Environmental Assessment of a Diesel Engine Under Variable Stroke Length and Constant Compression Ratio

Abstract

In the light of the energy crisis and the stringent environmental regulations, diesel engines are offering good hope for automotive vehicles. However, lot of work is needed to reduce the diesel exhaust emissions and give the way for full utilization of the diesel fuel’s excellent characteristics. This paper presents a theoretical study on the effect of variable stroke length technique on the emissions of a four-stroke, water-cooled direct injections diesel engine with the help of experimentally verified computer software designed mainly for diesel engines. The emission levels were studied over the speed range (1000 rpm to 3000 rpm) and stroke lengths (120 mm to 200 rpm) and were compared with those of the original engine design. The simulation results clearly indicate the advantages and utility of variable stroke technique in the reduction of the exhaust emission levels. A reduction of about 10% to 75% was achieved for specific particulate matter over the entire speed range and bore-to-stroke ratio studied. Further, a reduction of about 10% to 59% was achieved for the same range. As for carbon dioxide, a reduction of 0% to 37% was achieved. On the other hand, a less percent change was achieved for the case of nitrogen dioxide and nitrogen oxides as indicated by the results. This study clearly shows the advantage of VSE over fixed stroke engines. This study showed that the variable stroke technique proved a good way to curb the diesel exhaust emissions and hence helped making these engines more environmentally friendly

Tropospheric Oxidation of Ethyne and But-2-yne. 1. Theoretical Mechanistic Study

“…For the similar e2 − l step in the but-2-yne system it is 19.2 kcal mol -1 (29.4 for e2 − f ). Therefore, if the E2 or e2 intermediates were able to thermalize efficiently, the exceedingly easy NO-mediated process would appear as prevailing completely at any reasonable NO concentration, which can be considered as ranging from 10 8 molecules cm -3 , representative of an unpolluted situation, to 10 14 molecules cm -3 (a typical value in the engine exhaust, but peak values can be higher) . This is of course true only if the E2 or e2 intermediates are thermalized; otherwise the unimolecular step would prevail, because the bimolecular reaction is slower than thermalization.…”