A quick automatic computation method is presented for a ducted propeller combined to an engine. It is suitable to be used on a personal computer. Effects of a number of parameters, such as diameter, pitch, solidity, and rotational-speed-reduction-ratio on the resulting thrust, propulsive efficiency and balanced rotational speed etc. are easily and quickly evaluated.
To promote a better understanding of the H. H. C. which is considered as a most promising active vibration control concept for a helicopter, dynamic hub vertical load responses of a rotor in forward flight due to multiple frequency blade pitch variations were investigated with placing emphases on their aeroelastic behavior. The blade pitch control scheme are described by a linear combination of two sinusoidal terms with arbitrary frequencies which are varied around the integer multiple of the rotor speed so that the frequency discrepancy effects on the dynamic hub load responses can be clarified. To take unsteady wake effects properly into account, unsteady air loads acting on the blade were evaluated by the two dimensional unsteady airfoil theory using the combined two and three dimensional wake model. Applying the generalized harmonic balance method to the linear, modal equations of motion of the blade as the blade circulation equations, elastic motions and associated unsteady air load distributions were determined successively and the hub vertical load responses were expressed by the Fourier series in terms of the reduced blade azimuth angle. Effects of such control input parameters as frequency ratios, amplitude and phase angles on the hub vertical load responses were numerically examined at typical two advance radios and the existence of optimum combinations of control input parameters which could minimize the dynamic hub vertical loads by the H. H. C. were ascertained.