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Hydroacoustic projectors are useful for generating low frequency sounds in water. Existing works on hydroacoustic projectors require two significant enhancements, especially for designers. First, we need to understand the influence of important projector design parameters on its performance. Such insights can be very useful in developing a compact and efficient projector. Second, there is a need for an integrated model of the projector based on easily available and user-friendly numerical tools which do not require development of complex customised mathematical analogs of projector components. The present work addresses both such needs. Towards these goals, an experimentally validated, easy-to-build projector model was developed and used to conduct design sensitivity studies. We show that reductions in pipe compliance and air content in oil, and an increase in orifice discharge coefficient can yield remarkable improvements in projector’s SPL. We also show that reductions in pipe length and cylinder diameter cause moderate improvements in performance in mass and stiffness controlled regions, respectively. In contrast, the projector performance is insensitive to changes in pistonic mass, cylinder length, and diaphragm stiffness. Finally, we report that while pipe compliance and air content in oil can sharply alter system resonance, the effects of changes in pipe length and pistonic mass on it are moderate in nature.
Content available remote Challenges in design process of gear micropump from plastics
Plastics are more and more frequently applied in the construction of hydraulic components and systems, and recently, in the building of microhydraulic assemblies. The basic unit of the microhydraulic systems is a micropump. It is an object which is quite difficult to design and manufacture, especially when using plastics. The paper is a presentation of challenges that must be met in the process of designing gear pumps, and, at the same time, of the theoretical grounds for the designing of those objects. The challenges include the geometry and the gears, the construction of the pump body, the hydraulics of the pump, and the material—the plastic of which the pump is made. The knowledge on those issues was applied to make and to successfully test a prototype of a micropump.
The paper presents the global and European market of machinery and equipment, in particular the market of hydraulics and its main shareholders: USA, China, Japan and the CETOP countries. The dynamics of the transformation on the global, European market, also in some countries of significance in that area, are shown. The sharpness of the drop in the sales of hydraulic and pneumatics products has been related to the drop in the production of machinery and equipment as well as to the general economic situation, economies being in the state of slowdown, recession or crisis. The analysis of the state of the sector of hydraulics and pneumatics in a dozen or so most important countries is based on the comparisons of the sales and orders as well as on the forecasts of 2008 versus 2007. The most recent data, January-July 2009 versus 2008, are also presented.
The paper summaries the structure, analysis and testing of novel hybrid suspension, accommodating a cascade combination of two vibration isolators: an active electrohydraulic and a semiactive electropneumatic one. The developed mathematical of hybrid suspension supported by the simulation data are utilized in the synthesis of an adaptive control system with the reference model. Experimental tests performed for the purpose of verification demonstrate the good performance of the newly developed suspension.
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