A Three-Dimensional Actuator Disk Model for Fan Response to Inlet Distortion—Part II: Applications

Abstract

Abstract. A theory developed in a companion paper (Part I) for the distortion response of a fan stage is applied to several configurations. The first of these is a conventional single-stage fan comprising a rotor and a stator, subjected to a tip-dominated stagnation pressure distortion. The response is highly three-dimensional, featuring a strong radial cross-flow and a distortion transfer with considerably greater spatial complexity than the excitation. Upon varying the stage loading, it is found that, while the fan response near the tip is qualitatively similar to that obtained using parallel compressor theory, three-dimensional effects significantly alter the behavior in the inner span of the annulus. Variations in the shape of the radial work distributions have a minor effect on the response, although the behavior in the outer span exhibits a dependence on the gradient of the work distribution. Conversely, the effect of introducing an inlet guide vane (IGV) is observed to be substantial, particularly on the distortion transfer. This feature is exploited to optimize various aspects of the fan response by employing circumferentially and radially nonuniform IGVs. Finally, the response of the fan to a swirl distortion composed of counter-rotating vortices is examined. The upstream influence in this instance is observed to feature strong induced axial and radial velocities, while a substantial stagnation pressure response is generated downstream.