Frank Black

THE INFLUENCE OF AMBIENT TEMPERATURE ON TAILPIPE EMISSIONS FROM 1984-1987 MODEL YEAR LIGHT DUTY GASOLINE MOTOR VEHICLES

Motor-vehicle emissions are sensitive to a number of variables including ambient temperature, driving schedule (speed versus time), and fuel composition. Hydrocarbon, aldehyde, carbon monoxide, and oxides of nitrogen emissions were examined with nine recent technology 4-cylinder gasoline motor vehicles at 70F, 40F, and 20F. About 200 hydrocarbon and 12 aldehyde compounds were included in the organic emissions characterization. Two fuels and two driving schedules were used. Typically, hydrocarbon and carbon monoxide emissions were significantly increased by reduced ambient temperature. Oxides of nitrogen emissions also increased, but to a lesser extent. There were no predictable formaldehyde emissions trends with temperature. Paraffinic and aromatic hydrocarbon emission fractions were sensitive to fuel composition, but the olefinic emission fraction (dominated by ethylene and propylene) was not. With low temperature cold start tests, preceding transient driving with a 5 minute engine idle resulted in reduced carbon monoxide emission rates and elevated oxides of nitrogen emission rates. Hydrocarbon emission rates were not predictable sensitive to the preliminary idle.

Composition of Automobile Evaporative and Tailpipe Hydrocarbon Emissions

Mathematical modeling of ambient air photochemistry requires comprehensive mobile source hydrocarbon emission speciation. Passenger car tailpipe and evaporative hydrocarbon emissions have been examined using procedures described in the Federal Register for emissions certification. Hydrocarbon emission rates and compositions were determined for four passenger cars: a 1963 Chevrolet, a 1977 Ford Mustang II, a 1978 Mercury Monarch, and a 1979 Ford LTD-II. These vehicles are representative of a wide range of exhaust and evaporative emissions control configurations. Both emission rates and compositions were dependent on the emissions control devices used with the vehicles, and the fuel composition and vapor pressure. In agreement with the literature, tailpipe catalyst control systems removed unsaturated olefinic, aromatic, and acetylenic hydrocarbons to a greater extent than saturated paraffinic hydrocarbons. The impact of evaporative control devices on composition was not well defined, however the limited dat...

Motor vehicle emissions under reduced ambient temperature idle operating conditions

Freeway surveillance and control systems generally include surveillance of freeway mainline and ramp traffic using electronic loop detectors. The information collected by these detectors is used to indicate overall system status and as input to incident detection algorithms. Another possible use for this data is to provide travel time and delay information for individual freeway segments. This type of data is typically collected through labor-intensive and costly moving car field studies. The study investigated the feasibility of using data collected by loop detectors in a typical freeway surveillance and control system as a substitute for speed and travel time data collected through traditional travel time and delay field studies. Several relationships between field and system data collected at an existing freeway surveillance and control system were developed. With some calibration, these relationships should be applicable to other systems.

CHARACTERIZATION OF PARTICULATE EMISSIONS FROM IN-USE GASOLINE-FUELED MOTOR VEHICLES

Particulate emissions from 20 light-duty gasoline passenger cars and trucks were characterized using the Federal Test Procedure and Highway Fuel Economy Test driving cycles. Emission patterns were examined with 4 of the vehicles using three additional driving cycles, the hot start Federal Test Procedure, the Congested Urban Expressway and the New York City cycles. The test fleet consisted of 4 noncatalyst vehicles operated with leaded gasoline and 16 catalyst-equipped vehicles operated with unleaded gasoline. The vehicles, obtained from local rental agencies, dealers, and residents, ranged in age from model year 1970 through 1981 and in mileage accumulation from about 300 to 81,000 miles.

Control of motor vehicle emissions‐the U.S. experience

Abstract An historical overview of U.S. experience with highway motor vehicle emissions control is presented. The evolution of new motor vehicle emissions certification practice, end‐of‐assembly‐line inspection, in‐use surveillance and recall, inspection and maintenance, and antitampering programs is discussed. The changes in motor vehicle design and fuel formulation resulting from these practices are also described, along with associated changes in the characteristics of emissions. Although significant reductions of new motor vehicle emission rates have been experienced, excessive consumer tampering and poor maintenance, along with large increases in the number of roadway miles traveled, have decreased the magnitude of air quality improvements resulting from these control efforts. As a result of these and other observations, the U.S. Congress amended the Clean Air Act in 1990 to require more stringent new motor vehicle emission standards, changes in procedures for identification and repair of motor vehic...

Automotive Hydrocarbon Emission Patterns in the Measurement of Nonmethane Hydrocarbon Emission Rates

The advent of emission control technology has resulted in significant changes in both the total mass and detailed patterns of hydrocarbons emitted from automobiles. Emission rates of 56 hydrocarbons from 22 motor vehicles, including catalyst and noncatalyst configurations, were determined for the Federal Urban Driving Cycle. An increased relative abundance of methane is indicated for vehicles equipped with oxidation catalysts. In view of the photochemically non-reactive nature of methane, simple and economic procedures for determination of vehicle nonmethane hydrocarbon emission rates are evaluated. In general the procedures evaluated require independent total hydrocarbon and methane analysis, with the nonmethane hydrocarbon level calculated by difference. The procedures are evaluated by comparison of indicated nonmethane hydrocarbon emission rates with rates obtained by summation of individual compound rates determined by advanced gas chromatographic procedures.

