Dynamic properties of hydraulic lines for fluid power transmission, Research Works of Air Force

This paper presents the results of a hydraulic line dynamic properties analysis taki ng into account inertia of the fluid flowing i n rigid and flexible lines, the compressibility effect for this fluid and the viscous friction effect. The following are described and analyzed: solution of the wave equation in the form binding four variables: pressure and flow rate at the line input, and pressure and flow rate and t he line output; two of the above-mentione d variables should be regarded as independent (input) and the other two as dependent (output), the acc uracy comparison of distributed parameters model to lumped parameters model with regard t o applicability range i n hydraulic systems analysis, pressure value at given installation points as a response to rapid valve closing (transient response) or to valve opening (waterhammer effect). In these consi derations the hydraulic line is regarded as a two-port with two inputs and two outputs with a definite transmittance matrix. Main considerations concern the vari able resistance model. A general solution is given as a function of the Laplace operator. Introducing appropriate simplifications into the variable r esistance model, the co nstant resistance model and los sless line model is obtaine d. Also, general solutions for three different lump parameter models are presented. For the lumped parameters line presents t hree equivalent models possible, i.e. as: a symmetrical two-port, a two-port with shared resistance and a two-port with capacitance at the output