The mutual interactions between the two propellers result in unsteady periodic
blade loading oscillations during one full rotation.
The comparison of the wall skin friction,
blade loading, and hub-to-shroud loading losses should be done for different operating scenarios such as design (rated) mass flow-rate, reduced (part-load) flow-rates, etc.
as a percentage of blade span or chord) and the
blade loading (local pressure difference between blade pressure and suction surfaces).
As the axial compressor moves from the rated operating point to a near-stall operating point, the
blade loading increases and the flow structures become stronger and unsteady.
(10.) Alheid, RJ, "Flexible Blade Coating Arrangement and Method with Compound
Blade Loading." U.S.
Even though the fans are typically not operating during the period of normal train operation it is critical to give consideration to the
blade loading cycles that results from the pressure pulses.
Since >75% of the power is developed at radii more than halfway to the tip, the useful
blade loading can be approximated to a total circumferential force of 180kN distributed between the blades and acting at a radius of around 80m.
Examination of a few worn blades can identify the following items: uneven blade wear, holder or chamber alignment, blade contact angle, relative amount of
blade loading pressure and presence of ink contamination.
