Effect of Injection Parameters and Wall-Impingement on Atomization and Gas Entrainment Processes in Diesel Sprays

The objective of this investigation is to characterize the influence of injection parameters and spray-wall interaction on atomization and gas entrainment processes of high-pressure non-evaporative sprays injected into a high-pressure vessel using several imaging techniques. The effects of injection pressure on the droplet distribution, size and velocity were quantified using single and double nano second exposure photography techniques. A laser-sheet imaging method was employed to measure the two-dimensional gas velocity around the spray and to clarify the effects of the above parameters on the gas entrainment into the impinging sprays. It was found that increasing the injection pressure causes an increase in droplet number in both free and wall-jet regions of the sprays. Spray-wall impingement creates a large-scale gas vortex around the spray, which promotes the gas entrainment into sprays typically at the impinging zone, and it also affects the spatial distribution of droplets. Higher injection pressure gives a higher gas entrainment into the spray mostly at the impinging zone. Shortening the impinging distance drastically enhances the gas entrainment into the wall-jet spray. A smaller nozzle hole size lowers the gas entrainment into a spray.