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Stringent emission regulations have forced drastic technological improvements in diesel after treatment systems, particularly in reducing Particulate Matter (PM) emissions. Those improvements generally regard the use of Diesel Oxidation Catalyst (DOC), Diesel Particulate Filter (DPF) and lately also the use of Selective Catalyst Reduction (SCR) systems along with improved engine control strategies for reduction of NOx emissions from these engines. Studies that have led to these technological advancements were made in controlled laboratory environment and are not representative of real world emissions from these engines or vehicles. In addition, formation and evolution of PM from these engines are extremely sensitive to overall changes in the dilution process.

West Virginia University characterized the emissions and fuel economy performance of a 30-foot 2010 transit bus equipped with urea selective catalytic reduction (u-SCR) exhaust aftertreatment. The bus was exercised over speed-time driving schedules representative of both urban and on-highway activity using a chassis dynamometer while the exhaust was routed to a full-scale dilution tunnel with research grade emissions analyzers. The Paris speed-time driving schedule was used to represent slow urban transit bus activity while the Cruise driving schedule was used to represent on-highway activity. Vehicle weights representative of both one-half and empty passenger loading were evaluated. Fuel economy observed during testing with the urban driving schedule was significantly lower (55%) than testing performed with the on-highway driving schedule.

West Virginia University's Mechanical and Aerospace Engineering Department is studying the benefits of continuous payload volume in transforming projectiles. Continuous payload volume is the single largest vacancy in a vehicle that may be utilized. Currently there is a market for transforming projectiles, which are gun launched (or tube launched) vehicles stowed in an initial configuration; which deploy wings once exiting the launcher to become small unmanned aircraft. WVU's proposed design uses a helical hinge, which allows the wing sections to be externally stowed outside the UAV's fuselage. Additionally, the design positions the vehicles wing sections sub-bore (or smaller than the guns internal diameter), and flush (smooth and planer) to the surface of the fuselage. The typical transforming winged projectile design considered, stores its wing sections along the center axis of the fuselage. This bisects the payload space and limits the continuous payload carrying potential.

Particulate emission control from diesel engines is one of the major concerns in the urban areas in California. Recently, regulations have been proposed for stringent PM emission requirements from both existing and new diesel engines. As a result, particulate emission control from urban diesel engines using advanced particulate filter technology is being evaluated at several locations in California. Although ceramic based particle filters are well known for high PM reductions, the lack of effective and durable regeneration system has limited their applications. The continuously regenerated diesel particulate filter (CRDPF) technology discussed in this presentation, solves this problem by catalytically oxidizing NO present in the diesel exhaust to NO2 which is utilized to continuously combust the engine soot under the typical diesel engine operating condition.

Synthetic diesel fuel can be made from a variety of feedstocks, including coal, natural gas and biomass. Synthetic diesel fuels can have very low sulfur and aromatic content, and excellent autoignition characteristics. Moreover, synthetic diesel fuels may also be economically competitive with California diesel fuel if produced in large volumes. Previous engine laboratory and field tests using a heavy-duty chassis dynamometer indicate that synthetic diesel fuel made using the Fischer-Tropsch (F-T) catalytic conversion process is a promising alternative fuel because it can be used in unmodified diesel engines, and can reduce exhaust emissions substantially. The objective of this study was a preliminary assessment of the emissions from older model transit operated on Mossgas synthetic diesel fuel. The study compared emissions from transit buses operating on Federal no. 2 Diesel fuel, Mossgas synthetic diesel (MGSD), and a 50/50 blend of the two fuels.

Emissions of six 32 passenger transit buses were characterized using one of the West Virginia University (WVU) Transportable Heavy Duty Emissions Testing Laboratories, and the fixed base chassis dynamometer at the Colorado Institute for Fuels and High Altitude Engine Research (CIFER). Three of the buses were powered with 1997 ISB 5.9 liter Cummins diesel engines, and three were powered with the 1997 5.9 liter Cummins natural gas (NG) counterpart. The NG engines were LEV certified. Objectives were to contrast the emissions performance of the diesel and NG units, and to compare results from the two laboratories. Both laboratories found that oxides of nitrogen and particulate matter (PM) emissions were substantially lower for the natural gas buses than for the diesel buses. It was observed that by varying the rapidity of pedal movement during accelerations in the Central Business District cycle (CBD), CO and PM emissions from the diesel buses could be varied by a factor of three or more.

