Rotating stall control in a high-speed stage with inlet distortion: Part II - Circumferential distortion

This paper presents the first attempt to stabilize rotating stall in a sing le-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Researc h Center on a single-stage transonic core compressor inlet stage. Art array of 12 jet injectors located upstream of the compressor was used for forced response testing and feedback stabilization. Results for a circumferential total pressure distortion of about one dynamic head and a 120 deg extent ( DC(60) = 0.61) are reported in this paper. part I (Spakovszky et al., 1999) reports results for radial distortion. Control laws were designed using em pirical transfer function estimates determined from forced response results . Distortion introduces coupling between the harmonics of circumferential p ressure perturbations, requiring multivariable identification and control d esign techniques. The compressor response displayed a strong first spatial harmonic, dominated by the well-known incompressible Moore-Greitzer mode. S teady axisymmetric injection of 4 percent of the compressor mass flow resul ted in a 6.2 percent reduction of stalling mass flow. Constant gain feedbac k, using unsteady asymmetric injection yielded a further range extension of 9 percent. A more sophisticated robust H-infinity controller allowed a red uction in stalling mass flow of 10.2 percent relative to steady injection, yielding a total reduction in stalling mass flow of 16.4 percent.