1434112 Influencing meteorological conditions PHILAGRO 15 June 1973 [16 June 1972 20 Nov 1972 29 May 1973] 28591/73 Heading A1X A process for transforming the interior structure of clouds to prevent hail-storms comprises igniting an explosive mixture of acetylene and air in burner 13 fitted with an upwardly directed open chimney 14, thus producing a shock wave, which, when directed to hail forming clouds, modifies their internal structure. The explosions are repeated every 8-15 seconds to achieve optimum efficiency of transformation and coils. Acetylene either from cylinders or produced from the reaction of calcium carbide and water, cleaned and purified in a scrubber 3 and purifier 6 is passed to a three way valve 8, one outlet passing to a gasholder 10, another to the burner 13 and the third to a pilot jet 11. The heavy gauge steel cylinder burner 13 of diameter D has an air inlet 13a in the lower casing covered by an internal, pivoted, counterweighted or spring loaded flap arranged to close to an angle of 20?? with the wall. A chimney 14 of inverted frusto-conical shape is fixed to the upper conical portion of burner 13 forming a cylinder 30 of diameter "d" at the junction. In operation, gas fed from valve 8 to holder 10 is exhausted into burner 13, where it mixes with air drawn in from inlet 13a. Pilot jet 11 then ignites the mixture and an expolsion occurs, producing an upwardly directed shock wave. The explosion also causes the flap over inlet 13a to rebound, and permit a sudden entry of air, which contributes to satisfactory shock wave formation and propagation, improved by the presence of cylindrical portion 30. Optimum results are obtained when the expolsions are repeated at 8-15 second intervals, and where a burner of height 3D, the ratio D/d is between 4:1 to 2.5:1. Embodiments using automatic gas supply and ignition timing valves which operate on batteries Figs. 4, 5 (not shown), and the use of alternative and premixed explosive mixtures and alternative ignition mechanism i.e. spark plugs, pietzo-electric crystals, electrical resistances are described.
