Precleaner is used in Engine Air Intake system for supplying cleaned air to the combustion chamber by separating dust particles. It is very important that Precleaner should separate out maximum dust particles from the fresh air before it enters combustion chamber by keeping the total pressure drop (back pressure) across the Precleaner within critical limit. CFD helps in understanding the trajectories of various sizes of dust particles within Precleaner and it also helps in determining the dust separation ability of Precleaner.