The air how through a vane-cascade swirl generator is examined both experimentally and numerically to characterize the inlet combustion air flow entering a reference spray combustion facility at NIST. A three-dimensional model is used to simulate the aerodynamics in the 12-vane-cascade swirl generator that imparts the desired degree of angular momentum to the air in the annulus leading into the reactor. A numerical simulation using the renormalization group method (RNG) k-epsilon turbulence model results in a velocity profile consistent with experimental measurements, and correctly predicts a recirculation zone that is experimentally observed at the exit of the annular passage. The standard k-epsilon turbulence model does not compare as well with the experimental data and fails to predict the recirculation zone at the exit. This work is part of a larger project at NIST in which benchmark data are collected for input and validation of multiphase combustion models, and the results presented provide a well-characterized inlet condition for the spray combustion reactor. The good agreement between the experimental data and the simulation with the RNG k-epsilon turbulence model provides further validation for this model in confined, annular flows.