Full Stall Simulations of a Redesigned Ventilation Fan for the ISS

The concept of a stall is studied rigorously in the aerospace industry. From a design standpoint, instabilities such as stall are undesirable– operation in the stall regime has a tremendous impact on aerodynamic performance as well as structural integrity. In extreme cases, operating in stall conditions can cause failure. Further, stall can cause a loss of lift on aircraft wings or a loss of thrust in aircraft engines. In any case, stall continues to be a topic of interest in the aerospace industry. The present work aims to analyze the stall characteristics of a ventilation fan that was recently designed for the International Space Station (ISS). Although the ventilation fan has a rotor-stator design, this paper considers a rotor-only configuration. The FUN3D Computational Fluid Dynamic (CFD) solver developed by NASA Langley Research Center was used to simulate the operational characteristics of the ventilation fan. FUN3D solves the Unsteady Reynolds-Averaged Naiver-Stokes (URANS) equations using implicit time marching and a dynamic overset grid. The FUN3D solver was originally written for exterior flow fields; however, this work represents an extension of the FUN3D solver to turbomachinery or interior flow fields. The FUN3D results for the rotor-only ventilation fan accurately captured the operational characteristics inherent to compressors– the results shared similar performance trends when compared to the experimental results for the rotor-stator case. A peak adiabatic efficiency of 96% occurred at a MFR of 105.2 CFM, the minimum aerodynamically stable point. A computationally stable stall occurred at a mass flow rate of 43.8 CFM where the adiabatic efficiency dropped to 69%.