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Re: Parameters of Centrifugal Pump in SimHydraulics. The help is very necessary!
Posted:
Apr 18, 2008 9:47 AM


In article <fua667$1bd$1@fred.mathworks.com>, Evgeny wrote: > Prompt how correctly to set Centrifugal Pump parameters. > > I use "By two 1D characteristics". > > Parameters QP [0 0.02 0.04 0.06 0.08 0.1 0.12] m^3/s > Pressure P [4.4 4.8 5.2 5.2 4.8 4 2.4] atm > > Parametres NQ [0 0.02 0.04 0.06 0.08 0.1 0.12] m^3/s > N [2800 3100 3600 3900 4200 4800 5000] W > > Reference density 1000 kg/m^3 for water as I understood > > Reference angular velocity 3000 rpm > > I submit on an input 3000 rpm and it should turn out Q ~ = > 0.07 m^3/s at the expiration in atmosphere and P ~ = 4.4 > atm at the closed orifice. > > I have hydraulic flow rate turns out negative (((( > Around here we do lots of hydraulic modelling/simulation in Simulink (although we use our own models, not SimHydraulics  but the principles are the same).
Just because the pump will generate a positive head at the set speed does not mean the flow will necessarily be forwards. What about the pressure differential across the pump in the service conditions? If backpressuredifferential (outpet pressure less suction pressure) exceeds the pump head, then the flow will go backwards.
I don't know how good the pump modelling is in SimHydraulics; but a complete pump model should have a characteristic in all four quadrants of the head/flow curve (all combinations of +/ve head and flow).



