Switching Dynamics of Bistable Fluid Amplifiers

摘要

The report describes an experimental investigation of the transient switching of bistable amplifiers with low setbacks and variable configuration. The experimental observations were used to establish the mechanism of the switching action which was then used to guide the development of a theoretical model for the first two phases of the contacting-both-walls type of switching. The theory is based on the flow model for a two-dimensional jet attaching to an adjacent side-wall. The amplifier was of conventional design with straight and curved side-walls, cusped and pointed splitters and variable control port width. The power jet width was 3/4 in. and two aspect ratios, 3 and 1, were tested. Water was used as the fluid and the element was operated at three different Reynolds numbers based on the power nozzle width - 8000, 5000 and 2000. The control flow was always a step or pulse and it was varied from a maximum, i. e., Q sub c = Q sub o, to a minimum beyond which no switching could be initiated. Effects of loading, inertia of the fluid in the output legs and residual flows from the inactive control port were determined. Load changes were simulated by reducing the exit area of the output legs using a flat plate orifice. The flow field was made visible by generating hydrogen bubbles in the power nozzle and at the power nozzle exit. (Author)