Читать книгу Hydraulic Fluid Power - Andrea Vacca - Страница 50

1 2.1 A hydraulic cylinder is loaded such that the pressure in the piston chamber rises from 0 to 4000 psi (this chamber being blocked, for example, by a normally closed valve). Evaluate the motion Δx of the piston, in inches, as effect of oil compressibility. Assume no air entrapped in oil and Bliq = 2.2 · 105 psi (bulk modulus). The rod chamber is connected to atmosphere at null pressure. Neglect compressibility of the material of the cylinder.

2 2.2 The cylinder in figure is loaded from 0 to 4000 psi keeping the bore port blocked. Evaluate the motion Δx of the piston from its initial position, in inches (in.), as effect of oil compressibility. Assume no air entrapped in oil and Bliq= 2.2 · 105 psi (bulk modulus). The rod chamber is connected to atmosphere at null pressure. Neglect the compressibility of the material of the cylinder.How much is the force F?

3 2.3 A cylinder with a 3 in bore and an extension of 1.42 in from the retracted position is loaded from 0 bar to 5000 psi while keeping the bore port blocked (as in the previous problem figure). Evaluate the motion Δx of the piston, as effect of oil compressibility. Assume 5% air entrained in oil and Kliq = 2.2 105 psi. Neglect the compressibility of the material and of the cylinder walls. When evaluating the bulk modulus of the air, consider following two cases:Gradual (slow) process (isothermal)Fast process (adiabatic)

4 2.4 Measurements are taken on the piston chamber of a cylinder with a bore diameter of 250 mm. The bore port is blocked, and the rod chamber is connected to atmosphere (as in the previous problem figure). When the stroke (from retracted position) is 225 mm, the pressure is 70 bar. When the stroke is reduced to 222 mm, the pressure is 140 bar.Determine the bulk modulus of the fluid.