Comparisons of Mixed-Phase Icing Cloud Simulations with Experiments Conducted at the NASA Propulsion Systems Laboratory

This paper presents the evaluation of a numerical model for simulation of the icing cloud development at NASA Glenn Research Center’s Propulsion Systems Laboratory (PSL). The model is helping the icing facility and the fundamental ice-crystal icing physics research team to better understand the complex interactions between the test parameters and have greater confidence in the conditions at the test section of the PSL tunnel. The model attempts to explain the observed changes in test conditions by coupling the conservation of mass and energy equations for both the cloud particles and flowing air, while accounting for compressibility and the variable PSL geometry. A subroutine has been added to more accurately simulate the tunnel when water vapor conditions potentially exceed saturation. The model simulation results are compared to experimentally measured values that were taken during the first fundamentals of ice-crystal icing physics tests conducted at PSL in March 2016. The tests simulated ice-crystal and mixed-phase icing that relate to ice accretions within turbofan engines. Experimentally measured air temperature, humidity, total water content, liquid and ice water content, as well as cloud particle size, are compared with model predictions. The model showed good trend agreement with experimentally measured values, but often over-predicted aero-thermodynamic changes. This discrepancy is likely attributed to radial variations that this one-dimensional model does not address. One of the key findings of this work is that greater aero-thermodynamic changes occur when humidity conditions are low. In addition a range of mixed-phase clouds can be achieved by varying only the tunnel humidity conditions, but the range of humidities to generate a mixed-phase cloud becomes smaller when clouds are composed of smaller particles. In general, the model predicted melt fraction well, in particular with clouds composed of larger particle sizes.