Search Results

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an octane-boosting gasoline additive that has been used for over 50 years. This usage has been controversial; particularly in modern gasoline vehicles equipped with advanced emissions control systems. There is concern that extended use of MMT will lead to build-up of Mn-containing deposits on engine and emissions system components, thereby adversely affecting vehicle emissions performance and durability. This paper provides a comprehensive review of the literature regarding the effects of MMT on gasoline vehicles, with an emphasis on modern, Tier 2 vehicles. Numerous test programs have been conducted - including wide ranges of vehicle model years, technology types, and testing conditions. The reported MMT effects over this body of literature are not consistent.

Biodiesel is a renewable transportation fuel consisting of fatty acid methyl esters (FAME), generally produced by transesterification of vegetable oils and animal fats. The effects of biodiesel usage upon vehicle emissions have been investigated by numerous groups. A consensus view has developed that emissions of hydrocarbons (HC), carbon monoxide (CO) and fine particulate matter (PM) can be reduced by use of biodiesel, while oxides of nitrogen (NOx) increase slightly. This paper provides a review of the literature regarding the effects of biodiesel upon emissions of these four criteria pollutants. The emissions database was restricted to studies in which both biodiesel and a conventional diesel fuel were tested under identical dynamometer conditions. Both heavy-duty (HD) and light-duty (LD) engines/vehicles were considered.

Life-cycle assessments (LCA) of biodistillate fuels are becoming increasingly important for policy decisions regarding alternative fuels. However, due to the data-intensive and assumptive nature of LCAs, rarely do two different studies produce comparable results. To add to the complexity, effects of indirect land use changes are now being incorporated into LCA models. This development is influencing policy decisions and generating much controversy. A literature survey of 55 different LCA studies of bio-distillate fuels was conducted. The comparison of energy requirements and global warming potential (GWP) impacts of these studies help to illustrate which data inputs and assumptions most strongly affect the results, and wherein the major discrepancies lie. Life-cycle energy results are typically reported as energy return (ER), meaning the heating value of the biofuel divided by the total fossil energy inputs to produce the fuels.

Biodistillate transportation fuels include biodiesel (produced via transesterification of animal fats and vegetable oils) and renewable diesel (produced via catalytic hydroprocessing of the same feedstocks). Production and use of biodistillates are increasing dramatically, both in the U.S. and globally. This paper describes the policy drivers prompting growth of biodistillate fuels in the U.S., Europe, and selected other countries. Trends in fuel production volumes and feedstocks supplies are presented for these fuels. Current feedstocks are dominated by soybean oil in the U.S. and rapeseed oil in Europe. However, there is much interest in developing alternative, non-edible feedstocks such as jatropha and microalgae. Currently, biodiesel is the dominant biodistillate in use, though interest in renewable diesel is increasing. This paper describes different conversion processes used to manufacture these fuels, and discusses the pros and cons of each.

Diesel vehicles are significant sources of NOx and PM emissions, and to a lesser extent, emissions of CO, HC, and toxic species. For many years, biodiesel fuel (and blends of biodiesel) has been promoted as a “clean fuel” alternative to conventional diesel. Based upon previous reviews by EPA, a common understanding has arisen that biodiesel usage reduces CO, HC, and PM emissions significantly, but increases NOx emissions slightly. This paper discusses a recent review of 94 published reports, from the period of 2000-2008. Assessments were made of the emissions impacts of biodistillate fuels from various engine types, operating conditions, control technologies, and fuel type. In each situation, emissions from the biodistillate case were compared with emissions from a reference diesel fuel case.

A vehicle emissions test program was conducted to evaluate the impact of gasoline RVP reduction on CO emissions under conditions that are typical of CO exceedance days in Las Vegas and Los Angeles. Test results showed that CO emissions were reduced in the Las Vegas fleet when RVP was changed from 12 to 9 psi. In the Los Angeles fleet, the results were less consistent, perhaps due to the poorer integrity of evaporative emissions control systems on these vehicles. This suggests that an optimum emissions control strategy might include both RVP reduction and an effective vehicle inspection and maintenance (I&M) program.

In 1992, a Round Robin was sponsored by the CRC's Emissions Analysis Round Robin Subcommittee, to provide an opportunity for automotive emissions laboratories to compare their analytical methodologies with those used in other laboratories. Compressed gas samples were provided to participants to test hydrocarbon methodologies, while liquid samples were used for alcohol and carbonyl analyses. The results of this study were published in SAE 950780 and SAE 941944. A second Round Robin study was conducted in 1995, using the same basic structure as the first study. The results of the carbonyl analyses have been published separately (SAE 971609). The purpose of this paper is to compare methods used for hydrocarbon speciation of emissions by gas chromatography. As in the 1992 study, cylinders of a synthetic exhaust were prepared by using a fuel base, and adding components that would be expected as typical combustion products.

Voluntary RFG opt-in and use of reduced-RVP gasoline are two fuel options being considered in several ozone nonattainment areas. This paper describes methods for evaluating the relative benefits of these two options, with specific application in the Southeast Michigan area. Currently, the most defensible approach for estimating relative emissions reduction benefits of gasoline modifications utilizes a hybrid of two EPA models: MOBILE5a and the Complex Model. By employing appropriate fuel compositions, this hybrid approach showed that reduced-RVP gasoline was nearly as effective as RFG in reducing total VOC emissions in Southeast Michigan-both near-term and long-term. With both gasoline options, most of the VOC benefit arises from lower nonexhaust emissions, caused by reduced RVP levels.

Recent changes in regulatory practices have brought about a need for speciated analysis of the volatile organic components of vehicle exhaust. The purpose of this study was to allow interested laboratories to participate in a Round Robin so that each could assess its speciation methodologies for hydrocarbons, alcohols, and carbonyls. The results from analysis of the liquid samples (methanol, ethanol, and DNPH-derivatives of carbonyls) were reported in SAE 941944. For gaseous hydrocarbon samples, two gasolines from the Auto/Oil Air Quality Improvement Research Program (AQIRP) were used to prepare compressed gas cylinders of “synthetic exhaust.” These samples were also doped with typical light hydrocarbon combustion components, marker compounds, and MTBE (in one of the two sets of samples). The cylinders were circulated to 16 laboratories, which included automotive and petroleum companies, contract laboratories, and regulatory agencies.

A cooperative vehicle exhaust emissions test program was conducted by the California Air Resources Board and Chevron Research and Technology Company. The focus of the program was to determine the effect of aromatics content on nitrogen oxides (NOx) emissions. The program consisted of testing nine vehicles on three different fuels. The fuels ranged in aromatics content from 10% to 30%.* Other fuel properties were held as constant as possible. The tests were conducted in two different laboratories. In addition to the measurement of criteria emissions (hydrocarbons, carbon monoxide, and NOx), some of the hydrocarbon emissions were speciated and a reactivity of the exhaust was calculated. Only slight changes in the exhaust emissions and reactivity were observed for a change in aromatics content from 30% to 10%.

A comprehensive program encompassing laboratory engine, laboratory vehicle, and taxi fleet tests was undertaken to evaluate fuel variables and induction system deposits in modern spark-ignition engines. The widespread fuel injector deposit problem was the primary focus. Injector and vehicle design, driving cycle, and fuel composition were found to be major contributing factors to injector deposition. Commercial gasoline additives capable of preventing and removing injector deposits were also identified. Some of these additives control intake valve and port deposits as well, while others actually contribute to valve and port deposits. Like injector deposits, intake valve and port deposits are shown to have adverse effects on vehicle performance. Associated functional problems may be even more apparent in high-swirl, fast burn engines.