Hydraulic machinery

Most hydraulic machinery such as hydraulic turbines, pumps, fans, compressors, propellers, torque converters, fluid couplings, etc., operate at such high values of Reynolds Number that viscous forces are small compared with inertia forces. It is, therefore, eustomary and satisfactory to ignore Reynolds Number effects in the treatment of such problems. Hydraulie turbines are representative of this elass of equipment and will be briefly diseussed. 

Hydraulie turbines are used to convert the gravity potential energy of a body of water into shaft work. Such machines are of three general types 

The power developed (/ ) by a hydraulic turbine is an important dependent variable. A dimensional analysis for this quantity leads to the following equation, where all variables involved are defined in Table 7.2. Since three fundamental dimensions (F, L, T) are involved, there will be three dimensionally independent quantities which have been taken to bep, N, and d. 

It should be noted that both h and g enter this problem as a product because that is the way they influence the potential energy per unit mass available to do useful work. Treatment of (gh) as a single variable yields one less Pi quantity in the final result. 

As already mentioned, the Reynolds Number (pNd lp) plays a minor role and may be omitted from the analysis. Therefore  

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Brckkc. H.. C.G. Duan. R.K. Fisher, ami R, Schilling Hydraulic Machinery and Cavitation, World Scientific Publishing Company. Inc.. Riveredge, NJ. 1998, Furuya. G.1 Cavitation and Multiphase Flow Farum 1992, American Sociely ot Mechanical Engineers." New York. NY. 1992. 

Tons-on-Ram. The force that acts over a given area as in various types of hydraulic machinery. 

Beitler, S.R., Lindahl, E.J. (1947). Hydraulic machinery. Irwin-Famham Chicago IL. 

Cavitation, the phenomenon that causes liquids to rupture and to form vaporous/gas cavities when subjected to sufficiently low pressures, can occur in any machine handling liquid when requisite hydrodynamic conditions develop (Fig. 1). Cavitation, in many cases, is an undesirable phenomenon in hydraulic machinery that can Umit performance, lower efficiency, introduce sever structural vibration, generate acoustic noise, choke flow, and cause catastrophic damage [1]. The pernicious effects of hydrodynamic cavitation on conventional fluid machinery have been recognized and actively researched in the last century. Present knowledge (experimental and analytical) of cavitation has contributed immensely toward improving the design of conventional-scale fluid machinery. 

Hydraulic Machinery. Hydraulic turhines transform the drop in pressure (head) into electric power. Also, pumps take electric power and transform it into water head, thereby moving the flow in a pipe to a higher elevation. 

The remarkable story of tilting pad bearing invention and industrial introduction is thoroughly documented [1]. As highlighted in [1] tilting pad bearings were the direct results of engineering applications of Osborne Reynolds theory of fluid film lubrication and problems with hydraulic machinery promoted the inventions . 

Similarly, in erythrocytes, trans-membrane ventilation of C02 and 02 may be enhanced by sub-pressure fluctuations, generated by inwardly oriented pwasons due to ATPase activity of branched actin polymerization on membrane-attached filaments [71]. According to the pwason model, the rate and amplitude of these active membrane fluctuations are anticipated also for other membrane-attached hydrophilic ATPases [72]. Such hydraulic compression of the cell membrane might explain the peculiar observation of a higher internal hydrostatic pressure in an intact cellular state of partial inflation. Intracellular vesicles, bacteria or designed objects can utilize this hydraulic machinery for the actin-based propulsion inside the cell or in a cell-like medium [73]-... 

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