02 07 2025

Pagina 1

SECOND CALL OF FLUID MACHINES 02.07.2025 Ing. Meccanica - Ind. Propedeutico — Prof. Persico ,XERCISE 1 (10 POINTS) È CO et rosi i Perates at fixed angular speed, equal to m= 1500 rpm. The expressions of turing variable angular speed, while the second one o) ; ao ead NPSH-required curves of each pump, when operated at ni, read (H [m], Q [ms], NPSHE [m], H=35974350+35 N=0.792+1.4Q+0.1 NPSHr =0,70°+0.1 A i i E = a c height zo = 2 m, and by a lant is composed by an intake basin, operating at ambi essure (Po=1 bar) and placed at a Rak ow i 5 ni and piesa at oe 2, = 10 m. In the nominal conditions, the volume flow in the delivery tank, operating at pressure Ps = c : i indi i 4 ci nt: system is Qnom = 1 m/s | An experimental survey indicates that the mechanical energy dissipation in the suction duct amounts to Ys = 45 J/kg, when the flow rate is Q.,, = 0.6 m/s. In the delivery duct, the overall loss is equal to 10 kinetic heads. The ducts can be considered adiabatic and the diameter is D = 0.4 m for both, Requirements: > i, a) Determine the angular speed of the first Pump and the power adsorbed by the pumping SEU b) Determine the maximum installation height of the first pump for a cavitation-free operation, assuming Psat + Ppis= 0.05 bar and considering a safety margin of 3 m from the condition of cavitation onset. i 289 ©) The pressure in the delivery tank changes. Contextually, a total pressure measurement at the first pump inlet indicates Pr1=0.8 bar. Determine the new pressure in the delivery tank, assuming as angular speed of the first pump n= 1800 rpm. EXERCISE 2 (8 POINTS) 5 An optimized axial-flow turbine stage operating with steam (which can be considered a perfect gas with y=1.33 and MM = 18 keg/kmol) expands from total conditions Pro = 120 bar and Ty, =400°C to an…