Numerical Demonstration of the Humidity Effect in Engine Icing

The importance of the variation of relative humidity across turbomachinery engine components for in-flight icing is shown by numerical analysis. A species transport equation for vapor has been added to the existing CFD methodology for the simulation of ice growth and water flow on engine components that are subject to ice crystal icing. This entire system couples several partial differential equations that consider heat and mass transfer between droplets, crystals and air, adding the cooling of the air due to particle evaporation to the icing simulation, increasing the accuracy of the evaporative heat fluxes on wetted walls. Three validation cases are presented for the new methodology: the first one compares with the numerical results of droplets traveling inside an icing tunnel with an existing evaporation model proposed by the National Research Council of Canada (NRC). The second one compares humidity and the reduction in the outflow total temperature to the experimental data from NASA Glenn Research Center’s Propulsion Systems Laboratory (PSL). The third case shows that the vapor model improves our icing validation of the crowned cylinder case compared to the NRC experimental data. For the simulation technology demonstration, turbofan icing scenarios with inflow relative humidity varying between 30 and 100% are simulated using a generic engine intake that includes the first stages of the compressor. The inclusion of vapor transport and local relative humidity provide important additional modeling functionalities and increased simulation accuracy.