S.A.E. National Aeronautic Meeting: Summaries of the Papers Presented to the Meeting Held at Los Angeles, October 2–6, 1956

Abstract

The pressure control valve is a possible means of overcoming the effects of compliance between a hydraulic servo and its load. The valve consists of two stages; an open‐centre flow control valve schematically analogous to a resistance bridge, and a split‐slider valve. In order to study the dynamics of the system it is convenient to set up an electrical analogue for the mechanical system. This will give the non‐linear equations of the system. Several forms of the various impedance elements making up the system require consideration. The resistance of a length of hydraulic line can be obtained from the friction factor and will depend on the flow regime which prevails. In developing an expression for the inductance of a length of line the assumption is made that the wavelength of the oscillatory motion is long compared with the line length. In considering the resistance of orifices it is necessary to take into account the three regimes for flow through an orifice, laminar, transition, and turbulent flow. The inductive effect of an orifice arises from the acceleration of the fluid as the streamlines converge through the orifice; an expression can be derived by applying Newton's second law of motion to the column of oil passing through the orifice. The effective capacitance of a volume can be derived by considering wave motion in one dimension. An expression for the radiation resistance of a piston is derived, and also one for the incident and reflected waves. In constructing the electrical analogue for the slider valve the mass and viscous damping of the slider as well as Bernoulli forces must be represented.

Citation

(1957), "S.A.E. National Aeronautic Meeting: Summaries of the Papers Presented to the Meeting Held at Los Angeles, October 2–6, 1956", Aircraft Engineering and Aerospace Technology, Vol. 29 No. 1, pp. 21-24. https://doi.org/10.1108/eb032784