MNTRC Newsletter Vol. 20, Issue 3: Winter 2013

Biodiesel tests show possible use in transit buses

Ashok Kumar, PhD, Chair, Department of Civil Engineering

Laboratory equipment

Experimental setup used to simulate biodiesel fuels combustion emissions.

UNIVERSITY OF TOLEDO NEWS – Biodiesel is an alternative renewable fuel with growing use in transportation. The University of Toledo (UT) has been involved in research on biodiesel emissions for the last eight years. Today, however, UT is working on the “Combustion Chemistry of Biodiesel for the Use in Urban Transport Buses.” This comes under a research grant from the US Department of Transportation, Research and Innovative Technology Administration through Mineta National Transit Research Consortium (MNTRC).

The project is being directed by Ashok Kumar, PhD, Department of Civil Engineering and Dong-Shik Kim, PhD, Department of Chemical & Environmental Engineering. Mr. Hamid Omidvarborna and Mr. Sudheer Kumar Kuppili are participating in the project for their PhD and MS work respectively.

Many studies reported in the literature show that biodiesel could reduce exhaust emissions of particulate matter (PM) from vehicles. In this study, the research team performed idling tests on two engines installed with a catalytic convertor to characterize PM. Different urban transit buses installed with Cummin engines running on B20 (20 vol% of soybean biodiesel with 80 vol% Ultra Low Sulfur Diesel or ULSD) were selected. Tailpipe The team collected PM on filter papers and measured Total Particulate Mass (TPM).

Flash point test

In the flash point test, the blue flame occurs at specific temperatures during the fuel heating process. The igniter is passed over the fuel to torch the fuel fumes.

An accredited elemental laboratory carried out elemental analyses, Elemental Carbon (EC), and Organic Carbon (OC) of PM. The results showed that PM emissions significantly decreased when using B20, and that newer transit buses have a greater PM reduction than old buses when using ULSD.

More than 12 elements were considered for the elemental analyses, and the results showed that Calcium (Ca), Iron (Fe), and Sodium (Na) were found in the high concentrations. OC/EC analyses showed that more OC was emitted in cold idling (greater than %80) than hot idling (greater than %65). Furthermore, OC/EC ratio was greater for new buses with convertors (from 9.57 to 13.37) than for old buses without converters (from 1.85 to 4.55).

Positive Matrix Factorization (PMF) showed that four sources (fuel, oil and lubricant, engine parts, and ambient air) contributed heavily to PM generation in the exhaust. In the second paper to model the effect of process conditions on emissions, experimental study on the combustion parameters of biodiesel and characterization of the exhaust are studied. High oxygenated content of biodiesel makes biodiesel combustion more complete at higher temperature and pressure. To determine which emission elements are originating from the biodiesel fuel after combustion, the team performed elemental analyses on the collected PM samples. The results detected nine elements in the samples under the set of temperatures (750º F and 850º F), pressures (300 psi and 400 psi), and different blends of different biodiesels studied.

The combustion chamber experiment was carried out, and emission gas was analyzed using Gas Chromatograph (GC). The research showed that as the biodiesel volume percent increased, the linearly increased combustion temperature and pressure linearly increased. Aluminum (Al), Calcium (Ca), Chromium (Cr), Iron (Fe), Potassium (K), Magnesium (Mg), Sodium (Na), Sulfur (S), and Silicon (Si) were the major elements found in the PM emissions, with Na being the highest component. Understanding key elements of this chemistry is an important step toward intelligently selecting engine design, feedstock, combustion conditions, and next-generation alternative fuels.

This paper focuses on the development of a simple model to reproduce the reaction pathways of the biodiesel combustion observed in the laboratory. The general findings are also compared with transit buses running on B20 biodiesel.

Physical properties (cloud point, kinematic viscosity, and flash point) of biodiesel blends were measured. The physical properties of the biodiesel can be accounted for the pollutants released during its combustion in an engine.

Four different biodiesel blends (10, 20, 50, 100%) based on three feedstocks (white grease, soybean, and waste cooking oil) were tested, and the results were compared with ultra-low-sulfur diesel (ULSD). Of course, all tests were conducted according to the American Society for Testing and Materials (ASTM) standard methods.

The tested properties showed strong dependence on blends, which means that the percentage of biodiesel in a biodiesel/ULSD mixture is an important factor that determines the biodiesel properties. The research also found that the type of feedstock is a controlling factor in the biodiesel properties. Contents of saturated fatty acids and triglycerides at higher percentages are thought to be the main determinant of the degree of the dependence. It also causes undesired variations in the cold flow properties, kinematic viscosity, and flash point.

These variations may be controlled through modifications in the trans-esterification process or by using additives, which is much needed for a better future in which biodiesel plays a vital role in transportation. The physical properties of the biodiesel can be accounted for the pollutants released during its combustion in an engine.  

As a part of outreach activities, Mr. Omidvarborna and Mr. Kuppili will present individual posters at the Air and Waste Management Association’s (AWMA) 107th annual conference and exhibition in Long Beach, Calif., June 24-27, 2014.

Mr. Omidvarborna will present two papers – “Analysis of Particulate Matter (PM) from the Exhaust of Biodiesel Transit Buses under Idling Conditions” and “Experimental Evaluation of a Biodiesel Combustion Model Using a Laboratory Reactor” – in the technical and student poster sections.

Mr. Kuppili will present one paper, “Biodiesel Properties Depending on Blends and Feedstocks: Cloud Point, Kinematic Viscosity and Flash Point,” in the technical poster section.