| The air used in fluidic nozzle applications on airplanes is normally provided by engine compressor bleed. Compressor bleed has a significant negative impact on engine performance. In order to reduce the performance penalty, additional entrainment using an ejector or jet pump arrangement is beneficial. Two techniques of flow control leading to effective entrainment, active control devices and passive control devices, are investigated experimentally. Active control devices include loudspeakers, rotor valve pulsators and synthetic jet actuators. Passive control is achieved using ejector mixing tubes of specific shapes, including a cone, with cone angles of 21°, 30° and 40°, attached to either a constant diameter tube, a venturi nozzle or a bellmouth.; Results indicate that pumping effectiveness, the normalized ratio of the secondary mass flow rate to the primary mass flow rate, depends upon the square of the relative pulsation strength, defined as the ratio between the velocity pulsation amplitude and the mean velocity. (Abstract shortened by UMI.)... |
