What is the relationship between angular velocity and power efficiency of a twin blanded single rotor helicopter system, in hover?

A traditional helicopter requires 60 - 80% more power to hover than when in forward or lateral flight, making the manoeuvre extremely power inefficient. To maximise efficiency, industrially many properties of the helicopter and rotor have been changed and tested, for example: optimising blade shape, fuselage shape and changing weights of different helicopter components. This report in particular aims to find a relationship between power efficiency and angular velocity for a twin bladed hovering helicopter with a single rotor. The angular velocity of a blade measures the frequency of its revolution about a fixed point. A theoretical approach was first taken and then justified with empirical data. Firstly, a model for power efficiency was derived with William Froude’s momentum and blade element theory. The efficiency equations incorporated the thrust and power coefficients. Therefore, the research focused on determining values for these coefficients by manipulating equations, using industrial specifications and simulations from the XFOIL software. In order to validate the accuracy for such theoretically generated data, an experiment was conducted for a comparison. The theoretical and empirical data were concurrent, as they followed a similar trend and the empirical values overlapped within the theoretical error bars. The power efficiency for different angular velocities were then found by substituting values for the coefficients. The results demonstrated a positive relationship; where, as angular velocity increases, power efficiency increases too, then plateaus and repeats the same trend once again. The research raises many questions and could be extended by determining if a similar relationship exists for tri-copters and quadcopters.