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During the last three decades, the emissions measurement system for heavy duty vehicle testing has employed a Constant Volume Sampler (CVS) system to continuously measure the pollutant concentrations in the dilution tunnel. Subsequent gaseous emissions calculation methods were based on Code of Federal Regulations, Title 40 (CFR-40) in which a formula for calculating dilution factor (DF) was specified to account for background pollutants. However, it is recognized that due to the mechanism of the CVS system, the dilution factor varies from a constant during a test cycle. The DF calculation technique can introduce error in the emissions data, but the magnitude of potential error is small relative to the current emissions standards. However, as the engine technologies improve and cleaner burning fuels are adopted in the near future, the pollutant concentrations from engines will approach those in ambient air.

Torsional vibration usually causes noticeable sound disturbances, mechanical shakings, and component fatigue problems. It exists at one or more periods of the operating range in torsional systems. Determination of critical speeds or torsional natural frequencies in a design stage makes it possible to avoid early fractures and costly repairs of the machinery. In this paper, the method for predicting speed–related excitation frequencies of complex rotating systems is discussed and the computer program is developed and tested by actual examples. The natural frequencies and mode shapes of multi–branch torsional vibration systems with one or more junction points are calculated. A user–friendly graphic interface for modeling is presented. Some practical examples are given and the results of the simulations are compared to those obtained analytically as well as those given in references.

A correlation study of vehicle exhaust emissions measurements was conducted by the West Virginia University (WVU) Transportable Heavy-Duty Vehicle Emissions Testing Laboratory and the Los Angeles County Metropolitan Transportation Authority (MTA) Emissions Testing Facility. A diesel fueled transit bus was tested by both chassis dynamometer emissions testing laboratories. Exhaust emissions were sampled from the tested vehicle during the operation of the Federal Transit Administration (FTA) Central Business District (CBD) testing cycle. Data of gaseous and particulate matter emissions was obtained at each testing laboratory. The emissions results were compared to evaluate the effects of different equipment, test procedures, and drivers on the measurements of exhaust emissions of heavy-duty vehicles operated on a chassis dynamometer.

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.

Regulated gaseous and particulate emissions were obtained from in-use vehicles, two trucks and two buses, operated on the Transportable Heavy Duty Engine Emissions Testing Laboratory. Presented here is the data on transient emissions from a refuse truck with a Cummins LTA10-260 engine, a GMC tractor with a CAT 3176 engine and two buses with Detroit Diesel 6V-92TA engines (one with a particulate trap and the other without) when tested on different fuels. The reported study on in-use heavy duty vehicles is part of an on-going program aimed at establishing a database on the exhaust emissions from vehicles tested on a chassis dynamometer under conditions that represent the ‘real-world’ situations. The paper also discusses, briefly, the entire testing laboratory. The Transportable Laboratory can be effectively used in testing programs, such as recall, deterioration and emission factors.