The authors have developed a unique method for the accurate measurement of droplet sizes in a spray. The method is besed on liquid nitrogen freezing, in which the spray droplets are solidified by a low temperature atmosphere consisting
of vaporized nitrogen gas in a large cylindlical freezing chamber. At the ICLASS-91, it was reported that the accuracy of the freezing method was examined by comparing the droplet sizes obtained by the immersion sampling method, and the present technique was found to give a highly accurate value of droplet sizes. In this study, two types of laser light application technique, a phase-Doppler particle analyser (PDPA) and a Fraunhofer diffraction technique
(LDSA) , were compared with the freezing method by simultaneously measuring the droplet sizes of two types of spray. In the diesel spray test, Sauter mean diameters (SMD) along the spray axis measured by the PDPA were markedly smaller than those measured by the freezing method over the whole range of injection pres sure, i. e. from 6 MPa to 12 MPa, while the SMD measured by the LDSA at 1000 mm downstream of the spray nozzle agreed with those by the
freezing method. The second test was conducted with a low pressure spray (0.26 MPa) from a pintle type nozzle. Both the SMD measured by the PDPA and the LDSA agreed with those measured by the freezing method. The reasons for these
results may rely on the difference between the droplet size distributions.