In general, there are two different ways to sinulate in-cylinder processes of combustion engines: Zero- and one dimensional simulation, which considers the combustion chamber, intake and exhaust system as volumes and tubes. In this case, the combustion process (and thus the pressure and temperature characteristics in the cylinder) are represented in a simplified model. Example of commercial software: AVL Boost. The second possibility is based on CFD (Computational fluid dynamics) simulation, which builds up a finite elements mesh in the combustion chamber (and eventually in the intake and exhaust system. Due to the fact, that piston and valves are moving parts, this is a complicated modeling process. Exemplary software: AVL Fire, Star CC, Fluent

Kind regards,

Mario

A simple model can be a non diffusing droplet in air.  An unsteady state heat conduction for the droplet to achieve ignition temperature using the Biot and Fourier numbers can be undertaken.

A complicated model of a droplet with diffusion in a convective and radiative environment  can also be undertaken.  In this approach, the droplet radius vary with time.

As stated by Dr. Mario Hirz, you can also make use of the commercial CFD softwares available.