An experimental investigation of the effects of inlet geometry on the performance of a bistable fluid amplifier

The effects of varying inlet geometry on the performance of bistable fluid amplifiers were investigated experimentally on a large scale model flip-flop operated with air. Performance curves and power jet velocity profiles were taken for straight, right angle, and layer change entries to the power nozzle of the model. As the power nozzle inlet configurations were varied, the effects of additional parameters (external operating conditions, wall roughness, setback, and other geometric variables) on the amplifier performance were studied. The results are compared with typical commercial bistable fluid amplifiers.

When the flow entered the power nozzle from a right angle bend, a bias in the switching characteristics was found. For a fixed supply pressure, the left and the right control pressures differed, which caused the output to be easier to switch toward, or be biased toward, one of the output ports.

The power jet velocity profiles were found to be symmetric as the inlet configurations were changed. The magnitude and direction of the biased switching performance induced by inlet geometry was found to be independent of the operating conditions and the wall roughness. The direction of the bias was shown to depend upon the nozzle length, with the direction of the bias reversing for very short power nozzles. Increasing the setback and lengthening the nozzle were both found to decrease the bias. The bias in switching performance was found to be eliminated by the use of change-of-plane entries.