Array Of Cylindrical Elements Research Articles

Effectiveness of using jet control blowers to change the characteristics of a centrifugal stage

Jet blowers that are used to change the twist of a stream at the inlet to a turbomachine rotor by blasting the stream at an angle to its main flow possess a series of advantages over control devices with rotating vanes. In order to make a preliminary evaluation of the effectiveness of jet blowers, several models of control devices of axial and radial configuration were produced and tested. The gas-dynamic characteristics of the axial stage were obtained for fixed mounting angles and relative injection gas flow rate, regulating operating modes of the stage by changing the resistance of the circuit with the aid of barriers in the exit sleeve. In the radial stage, the characteristics were varied by varying the value of the gas flow rate with a constant value of the mounting angle. An analysis of the static blast tests of the first axial stage modification showed that the gas current does not flow satisfactorily around an array of cylindrical elements because of the high frontal resistance. The maximum efficiencies and head coefficients for the two-level stage turn out to be 1-2% higher than in the single-level devices and the flow rate control limits are not changed. It ismore » concluded that the design modifications of the jet blowers are as a whole less efficient than vane devices.« less

Scattering of a plane electromagnetic wave by a linear array of cylindrical elements

An approximate method for numerically calculating the scattered field of a linear array of center-loaded cylindrical elements illuminated by a plane wave incident in the H plane of the array is described. To illustrate the use of the approximation technique, the H -plane scattered field of an eight-element model array is calculated for various conditions of impedance loading and illumination. From extensive calculations, it is found that the H plane scattered field of the array can be represented approximately by the product of the electric field scattered in the reflected direction and an interference factor. The interference factor is the equivalent of the complex array factor of the model array when excited with uniform amplitude and an element-to-element phase progression proportional to the sine of the angle of incidence of the illumination.