4401 (RP-1019) -- Air Temperature Depression and Potential Icing at the Inlet of Stationary Combustion Turbines PDF

The research reported in this paper concerns the investigation of ambient or cooled air temperature depression and the corresponding potential for the formation of condensation and ice on the surfaces of the inlet air housing, bellmouth, and inlet guide vanes of gas (combustion) turbines. Ice formation on the bellmouth or inlet guide vanes could possibly release and damage the first stage of compressor blades. This research is based upon numerical model simulations of surface temperatures, air velocities, and pressures through the inlet duct, bellmouth, and inlet guide vanes using the geometries of three stationary turbine installations. The air and surface temperatures were predicted for a range of ambient or cooled inlet air temperatures at the design inlet air velocity. The occurrence of surface condensation was assumed when the recovery factor corrected surface temperature was less than the corresponding saturation temperature of the air. The simulation results revealed that the leading edge of the inlet guide vanes experiences the lowest surface temperature and therefore is the most susceptible area for condensation and icing. The simulations predicted formation of fog and ice that are generally substantiated by observations of turbine-operating personnel. At 100% relative humidity, the ambient/cooled inlet air temperature is limited to between 35°F and 40°F (1.7°C and 4.4°C) to prevent condensation and possible ice formation on the inlet guide vanes. If the relative humidity is sufficiently low, such that the saturation condition is not reached at the reduced pressure inside the bellmouth, cooled or ambient inlet air temperature can be as low as desired.

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