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

Abstract

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