the University of Engineering and Technology, Lahore in 2007. He worked as a Trainee Engineer in British Oxygen Company, Pakistan for a year before completing his Laurea Specialistica in Mechanical Engineering from Politecnico di Milano, Italy in 2010. After which he joined Genport S.r.l and worked as a Fuel Cell Development Research Engineer.

He joined the Clean Combustion Research Center for his Ph.D. research in 2011. His Ph.D. research was focused on developing a high-pressure experimental setup for soot studies and investigate soot morphology in pressurized flames using intrusive and non-intrusive diagnostics.