Atomization and combustion of liquid biofuels

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dc.contributor Daly, Daniel T.
dc.contributor Midkiff, K. Clark
dc.contributor Schreiber, Willard C.
dc.contributor Taylor, Robert P.
dc.contributor.advisor Agrawal, Ajay K. Simmons, Benjamin 2017-03-01T14:46:58Z 2017-03-01T14:46:58Z 2011
dc.identifier.other u0015_0000001_0000706
dc.identifier.other Simmons_alatus_0004D_10827
dc.description Electronic Thesis or Dissertation
dc.description.abstract Biofuel research will continue to be important as the world seeks to address limited fossil fuel supplies, concerns over greenhouse gases, and demand for energy independence. Biofuels can meet these needs by being a potentially carbon neutral energy source that can be utilized wherever any of a vastly varied feedstock is available. Since much of the energy infrastructure is set up for liquid fuels, liquid biofuels should fill many needs. One common biofuel is biodiesel, produced from bio-oil to match physical properties (like viscosity) of conventional fuels such as diesel. Biodiesel is produced through the transesterification of a source bio-oil and results in the byproduct, glycerol. This study seeks to investigate the combustion performance of a soy biodiesel, the source vegetable oil (VO), and the byproduct glycerol, while using number 2 diesel as the baseline for comparison. This study implements a novel fuel atomization technique known as flow-blurring (FB) atomization to atomize and cleanly combust not only biodiesel but also VO and glycerol. FB atomization uses a simple geometry to create a two-phase air/fuel mixture upstream of an orifice to produce which results in very fine sprays which burn cleanly and produce lower CO and NOX as compared to standard air-blast (AB) fuel injectors. First, the combustion performance of biodiesel and VO are compared to a diesel baseline. Results indicate that the FB mechanism provides a simple technique that can be used to successfully atomize and combust VO with resulting emissions comparable to diesel fuel. It was also observed that the FB atomizer incurred no adverse pressure drop penalties when operating with VO or biodiesel. Next, a study into the combustion performance of glycerol was conducted. First glycerol was co-fired with methane in an un-insulated quartz combustor. Results show high combustion efficiency, although CO emissions at the combustor wall were high (~5000 ppm) because of heat loss. Insulating the combustor made it possible to burn pure glycerol flames. An optimum air to liquid mass ratio (ALR) was found and used to investigate combustion performance at three different heat release rates. Residence time in the combustor was found to be an important parameter to achieve low CO emissions. Finally, glycerol/ methane flames were investigated in the insulated chamber to demonstrate dual fuel capabilities of the combustor. The emissions were minimized by splitting methane flow between primary and atomizing air lines. Next, spray characteristics of the FB atomizer were compared to the AB atomizer using a phase Doppler particle analyzer (PDPA) system. Results for water as the liquid show that the FB atomizer produces sprays with smaller droplets and also a narrower range of droplet sizes. The FB injector also incurred a smaller pressure drop in the atomizing air line. The FB atomizer incurred higher pressure drop in the liquid supply line resulting from the intense two-phase mixing at the tip of the liquid tube. Next, non-reacting VO and diesel sprays were compared using the PDPA technique. Diesel sprays resulted in smaller droplets compared to VO sprays. Upon further investigation it was revealed that the majority of the fuel mass flow within both sprays passes through a region with similar droplet diameter. Therefore, the mass-weighted Sauter mean diameter (SMD) was similar for VO and diesel sprays in spite of the large difference in their kinematic viscosity. Finally, a reacting glycerol spray flame was investigated with the PDPA technique to establish velocity and droplet size trends. Glycerol sprays contain droplets comparable to those from VO cold sprays. In summary, this study establishes the potential of the FB atomizer: the ability to successfully atomize and combust highly viscous fuels with performance much superior to AB atomizers.
dc.format.extent 201 p.
dc.format.medium electronic
dc.format.mimetype application/pdf
dc.language English
dc.language.iso en_US
dc.publisher University of Alabama Libraries
dc.relation.ispartof The University of Alabama Electronic Theses and Dissertations
dc.relation.ispartof The University of Alabama Libraries Digital Collections
dc.relation.hasversion born digital
dc.rights All rights reserved by the author unless otherwise indicated.
dc.subject.other Mechanical engineering
dc.title Atomization and combustion of liquid biofuels
dc.type thesis
dc.type text University of Alabama. Dept. of Mechanical Engineering Mechanical Engineering The University of Alabama doctoral Ph.D.

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