Cem Sorusbay

Exhaust emission and fuel consumption of CNG/diesel fueled city buses calculated using a sample driving cycle

In this study the reduction of pollutant emissions from city buses converted to dual fuel operation was investigated. Exhaust emission and fuel consumption maps were obtained under laboratory conditions for an engine converted to CNG diesel fuel operation. These values are then used in the simulation model to predict the total exhaust emission and fuel consumption on a driving cycle evaluated from actual recordings. Calculations showed a significant decrease in PM emissions as expected, while with total CO emissions minor changes have been observed. For dual fuel operation NOx emissions were kept at the same level as in pure diesel operation with retarded pilot injection. Fuel cost calculations showed a decrease up to 30 % with current prices of diesel fuel and CNG.

Experimental and numerical investigation of diesel spray behaviour in high pressure common-rail systems

The behaviour of a diesel spray, generated by a common-rail injection system, has been investigated. The experimental investigation was carried out by testing a high pressure injection system, for heavy duty direct injection marine diesel engines, to calibrate a reliable model for the simulation of liquid jet atomisation and droplet break-up of the fuel spray. The experimental facility comprised instantaneous measurements of the fuel injection rate and the characterisation of the spatial and temporal evolution of the diesel spray, injected in a high pressure, non-evaporative quiescent vessel. The fuel tip penetration was estimated by digital processing of spray images captured at different instants after the start of injection. The spray was modelled using KIVA-3v algorithm, with a Kelvin-Helmholtz, Rayleigh-Taylor spray break-up model on a 45° sector grid. The mathematical model was verified with experimental results and a reasonable agreement was obtained.

Control of NOx emissions from diesel engines by the optimisation of fuel injection strategies

A multidimensional modelling approach using the KIVA3v algorithm has been applied to investigate the effects of fuel injection strategies on engine performance, NOx and soot emissions. Results were compared with experimental data obtained for a Ford Ecotorq NHDD diesel engine with a common-rail fuel system. After the verification of the developed model for different operating conditions of various load and engine speed, different split injection schemes with multiple pulses per cycle were considered. Results show that timing and duration of injection pulses and mass ratio of fuel injected have the major influence. NOx emissions can be reduced with a two-stage combustion resulting from early preinjection and late main injection with almost equal amounts of fuel mass fraction. Fuel mass fraction values of less than 20% in preinjection do not result in noticeable improvement.