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An extensive literature search was conducted and potential additive candidates were identified to improve the safety aspects associated with the use of methanol as a motor fuel. Before any laboratory measurements were conducted, candidate additives were evaluated for possible formation of known or suspected toxic compounds as combustion products. The remaining potential additives were then screened for their effectiveness in improving methanol fuel properties in a laboratory test program emphasizing flame luminosity, lubricity, and flammability. Flame luminosity was measured with a specially designed system to monitor the light produced by the flame in lux. Lubricity was measured with a Ball-on-Cylinder Lubricity Evaluator (BOCLE). For flammability limits, a device was designed to determine the presence of flammable vapors above the liquid at different additive concentrations.

In the United States, most school buses are powered by diesel engines. Some have advocated replacing diesel school buses with natural gas school buses, but little research has been conducted to understand the emissions from school bus engines. This work provides a detailed characterization of exhaust emissions from school buses using a diesel engine meeting 1998 emission standards, a low emitting diesel engine with an advanced engine calibration and a catalyzed particulate filter, and a natural gas engine without catalyst. All three bus configurations were tested over the same cycle, test weight, and road load settings. Twenty-one of the 41 “toxic air contaminants” (TACs) listed by the California Air Resources Board (CARB) as being present in diesel exhaust were not found in the exhaust of any of the three bus configurations, even though special sampling provisions were utilized to detect low levels of TACs.

The use of methanol as a “clean fuel” appears to be a viable approach to reduce air pollution. However, concern has been expressed about potentially high formaldehyde emissions from stoichiometrically operated light-duty vehicles. This paper presents results from an emission test program conducted for the California Air Resources Board (CARB) and the South Coast Air Quality Management District (SCAQMD) to identify and evaluate advanced catalyst technology to reduce formaldehyde emissions without compromising regulated emission control. An earlier paper presented the results of evaluating eighteen different catalyst systems on a hybrid methanol-fueled test vehicle. (1)* This paper discusses the optimization of three of these catalyst systems on four current technology methanol-fueled vehicles. Emission measurements were conducted for formaldehyde, nonmethane organic gases (NMOG), methanol, carbon monoxide, and oxides of nitrogen emissions.

A 1991 Toyota Camry equipped with an electrically-heated catalyst (EHC) system was evaluated in duplicate over the Federal Test Procedure (FTP) with three different fuels. Evaluations were conducted with the EHC in place but without any external heating, and with the EHC operated with a post-crank heating strategy. The EHC system was placed immediately upstream of an original production catalyst, which was then moved to a location 40.6 cm from the exhaust manifold. The three test fuels were: 1) the Auto/Oil industry average gasoline, RF-A; 2) a fuel meeting California's Phase II gasoline specifications; and 3) a paraffinic test fuel. Non-methane organic gas (NMOG) emission rates with the EHC active were similiar with all three fuels, with absolute levels less than or equal to California's 50,000 mile Ultra-Low Emission Vehicle (ULEV) standard. Substantial differences, however were observed in the ozone forming potential of these fuels with the EHC active.

Two additive blends proposed for improving the flame luminosity in neat methanol fuel were investigated to determine the effect of these additives on the exhaust emissions in a dual-fueled Volkswagen Jetta. The two blends contained 4 percent toluene plus 2 percent indan in methanol and 5 percent cyclopentene plus 5 percent indan in methanol. Each blend was tested for regulated and unregulated emissions as well as a speciation of the exhaust hydrocarbons resulting from use of each fuel. The vehicle exhaust emissions from these two fuel blends were compared to the Coordinating Research Council Auto-Oil national average gasoline (RF-A), M100, and M85 blended from RF-A. Carter Maximum Incremental Reactivity Factors were applied to the speciated hydrocarbon emission results to determine the potential ozone formation for each fuel. Toxic emissions as defined in the 1990 Clean Air Act were also compared for each fuel.

This paper describes experiments to determine the effect on exhaust emissions of starting on compressed natural gas (CNG) and then switching to gasoline once the catalyst reaches operating temperature. Carbon monoxide, oxides of nitrogen, and detailed exhaust hydrocarbon speciation data were obtained for dedicated CNG, then unleaded gasoline, and finally CNG start -gasoline run using the Federal Test Procedure at 24°C and at -7°C. The result was a reduction in emissions from the gasoline baseline, especially at -7°C. It was estimated that CNG start - gasoline run resulted in a 71 percent reduction in potential ozone formation per mile.

