Development and analysis of a fluid power test facility

The work described in this thesis was undertaken as part of a project to design and build an electro-hydraulic vibration testing machine of unusual configuration using the limited manufacturing facilities of the departmental workshops of the Engineering School of the University of Tasmania. A sketch showing the basic concept of the vibrator design is shown in Chapter 1. Technical limitations concerning available means of measurement and manufacture resulted in the development of a series of four-way spool valves featuring thin axial flutes milled in the spool lands to limit the area gradient and allow , a long stroke relative to the flow rating of the valve. An experimental rig to measure spool forces and flow characteristics under various static and dynamic conditions is described in detail. Difficulties experienced in the operation of the rig are discussed together with suggested lines of rig development. Digital simulation of hydraulic servo-mechanisms by the Runge Kutta technique is examined in detail particularly with respect to the causes of numerical instability. An alternative approach based on the Method of Characteristics is also described and found to be particularly useful for systems containing long pipelines. The latter method is based on the velocity of pressure propagation in the fluid media and the results of an experimental investigation to determine this velocity as a function of pressure in a flexible high pressure hose are presented.