Influence of Inlet Pressure Distortion on a Convertible Engine Fan

Abstract

An experimental and computational study of the e owe eld of a fan with uniform and distorted inlet e ow is presented. The research facility is a full-scale integrated engine with a constant-speed turbofan. The blade-incidence angles of the fan ‐ rotor can be changed during the operation. Thrust variation is thus achieved by altering the incidence of the fan ‐ rotor blades in the same manner as a variable-pitch propeller. The e owe eld of the fan with a uniform inlet e ow was e rst studied by a quasi-three-dimensional approach based on a radial-equilibrium method. The radial-equilibrium solutions are within 1.5 ‐ 10% of experimental measurements. The results indicated the stable operating range of the fan as a function of the rotor-blade-incidence angles. Then, the results obtained with the uniform inlet e ow were used as a reference basis for the study of the distorted inlet e ow. The small-perturbation method was very useful to design the distortion screens and to study the propagation characteristic of the distortion. The results revealed that the fan attenuation capacity is augmented when the fan load increases. The distribution of the periodic and random velocity e uctuations at the rotor inlet and outlet was obtained by hot-e lm probes by using an ensemble-averaging technique. This technique proved to be a useful tool for the assessment of distorted e ow characteristics.