scholarly journals Differences of Flow Patterns and Pressure Pulsations in Four Prototype Pump-Turbines during Runaway Transient Processes

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5269
Author(s):  
Zhiyan Yang ◽  
Zirui Liu ◽  
Yongguang Cheng ◽  
Xiaoxi Zhang ◽  
Ke Liu ◽  
...  
Keyword(s):  
Pressure Fluctuations ◽  
Flow Patterns ◽  
Pressure Pulsations ◽  
Power Stations ◽  
Lean Angle ◽  
Specific Speed ◽  
Runner Design ◽  
Flow Transitions ◽  
Pumped Storage ◽  
Different Characteristics

Frequent working condition conversions in pumped-storage power stations often induce stability problems, especially when the operating point enters the S-shaped region, during which flow transitions and pressure fluctuations are serious. The pump-turbines with different specific speed values show different characteristics, but their differences in stability features are still not clear. In this study, four different pump-turbines were selected to simulate the runaway processes from turbine modes. The similarities and differences of flow patterns and pressure fluctuations were analyzed. For the similarities, pressure pulsations increase gradually and fluctuate suddenly once the backflows occur at the runner inlets. For the differences, the evolutions of backflows and pressure pulsations are related to specific speeds and runner shapes. Firstly, it is easier for the lower specific speed turbines to enter the reverse pump mode. Secondly, the blade lean angle influences the position where backflows occur, because it determines the pressure gradient at the runner inlets. Thirdly, the runner inlet height influences pressure pulsations in the vaneless space, because the relative range of backflow transitions will be enlarged with the decrease of specific speed. Overall, investigating the mechanisms of flow pattern transitions and pressure variations is important for runner design and transient process control.

Experimental Investigation of Flow Characteristics in a Spout-Fluid Bed

2005 ◽  
Author(s):  
Wenqi Zhong ◽  
Mingyao Zhang
Keyword(s):  
Power Spectrum ◽  
Shannon Entropy ◽  
Gas Flow ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Digital Camera ◽  
Flow Patterns ◽  
Sampling System ◽  
Fluid Bed ◽  
Different Characteristics

Pressure fluctuation time series were obtained at various bed locations in a spout-fluid bed with its dimension of 300mm × 30mm × 2000mm. Power spectrum and Shannon entropy analyses of pressure fluctuations were developed to characterize the flow characteristics. A multi-channel pressure sampling system was established and a high-resolution digital camera was used to record the flow patterns. The effects of two important operating parameters, i.e. spouting gas velocity and fluidizing gas flow rate on the power spectrum major frequency and Shannon entropy were tested. Shannon entropies of different flow patterns were found to have different characteristics, thus Shannon entropy was developed to identify the flow patterns. The results show that power spectrum and Shannon entropy analyses are two helpful ways to realize the complex gas-solid flow characteristics in spout-fluid beds.

scholarly journals Damping Pressure Pulsations in a Wave-Powered Desalination System

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Brandon J. Hopkins ◽  
Nikhil Padhye ◽  
Alison Greenlee ◽  
James Torres ◽  
Levon Thomas ◽  
...  
Keyword(s):  
Constant Pressure ◽  
Low Cost ◽  
Pressure Fluctuations ◽  
Cost Effective ◽  
Coastal Communities ◽  
Pressure Pulsations ◽  
Pressure Flow ◽  
Reliable Source ◽  
Effective Option ◽  
Elastic Pipes

Wave-driven reverse osmosis desalination systems can be a cost-effective option for providing a safe and reliable source of drinking water for large coastal communities. Such systems usually require the stabilization of pulsating pressures for desalination purposes. The key challenge is to convert a fluctuating pressure flow into a constant pressure flow. To address this task, stub-filters, accumulators, and radially elastic-pipes are considered for smoothing the pressure fluctuations in the flow. An analytical model for fluidic capacitance of accumulators and elastic pipes are derived and verified. Commercially available accumulators in combination with essentially rigid (and low cost) piping are found to be a cost-effective solution for this application, and a model for selecting accumulators with the required fluidic-capacitance for the intended system is thus presented.

