Application of Fluid Mechanics to Pumps and Turbines

Abstract

Pumps for raising water (hydraulic pumps) have been known since antiquity. As Pitot rightly pointed out, ‘pumps occupy the first rank among all the machines used to raise water. Their usefulness and the great and widespread use made of them in all countries has caused many excellent mechanics to work on perfecting them’. They are not the only machines used to raise water, however, and in this respect we ought to remember the waterwheel with buckets and its derivations. However, as opposed to these, pumps enjoyed numerous advantages such as energy yield, size, versatility, etc., which explains the interest devoted to them by the sages of the time. Although descriptions of pumps were frequent, the first analyses subjecting them to theoretical consideration are found in Pitot, even though he mentions previous attempts which, for several reasons, were unsuccessful. We find a precedent in the Hydrodynamica of Daniel Bernoulli, but he refers to somewhat more elemental machines, almost static, rather than pumps, and only makes use of the mechanical law of conservation of energy. Chronologically, studies on pumps progressed from these analyses of Bernoulli, almost within hydrostatics, up to the inclusion of narrowing and losses in movement of the liquid in their interior, clearly within the dominion of hydrodynamics. In this respect we emphasize the works of Pitot, Euler and Borda. As regards the second group of machines, which we have designated as reaction machines, these include all those that generate movement by the reaction of a jet of fluid launched to the exterior, and whose theoretical justification is the principle of action and reaction explained in the Newton’s third law.5 There are two very significant applications: propelling ships by a water jet, and the reaction turbine. The first is described in Hydrodynamica, and the second we have called Segner-Euler turbine, as it was proposed by the first, and perfected by the second. We shall describe both.