Characterization of Real-World Activity, Fuel Use, and Emissions for Selected Motor Graders fueled with Petroleum Diesel and B20 Biodiesel

摘要

Motor graders are a common type of nonroad vehicle used in many road construction and maintenance applications. In-use activity, fuel use, and emissions were measured for six selected motor graders using a portable emission measurement system (PEMS). Each motor grader was tested on petroleum diesel and B20 biodiesel. Duty cycles were quantified in terms of the empirical cumulative distribution function (ECDF) of manifold absolute pressure (MAP), which is an indicator of engine load. The motor graders were operated under normal duty cycles for road maintenance and repair at various locations in Wake and Nash Counties, NC. Approximately 3 hours of quality assured second-by-second data were obtained during each test. An empirical modal-based model of vehicle fuel use and emissions was developed, based on stratifying the data with respect to ranges of normalized MAP, in order to enable comparisons between duty cycles, motor graders, and fuels. Time-based emission factors were found to increase monotonically with MAP. Fuel-based emission factors were mainly sensitive to differences between idle and non-idle engine operation. Cycle average emission factors were estimated for road 'resurfacing,' 'roading,' and 'shouldering' activities. On average, the use of B20 instead of petroleum diesel leads to a negligible decrease of 1.6 percent in nitric oxide (NO) emission rate, and decreases of 19 to 22 percent in emission rates of carbon monoxide (CO), hydrocarbons (HC), and particulate matter (PM). Emission rates decrease significantly when comparing newer engine tier vehicles to older ones. Significant reductions in tail-pipe emissions accrue especially from the use of B20 and adoption of newer vehicles.