Spray Transport Past Cylindrical Elements found in a Generic Aircraft Engine Nacelle: A PIV and PDA Comparison

ABSTRACT To better address the fire protection challenges which exist in aircraft engine nacelles, it is important to understand the transport of high boiling point liquids as they are sprayed past generic clutter elements that are found in aircraft engine nacelles. Specifically, there is a lack of reliable velocity and drop size measurements located downstream of an arrangement of clutter elements found in aircraft engine nacelles. To this end the need to non-intrusively record the drop size and velocity of fire suppressants in generic cluttered nacelle environments are critical. Two common nonintrusive optical methods, particle image velocimetry (PIV) and Phase Doppler Anemometry (PDA) were applied to a suppressant spray nozzle characterization. This characterization was performed upstream and downstream of a cylindrical tube array, which is of special interest in aircraft engine nacelle fire suppressant transport and distribution. A comparison between these two measurement techniques were conducted to analyze and highlight the strengths and limitations of each technique when applied to practical applications with large dynamic ranges. The experimental results demonstrate significant differences in velocity measurements between PIV and PDA due to the methodology each system employs; however, the characteristic trends of the velocity profiles were found to be consistent. In addition the high shear and vortex shedding which follow the clutter elements also contribute to this discrepancy between the two measurement approaches. The following data suggests that careful consideration must be taken when choosing an optical approach for the measurement of applications with large dynamic range applications, as those found in fire suppressant transport.