<p>There has been an unending competition between the world’s gas turbines manufacturers to increase the thermal efficiency and output power of&nbsp; industrial gas turbines. One of the most common techniques to increase the thermal efficiency and output power is to increase the turbine inlet temperature (TIT) and the pressure ratio. In most modern industrial gas turbines, the turbine inlet temperature reaches the range of 1400-1700°C (2552-3092°F); hence, the main challenge to this continuous implementation of ever-increasingTIT is to protect the airfoils without using more cooling air. This paper describes 2-D and 3-D numerical investigations to study the film cooling effectiveness of injecting mist (tiny water droplets) into the cooling air to protect the first stage gas turbine airfoils under the influence of stator-rotor interaction-induced wake and shock wave disturbances. The discrete phase model (DPM) is used to simulate and track the evaporation and movement of the tiny water droplets. Linear and rotational sliding mesh techniques are used to study the transient stator-rotor interaction for the 2-D and 3-D cases, respectively. The results show that the passing unsteady wake caused by the blade rotation kept the mist coming out from the holes on the blade suction side flowing near the blade surface and providing better film cooling effectiveness. The weak oblique shock waves did not have a significant effect on the air/mist cooling effectiveness. A parametric study was conducted to investigate the effect of using different mist mass ratios (10% and 20%) and different mist droplet sizes (20 µm and 30 µm) on the cooling enhancement and the behavior of the vortices in this gas turbine stage. The transient dynamic film cooling effectiveness and its average results are analyzed.&nbsp; The results show that the temperature reduction values are about 150 K to 200 K on the outer surface of the vane and 70 K to 120 K on the outer surface of the blade. The results of using bigger droplet size or higher mist flow rates are shown to further improve the heat transfer enhancement.</p>

Simulation of Air/Mist Cooling Among Shock Waves and Passing Wakes Interactions in a Transonic Gas Turbine Stage

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

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