I was wondering if there was a way of converting the example model to a GDI engine?
Is it a matter of defining different heat release laws?
Yes; from a 1D model point of view, I agree that basic difference between Diesel and petrol engines is in-cylinder heat release law.
If it is too complicated, is there a way of altering the combustion pattern of the diesel engine
so it is similar to that of a petrol one?
Diesel combustion process is usually modeled by using up to four Wiebe functions (more info at: http://openwam.webs.upv.es/manual/index.php?title=Four_Wiebes_simulation ). However it seems that for typical petrol engines, one Wiebe function is enough. So if I had to convert the example model I would:
– Go to the “Define heat release laws… ” option (when you right-click over the engine yellow box)
– Remove all the laws but one
– Select just “Diffusion” just as shown in the attached file
– Give values for engine speed, air and fuel mass flow (just for the model to run; they won’t be used since no interpolation procedure is calculated since you only have 1 law)
– Make Beta=1, since you only have one law
– Give reasonable values for Wiebe’s coefficients: m, C, combustion duration and combustion start. This can be a good paper to review:
F. Bonatesta, B. Waters, P.J. Shayler, Burn angles and form factors for Wiebe function fits to mass fraction burned curves of a spark ignition engine with variable valve timing, International Journal of Engine Research 11 (2) (2010) pp.177-186
Hope it helps.
Héctor
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