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The Environmental Protection Agency (EPA) recently tested a clean diesel fuel developed by Dion & Sons for use in stationary sources. This fuel is known as Amber 363 in Southern California and its technology is licensed outside of the Southern California area to Shell Oil Products Company for use as a stationary source fuel. The fuel, hereafter referred to as “Shell LOW NOX Fuel,” was tested in a 1990 model year heavy heavy-duty diesel engine using both the transient Federal Test Procedure (FTP) for on-highway heavy-duty engines, the steady-state FTP for nonroad heavy-duty engines, and the steady-state generator set test cycle. For each test, EPA measured hydrocarbon (HC), carbon monoxide (CO), nitrogen oxides (NOx) and particulate matter (PM) emissions. Transient testing showed that the Shell LOW NOX Fuel lowers NOx, HC and PM emissions with no statistically significant change in CO emissions for both cold-starts and hot-starts when compared to diesel certification test fuel.

Regulated emissions (THC, CO, NOx, and PM) and particulate SOF and sulfate fractions were determined for a 1995 Detroit Diesel Series 50 urban bus engine at varying fuel sulfur levels, with and without catalytic converters. When tested on EPA certification fuel without an oxidation catalyst this engine does not appear to meet the 1994 emissions standards for heavy duty trucks, when operating at high altitude. An ultra-low (5 ppm) sulfur diesel base stock with 23% aromatics and 42.4 cetane number was used to examine the effect of fuel sulfur. Sulfur was adjusted above the 5 ppm level to 50, 100, 200, 315 and 500 ppm using tert-butyl disulfide. Current EPA regulations limit the sulfur content to 500 ppm for on highway fuel. A low Pt diesel oxidation catalyst (DOC) was tested with all fuels and a high Pt diesel oxidation catalyst was tested with the 5 and 50 ppm sulfur fuels.

An exhaust carbon monoxide (CO) emissions model has been developed. This model uses the fuel properties oxygen content, sulfur content, RVP, olefin content, distillation parameters E200 and E300, and aromatic content to predict exhaust CO emissions. This predictive model is based on emissions measured under summer conditions. The model was developed using the same statistical techniques used to develop the exhaust VOC and NOx models (Complex Model) presented in the Environmental Protection Agency's (EPA) regulations for the final rule on reformulated gasoline. It is the objective in this work to briefly outline the procedure used to develop the exhaust CO model, to look at the behavior of the developed model, to examine the predictability of the developed model and to state the limitations of the model.

Due to continuing reductions in EPA's emission standard values for exhaust particulate emissions, industry production has shifted towards engines that produce very low amounts of particulate emissions. Thus, it is very possible that future engines will challenge the error range of the current instrumentation and procedures used to measure particulate emissions by being designed to produce extremely low levels of particulates. When low particulate emitting engines are sampled at low flowrates, the resulting filter loadings may violate the minimum filter loading recommendation in the Heavy Duty Federal Test Procedure [1]. Conversely, higher flow rates may be an inappropriate option for increasing filter loading due to the possibility of stripping volatile organic compounds from the particulate sample or otherwise artificially reducing the accumulated mass [2].

A sensitivity analysis can be used to examine the extent to which random error in exhaust emission regressions influences the models' results. In this study, the analysis is conducted by first simulating the random error by introducing small errors in the dependent emission variables (Nitrogen Oxide emissions (NOx) and Non-Methane Hydrocarbon emissions (NMHC)) and then by examining the resultant effects on the models' predictability. Previously published data from EPA's testing programs (ATL-Phase I and ATL-Phase II) are used to generate the regression models relating exhaust emissions of NOx and NMHC to fuel parameters oxygen, sulfur, E200, E300, olefins, aromatics and RVP. Two different regression techniques are used to generate the baseline models for the sensitivity analyses. A sensitivity analysis is run for each technique and the results are compared.

A vehicle test program was conducted at the Environmental Protection Agency's National Vehicle and Fuel Emissions Laboratory to provide data on the relationship between fuel properties and exhaust emissions of nonmethane hydrocarbons (NMHC), NOx, and CO. This study, Phase III, is the third in a series of programs sponsored by the Agency. This Phase III program consisted of 19 light-duty high and normal emitting vehicles tested on 10 different fuels. The properties for each test fuel were specified in order to examine seven separate fuel effects on exhaust emissions; interactions between olefins and volatility, interactions between olefins and sulfur, very high and very low levels of sulfur, low levels of aromatics, low volatility, and low levels of olefins. For all of the fuels tested, the normal emitter vehicles produced greater percentage reductions than the high emitters. The data in this work showed lower NMHC emission reduction than predicted by the complex model.

Six in-use vehicles were tested on a baseline gasoline and nine gasoline/ethanol blends to determine the effect of ethanol content in fuels on automotive exhaust emissions and fuel economy. The baseline gasoline was representative of average summer gasoline and served as the base from which the other fuels were blended. For the majority of the vehicles, total hydrocarbon, and carbon monoxide exhaust emissions as well as fuel economy decreased while NOx and acetaldehyde exhaust emissions increased as the ethanol content in the test fuel increased. Formaldehyde and carbon dioxide emissions were relatively unaffected by the addition of ethanol. The emission responses to the increased fuel oxygen levels were consistent with what would be expected from leaning-out the air/fuel ratio for a spark ignition engine. The results are shown graphically and a linear regression is performed utilizing the method of least squares to investigate statistically significant trends in the data.

This study is the second in a series of three EPA studies to investigate the effect of fuel reformulations and modifications on exhaust emissions. Both the first and second study in this series of studies were used to support the development of EPA's complex model for the certification of reformulated gasolines. Phase I of the study tested eight fuels on forty vehicles. This study, termed Phase II, tested twelve fuels on a separate fleet of 39 light-duty vehicles. The Phase II fuel parameters studied included Reid Vapor Pressure (RVP), the 50% and 90% evaporated distillation temperatures (T50 and T90), sulfur content, aromatics content, olefin content, oxygenate type and oxygen content. Measured exhaust emissions included total hydrocarbons (THC), oxides of nitrogen (NOx), carbon monoxide (CO), carbon dioxide (CO2), benzene, 1,3-butadiene, acetaldehyde and formaldehyde.

This study was the first of three EPA studies to investigate the effect of gasoline fuel parameters on hydrocarbon, nonmethane hydrocarbon, nitrogen oxides, benzene, formaldehyde, and acetaldehyde exhaust emissions of 1990 model year or equivalent vehicles. The fuel parameters tested in this program were oxygen concentration, Reid Vapor Pressure (RVP), ninety percent evaporative distillation temperature (T90), and sulfur concentration. Sulfur concentration was found to have the greatest effect on hydrocarbon and nitrogen oxide emissions. Increasing oxygen concentration and RVP reduction was found to reduce hydrocarbon emission more for high-emitting than normal-emitting vehicles. Oxygenate concentration was found to have a significant effect on aldehyde emissions.