Above: North Carolina State University graduate researcher Brandon Graver takes a break from locomotive engine testing in the Raleigh, NC rail yard to catch up on some emails.
Measurement and Comparison of Locomotive Engine Emissions
Brandon M. Graver is a Graduate Researcher at North Carolina State University; Dr. H. Christopher Frey is Brandon's Faculty Advisor. His ongoing research is supported by the STC and the North Carolina Department of Transportation. Following is Brandon's summary of his research. - ed.
There are 22,800 Class I locomotives in the United States. The U.S rail infrastructure includes 95,800 miles of Class I freight rail, 22,000 miles of Amtrak passenger rail, and 10,600 miles of transit rail. Rail infrastructure, motive power, and rolling stock may undergo significant upgrading, at least in selected corridors, as a result of targeted Federal funding. In March 2008, the U.S. Environmental Protection Agency (EPA) finalized new rules on locomotive emissions. These rules apply to new and remanufactured locomotives. A locomotive chassis can be in service for decades, during which time the prime mover engine may be rebuilt perhaps every decade.
In this research, we focus on comparative assessment of the energy use and emissions of an existing fleet of five in-service passenger locomotives owned and operated by the North Carolina Department of Transportation. NCDOT operates a passenger rail service between Raleigh and Charlotte in cooperation with Amtrak. These passenger locomotives have 3,000 hp 2-stroke prime mover engines connected to a direct current generator in order to supply power to the traction motors, and a head-end power (HEP) engine of approximately 600 hp and 4-strokes connected to an alternating current generator to supply power for "hotel" services to the passenger train consist. We have used Portable Emission Measurement Systems (PEMS) to conduct rail yard tests for the purpose of benchmarking selected locomotives (three to date, with two additional planned) and as an aid in making decisions regarding the environmental goals for engine rebuilds.
In the rail yard tests, we quantified fuel-based (g/gallon) emission factors for nitric oxide (reported as equivalent NO2), carbon monoxide, hydrocarbons, and opacity for each of eight throttle notch settings plus idle. One of the locomotives, a GP40 originally manufactured in 1968, has since undergone a rebuild of the EMD16-645 mechanically governed prime mover engine. The remanufacturing facility where the rebuild occurred has a water brake dynamometer used for performance evaluation of the engine before it is re-installed in the locomotive, but does not have an emissions measurement capability. The use of certification test procedures and facilities for comparative assessments is prohibitively costly. We conducted PEMS measurements in combination with the performance dynamometer testing in order to provide real-time data to help optimize the engine configuration. Factors such as injector type and injection timing were varied from one test to another. The GP40 with remanufactured engine has returned to the rail yard in Raleigh and another rail yard test was completed in November 2009, which was used to assess the impact of the engine rebuild on energy use and emissions. Furthermore, over-the-rail measurements were conducted in December 2009.
The following research findings were presented at the 20th Coordinating Research Council On-Road Vehicle Emissions Workshop in March 2010: (1) the prime mover engine rebuild and optimization reduced fuel use and emission rates; (2) a typical duty cycle was inferred from over-the-rail testing; (3) the emission and fuel use rates from over-the-rail testing are approximately consistent with rail yard test results; and (4) the test method demonstrated is relatively inexpensive and enables a small railroad to assess trends and evaluate effectiveness of emission reduction strategies.
Future research plans include: (1) a continuation of rail yard, dynamometer, and over-the-rail testing of all locomotives in NCDOT's fleet; (2) a comparison of emissions for the prime mover engines for B20 biodiesel to ultra low sulfur diesel use; and (3) a comparison of over-the-rail fuel use and emissions on a per passenger basis to avoided highway vehicle fuel use and emissions.