Abstract :
A newly developed heavy duty diesel engine in dual fuel mode of operation has been studied in detail. The main fuel
would be natural gas and diesel oil as pilot injection. The importance and effects of mixture preparation and formation
through ports, valves and in cylinder flow field with different swirl ratio and tumble on diesel combustion phenomena
is an accepted feature which has been studied using a developed CFD model. This analysis is capable to investigate
engine geometry, valves lift, valves timing and turbo charging, and its effects on dynamic flow field with variable dual
fuel ratio on power and emission levels output. This complete open cycle study of a dual fuel engine has been carried
out originally and for the first time and by considering complete grid consisted of four moving valves, two intake
ports, two exhaust ports, and the port runners. It is found that important complex flow structures are developed
during the intake stroke. While many of these structures decay during the compression stroke, swirl and tumble can
survive. The effect of increased swirl ratio at the end of the compression stroke for the D87 engine with a
piston bowl is clearly observed in this study. This is important for aiding in good fuel spray atomization. The
formation, development, and break-up of tumble flow are seen, contributing to an increase in turbulent kinetic energy
at the end of the compression stroke. The complete engine flow field, i.e. the inlet jet, and formation of swirl in
the intake ports, is also clearly shown in the study. Results of these simulations assist in the improved understanding
of the intake process and its influence on mixture formation and flow field in a dual fuel engine.
