Proceedings of the 3rd BSME-ASME International Conference on Thermal Engineering 20-22 December, 2006, Dhaka, Bangladesh COMPUTATION TECHNIQUE FOR VARIOUS COMBUSTION AND EMISSION RELATED PARAMETERS WITH DIFFERENT FUELS Md. Nurun Nabi , Md. Shamim Akhter, Mustafizur Rahman and Md. Jalal Uddin Department of Mechanical Engineering, RUET, Rajshahi-6204 Email: nahin1234@yahoo.com ABSTRACT Lower heating values, theoretical air-fuel ratios, adiabatic flame temperature, carbon dioxide (CO 2 ), and nitric oxide (NO) emissions, which are elementary parameters related to engine combustion and emission were investigated with computations for various paraffin and oxygenated fuels. The computed results showed that almost all of the above combustion and emission related parameters are closely related to carbon and hydrogen content in the fuels regardless of the kinds or chemical structures of the paraffin and oxygenated fuels. It was found that with the increase in hydrogen content in the fuels the ratios between the lower heating values and the theoretical air fuel ratios remain almost constant independent of the hydrogen content or the kinds or chemical structures of the paraffin and oxygenated fuels. This indicates that the indicated mean effective pressure (IMEP) as well as engine output power are unchanged for different paraffin and oxygenated fuels because IMEP is mainly determined by the ratios between the heating values and theoretical air fuel ratios. Keywords: Combustion and emission related parameters, paraffin and oxygenated fuels. 1. INTRODUCTION It has been examined with great throughness that the oxides of nitrogen (NOx) and particulate matter (PM) emissions from diesel engines, particularly from high-speed diesel engines are serious environmental problem. Research and development for controlling these emissions have been dealt with three aspects - combustion and fuel injection system, exhaust after-treatment systems and fuel properties. Of these three, the design of the combustion and fuel injection systems has been the major counter measure to control both NOx and PM emissions. These includes the tuning the combustion chamber configuration, high-pressure fuel injection with small nozzle diameters, retarded fuel injection timings, exhaust gas recirculation (EGR), electronic injection control and others. A combination of these techniques has improved diesel emission to a considerable extent. However, other technologies for further improving the emissions has remained less investigated. Recently fuel properties and new fuels to improve diesel emissions have remarkably attracted a great interest since the establishment of NOx and PM after-treatment technologies seems to need more investigation before practical use [1-2]. As for the fuels in diesel engines, research has been conducted to clarify the effects of fuel properties on combustion and exhaust emissions. For instance, sulfur content in fuels has been reduced in order to remove the acid rain problem and also to improve the characteristics of after-treatment systems. Other fuel properties related to the improvement of engine performance and emissions include density, viscosity, distillation temperature, oxygen and aromatic content [3-10]. Regarding oxygen content or oxygenated fuels, the addition of lower alcohols, such as, methanol and ethanol to diesel fuel was reported to be effective to reduce diesel particulate emissions without sacrificing other emission components[11-14]. Non-alcohol oxygenated organic compounds have also been investigated to improve diesel combustion and emissions [15-17]. Methyl-t-butyl ether (MTBE) is an oxygenated fuel, which has already been used as an octane improver in gasoline, although it has a slightly toxic property. While having poor solubility in diesel fuel, dimethyl ether (DME) is a recent promising oxygenated fuel easily made From methanol, natural gas or coal [12-15]. The DME has high ignitability, different from lower alcohols and