Preparation of automobile organic emission surrogates for photochemical model validation

Abstract Irradiation chamber studies of the photochemistry of motor vehicle emissions generally use relatively simple surrogates (often fewer than 30 compounds) of complex emissions (often greater than 250 compounds). The question is often asked: Can the photochemistry of complex organic mixtures be adequately simulated by chamber studies using simple surrogate mixtures? The complexity of the compositional profile of motor vehicle organic emissions results in large part from the complexity of the fuel (i.e., the combustion derived compounds are relatively small in number). An experimental protocol is described by permitting preparation of representative complex (greater than 250 compounds) emission surrogates adding a small number (fewer than 30) of selected compounds to the vehicle fuel. Irradiation chamber runs of actual motor vehicle exhaust samples are contrasted with similar runs of associated complex mixture emission surrogates demonstrating the accuracy with which the exhaust photochemistry can be simulated using the surrogate. Time-resolved profiles of NO, NO x –NO, and ozone concentrations, and selected 12.5xa0h product concentrations, are presented as examples of the comparability of the exhaust and surrogate photochemistry. The observed exhaust and surrogate concentration profiles product distributions are very similar.

EMISSION FROM IN-USE HEAVY-DUTY GASOLINE TRUCKS

Apportionment of air pollution to sources requires knowledge of source emission strengths and/or chemical and physical characteristics. The literature is deficient in data useful for this purpose for heavy-duty motor vehicles, which can be important sources of air pollution in certain microenvironments. Emissions factors are developed in this study for heavy-duty gasoline trucks using chassis dynamometer simulations of urban driving conditions. The sensitivity of the emissions to such considerations as the characteristics of the speed-time driving schedule, vehicle payload, and chassis configuration are examined. Emissions characterization includes total and individual hydrocarbons, aldehydes, carbon monoxide, oxides of nitrogen, total particulate matter, particulate organics, lead, bromine, chlorine, and the fraction of total particulate less than 2 ..mu..m. Preliminary comparisons of emissions obtained using transient engine and transient chassis test procedures are also reported.

Impact of Gasohol on Automobile Evaporative and Tailpipe Emissions

National interest is growing in the use of gasohol, a blend of ethanol and unleaded gasoline, as an alternate fuel to gasoline. In order to assess its viability as a transportation fuel, gasohols impact on vehicle emissions, fuel economy, and driveability must be considered, along with the cost of production and the physical compatibility of ethanol with gasoline. Both tailpipe and evaporative emissions were examined on two passenger cars, a 1977 Ford Mustang II and a 1979 Ford LTD II. In addition to determining total hydrocarbon, ethanol, carbon monoxide and nitrogen oxides content, fuel economy and driveability were also examined. The procedures used for emissions measurement are described in the Federal Register for LDV Certification. Five fuels were used in the program, including two base fuels and three gasohol blends, each car tested with the fuels in sequential order. Generally, the addition of ethanol to gasoline reduced tailpipe emissions of hydrocarbons and carbon monoxide, but increased emissions of nitrogen oxides. Since the stoichiometric air/fuel (A/F) ratio for ethanol is lower than that for gasoline, adding ethanol to gasoline results in a lean shift in combustion stoichiometry, which generally results in a decrease of hydrocarbons and carbon monoxide emissions and anmorexa0» increase in oxides of nitrogen emissions. Coldstart driveability problems were experienced with the LTD II. Little change in fuel economy was observed with either vehicle. The use of gasohol substantially increased the evaporative emissions of both vehicles. Two final areas examined during this program were the adequacy of a one hour test period for determination of hot soak evaporative emissions and the sensitivity of the emissions to vehicle preconditioning. Hot soak evaporative emissions increased during the second hour of examination and both tailpipe and evaporative emissions were sensitive to vehicle preconditioning.«xa0less

STUDY OF MODELS FOR THE PREDICTION OF AVERAGE ROAD LOAD OF IN-USE DELIVERY TRUCKS

Coast-down studies of Class 6 trucks were conducted at near-zero road grade and wind conditions. Speed-versus-time data were recorded, smoothed to a quadratic equation to calculate deceleration rates, and reduced by the least-square method using two-, three-, and five-parameter linear models. The estimated parameters were analyzed statistically and compared to the U. S. Environmental Protection Agency (EPA) recommended procedure. The averages of the individual truck road loads for the three models were consistent within 4% when reference conditions of 40 mi/h, 15,000 lb weight, and 65 sq ft projected frontal area were used. These reference conditions represent the median values of experiment conditions that were varied during coast-down tests. At these conditions, road load variations among the trucks averaged 10% and 16% for the two- and five-parameter models, respectively. The coefficients of the five-parameter model displayed instability during sequential estimation, showing multicollinearity. Because of this instability and the significance of the truck-to-truck variations, the two-parameter model seemed most appropriate for predicting the truck road load. At reference conditions, the two-parameter model road load was 10% greater than that from the EPA recommended procedure.