This paper describes experiments conducted to determine the regulated emissions, ozone-forming potentials, specific reactivities, and reactivity adjustment factors for eight butane and propane alternative fuel blends run on a light-duty vehicle, emission certified to be a California transitional low emission vehicle (TLEV) and converted to operate on liquefied petroleum gas (LPG). Duplicate EPA FTP emission tests were conducted with each fuel. Hydrocarbon speciation was utilized to determine reactivity-adjusted non-methane organic gases (NMOG) emissions for one test on each fuel. Results showed that all eight fuels could allow the converted vehicle to pass California ultra-low emission vehicle (ULEV) NMOG and oxides of nitrogen (NOx) standards. Six of the eight fuels could allow the vehicle to pass ULEV carbon monoxide (CO) standards. BUTANE has been an important gasoline blending component for many years.

This paper describes experiments conducted to determine Federal Test Procedure (FTP) exhaust emissions, ozone-forming potentials, specific reactivities, and reactivity adjustment factors for several butane/propane alternative fuel blends run on a light-duty EHC-equipped gasoline vehicle converted to operate on liquefied petroleum gas (LPG). Duplicate emission tests were conducted on the light-duty vehicle at each test condition using appropriate EPA FTP test protocol. Hydrocarbon speciation was utilized to determine reactivity-adjusted non-methane organic gas (NMOG) emissions for one test on each fuel.

This paper describes the effort to characterize regulated and unregulated exhaust emissions from four gasoline powered passenger cars equipped with three-way catalyst control systems. The vehicles have been evaluated over four test cycles, with three fuels at four mileage accumulation points. In addition to the currently regulated automobile emissions, exhaust emission components measured include: sulfate, aldehydes, ammonia, sulfur dioxide, cyanide, and several other compounds. From the standpoint of toxicity, the most significant emissions from three-way catalyst systems are the currently regulated emissions, followed to a lesser degree by the sulfate emissions.

This paper describes the characterization of regulated and unregulated exhaust emissions from two methanol-fueled automobiles. For comparison, two gasoline-fueled automobiles of the same make and model were also evaluated. These automobiles were evaluated over the Light-Duty Federal Test Procedure and the Highway Fuel Economy Driving Schedule. Additional evaluations with the methanol-fueled automobiles were conducted using promoted base metal catalysts, and one of these automobiles was tested in a non-catalyst configuration. Exhaust constiuents sampled for, in addition to the regulated emissions, include: aldehydes, particulate, individual hydrocarbons, methanol, ethanol, ammonia, cyanide, amines, nitrosamines, and methyl nitrite.

This paper describes the characterization of regulated and unregulated exhaust emissions, particularly aldehydes, from ten 1978 and 1979 high mileage catalyst-equipped gasoline fueled automobiles which have been driven for approximately 50,000 miles. The ten automobiles were evaluated as-received and after a tune-up to manufacturer’s specifications, over the Light-Duty Federal Test Procedure (FTP) and the Highway Fuel Economy Driving Schedule (HFET). Exhaust constituents measured, in addition to the regulated emissions, include: aldehydes, particulates, sulfides, amines, and several additional compounds.

This paper reviews the use of additives to improve safety aspects associated with the use of methanol as a motor fuel. A survey of the literature was conducted to determine candidate additives for methanol that produce one or more of the following properties: provide a visible or luminous flame, reduce the potential for skin contact, give a foul or unpleasant taste and odor, and act as an emetic. Candidate additives were reviewed to determine potential effectiveness, cost, east of production, health problems, and effects on vehicle performance. Potential additives include complex hydrocarbon mixtures such as gasoline, alcohol soluble dyes and unpalatable compounds such as denatonium benzoate.

The influence of fuel composition on exhaust emissions from four 1982 model light-duty diesel vehicles was studied on the FTP cycle and at two steady-state conditions, but only the FTP results are presented and discussed in this paper. Nine test fuels were blended specifically for the program, with intentional variation in aromatic content, 90% boiling point, and 10% boiling point. Limited data were also acquired with injection timing at advanced and retarded settings, in addition to the main body of data taken with the engines adjusted to recommended timing. A comparatively small effort was also made to evaluate a tenth fuel consisting of a blend of two of the original nine fuels. Of the fuel characteristics varied intentionally, aromatic content generally had the greatest effect on most emissions of major interest (hydrocarbons, oxides of nitrogen, particulate, soluble organic fraction, polynuclear aromatic hydrocarbons, and mutagenicity of extract by Ames bioassay).

Neat methanol fuel (M100) has many advantages for achieving low emission levels as an automotive fuel, but there are several items that require attention before this fuel can replace conventional fuels. One item involves the low flame luminosity of methanol. An extensive literature search and laboratory evaluation were conducted to identify potential additive candidates to improve the luminosity of a methanol flame. Potential compounds were screened based on their concentration, luminosity improvement, and duration of luminosity improvement during the burn. Three compounds were found to increase the flame luminosity for segments of the burn at relatively low concentrations: toluene, cyclopentene, and indan. In combination, these three compounds markedly improved the luminosity of methanol throughout the majority of the burn. The two combinations were 1) 4 percent toluene plus 2 percent indan and 2) 5 percent cyclopentene plus 5 percent indan in methanol.