A Correction Method for Spray Intensity Measurements Obtained via Phase Doppler Interferometry

A phase Doppler interferometer (PDI) was used to measure the intensity (i.e., the expected number of droplets measured per unit time) of a swirling methanol spray flame. Gaps observed in the data, which have been previously reported (McDonell and Samuelsen 1995), correspond to periods where the PDI was inactive. The intensity of the spray as a function of position within the flame was determined from the distribution of interarrival times (time between subsequent droplets entering the probe volume of the PDI), and a statistical simulation was developed to correct for the regularly occurring intervals in which the PDI does not accept data. The duration of this dead time was determined to be ca 5.2 ms for all points in the flame for which data were collected. The intensity of the spray varied by over two orders of magnitude throughout the flame. A statistical model is presented to correct for the observed behavior of the PDI, and the good agreement between the simulations and the experimental data indicate that the spray can be adequately modeled by Poisson processes.