The impact of a fan inlet guide vane blades design effect on its characteristics

Аuthors

Glushkov T. D.^*, Mitrofovich V. V.^**

Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia

*e-mail: dianno@bk.ru
**e-mail: vvmitrof@yandex.ru

Abstract

During the definition of one of the modern helos’ cooling fan system’s aerodynamic perfomance, it was estimated that its aerodynamic efficiency at the operation points is much lesser then pre-calculated meaning. When analyzing velocity distribution in blade passages of pre-seriesly-built fan prototype and its high-scale model, it was determined that the reason of prototype performance reduction is insufficient flow angle at inlet guide vane (IGV) outlet. As result negative rotor airfoil cascade angle of attack α leads to insufficient energy transfer from the rotor to the airflow and reduction of fan performance.

The pre-seriesly-built prototype of fan had certain deviations from the recommended shape of the input guide vane blades, in particular, great radial tips at hub and shroud, and through slot, presented at the IGV blades peripheria, that permits to hub and shroud tip leakage flows. Downwash of flow resulted in sufficient reduction of IGV outflow angle and cutting the full pressure ψ and power λ factors. Testing of same prototype with IGV radial gaps deleted, shown that radial gaps deletion sufficiently lessens the negative impact of vane design drawbacks.

Inlet guide vane blades stagger angles θ_IGV significantly impacts on size, angle and direction of downwash. When θ_IGV<95° IGV downwash direction is contrary to rotor rotation, as result rotor inflow angle if relative movement decreases, rises airfoil cascade angle of attack and energy transfer to the airflow. If θ_IGV~95° IGV outflow has axial direction, and velocity distribution at rotor inlet consists to expected. When θ_IGV>95° IGV downwash direction coincides to rotor rotation and fan performance decreases.

It was also shown that even minor deviations from the recommended vanes coronets’ shape significantly impact upon the overall aerodynamic and cinematic features of the fan installation.

Keywords:

axial fan, inlet guide vane blades, flow leakage, flow angularity

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