LDV Measurements of Air Entrainment Produced by the Impact of a Diesel Spray on a Flat Wall

Normal impingement of a transient diesel spray onto a flat wall has been investigated by LDV measurements of the gas phase flow generated in the region surrounding the impinging spray and the resulting wall jet. The observed time evolution of the air flow pattern can be understood by a qualitative model based on momentum exchange between liquid drops and surrounding air. Quantitative measurements of the air mass flow rate entrained into the spray, performed with sufficiently high space-time resolution, allowed to separate the wall jet contribution to entrainment from that of the impinging spray. The results indicate that entrainment into the wall jet contributes significantly to the increase of the total entrained mass flow rate compared to the unconfined spray.