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Measurements of flow velocity and temperature of dust-laden hot air in the condition of coal dust ex |
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Measurements of flow velocity and temperature of dust-laden hot air in the condition of coal dust explosions Authors: J. Rysz, P. Ligęza
Measurements of air flow velocity and temperature in mine headings after coal dust explosions pre-sent major difficulties due to a wide variability range physical parameters describing the state of gas and their quick changes. Conventional impact tubes prove inadequate because the coal particles block the piezometric hole for total pressure registering. Besides, the values of total pressure tend to be overstated due to the momentum exchange between the suspension particles and the gas. The probe design utilises the impact tube with a scavenge duct enabling the measurements of total, static and dynamic pressure in flow of dust-laden air. On that basis the authors designed and engineered a special probe intended for measurements of flow velocity and temperature of hot, dust-laden air in the conditions of coal dust explo-sions. The measurements are taken with the use of a thermocouple chromel-alumel placed in a separate flow duct. The paper explores the probe design, its operating principles and main technical parameters. The probe consists of three fundamental components: an impact tube, the temperature-measurement duct and a probe casing incorporating the eleetronic circuits. The probe was first tested in a wind tunnel at the Strata Mechanics Research Institute of the Polish Academy of Sciences in Cracow. The testing program-me was adapted to the measurement capabilities of the wind tunnel. The obtained results seem to confirm the adequacy of design objectives, which will be finally verified in the real-life applications in the conditions of coal dust explosions. The probe was commissioned by the Central Mining Institute who also provided assistance in research investigations, being a part of the research program to check the perfor-mance of fire prevention dams built from closed containers. Tests conducted in an experimental heading in an underground mine "Barbara" confirmed the good probe performance in those conditions. Potential applications of the probe include the testing of explosives.
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2009