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1988
Conference Paper
Titel
Experimental investigations into the deflagration of flat premixed hydrocarbon/Air gas clouds
Abstract
In a test program consisting of a series of 17 tests, experimental studies of the combustion of "pancake-shaped" free clouds of near-stoichiometric methane/ethane/air and propane/air mixtures of a volume of up to 13.000 cubicmeter under different test conditions were carried out. The parameters were the geometry and size of the cloud, geometry of the source of ingnition (are, line, and point ignition), geometry and arrangement of obstacles (cubic and/or cylindrical), and generation of different turbulence fields. The flame propagation and the pressure/time course of the pressure waves produced by the flame were measured. In undisturbed clouds the maximum flame speeds did not exceed 6-8 m/s and the maximum overpressures were 1-2 mbar. The results indicate a slight increase in flame speed as a function of the distance traveled by the flamed front due to flame-induced turbulence. Additional turbulence and obstacles increase the flame speed significantly. For a rms turbulent velocity of u ' = 0,56 m/s (20% turbulence level), typical flame speeds of up to 20 m/s and corresponding overpressures of about 5 mbar were measured. At obstacles, gaps, and entries and exits of lanes, higher turbulence levels were generated, resulting in local increases in flame speeds and overpressures of up to 80 m/s and 80 mbar, respectively. The peak overpressures were found to be approximately proportional to the square of the flame speed.