An Analytical and Experimental Study of Aircraft Hydraulic Lines Including the Effect of Mean Flow

摘要

A mathematical model of a fluid transmission line was developed which included the effect of mean flow coupling with oscillatory flow. The analysis centered on solving the nonhomogeneous confluent hypergeometric equation with complex parameters using an infinite series and evaluating the solution using Ward's method. Experiments were run using an aircraft hydraulic system. The frequency response, vibration displacement, and standing pressure half wave were measured in a straight line and a line with bends for flow rates up to 9.5 gpm. A clampon transducer, which did not distrub the flow and could be easily moved, was used for the pressure measurements. In the absence of vibration the clampon transducer measurements were within 5% of readings taken with a conventional Statham in-line transducer. A sensitivity analysis showed the effect of small changes in geometry, temperature, steady-state pressure, fluid properties, entrained air content, and element volume. Using the new mathematical model, the attenuation and phase constant were calculated for hydraulic and air lines. Results compared well with experiment and published data. The new analysis and line mode provide a means for the fluid systems engineer to accurately account for mean flow effects. (Author)