Session: 03-06 Liquid fuels

Paper Number: 80430

80430 - Spray Characterization of a Preheated Bio-Oil Surrogate at Elevated Pressures 

This research is an effort to facilitate the deployment of pyrolysis bio-oil derived from non-food biomass in micro gas turbines for power and/or heat generation. Bio-oil is widely regarded as one of the most economically feasible energy solutions with the potential to bridge the gap between fossil fuels and renewable energy resources. However, its utilization as a practical fuel is challenging due to the difficulties in its atomization and combustion, originating from the unfavorable physicochemical properties of bio-oils compared to those of conventional fossil oils. These include high viscosity, high water and oxygen contents, low energy density and thermo-chemical stability, as well as containing suspended solid particulates and non-volatile residue. Therefore, controlling and optimizing the operating conditions of a liquid-fueled gas turbine engine, particularly its atomizer, is necessary before the engine can be switched over from conventional fossil oils to bio-oils.

A wide variety of atomizers have been reported in the literature for the bio-oil atomization in micro gas turbines, from pressure nozzles to twin-fluid ones. Each of the nozzle designs works based on a specific atomization mechanism depending on the liquid injection pressure or atomizing airflow rate, which along with differences in their internal geometries, liquid properties (e.g., viscosity and surface tension), and ambient conditions (e.g., engine operating pressures), adds more complexities to the characterization of resulting sprays. In addition, different fuel preheating temperatures (up to 80°C) have been recommended to reduce the viscosity of bio-oils and facilitate their utilization in practical applications. All these variables increase the number of controlling parameters in the atomization of bio-oils, necessitating a detailed study on the spray characterization of bio-oils at realistic operating conditions.

The present study, therefore, aims at identifying proper conditions for the atomization of a preheated bio-oil at high pressure conditions (up to 7 bar), in the range of the working pressures of a micro gas turbine engine, by using its original equipment manufacturer (OEM) atomizer, named externally mixed twin-fluid nozzle. However, bio-oil mist must avoid being swallowed, inhaled, or exposed to direct eye contact. It can also cause corrosion and window-fouling challenges when using high precision measurement systems or sophisticated test facilities for cold spray evaluations in laboratory environments. Therefore, a safe, clean, and transparent surrogate of a bio-oil, developed in our previous study for different preheating temperature, is used for spray sizing and velocimetry at elevated pressures. In doing so, various optical diagnostics including phase doppler particle analyzer, laser diffraction particle analyzer, and laser sheet imaging are used. The spray characteristics of the bio-oil surrogate are compared with those of a nozzle calibration fluid, named MIL-PRF 7024E Type II, at similar test conditions to shed more lights on the practicality of replacing conventional fossil oils with bio-oils in micro gas turbines. The experimental results are also used to validate the previous spray correlations proposed for the nozzle investigated. The work would define the optimal parameters required for the efficient atomization of bio-oils at high pressure conditions, along with generating data which could be used to enhance the capabilities of the numerical simulations of micro gas turbine engines running on bio-oils.

Presenting Author: Mohsen Broumand University of Toronto; National Research Council Canada

Presenting Author Biography: Dr. Mohsen Broumand has received his PhD degree in Mechanical Engineering from the University of Manitoba in Canada and now is a joint postdoctoral fellow with the University of Toronto and the National Research Council of Canada (NRC). <br/>His research interests include Thermo-Fluids, Multiphase Flow, Heat Transfer and Combustion sciences with application in a broad range of topics; such as: Energy and the Environment, Nanotechnology and Manufacturing, Biotechnology, and Microfluidics. He is particularly intrigued by studying the heat transfer and fluid mechanics concepts in multiphase flows, as well as investigating their interfacial instabilities and transport phenomena when interacting with turbulence, acoustic perturbations, and electromagnetic waves. He has authored or co-authored a series of peer-reviewed papers on these topics.

Authors:

Mohsen Broumand University of Toronto
Murray Thomson University of Toronto
Sean Yun National Research Council Canada
Zekai Hong National Research Council Canada