The Ammonia and Diazo Technique With CO2-Calibration for Highly Resolving and Accurate Measurement of Adiabatic Film Cooling Effectiveness With Application to a Row of Holes

The ammonia and diazo technique with CO2-calibration for highly resolving measurement of adiabatic film cooling effectiveness distribution has been developed and improved with respect to high accuracy.Both parts of the technique are based on the analogy between heat and mass transfer. In the ammonia and diazo part a mixture of ammonia and air is injected through the film cooling holes. Downstream of the injection a diazo film is mounted on the experimental surface. Depending on the local ammonia concentrations along the wall the diazo film turns blue. In the CO2-calibration part carbon dioxide is used as a tracer gas. Gas samples are sucked off and analyzed, thus giving the adiabatic film cooling effectiveness at certain locations on the surface. Relating the effectiveness values to the color intensities of the diazo film at the corresponding locations a calibration curve is derived.This calibration can be applied to the whole color distribution of the diazo film resulting in a highly resolved distribution of the adiabatic film cooling effectiveness. The scattering of the measured values along the calibration curve directly indicates the quality of the measurement.The ammonia and diazo technique with CO2-calibration has been applied to injection through a row of holes (α = 35°, p/D = 3) in the flat wall of a wind tnnnel for different blowing rates. The results show a very good suitability of this technique, especially, but not only, if the region around the film cooling holes is of special interest.Copyright © 1996 by ASME