[MFGT]

Hello,

i wanted to create a topic about the surrogate fuels, because i came across a few difficulties and would like to exchange knowledge and experience regarding this. My main fuel is gasoline with RON of around 92 and MON about 84, simulated in a Gasoline DI engine. Target OP is 8 bar bmep at 2000 rpm.

Previously i was using the simple approach with Iso-Octane and n-Heptane, blending both by volume according to the Octane number. However, that blend does not have the right LHV and also the H/C ratio and LSt are too high.

Adding Toluene and using the the method described here (http://www.sciencedirect.com/science...10218010000337) i got a three component fuel, which better matches the LHV and LSt, although H/C is a bit too low now.

Ive set up the same simulation using PRF and TRF each, with corresponding Jia mechanisms included in the CONVERGE example cases. At the IN- and OUTFLOW boundaries, i use pressure and temperature profiles of a GT-Power model, which is matched measurement data.
Due to the different fuel density, my discharge coefficent slighty changes. Furthermore, I have added another mutlizone dimension to account for the third fuel component.

Beside that the simulation duration was increased by 25% (multizone dimension and bigger reaction mechanism), i noticed the following points:

• As previously described, the LSt had changed and therefore my Lambda is different. With nearly the same fuel and oxidizer masses, i receive a Lambda of 0.96 (PRF) compared to 1.02 (TRF). I have also calculated these values on my own for validation. Here, TRF seems to be better suited, as LSt was closer to original fuel.
• Due to the different mixture composition, i have a difference in kappa and cp. Compared to GT Power, the PRF matches these values better.
• A difference in kappa means also a difference during the compression stroke. At spark timing, the pressure of 15 bar is increased by 0.3 bar simply due to the TRF. PRF matches the compression stroke profile very good.
• Finally, there is a big difference in pressure profile/heat release during combustion. PRF matches my pressure profile of GT-Power at the second cycle. TRF has a slower burn rate and slower pressure rise. Difference in peak pressure is around 8 bar (44.6 vs 37 bar).

From the points mentioned above, i have concluded that i will use PRF in future, due to the simplicity and better results (at least in this case). I am not looking at emissions or knock phenomena yet.



What are the experiences that other users have with this? Does someone has investigated this as well?