Water spray spatial distribution by novel optical measurement for cooling suction air of gas turbine and its influence on cooling performance

Abstract

Air cooling performance and water spray characteristics are experimentally evaluated to obtain the basic knowledge for the suction air cooling of power plant. Novel optical measurement technique is proposed for measuring spatial number density of water droplet and water quantity in the air flow. The technique is based on Lambert-Beer law. An attenuation rate of the power of a laser beam passing through the mist flow is measured and the number of droplets is evaluated. Characteristics of the water spray are also evaluated by a phase Doppler anemometer (PDA). The data are compared with cooling performance. All experiments are tested in a wind tunnel with 1m x 1m square shape and 2 m in length. Mean velocity of main flow is set at 2 m/s, temperature at inlet of wind tunnel is set at 33 degree Celsius. Humidity of the inlet air is varied from 60 % to 90 %. The results show that the cooling efficiency by the water spray is depended on the water droplet diameter and humidity. The PDA data and the cooling efficiency are well correlated. The proposed method can present the data related with the droplet number and quantity.