A comparative study of the photon pressure force, the photophoretic force, and the adhesion van der Waals force

A comparative study of the photon pressure force, the photophoretic force, and the adhesion van der Waals force acting on particles attached to an optical window was presented. The goal is to explore the use of radiation forces for in situ cleaning of engine optical access windows. Using aluminum, glass, fly ash and soot particles on a glass substrate the calculations show that radiation forces could be several times greater than the van der Waals force and they are very effective for particle removal applications if radiation intensity is above a certain critical level. For soot and fly ash particles, which are typically present in many combustion environments, the photon pressure forces were about 3 times and the photophoretic forces were about 3 orders of magnitude greater than the van der Waals force.