Students: |
Shirish Bhide, Elana Chapman |
Faculty/Supervisors: |
Prof. Joseph Perez, Department of Chemical Engineering David Klinikowski, Pennsylvania Transportation Institute Dr. James Hansel, Air Products and Chemicals, Inc. Prof. André Boehman, Director of the Combustion Laboratory |
Sponsors: |
Pennsylvania Department of Environmental Protection, Program Manager - Susan Summers Federal Energy Technology Center, US Department of Energy, Program Manager - John Winslow Air Products and Chemicals, Inc., Program Manager - Peter J. A. Tijm Navistar International, Technical Consultants - X. Gui and Pranab Das Champion Motor Coach, Technical Consultant - Gerald Buck |
Objective: |
To determine a methodology for operating a production turbodiesel engine on dimethyl ether and demonstrate the performance, emissions and durability of the conversion approach in a Faculty/Staff shuttle bus on the University Park campus of the Pennsylvania State University. |
Approach: |
To protect the fuel pump and injectors from excessive wear, due to the lack of lubricity for DME, diesel and DME will be blended at levels that will provide sufficient lubricity to protect the fuel injection system. An external pressurized fuel delivery system will maintain 90 psi in the fuel lines to keep DME in the liquid phase and in solution with the diesel fuel. After the laboratory engine conversion, we will examine a range of DME/diesel blend ratios and will seek to operate the engine on as high a DME concentration as is possible, while still protecting the engine from excessive wear. Then, this conversion approach will be implemented on a Champion Motor Coach "Defender" model shuttle bus, equipped with the Navistar T444E. The Pennsylvania Transportation Institute will perform periodic performance and emissions tests on the shuttle bus during several years of operation on the University Park campus. |
Results: |
The laboratory studies have included combustion and emissions analyses in an engine test cell and fuel property studies in fuel characterization instruments at the Energy Institute. Laboratory engine tests were completed at 5 and 10 wt.% oxygen addition by blending DME and diesel fuel, which is equivalent to 15 vol.% (12.5 wt.%) and 30 vol.% (25 wt.%) DME addition, respectively. This work was reported in a Society of Automotive Engineers technical paper that was written on the results from the DME-diesel blend studies (SAE 2001-01-3626). The combustion and emissions studies demonstrated reduced particulate emissions with increasing DME blend ratio. However, the other emissions showed scattered results across the test modes. One reason for scatter in the gaseous emissions data was that the injection timing and injection pressure were changing as DME content increased at a particular speed and load. The fuel characterization tests focused on measurements of the viscosity of the fuel mixtures, which is seen to fall sharply as DME content increases. At 25-weight percent addition of DME, the viscosity of the fuel blend is near the lower limit of the allowable viscosity for diesel fuels. The combination of these laboratory studies provided the testing parameters and the expectations for the field demonstration. The fieldwork began with a detailed design process for implementation of the fuel blends and the fueling strategy on the shuttle bus. The rigorous design process for the system on the shuttle bus included a complete Failure Modes Effects Analysis, performed in collaboration with Air Products and Chemicals. The outcome was a fuel system design that anticipates and accounts for a variety of failure modes and potential hazards. This ensures maximum safety for the shuttle bus and its occupants. Also, the successful operation of the shuttle bus using blends of DME and diesel fuel has made this a unique project the world over. No other vehicle in operation uses DME- diesel blends, and only a handful of vehicles are running on DME at all. |
Photograph of the Navistar T444E V-8 turbodiesel engine that will be converted to DME fueling