Semester

Spring

Date of Graduation

2011

Document Type

Dissertation

Degree Type

PhD

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

W. Scott Wayne.

Abstract

The Center for Alternative Fuels, Engines, and Emissions (CAFEE) of West Virginia University (WVU) is developing the Integrated Bus Information System (IBIS), an information resource on transit bus emissions for vehicle procurement purposes. IBIS provides the transit bus industry with exhaust emissions information, including an emissions database, and predictive models for fuel economy (F.E.) and emissions. Inputs for the models are in the form of drive cycle metrics, but the knowledge of such metrics is not readily available for transit agencies.;The first part of this dissertation was an effort to close the gap between engineering drive cycle metrics and the information available to transit bus operators. In cooperation with WMATA Transit, an extensive evaluation to characterize transit bus operation was performed. This evaluation was based on GPS and ECU logs of diverse bus routes. Instantaneous speed and road grade were determined for all the routes. Transit operation was classified in four main service groups: Inner-City, Urban, Suburban, and Commuter. Characterizing transit bus operation played an important role because it defined the parameters, and their ranges, to be used in F.E. and emissions models.;The second part of the dissertation studied the effects that drive cycles have over emissions and F.E. of diesel-electric hybrid buses, focusing specifically in MY 2007--2009 diesel-electric serieshybrid 40' transit buses. Using ANL's PSAT, the hybrid bus was dynamically modeled and validated against chassis dynamometer test data. As part of the vehicle dynamic model, a model was developed for fuel consumption and NOx emissions of the Cummins ISB 260H diesel engine. The vehicle model was simulated over a variety of duty cycles assuming zero grade, producing a database of instantaneous fuel and NOx rates, with all tests satisfying SAE J2711's restriction for state of charge.;A regression based method was devised for predicting cycle F.E., CO 2, and NOx, in which the inputs were average speed, percentage idle, and characteristic acceleration. Fuel consumption and NOx were broken into the idle and driving contributions. The driving portion was predicted with average speed without idle and characteristic acceleration without grade, and then aggregated with the idle contribution. The proposed approach produced excellent predictions with coefficients of determination of 0.96 for F.E., 0.99 for CO2, and 0.99 for NOx.;A tool was developed to allow transit agencies to place hybrid buses in routes that take the most advantage of the hybrid-electric capabilities and to evaluate emissions impacts in strategic planning and vehicle procurement. The selection of the best routes is based on fuel savings. Depending on the route, hybrid transit buses have the potential for saving between 0.5 and 1.2 gallons of fuel per hour per vehicle and 5 to 12 kg of CO2 per hour.

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