Phase discrimination inside a spray: LDV measurements using fluorescent seeding particles (FLDV)

Laser Velocimetry measurements in the vicinity of reflecting surfaces are still a major problem in many fluid mechanical applications such as measuring close to walls or wall film surfaces, respectively. Moreover, in any kind of two phase flow an unambiguous separation of the gas and the liquid phase is of particular interest. Commonly used techniques like Phase Doppler Analysers (PDA) with size discrimination are limited to two phase flows where the smallest particle of the dispersed phase is significantly larger than the seeding particles. This condition can rarely be fulfilled in technically relevant spray/air systems. One of the most promising approaches is a phase discrimination using fluorescent tracer particles for the gas phase. In this paper the working principle of the “fluorescent” LDV (FLDV) will be explained. Moreover, the applicability of different fluorescent dyes will be discussed. Finally, a comparison between PDA results using size discrimination and FLDV results inside a hollow cone spray will be presented.