[M-J-Hastings]

Hello,

I am trying to set up an accurate simulation of a compression ignition Diesel engine compression and combustion stroke. Subsequently I want to analyse the effects of displacing incremental proportions of the total fuel mass from Diesel to Hydrogen.

I would like to check that a method that I have developed, for altering the mass ratio of Diesel and Hydrogen while maintaining the total mass flow, is correct.

1) I run an initial case (C1) for pure diesel. To calculate the total mass of Diesel (m(tot)) injected into the chamber, I integrate my Diesel injection profile wrt time.
2) In the subsequent cases (C2-5), I must take the the sum of mass of Diesel and Hydrogen to be fixed at m(tot).
3)So, if I want to substitute 2.5% of m(tot) with Hydrogen, I write a new Diesel injection profile, whose mass flow rate at all points is x0.975 that in C1.
4)Having reduced the mass of Diesel by 2.5%, I replace this mass with Hydrogen (m(h2)) in the air in the chamber.
5)Now, I calculate the mass of Oxygen (m(o2)) required for stoichiometric combustion of the Diesel and Hydrogen.
6) Now I calculate the mass of N2 (m(n2)), CO2 (m(co2))and H2O (m(h20)) based on mass ratios at atmospheric conditions.
7) I convert these in-cylinder masses into in-cylinder mass ratios (which are different to those used above because there is now a significant mass of Hydrogen present). r(m(n2)) for the ratio of N2 for example.
8) In ICE Solver Setup < Physics Settings < Boundary, I set the following:
Fuel stream - Diesel = 1
Air - N2 = r(m(n2)), O2 = r(m(o2))....H2 =....CO2 =...

Will this method work as I intend? - to keep the total fuel mass constant and change the ratio of Diesel and Hydrogen.

Am I correct in thinking that the number in the Diesel box will be 1 independent of the amount of Hydrogen? - as this number represents the injection stream, which for all cases is pure Diesel.

Additionally, as far as I can see, the only way to make sure I have the correct mass ratio of Oxygen and fuel is to either keep the geometry constant (and therefore the mass of oxygen contained within) and vary the Diesel mass flow rate values, or vice versa.