Natural Gas engines are viewed as an alternative to diesel power in the quest to reduce heavy duty vehicle emissions in polluted urban areas. In particular, it is acknowledged that natural gas has the potential to reduce the inventory of particulate matter, and this has encouraged the use of natural gas engines in transit bus applications. Extensive data on natural gas and diesel bus emissions have been gathered using two Transportable Heavy Duty Vehicle Emissions Testing Laboratories, that employ chassis dynamometers to simulate bus inertia and road load. Most of the natural gas buses tested prior to 1997 were powered by Cummins L-10 engines, which were lean-burn and employed a mechanical mixer for fuel introduction. The Central Business District (CBD) cycle was used as the test schedule.

A mathematical model has been developed to transfer Chassis Dynamometer (CD) test cycles for heavy duty vehicles to the equivalent Engine Dynamometer (ED) test cycles. The model assumed a generalized drivetrain layout, and a variable drive line efficiency. An interactive computer code was written to represent the mathematical model for different drivetrain systems. Several CD test cycles were used to obtain equivalent ED test cycles for a sample based upon an urban bus equipped with an automatic transmission. Results showed the possibility of simulating CD test cycles with equivalent ED test cycles for heavy-duty urban buses under certain assumptions.

Emissions from light duty vehicles have traditionally been measured using a chassis dynamometer, while heavy duty testing has been based on engine dynamometers. However, the need for in-use vehicle emissions data has led to the development of two transportable heavy duty chassis dynamometers capable of testing buses and heavy trucks. A test cycle has been developed for Class 8 trucks, which typically have unsyncronized transmissions. This test cycle has five peaks, each consisting of an acceleration, cruise period, and deceleration, with speeds and acceleration requirements that can be met by virtually all vehicles in common service. Termed the “WVU 5 peak truck test”, this 8 km (5 mile) cycle has been used to evaluate the emissions from diesel and ethanol powered over-the-road tractors and from diesel and ethanol powered snow plows, all with Detroit Diesel 6V92 engines.

The West Virginia University (WVU) Transportable Heavy-Duty Vehicle Emissions Testing Laboratory was employed to conduct chassis dynamometer tests in the field to measure the exhaust emissions from heavy-duty buses and trucks. This laboratory began operation in the field in January, 1992. During the period January, 1992 through June, 1993, over 150 city buses, trucks, and tractors operated by 18 different authorities in 11 states were tested by the facility. The tested vehicles were powered by 14 different types of engines fueled with natural gas (CNG or LNG), methanol, ethanol, liquified petroleum gas (LPG), #2 diesel, and low sulfur diesel (#1 diesel or Jet A). Some of the tested vehicles were equipped with exhaust after-treatment systems. In this paper, a total of 12 CNG-fueled and #2 diesel-fueled transit buses equipped with Cummins L-10 engines, were chosen for investigation.

Exhaust gas composition and particulate matter emission levels were obtained from in-use heavy duty transit buses powered by 6V-92TA engines with different fuels. Vehicles discussed in this study were pulled out of revenue service for a day, in Phoenix, AZ, Pittsburgh, PA and New York, NY and tested on the Transportable Heavy Duty Vehicle Emissions Testing Laboratory employing a transient chassis dynamometer. All the vehicles, with engine model years ranging from 1982 to 1992, were operated on the Federal Transit Administration Central Business District Cycle. Significant reductions in particulate matter emissions were observed in the 1990-1992 model year vehicles equipped with the trap oxidizer systems. Testing vehicles under conditions that represent “real world” situations confirmed the fact brought to light that emission levels are highly dependent upon the maintenance and operating conditions of the engines.