John F.
Widmann Cary
Presser Stefan D.
Leigh ABSTRACT It has been well established that the dynamic range of phase Doppler interferometry (PDI) size measurements is limited by the dynamic range of the photomultiplier tube detectors (PMT). A statistical method is presented to overcome this limitation by combining data sets collected using different PMT gains, which allows discrimination between different size ranges. The method is discussed and validated using a simulation in which droplets are sampled from monomodal and multi-modal size distributions. The technique is also applied to experimental data collected in a reacting methanol spray. Experimental measurements of monodisperse droplets and polydisperse particles are presented showing that PMT saturation does not preclude accurate size measurements when using frequency-domain signal processors that operate with one-bit analog-to-digital conversion. The results presented question the accepted dynamic range limitation of PDI systems, as well as the methods of optimizing the PMT gain reported in the literature.
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