Correlating Propeller Performance
with Kt/Kq Multipliers
A HydroComp Technical Report
Product link: NavCad,
and M-AU (modified AU) propellers are a series of aerofoil
blade section propellers popular in Japan and the Far East. The
basic geometry of the series is quite similar to the Wageningen
B-Series developed at NSMB.
the B-series, the thrust and torque performance has never been
developed into polynomial expressions for the calculation of Kt
and Kq. It is possible to adequately predict the performance of
the AU/M-AU series through the use of Kt and Kq multipliers.
Kt and Kq multipliers shift the predicted curves for the chosen
series (B-series in this case), to make them closer to what is
expected from the actual propeller (AU/M-AU). HydroComp has identified
that to predict AU/M-AU series performance:
suitable scale corrections and options as for the B-series
plot of actual AU/M-AU performance compared to multiplier-corrected
B-series performance is shown below. This was performed at model
scale for a 5-bladed propeller with 0.80 expanded area ratio and
pitch/diameter ratio of 0.80. The multiplier was chosen to minimize
the error in the range of the maximum efficiency. The calculation
tended to overpredict (less than 4%) below the point of maximum
efficiency, and underpredict above.