Numerical investigation on transient flow of a high head low specific speed pump-turbine in pump mode

2015 ◽  
Vol 7 (6) ◽  
pp. 063111 ◽  
Author(s):  
Deyou Li ◽  
Ruzhi Gong ◽  
Hongjie Wang ◽  
Xianzhu Wei ◽  
Zhansheng Liu ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Transient Flow ◽  
Pump Mode ◽  
Pump Turbine ◽  
Low Specific Speed ◽  
High Head ◽  
Specific Speed

Hydraulic Optimization and Loss Analyses of a Low Specific-Speed Centrifugal Pump With Variable-Thickness Blades

2016 ◽  
Author(s):  
Shiyang Li ◽  
Peng Wu ◽  
Dazhuan Wu
Keyword(s):  
Energy Loss ◽  
Centrifugal Pump ◽  
Cfd Simulation ◽  
Transient Flow ◽  
Thickness Distribution ◽  
Dynamic Performance ◽  
Thermodynamic Efficiency ◽  
Constant Flow Rate ◽  
Low Specific Speed ◽  
Specific Speed

This paper investigates the hydraulic and dynamic performance of a low specific-speed centrifugal pump with CFD simulation. Three different impellers are designed with different thickness distributions along the same mean line of the blades. The entropy production is introduced to study the energy losses in the three models and the energy loss distributions of the whole flow passages are fully revealed. The simplified energy loss equation is carefully validated by comparing the thermodynamic efficiency to the traditional hydraulic efficiency, and the errors between them can be considered acceptable. The circumferential Euler head distribution out of the impeller is used to predict the uniformity of the flow into the volute. To obtain the transient flow characteristics, the sliding mesh technique and the unsteady CFD simulation are applied and the pressure pulsations in the volute are well captured. The head fluctuation intensities of the three models are quantitatively compared under constant flow rate. The results show that the thickness distribution can affect the hydraulic performance to a large extent, and it can strongly affect the pressure pulsation in the volute.

scholarly journals On the Rotor Stator Interaction Effects of Low Specific Speed Francis Turbines

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Einar Agnalt ◽  
Igor Iliev ◽  
Bjørn W. Solemslie ◽  
Ole G. Dahlhaug
Keyword(s):  
Guide Vane ◽  
Pressure Fluctuations ◽  
Angular Position ◽  
Pressure Sensors ◽  
Pump Turbine ◽  
Blade Loading ◽  
Loading Case ◽  
Rotor Stator Interaction ◽  
Low Specific Speed ◽  
Specific Speed

The rotor stator interaction in a low specific speed Francis model turbine and a pump-turbine is analyzed utilizing pressure sensors in the vaneless space and in the guide vane cascade. The measurements are analyzed relative to the runner angular position by utilizing an absolute encoder mounted on the shaft end. From the literature, the pressure in the analyzed area is known to be a combination of two effects: the rotating runner pressure and the throttling of the guide vane channels. The measured pressure is fitted to a mathematical pressure model to separate the two effects for two different runners. One turbine with 15+15 splitter blades and full-length blades and one pump-turbine with six blades are investigated. The blade loading on the two runners is different, giving different input for the pressure model. The main findings show that the pressure fluctuations in the guide vane cascade are mainly controlled by throttling for the low blade loading case and the rotating runner pressure for the higher blade loading case.

scholarly journals Numerical investigation on the effects of leakage flow from Guide vane-clearance gaps in low specific speed Francis turbines

2020 ◽  
Vol 1608 ◽  
pp. 012016
Author(s):  
Saroj Gautam ◽  
Ram Lama ◽  
Sailesh Chitrakar ◽  
Hari Prasad Neopane ◽  
Biraj Singh Thapa ◽  
...  
Keyword(s):  
Numerical Investigation ◽  
Guide Vane ◽  
Leakage Flow ◽  
Low Specific Speed ◽  
Specific Speed

Very Low Specific Speed Centrifugal Pump—Hydraulic Design and Physical Limitations

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Grunde Olimstad ◽  
Morten Osvoll ◽  
Pål Henrik Enger Finstad
Keyword(s):  
Centrifugal Pump ◽  
Low Flow ◽  
Centrifugal Pumps ◽  
Hydraulic Design ◽  
New Findings ◽  
Gear Pumps ◽  
Disk Friction ◽  
Low Specific Speed ◽  
High Head ◽  
Specific Speed

For low-flow and high-head applications, pump types such as progressive cavity or gear pumps are often used. However, centrifugal pumps are much more robust and wear resistant, and are beneficial if they can handle the rated head and flows. By challenging the limitations of low specific speed (Nq), centrifugal pumps can be made to handle a combination of low flow and high head, which previously required other pump types. Conventional centrifugal pumps have specific speed down to 10, while in this paper a design with specific speed of 4.8 is presented. The paper describes several iterative steps in the design process of the low Nq pump. These iterations were done one physical pumps, which were successively tested in a test rig. Motivation for each step is explained theoretically and followed up by discussion of the measured results. Four different geometries of the pump were tested, all of them manufactured by rapid prototyping in nylon material. A substantial question is how low the specific speed of a centrifugal pump can be. Limitations of low Nq pumps are discussed and new findings are related to volute cavitation. In addition, limitations due to disk friction, volute losses, leakage flow, and pump stability are discussed and show to limit the design space for the pump designer.

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