Abstract
In order to get a device able to determine droplet sizes with high accuracy and reliability, liquid nitrogen freezing method has been developed since 1971 and this time the seventh and final setup was built.
The cooling chamber is air-proved to avoid generation of cloud in the chamber. Liquid nitrogen fed in the double wall space vaporizes and forms cooling atmosphere. Liquid to be tested is injected downwards through the nozzle and its frozen particles fall onto the film set on the bottom end plate. In order to avoid the severe problem on frosting and optical difficulty, simple photogram method was adopted to get shadows of particles. Prior to construction of the device, distanCe necessary for drops to freeze was computed and the influences of temperature shock and long time contact with fuel and metal on photographic emulsion were investigated. Using the device thus constructed adequate exposure time and temperature gradient in the chamber were searched by trial and error method.
The achieved device can provide well photographs of frozen particles even for gasoline and alcohol. The comparison of the results thus obtained with those by immersion liquid method was also performed. These test results have revealed that this device would be usable not only for conventional measurement but also for calibration of other method.
