OCR Text |
Show transmitter with a beam splitter and a three detector element receiver, which are typically separated by a distance of one meter. The receiver signal is first sent to a signal processor and subsequently to a computer for data reduction, correction, storage and display. With the exception of hardware positioning and focusing, all test and control parameters are set at the computer. Droplets that pass through the intersection of the split beams scatter the monochromatic light. As a droplet passes through the intersection of the two beams, a Doppler burst signal produced by each of the three detectors appears to move at the Doppler difference frequency but with relative phase shift. This frequency is proportional to the beam intersection angle and particle velocity. The phase shift is proportional to the beam intersection angle, detector spacing and the droplet diameter. The major benefits of this system, over a laser diffraction system are the ability to gather, locally, both size and velocity data, and the ability to measure directly the actual distribution of droplet diameters. The phase doppler system, also, has an improved ability to gather data in very dense sprays. Combustion Components Associates (CCA) inhouse computer codes relate the measured performance of the atomizer in the laboratory to its expected performance in the field. The code accounts for fluid property differences between water/air used in the laboratory and the heated oil and atomizing fluid (steam or air) used in field operation. The continuity, momentum and energy balances in the computer code permit any fluid and any atomizing media to be simulated provided their thermodynamic properties are known. With the atomizer operating at the manufacturers specified design condition (fuel pressure and atomizing fluid differential pressure), AFRC89 8 |