Andrew J. Kean

A Fuel-Based Assessment of Off-Road Diesel Engine Emissions

ABSTRACT The use of diesel engines in off-road applications is a significant source of nitrogen oxides (NOx) and particulate matter (PM10). Such off-road applications include railroad locomotives, marine vessels, and equipment used for agriculture, construction, logging, and mining. Emissions from these sources are only beginning to be controlled. Due to the large number of these engines and their wide range of applications, total activity and emissions from these sources are uncertain. A method for estimating the emissions from off-road diesel engines based on the quantity of diesel fuel consumed is presented. Emission factors are normalized by fuel consumption, and total activity is estimated by the total fuel consumed. Total exhaust emissions from off-road diesel equipment (excluding locomotives and marine vessels) in the United States during 1996 have been estimated to be 1.2 × 109 kg NOx and 1.2 x 108 kg PM10. Emissions estimates published by the U.S. Environmental Protection Agency are 2.3 times higher for both NOx and exhaust PM10 emissions than estimates based directly on fuel consumption. These emissions estimates disagree mainly due to differences in activity estimates, rather than to differences in the emission factors. All current emission inventories for off-road engines are uncertain because of the limited in-use emissions testing that has been performed on these engines. Regional- and state-level breakdowns in diesel fuel consumption by off-road mobile sources are also presented. Taken together with on-road measurements of diesel engine emissions, results of this study suggest that in 1996, off-road diesel equipment (including

Important student misconceptions in mechanics and thermal science: Identification using Model-Eliciting Activities

As any engineering faculty member teaching undergraduates knows, students possess a wide variety of misconceptions about fundamental engineering concepts. In the thermal sciences, there are numerous misconceptions about heat, energy, and temperature; mechanics students hold misconceptions about inertia, angular velocity, and energy. This is complicated by the fact that we possess many years of everyday experiences with energy flows, forces, and kinematics. Due to previous experiences, it is often difficult to repair these misconceptions - simple classroom lecturing often fails to instill correct conceptual knowledge. In order to provide real-world context, we are developing model-eliciting activities (MEAs) to help repair misconceptions in dynamics and the thermal sciences. An MEA is a client-driven problem that requires student teams to develop an engineering model or procedure. This approach creates an environment where students value abilities beyond using the traditional prescribed equations and models. During this process, we hypothesize that rich discussion and model re-formulation will help students recognize and repair misconceptions, and that the real world context will help them remember these critical concepts.

Trends in Exhaust Emissions from In-Use California Light-Duty Vehicles, 1994-2001

Major efforts to control motor vehicle emissions have been made in recent years, both through improved emission control technologies and through gasoline reformulation. Our assessment of the impacts of these efforts was conducted in the San Francisco Bay Area, in lanes of a highway tunnel where heavy-duty vehicles are not allowed. This study focuses on the afternoon rush hour, during which over 4000 vehicles per hour travel uphill through the tunnel. Concentrations of CO, CO2, NOx, and total and speciated non-methane organic compounds (NMOC) have been measured during summers 1994-1997, 1999, and 2001. Emission factors for CO, NMOC, and NOx decreased by factors of 2-3 over the 7-year period between 1994 and 2001, with CO and NMOC showing greater percentage reductions than NOx. From our data, fleet turnover appears to have a greater overall impact on exhaust emissions than fuel changes for most pollutants. However, emissions of benzene have been greatly affected by changes in fuel composition.

Arc Fault Characterization System for the Low Voltage DC Arc Fault Circuit Interrupter

Arc faults are a fire-safety risk in both AC (alternating current) and DC wiring, but reliable detection of arc faults and determining the appropriate response is particularly difficult in DC plug-load circuits. This paper presents the development of AFCI lab setup to characterize DC arc current in DC circuits operating at 24-80 volts. The process to characterize the arc current utilizes the frequency spectrum of the arc current along with signal processing and a unique algorithm that allow us to develop an effective method to determine DC arcing occurrence. Once identified, an arc fault current interrupter circuit may then be designed to adequately eliminate the arc. Laboratory test setup and equipment for identifying DC arc will be described in this paper. Different scenarios for DC arcing occurrences in the development of the lab test setup will be explained. Several test results using the developed test setup to show the characteristic of arc current will also be presented.

Development of arc fault interrupter laboratory testing for low voltage DC electricity

Arc faults are a fire-safety risk in both AC (alternating current) and DC wiring, but reliable detection of arc faults and determining the appropriate response is particularly difficult in DC plug-load circuits. This paper presents the development of AFCI testing for DC circuits operating at 24–80 volts. Protecting these circuits from arcing is more difficult than the more prevalent Photovoltaic circuits because of the diversity of loads that may be present. The AFCI testing described in this paper will allow us to identify an effective method to determine DC arcing occurrence. Once identified, an interrupter may then be designed to adequately eliminate the arc. Laboratory test setup and equipment for identifying DC arc will be detailed in this paper. Different scenarios for DC arcing occurrences in the development of the lab test setup will be explained. Several test results of the developed testing tool will also be presented.