PDA Measurements in Spray Generated by Twin-Jet-Nozzles

Generating fine widely dispersed sprays is the current focus of research. For this purpose, different types of nozzles are available. In the present paper, the continuous spray formation generated by the collision of two individual water jets is examined. All measurements are conducted in steady-state at ambient temperature and pressure. A non-invasive Phase-Doppler-Anemometry (PDA) laser measurement system enables the spray characteristics to be determined, the droplet distribution and the droplet velocity. Twin-jet-nozzles generate a fine but dense spray. The PDA measurement technique is an optical measurement application. The intensity of the light scattered by the droplets is proportional to the droplets squared diameter. Especially, in dense sprays, a high intensity of light signals is required for high quality data acquisition. Furthermore, the outcome of PDA measurement depends mainly on three aspects: One aspect is the influence of the laser power on the signal intensity. The second important parameter is the voltage of the Photo-Multiplier-Tubes. The third aspect is the orientation of transmitter and receiver of the measurement equipment relative to the spray. In this paper, the precision of PDA measurements in dense sprays influenced by the PMT voltage is analyzed and discussed.