THE EFFECT OF LENS/APERTURE SELECTION ON PHASE DOPPLER ANEMOMETER MEASUREMENTS

An investigation into the effects of a less than optimum optical configuration on Phase Doppler Anemometry (PDA) measurements is presented. A typical three dimensional PDA system was configured with several transmitting/receiving lens and receiving aperture combinations and used to acquire velocity and drop diameter data downstream of an air/water spray nozzle. The experimental results show velocity measurements are relatively unaffected by the lens/aperture configuration. However, the measured drop diameters can show considerable bias when a less than optimum optical configuration is utilized. When the range of drop sizes is unknown, it can be difficult to choose the proper transmitting and receiving lenses, and receiving aperture (or mask). This paper describes an experimental approach used to minimize the bias caused by different lens/mask configurations and provides the user with a straightforwar d selection method.