• Ahmad Naveed Department of Mechanical Engineering, University of Engineering and Technology, Lahore 54000, Pakistan.
Keywords: Compression ignition engine, regulated emissions, injector nozzle, tip penetration, injection timing


The climate changes and increase in global temperature are the key factors that have mainly amplified the exploration
studies of changing fuel injection and other constraints of compression ignition (CI) engines for the abatement
of exhaust emissions. In current study, a direct injection (DI), CI engine was run on a test bench for the performance
and emission analyses using different nozzles and injection timings. During the experiments, two types of nozzles
known as sac and valve covered orifice (VCO) were used with hemispherical cavity and toroidal cavity pistons,
respectively. Besides an already existing set of sac type nozzles, six distinct combinations of nozzles with varying
cone angles and tip penetration (protrusion) lengths (designated as 135° × 3.5 mm, 140° × 3.5 mm, 145° × 3.5 mm,
150° × 3.5 mm, 150° × 2.5 mm, and 150° × 1.5 mm) were used at three different injection timings comprising 16°
before top dead center (BTDC), 13°BTDC and 10°BTDC. Experimental results reveal that VCO nozzles in toroidal
combustion chamber (CC) are better than sac nozzles with hemispherical CC, and that wider cone angle nozzles
at 10° BTDC give the optimum results in terms of emissions and performance, relative to those of narrower cone
angles. The 150° nozzles with 1.5 mm tip penetration give abated carbon monoxide (CO), hydrocarbon (HC) and
smoke emissions along with better performance characteristics such as brake specific fuel consumption (BSFC) and
brake power (BP), while exhibit slightly higher oxides of nitrogen (NOx) relative to other combinations. Moreover,
the same combination also proves to be effective on emission control at 8 mode steady-state cycle.


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