John T. Kubesh

Development of a Clean, Efficient, Propane-Fueled Tractor

Southwest Research Institute has developed a modern propane-fueled John Deere 5410 tractor through funding provided by the Propane Education and Research Council and the Texas Alternative Fuels Council with support from the John Deere Product Engineering Center. The project began in June 2001 and the tractor was completed in March 2002. The objective of this project was to develop an economical, commercially-viable propane-fueled heavy- duty engine for an off-road vehicle. Propane-fueled agricultural and construction equipment would be appropriate new applications for this engine. For example, large numbers of small agricultural tractors are used in both rural and urban settings for such tasks as mowing, right of way maintenance, etc. Use of diesel powered equipment in an urban environment contributes to ozone formation and particulate matter emissions, which are both air quality concerns. According to the Equipment Manufacturers Institute, in 1999, 47,181 tractors in the 30 - 75 kW range were sold in the U.S. The two states with the most purchases were Texas and California, both states that have documented air quality problems. The final converted LPG engine emissions, output power, and noise emissions compare favorably to the original diesel configuration. The diesel engine greatly exceeds the Tier 3 limits in terms of NO x + NMHC and PM. Although the propane engine produced slightly less power (∼ 8%) than the diesel engine, the NO x + NMHC emissions output was substantially reduced. The propane engine NO x + NMHC was approximately 44 percent that of the diesel engine. This reduction was primarily due to a large decrease in NO x , since the NMHC emissions from the propane engine were higher. The propane engine and diesel engine has similar CO levels. The propane engine had significantly lower particulate matter (PM), with a 92 percent reduction compared to the diesel engine. Following the laboratory engine and control system development, the engine was installed in a John Deere medium-duty model 5410 tractor. Fuel storage was provided by multiple conformable storage tanks, and a central refueling port was utilized for convenient refueling. All propane equipment installation was supervised by the Texas Railroad Commission. Further development of the control system for driveability was performed, in addition to troubleshooting of engine and propane system components.

Uncertainty in the Determination of Thermal Efficiency in Natural Gas Engines

This paper discusses the measurement of thermal efficiency for natural gas-fueled engines and the resulting uncertainty. Two methods for determining thermal efficiency are described in detail. For each method, the sources of uncertainty are identified and quantified, and an estimate of the overall uncertainty is calculated. The analysis indicates that a thermal efficiency calculation that uses a mass fuel flow rate measurement directly as a basis for the energy input rate provides less uncertainty than the other method that uses a volumetric flow measurement.Copyright