Effect of Abnormal Blade Incidence on Internal Entropy Generation in Axial-flow Fans

The OB-84 axial-flow fan was numerically simulated at abnormal angles of blade incidence using Fluent software, while the characteristics of entropy generation in the axial-flow fan investigated and analyzed at cocurrent and reverse deviation of blade incidence based on entropy generation theory. Simulation results show that the entropy generation is mainly caused by turbulent dissipation; the entropy generation rate is relatively high in the area of moving blade and guide vane, and is relatively low around collector and diffuser; however, the total entropy generation is in the same order of amplitude respectively in regions of moving blade, guide vane and diffuser. The deviation of blade incidence influences the entropy generation of fan in different degrees; the entropy generation will be higher than normal condition inclusive of installation angle deviation Δβ=±10°, and it increases with the growth of Δβ; however, the influence of Δβ on entropy generation reduces in the case of Δβ>30°. Strip areas of high entropy generation including several flow passages will be produced along downstream of abnormal blade at cocurrent deviation, whereas only scattered high entropy generation regions will be formed at reverse deviation. At the same deviation of blade incidence, the influence of cocurrent deviation is generally higher than that of reverse deviation.