Cavitating flows of viscous oils in an experimental centrifugal pump with low specific speed are modeled and simulated by using the time-averaged Navier–Stokes equations and standard turbulence model as well as full cavitation model based on the computational fluid dynamics method, when the pump operates in the reverse direction as turbine to generate power. The cavitation characteristics are identified at part-load, best efficiency and over-load points and five viscosities. Effects of viscosity on net positive suction head required are clarified. Net positive suction head required correction factor and conversion factor curves are obtained and correlated to impeller Reynolds number. The flow and cavitation models are validated with the existing experimental results and empirical correlations. Pressure and helix angle profiles at the draft tube entrance, cavity shape, swirling flow pattern in the draft tube, and the pressure coefficient distribution over the blade surfaces are presented. The presented results can be useful for design, selection, performance prediction, and impeller redesign of a pump as turbine.
KoyamaN. Utilization of centrifugal pumps used as hydraulic turbines. J Jpn Soc Mech Engrs1971; 74: 1584–1587.
2.
WilliamsAA. The turbine performance of centrifugal pumps: A comparison of prediction methods. Proc IMechE, Part A: J Power and Energy1984; 208: 59–66.
3.
Alatorre-Frenk C. Cost minimisation in micro-hydro systems using pumps-as-turbines. PhD Thesis, University of Warwick, UK, February 1994.
4.
VentroneGArdizzonGPavesiG. Direct and reverse flow conditions in radial flow hydraulic turbomachines. Proc IMechE, Part A: J Power and Energy2000; 214: 635–644.
5.
SinghPNestmannF. An optimization routine on a prediction and selection model for the turbine operation of centrifugal pumps. Exp Therm Fluid Sci2010; 34: 152–164.
6.
BarbarelliSAmelioMFlorioG. Predictive model estimating the performance of centrifugal pumps as turbines. Energy2016; 107: 103–121.
7.
TanXEngedaA. Performance of centrifugal pumps running in reverse as turbine: Part II-systemic specific speed and specific diameter based performance prediction. Renew Energy2016; 99: 188–197.
8.
ShinhamaHFukitomiJNakaseYet al.Study on reverse running pump turbine. Trans JSME Ser B1999; 65: 3399–3406.
9.
Fernandez1JBlancoEParrondoJet al.Performance of a centrifugal pump running in inverse mode. Proc IMechE, Part A: J Power and Energy2004; 218: 265–271.
10.
DerakhshanSNourbakhshA. Experimental study of characteristic curves of centrifugal pumps working as turbines in different specific speeds. Exp Therm Fluid Sci2008; 32: 800–807.
11.
DerakhshanSNourbakhshA. Theoretical, numerical and experimental investigation of centrifugal pumps in reverse operation. Exp Therm Fluid Sci2008; 32: 1620–1627.
12.
NautiyalHVarun KumarAYadavS. Experimental investigation of centrifugal pump working as turbine for small hydropower systems. Energy Sci Technol2011; 1: 79–86.
13.
YangSSDerakhshanSKongFY. Theoretical, numerical and experimental prediction of pump as turbine performance. Renew Energy2012; 48: 507–513.
14.
Raman N, Hussein I, Palanisamy K, et al. An experimental investigation of pump as turbine for micro hydro application. In:IOP conference series: Earth and environmental science, 2013, vol. 16, pp. 1–4.
15.
YangSSKongFYJiangWMet al.Effects of impeller trimming influencing pump as turbine. Comput Fluids2012; 67: 72–78.
16.
JainSVSwarnkarAMotwaniKHet al.Effects of impeller diameter and rotational speed on performance of pump running in turbine mode. Energy Convers Manage2015; 89: 808–824.
17.
YangSSKongFYChenHet al.Effects of blade wrap angle influencing a pump as turbine. J Fluids Eng2012; 134: 061102–8.
18.
PuglieseFDe PaolaFFontanaNet al.Experimental characterization of two pumps as turbines for hydropower generation. Renew Energy2016; 99: 180–187.
19.
SedlarMSoukalJKomarekM. CFD analysis of middle stage of multistage pump operating in turbine regime. Eng Mech2009; 16, 413–421.
