Influence of Piston Crown Shape with Spark, Fuel injector positions, EGR and Fuel System Control on Emissions of Modified GDI Engines over base Diesel Engine

Abstract

In the present work, developed the combustion chamber profiles for spray, wall, and air guided mode GDI engines. Modified the piston top surface for each combustion chamber geometry of GDI engine from hemispherical bowl to trapezoidal bowl and pent roof shape which include a scoop type bowl on one side (towards injector position) to impart better squish, swirl, tumble and turbulence effects required to improve the mixture formation. Also, modified the cylinder head to each combustion chamber with different locations of spark plug and fuel injector. Optimized the fuel split injections with durations, ignition timing and percentage of exhaust gas recirculation towards emissions reduction, especially soot and oxides of nitrogen. Emission tests were conducted on base diesel engine and all three modified combustion chamber geometry GDI engine. It is clear from the results that oxides of nitrogen emission in wall guided mode was reduced up to 5% till 75% of the loads when compare with both spray-guided and air-guided combustion modes, and later it is increased. Overall, wall guided combustion chamber geometry GDI engine shows better results at 150 bar FIP, when compare with base Diesel engine; oxides of nitrogen emissions were reduced from 377 ppm to 77 ppm and soot emissions were reduced from 29.3 g/km to 4.5 g/km at high torque.