Hingeless helicopter rotor with improved stability

Improved stability was provided in a hingeless helicopter rotor by inclining the principal elastic flexural axes and coupling pitching of the rotor blade with the lead-lag bending of the blade. The primary elastic flex axes were inclined by constructing the blade of materials that display non-uniform stiffness, and the specification described various cross section distributions and the resulting inclined flex axes. Arrangements for varying the pitch of the rotor blade in a predetermined relationship with lead-lag bending of the blade, i.e., bending of the blade in a plane parallel to its plane of rotation were constructed

Comparison of calculated and experimental cascade performance for controlled-diffusion compressor stator blading

The mid-span section of a previously reported controlled-diffusion compressor stator has been experimentally evaluated in cascade. Measurements are taken over a range of incidence angles for blade chord Reynolds numbers from 470,000 to 690,000. Blade chord length is 12.7 cm, aspect ratio is 2.0, and solidity is 1.67. Measurements include conventional cascade performance parameters as well as blade surface pressures. Computations are made for the inviscid flow field, surface boundary layers, and loss for several of the blade inlet angle conditions, are compared against corresponding data

Are inclined screw blades for vertical grain augers advantageous?

Due to modern technology, screw blades are often manufactured by rolling them out of one single strip of steel. When simultaneously some blade inclination is applied, less residual stresses and/or larger possible ratios between outer and shaft diameter are claimed by some manufacturers, which seems plausible. However, it is sometimes also claimed that the efficiency of the conveyors is increased by such an inclined blade. The underlying idea is that the blade will cause extra pressure between the material to be conveyed and the tube of the conveyor. This in turn would delay the angular speed of the material, thus resulting in a steeper upward motion.\ud \ud In order to investigate this phenomenon, previous investigations based upon the conveyance of a single point mass have been modified for an inclined screw blade. It appeared that such a blade has no significant advantages over a normal one, which was confirmed by a series of tests. For completeness, tests were also carried out with a leading screw, resulting in worse results.\ud \ud In the case that the pitch equals the diameter and for friction coefficients of 0.3 at both screw blade and tube wall, an increase of no more than 5% in capacity will occur, even for blade inclination angles up to 30°. At the same time, however, the efficiency can drop by 15%

Alleviation of unbalanced rotor loads by single blade controllers

A novel approach to reducing the unbalance rotor loads by pitch control is presented in this paper. Each blade has its own actuator, sensors and controller. These localised blade control systems operate in isolation without need of communication with each other. This single blade control approach to regulation of unbalanced rotor loads has several advantages including being straightforward to design and easy to tune. Furthermore, it does not affect the operation of the central controller and the latter need not be re-designed when used in conjunction with the single blade controllers. Their performance is assessed using BLADED simulations

High resolution computation of the aerodynamics and acoustics of blade vortex interaction

In the present work, high resolution CFD simulations have been performed on an idealised problem of the interaction of an independently generated vortex with a rotor blade, including a case where the vortex directly impacts on the blade. The resulting blade pressures and acoustics are comprehensively compared against experimental measurements. Two different modelling approaches are used: the first is to impose the vortex as a perturbation to the velocity field, and the second is to fully resolve the vortex formation, evolution and its interaction with the blade. For a case in which the vortex passes near the blade surface, the the fully resolved approach is confirmed to accurately preserve the vortex structure. The far field acoustic predictions offered by the fully resolved approach are seen to be very accurate and definite improvements are observed in the computed blade pressures and acoustics over the imposed vortex approach and other similar works in the literature. For a case in which the vortex axis passes through the blade, the shape and width of the acoustic pulse in the far field is accurately represented by the fully resolved approach, while the magnitude is slightly underpredicted. The improvement in prediction offered by the fully resolved approach is because this method allows for a more realistic representation of phenomena, such as dynamic change in vortex structure and trajectory due to the blade passage, that become important when the vortex miss-distance becomes small

Development of high performance composite bend-twist coupled blades for a horizontal axis tidal turbine

Development of a design methodology for a composite, bend-twist coupled, tidal turbine blade has been undertaken. Numerical modelling was used to predict the response of the main structural member for the adaptive blade. An experimental method for validation is described. The analysis indicates a non-linear blade twist response

A novel approach to structural load control using intelligent actuators

The recent trend towards large multi-MW wind turbines resulted in the role of the control system becoming increasingly important. The extension of the role of the controller to alleviate structural loads has motivated the exploration of novel control strategies, which seek to maximise load reduction by exploiting the blade pitch system. The reduction of blade fatigue loads through individual blade pitch control is one of the examples. A novel approach to reduction of the unbalanced rotor loads by pitch control is presented in this paper. Each blade is equipped with its own actuator,sensors and controller. These local blade control loops operate in isolation without a need of communication with each other. The single blade control approach to regulation of unbalanced rotor loads presented in this paper has an important advantage of being relatively easy to design and tune. Furthermore, it does not affect the operation of the central controller and the latter need not be re-designed when used in conjunction with the single blade controllers. Their performance is assessed using BLADED simulations

Supersonic fan blading

Radially extending rotor blades are disposed on a hub to form a supersonic propulsion fan for a turbofan engine. The peripheral spacing of the blades is such as to avoid forming a channel or passageway between adjacent blades. Each has a flat trailing surface extending from the leading edge at least as far to the rear as to cause any pressure waves which might originate on the blade surface to strike the leading surface of the following blade rather than propagate upstream of the blade row. The flat trailing surface of each blade makes an angle with the axis of rotation such that the blade is parallel to a gas inflow into the blades