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Due to increasing interest in the emissions-producing characteristics of today's automobiles, emissions testing procedures have come under close scrutiny. In addition, development of procedures to measure emissions of vehicles operating in “on-road” conditions have been proposed to gain knowledge of the instantaneous mass flow rates of various legislated gaseous emissions. The problem with the measurement of these instantaneous flow rates is that the responses of modern emissions analyzers to transients are too slow for reliable results. Therefore, a method for improving the dynamic response of these instruments is needed. A method is described which utilizes generalized predictive control theory concepts in conjunction with system identification techniques to produce a software “filter” which reconstructs the distorted output of these analyzers.

Alcohols (methanol and ethanol) have been identified as having the potential to improve air quality when used to replace conventional gasoline. This potential is primarily due to the different organic species that are emitted by alcohol-fueled engines. The use of “near neat” alcohols gives greater benefits than fuels containing lower levels of alcohol, but neat alcohols present a significant cold starting problem. The primary objective of this study was to develop a rich combustor device which will extend the cold start range of alcohol fueled engines to -30° C. In this approach a portion of the fuel is burned outside the engine under fuel-rich conditions. This rich combustion creates a product stream that contains significant amounts of hydrogen and carbon monoxide (along with other gases such as carbon dioxide, nitrogen, water vapor, and organics). The hydrogen and carbon monoxide are combustible and non-condensable and provide the fuel for starting the engine.

A methodology for developing modal vehicle emissions and fuel consumption models is described. These models, in the form of look-up tables for fuel consumption and emissions as functions of vehicle speed and acceleration, are designed for simulations such as the Federal Highway Administration's TRAF-series of models. These traffic models are used to evaluate the impacts of roadway design on emissions and fuel consumption. Vehicles are tested on-road and on a chassis dynamometer to characterize the entire operating range of each vehicle. As a verification exercise the models were used to predict cycle emissions and fuel consumption, and the results were compared to certification-type tests on a different population of vehicles. Results of the verification exercise show that the developed models can generally predict cycle emissions and fuel consumption with error comparable to the variability of repeat dynamometer tests.

The use of compressed natural gas (CNG) as a fuel for small vehicles presents challenges associated with the vehicle cost, system packaging, and vehicle range. The University of Tennessee with primary support from the Saturn Corporation has adapted a Saturn SL1 to dedicated CNG operation with the objective being to do so with a minimal impact on the production of the base vehicle. The adapted vehicle meets the California ULEV emission values at low mileage, achieves a gasoline-equivalent fuel economy of 21 km per liter (49 miles per gallon) at a steady speed of 90 km/hr (55 miles per hour), and has a range (at 90 km/hr) of over 400 km (240 miles) when fueled with an initial tank fill of 24.8 MPa (3600 psig). As expected, wide-open throttle performance of the adapted vehicle was degraded from the gasoline baseline vehicle. The vehicle design features are compared with two similar pre-production vehicles that have been described in the literature.

Proof-of-concept testing was performed to determine the effectiveness of a computer controlled air pump (CCAP) in reducing the unburned hydrocarbons (UHC) and carbon monoxide (CO) emitted from automobile engines. For the initial phase of testing, a prototype CCAP was designed and evaluated on a dynamometer test-stand at the University of Tennessee. This CCAP maintained the engine's exhaust at a stoichiometric air/fuel ratio by utilizing a second oxygen sensor mounted downstream from the catalyst. In this way, the catalyst's conversion efficiency for CO and UHC was always high, even if the engine was running rich. Results of this steady-state testing indicated that the CCAP was able to reduce UHC and CO emissions without a corresponding increase in oxide of nitrogen (NOx) emissions. Additionally, catalyst temperatures did not increase dramatically.

The use of methanol as a fuel for transportation vehicles has air quality and energy security implications. One disadvantage of methanol fuels, however, is associated with cold starting engines utilizing these fuels. Although several approaches have been used to overcome this problem, no approach has been shown to be entirely satisfactory. The present study was conducted to investigate the feasibility of dissociating some of the methanol into hydrogen and carbon monoxide and using this dissociated fuel to start the engine. To accomplish quick dissociation under cold conditions, a portion of the methanol is burned under fuel-rich conditions. Additional methanol is then sprayed into the hot products of combustion to cool the gases prior to their introduction into the engine. Tests at -30°C demonstrated that the concept worked on an unmodified spark ignition engine fueled with M100.

Tests were conducted using an ASTM Aviation Supercharge CFR engine to determine whether high levels of fuel-bound nitrogen lead to increased nitric oxide emissions in a supercharged engine. Fuel nitrogen levels were formulated by doping several different fuels with pyridine. The results of the testing on this particular engine indicate that the effects of fuel nitrogen on nitric oxide emissions were so small that they were masked by the uncertainties associated with the experimental procedures used. Comparisons with the results from other researchers suggest that the results of this study are probably associated with stratification of the fuel-air mixture. It is recommended that additional tests be conducted to investigate the effects of fuel-air mixing on fuel-nitrogen conversion.