1. Correct the mistake in the sensitivity of `src/particles/coal/CharCombustion/CCK/CharSpeciesRHS.h`. The missing nagative sign is added.
2. Modifying the sensitivity of CCK model. Our results have shown that using the real sensitivity or setting the sensitivity to be zero does not affect the results. So, we can set the sensitivity to be zero for most of our cases
because the simulation will be faster. We can turn on/off this in the input file by “Particles: CharModel: SensitivityOfCCK: ON/OFF”. The default value of “SensitivityOFCCK” is OFF.
3. The normalized number fraction of particles per gas mass (n_p,norm), instead of the real number fraction of particles per gas mass (n_p) is solved now. n_p,norm=n_p/n_p,stand. The standard value (n_p,stand) can be given in the input file by “Particles: StandardNumFrac:“. Its default value is 1e9. The reason for this is that very big sensitivity is obtained when using CCK model, because n_p is very big (In equation dn_p/dt=-n_p*S_mg/rho_g/u. The sensitivity of the numerator is dn_pdv*S_mg+n_p*dS_mgdv. The second term is big because n_p is very big. Thus, big sensitivity is obtained from this).