Testing of Hygroscopic Flares for Particle Size Generation

The use of hygroscopic flares for precipitation enhancement is increasing in scope. Model studies have shown that the particle sizes generated by these flares can have a significant impact on the effectiveness for precipitation enhancement. At this time there are no known detailed studies on the particle sizes produced by the various flares in use, or on ways to vary the flare composition and particle sizes produced. We have constructed a test facility that simulates the burning of a flare on an aircraft wing. The facility consists of a large blower unit that will produce an airflow of approximately 50 m/s. The plume from the flare then expands into a cooling region where a variety of measurements are made on the particles. The measurements include total particle number, particle size, and particle CCN activity. Environmental measurements of temperature and dew point are also made. Data will be presented on the operation of the test facility and preliminary results from some hygroscopic flares currently in use.