The secondary flow forced into primary flow through wall holes (injection flow) has numerous uses in industry as an example film cooling. Usually, earlier-stage of nozzle guide vane and gas turbine blades are under the influence of very hot approaching primary flow (hot gases from combustion chamber) with a temperature which is considerably higher than the melting point of the any metals. One way of safeguarding gas turbine blades is to redirect a portion of compressor air and pass it through the nozzles and turbine blades. This cool air (comparing to primary hot gases) forced out from holes within the nozzles and blade makes a layer of cool air around the nozzles and blades (Fig. 1). The gas turbine manufacturers are curious to know both pressure losses and heat exchange in this area.
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