Pumped-Storage Power Stations

1999 ◽  
Author(s):  
Peter B. Luh ◽  
Daoyuan Zhang ◽  
Houzhong Yan
Keyword(s):  
Power Stations ◽  
Pumped Storage

Operating policies for wind-pumped storage hybrid power stations in island grids

2009 ◽  
Vol 3 (3) ◽  
pp. 293 ◽  
Author(s):  
S. Papaefthimiou ◽  
E. Karamanou ◽  
S. Papathanassiou ◽  
M. Papadopoulos
Keyword(s):  
Hybrid Power ◽  
Power Stations ◽  
Operating Policies ◽  
Pumped Storage

Effects of short blades on performance and inner flow characteristics of a low-specific-speed centrifugal pump

2017 ◽  
Vol 231 (4) ◽  
pp. 290-302 ◽  
Author(s):  
Can Kang ◽  
Ning Mao ◽  
Chen Pan ◽  
Yang Zhu ◽  
Bing Li
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Low Flow ◽  
Back Surface ◽  
Flow Rates ◽  
Pump Operation ◽  
Low Specific Speed ◽  
Specific Speed

A low-specific-speed centrifugal pump equipped with long and short blades is studied. Emphasis is placed on the pump performance and inner flow characteristics at low flow rates. Each short blade is intentionally shifted towards the back surface of the neighboring long blade, and the outlet parts of the short blades are uniformly shortened. Unsteady numerical simulation is conducted to disclose inner flow patterns associated with the modified design. Thereby, a comparison is enabled between the two schemes featured by different short blades. Both practical operation data and numerical results support that the deviation and cutting of the short blades can eliminate the positive slope of pump head curve at low flow rates. Therefore, the modification of short blades improves the pump operation stability. Due to the shortening of the outlet parts of the short blades, velocity distributions between impeller outlet and radial diffuser inlet exhibit explicitly altered circumferential flow periodicity. Pressure fluctuations in the radial diffuser are complex in terms of diversified periodicity and amplitudes. Flow rate influences pressure fluctuations in the radial diffuser considerably. As flow rate decreases, the regularity of the orbit of hydraulic loads exerted upon the impeller collapses while hydraulic loads exerted upon the short blades remain circumferentially periodic.

Effect of the volute tongue cut on pressure pulsations of a low specific speed centrifugal pump

2020 ◽  
Vol 32 (4) ◽  
pp. 758-770 ◽  
Author(s):  
Ning Zhang ◽  
Bo Gao ◽  
Bin Xia ◽  
Qi-feng Jiang
Keyword(s):  
Centrifugal Pump ◽  
Pressure Pulsations ◽  
Low Specific Speed ◽  
Specific Speed

Development and present situation of hydropower in China

Water Policy ◽  
2019 ◽  
Vol 21 (3) ◽  
pp. 565-581 ◽  
Author(s):  
Xingsong Sun ◽  
Xiaogang Wang ◽  
Lipeng Liu ◽  
Ruizhi Fu
Keyword(s):  
Development Strategy ◽  
Energy Development ◽  
Small Hydropower ◽  
Important Place ◽  
The Sustainable Development ◽  
The Past ◽  
Power Stations ◽  
Pumped Storage ◽  
Under Construction ◽  
Installed Capacity

Abstract As a clean and renewable energy, hydropower holds an important place in energy development for every country. China has the richest hydropower resources with 541 GW technical exportable installed capacity, a 17% global share. Hydropower is a key point of energy conservation and comprehensive utilization of resources to ensure the sustainable development strategy of China. This paper investigates the hydropower development of China and provides a summary of the current situation of the development. Over the past 100 years, China's hydropower developed tremendously. The total installed capacity of hydropower is 341.19 GW by the end of 2017 and the installed capacity of small hydropower is 79.27 GW. By the end of June 2018, 33 pumped-storage power stations had been constructed and 32 are under construction. The total installed capacity of pumped-storage power is 72.64 GW. More development will be achieved in the next decades according to China's development strategy.

Experimental Study of Flow Patterns, Pressure Drop and Flow Instabilities in Parallel Rectangular Minichannels

2004 ◽  
Author(s):  
Prabhu Balasubramanian ◽  
Satish G. Kandlikar
Keyword(s):  
Pressure Drop ◽  
High Speed ◽  
Flow Instability ◽  
Flow Boiling ◽  
Pressure Fluctuations ◽  
Flow Patterns ◽  
Flow Instabilities ◽  
Stable Operation ◽  
Phase System ◽  
High Heat Flux

The use of phase change heat transfer in parallel minichannels and microchannels is one of the solutions proposed for cooling high heat flux systems. The increase in pressure drop in a two phase system is one of the problems, that need to be studied in detail before proceeding to any design phase. The pressure drop fluctuations in a network of parallel channels connected by a common head need to be addressed for stable operation of flow boiling systems. The current work focuses on studying the pressure-drop fluctuations and flow instabilities in a set of six parallel rectangular minichannels, each with 333 μm hydraulic diameter. Demonized and degassed water was used for all the experiments. Pressure fluctuations are recorded and signal analysis is performed to find the dominant frequencies and their amplitudes. These pressure fluctuations are then mapped to their corresponding flow patterns observed using a high speed camera. The results help us to relate pressure fluctuations to different flow characteristics, and their effect on flow instability.

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