ContribDieselFoamChemistryPropertiesInitialChemicalTimeStep
From OpenFOAMWiki
initialChemicalTimeStep
Chemical reaction calculations are sub-cycled and for the first iteration the integration step can be too large for the chemical reactions and the calculation will blow up, due to the initial guess will create NaN's or negative concentrations.
Setting this value to something smaller than the timeStep value in the controlDict is a good idea if the ignition time is on the same time scale as the timeStep.
