No abstract

No abstract

SUMMARYThis paper deals with the experimental study that aims to examine the e!ects of octane number of three di!erent fuel oxygenates on exhaust emissions of a typical spark ignition engine. Three commonly used oxygenates, namely methyl tertiary butyl ether (MTBE), methanol, and ethanol, which were blended with a base unleaded fuel in three ratios (10, 15 and 20 vol%), were investigated. The engine emissions of CO, HC, and NO V were measured under a variety of engine operating conditions using an engine dynamometer set-up. It is found that generally as the octane number of the fuel increases the CO and HC emissions decrease but the NO V emission increases for all three blends. Further, for the leaded fuel (RON of 92), as the speed of the engine increases the CO and NO V emissions decrease but the HC emission decreases. A similar trend was found for MTBE blends also. These emission results are presented in terms of octane number and their e!ects are discussed in this paper.

No abstract

No abstract

The current experimental study aims to examine the effects of using oxygenates as a replacement of lead additives in gasoline on performance of a typical SI engine. The tested oxygenates are MTBE, methanol, and ethanol. These oxygenates were blended with a base unleaded fuel in three ratios (10, 15, and 20 vol.%). The engine maximum output and thermal efficiency were evaluated at a variety of engine operating conditions using an engine dynamometer set-up. The results of the oxygenated blends were compared to those of the base fuel and of a leaded fuel prepared by adding TEL to the base. When compared to the base and leaded fuels, the oxygenated blends improved the engine brake thermal efficiency. The leaded fuel performed better than the oxygenated blends in terms of the maximum output of the engine except in the case of 20 vol.% methanol and 15 vol.% ethanol blends. Overall, the methanol blends performed better than the other oxygenated blends in terms of engine output and thermal efficiency.

The laser processing of engineering materials requires an in-depth analysis of the applicable heating mechanism. The modelling of the laser heating process offers improved understanding of the machining mechanism. In the present study, a closed-form solution for a step input laser heating pulse is obtained and a numerical scheme solving a three-dimensional heat transfer equation is introduced. The numerical solution provides a comparison of temperature profiles with those obtained from the analytical approach. To validate the analytical and numerical solutions, an experiment is conducted to measure the surface temperature and evaporating front velocity during the Nd-YAG laser heating process. It is found that the temperature profiles resulting from both theory and experiment are in a good agreement. However, a small discrepancy in temperatures at the upper end of the profiles occurs. This may be due to the assumptions made in both the numerical and the analytical approaches. In addition, the equilibrium time, based on the energy balance among the internal energy gain, conduction losses and latent heat of fusion, is introduced.of evaporation (kJ/kg) I power intensity ( W/m2) I 0 peak power intensity ( W/m2) k thermal conductivity ( W/m K) 1 INTRODUCTION k B Boltzmann's constant m atomic weight (kg)The laser finds increasing commercial use as a machine p pressure (Pa) tool. However, for its use to be consolidated, it is necesp s recoil pressure (Pa) sary to explore the laser workpiece interaction mechanp z axial pressure (Pa) ism. Therefore, modelling the physical process can yield r radial distance (m) much insight into the complex phenomena occurring s, x distance from the surface (m) within the region activated by the laser beam. t time (s) Furthermore, modelling can substantially reduce the t eq equilibrium time (s) time required for process optimization, scale-up and T temperature ( K ) control. T s surface temperature ( K ) The modelling of temperature distribution induced by T sup superheat temperature ( K ) laser radiation in solids was previously investigated by V instantaneous velocity (m/s) several researchers (1-3) for stationary beam and for V liq liquid front velocity (m/s) moving beam interaction. In laser interaction mechan-V r evaporating surface velocity in the radial ism, the laser energy is absorbed at the surface by Fresnel direction (m/s) as well as surface plasma absorption (4). As the absorp-V vap vapour front velocity (m/s) tion is substantiated, the metal vapour reaches tempera-V z evaporating surface velocity in the axial tures much higher than the evaporation temperature, direction (m/s) resulting in strong ionization. The resulting plasma absorbs the laser radiation mainly by the effect of inverseThe MS was

No abstract