Suchergebnisse

An experimental investigation was conducted to specify the effect of diesel fuel composition and its physical and chemical properties on direct injection (DI) diesel engine performance characteristics and pollutant emissions. Engine tests were made on a single-cylinder naturally aspirated DI diesel engine (Lister LV1), which is located at the laboratory of the authors, at various operating conditions using seven conventional diesel fuels. The test fuels indicate variable hydrocarbon composition and physical and chemical properties, and they were prepared under a European Union research program aiming to identify future fuel formulations for use in modern DI diesel engines. Emphasis was given to the examination of the effect of diesel fuel density, viscosity, and compressibility factor on the fuel injection system, engine combustion characteristics, and diesel-emitted pollutants. Having observed that many diesel fuel parameters are strongly interrelated, we carried out a multivariable statistical analysis to determine the fuel property pairs that are statistically independent. Using experimental findings for pollutant emissions and independent fuel property pairs, a linear multiple regression analysis was conducted to identify potential correlations between diesel-emitted pollutant emissions and the fuel parameters. The sensitivity analysis revealed that soot emissions depend upon fuel viscosity, cetane number, and fuel volatility, whereas NO, CO, and HC emissions mainly depend upon fuel aromatic content. The evaluation of experimental results showed that reductions of soot, NO, and CO emissions can be attained with the reduction of the distillation temperature and the increase of paraffinics/napthenics ratio, which mainly provide the reduction of fuel viscosity and, secondarily, the decrease of the density and increase of the compressibility factor.

DI diesel engines are well established today as the main powertrain solution for trucks and other relevant heavy duty vehicles. At the same time emission legislation (mainly for NO, and particulate matter) becomes stricter, reducing their limit to extremely low values. One efficient method to control NO, in order to achieve future emissions limits is the use of rather high exhaust gas recirculation (EGR) rates accompanied by increased boost pressure to avoid the negative impact on soot emissions. The method is based on the reduction of gas temperature level and O-2 availability inside the combustion chamber, but unfortunately it has usually an adverse effect on soot emissions and brake specific fuel consumption (bsfc). The use of high EGR rates creates the need for EGR gas cooling in order to minimize its negative impact on soot emissions especially at high engine load were the EGR flow rate and exhaust temperature are high. For this reason in the present paper it is examined, using a multi-zone combustion model, the effect of cooled EGR gas temperature level for various EGR percentages on performance and emissions of a turbocharged DI heavy duty diesel engine operating at full load. Results reveal that the decrease of EGR gas temperature has a positive effect on bsfc, soot (lower values) while it has only a small positive effect on NO. As revealed, the effect of low EGR temperature is stronger at high EGR rates. (C) 2007 Elsevier Ltd. All rights reserved.

In recent years, NATO and U.S. military forces have decided to implement a single fuel (JP-8) for all land-based military aircraft, vehicles, and equipment during war and peace times. This is referred to as the single fuel forward concept. However, possible environmental pollution problems have been identified in the process of implementing this single fuel concept. This work presents data on the operational and, especially, environmental evaluation of the JP-8 fuel that is burned in diesel engines and furnaces. The investigation is conducted in a comparative manner between the JP-8 fuel and the proverbial Diesel Oil No. 2, which is being substituted. The two fuels were burned under identical conditions in disparate types of combustors, including direct injection (DI) and indirect injection (IDI) diesel engines as well as a laminar-flow muffle furnace. The primary goal was to contrast the emissions of the two fuels, because JP-8 is a substitute for diesel oil in military applications, such as engines of ground vehicles and power generators, as well as other burners. Regulated emissions of CO, particulate matter (soot), oxides of nitrogen, and total unburned hydrocarbons have been examined. In the case of the combustion of the two fuels in the furnace, unregulated organic compounds have also been monitored. Moreover, the operational behaviors of the two fuels in the engines have been discussed. Results demonstrated that, for both fuels, the magnitude of the emissions, as well as the trends with operating conditions, were influenced by the type of combustor. However, the emissions from the two fuels, when burned in the same combustor, were comparable overall, both qualitatively and quantitatively. © 2004 American Chemical Society.