20.
PascoaJCSilvaFJPinheiroJSet al.A new approach for predicting PAT-pumping operating point from direct pumping mode characteristics. J Scient Ind Res2012; 71: 144–148.
21.
SinghPNestmannF. Internal hydraulic analysis of impeller rounding in centrifugal pumps as turbines. Exp Therm Fluid Sci2011; 35: 121–134.
22.
MorrosCSOroJMFDiazKMA. Numerical modelling and flow analysis of a centrifugal pump running as a turbine: Unsteady flow structures and its effects on the global performance. Int J Numer Methods Fluids2011; 65: 542–562.
23.
BarrioRFernandezJBlancoEet al.Performance characteristics and internal flow patterns in a reverse-running pump–turbine. Proc IMechE, Part C: J Mechanical Engineering Science2013; 226: 695–708.
24.
FecarottaOCarravettaARamosHM. CFD and comparisons for a pump as turbine: Mesh reliability and performance concerns. Int J Energy Environ2011; 2: 39–48.
25.
Bogdanovic-JovanovicJBMilenkovicDRSvrkotaDMet al.Pumps as turbines-power recovery, energy efficiency, CFD analysis. Therm Sci2014; 18: 1029–1040.
26.
NakatakeYKumaYMiyaoAet al.Study on performance and improvement of efficiency for reverse running pump turbine. Memoirs of Kurume National College of Technology2001; 17: 1–6.
PatelVAJainSVMotwaniKHet al.Numerical optimization of guide vanes and reducer in pump running in turbine mode. Procedia Eng2013; 51: 797–802.
29.
CouzinetAGrosLPierratD. Characteristics of centrifugal pumps working in direct or reverse mode: Focus on the unsteady radial thrust. Int J Rotat Mach2013; 2013. Article ID 279049.
30.
SuXHunagSZhangXet al.Numerical research on unsteady flow rate characteristics of pumps as turbine. Renew Energy2016; 94: 488–495.
31.
EscalerXEkangerJVFranckeHHet al.Detection of draft tube surge and erosive blade cavitation in a full-scale Francis turbine. J Fluids Eng2015; 124: 943–950.
32.
ArndtREAVoigtRLSinclairJPet al.Cavitation erosion in hydroturbines. J Hydraul Eng1989; 115: 1297–1315.
Singh P.Optimization of internal hydraulics and of system design for pumps as turbine with field implementation and evaluation. PhD Thesis, University of Karlsruhe, Germany, 2005.
36.
Goodarzvand-CheginiFFarkhondehkavakiMGougolM. Application of heat integration in hydrocracking process. Asia-Pacific J Chem Eng2010; 40.
37.
LiWG. Effects of viscosity on turbine mode performance and flow of a low specific speed centrifugal pump. Appl Math Model2016; 40: 904–926.
38.
Fluent Inc. FLUENT 6.2 user’s guide2005; vols 1 and 2, Lebanon, NH: Fluent Inc.
39.
SinghalAKAthavaleMMLiHet al.Mathematical basis and validation of the full cavitation model. J Fluids Eng2002; 124: 617–624.
40.
LiWG. Modelling viscous oil cavitating flow in a centrifugal pump. J Fluids Eng2016; 138: 011303-1–2.
41.
Li WG and Zhang YL. Numerical simulation of cavitating flow in a centrifugal pump as turbine. Proc IMechE, Part E: J Process Mechanical Engineering 2018; 232: 135–154.
42.
Avellan F. Introduction to cavitation in hydraulic machinery. In: Proceedings of the 6th international conference on hydraulic machinery and hydrodynamics, Timisoara, Romania, 21–22 October 2004.
43.
CEI/IEC 60193. Hydraulic turbines, storage pumps and pump-turbines–model acceptance tests, 2nd ed. Geneva, Switzerland: International Electro-technical Commission, 1999.
44.
AizenshteinMD. Centrifugal pumps for the petroleum industry, Moscow: Gostoptekhizdat, 1957.
45.
CaoGJWuYLLiuSHet al.Influence of the shaft speed to the centrifugal oil pump cavitation characteristics and conversion study. J Eng Thermophys2008; 29: 65–67.
