scholarly journals Numerical Simulation of Transient Characteristics of Start-Up Transition Process of Large Vertical Siphon Axial Flow Pump Station

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaowen Zhang ◽  
Fangping Tang ◽  
Chao Liu ◽  
Lijian Shi ◽  
Haiyu Liu ◽  
...  
Keyword(s):  
Flow Field ◽  
Entropy Production ◽  
Large Scale ◽  
Axial Flow ◽  
Blade Surface ◽  
High Entropy ◽  
Weir Flow ◽  
Start Up ◽  
Production Area ◽  
Flow Stage

In order to explore the transient characteristics of the large-scale vertical siphon axial flow pumping station during the start-up and exhaust process, numerical simulations were carried out on the start-up process of the axial flow pumping station under the two starting modes of pre-opening the vacuum breaking valve and keeping the vacuum breaking valve closed. The calculation results show that during the start-up phase of the unit, the flow separation phenomenon of the impeller channel of the pump device with the vacuum breaking valve closed is serious, the large-scale vortex in the guide vane blocks the flow channel, and the instantaneous impact on the blade surface is strong. The flow field of the pump device with pre-open vacuum failure valve is obviously less affected by the instantaneous impact characteristics during the start-up of the pump. The range of high entropy production area in the impeller channel is reduced, the duration of high entropy production area is significantly shortened, and the instantaneous impact on the blade surface is weak. Under the two starting modes, the internal flow field of the pump device is similar in the evolutionary law. The unstable flow phenomenon of the pump device is most prominent in the weir flow stage. The maximum instantaneous impact on the blade surface also mainly occurs in the weir flow stage. A very small part of the remaining gas in the siphon formation stage is difficult to discharge and takes a long time. After the pump device is exhausted and enters a stable operation state, the external characteristic parameters are in good agreement with the test results. Compared with the starting method in which the vacuum breaking valve is kept closed, the method of pre-opening the vacuum breaking valve reduces the maximum starting head by 20% and the exhaust time by 43%. The pre-open vacuum breaking valve effectively avoids the system instability caused by the start-up and exhaust of the pump device.

scholarly journals Theoretical Analysis of Entropy Generation at the Blade Interface of a Tubular Turbine Under Cooperative Conditions

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhenggui Li ◽  
Chuang Cheng ◽  
Shengnan Yan ◽  
Shengyang Peng ◽  
Biao Ma
Keyword(s):  
Entropy Production ◽  
Entropy Generation ◽  
High Speed ◽  
Sharp Change ◽  
Flow Conditions ◽  
Navier Stokes Equation ◽  
High Entropy ◽  
Turbine Efficiency ◽  
Production Area ◽  
The Impact

To study the influence of the blade entropy production range on the efficiency of a tubular turbine under coassociated conditions, the renormalization group K–ε turbulence model was used to simulate the full flow passage of the tubular turbine based on the Navier–Stokes equation, and the blade interface was analyzed using the eddy analysis method and entropy production theory. The results reveal that there is a strong correlation between the size of the high-entropy production area and the level of association. If the level of association is high, the size of the high-entropy production is small, and the turbine efficiency is high. Furthermore, if the level of association is low, the size of the high-entropy production area is large, and the turbine efficiency is low. Under small opening and small flow conditions, the blade entropy generation is due to the sharp change in the velocity gradient caused by the vortex on the blade. Under large opening and large flow conditions, the blade entropy production is mainly due to the friction loss caused by the impact of high-speed water flow.

Measurements of Wake-Generated Unsteadiness in the Rotor Passages of Axial Flow Turbines

1985 ◽  
Vol 107 (2) ◽  
pp. 467-475 ◽  
Author(s):  
H. P. Hodson
Keyword(s):  
Major Part ◽  
Large Scale ◽  
Free Stream ◽  
Axial Flow ◽  
Rotor Blades ◽  
Small Scale ◽  
Blade Surface ◽  
Air Turbine ◽  
Visualization Experiment ◽  
Water Turbine

This paper describes an investigation into the free-stream unsteadiness which is found in the rotor passages of axial flow turbines and which is caused by the interaction of the stator wakes with the rotor blades. The major part of this investigation was conducted at the midspan of the rotor of a large-scale, single-stage air turbine. Measurements are presented of the unsteady free-stream velocities and blade surface pressures. These are supplemented by further results which were obtained during a flow visualization experiment in a small-scale water turbine. It is shown that the unsteadiness is dominated by the convected phenomena associated with the passage of the wakes through the rotor.

Improvement of Performance on Flow-Cutoff of Flap Valves Set in the Pressurized Tank of Pumping Station Based on Numerical Simulation

2013 ◽  
Vol 419 ◽  
pp. 86-90
Author(s):  
Yong Hai Yu ◽  
Bin Cheng
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Large Scale ◽  
Axial Flow ◽  
Free Water ◽  
Flow Distribution ◽  
Pumping Station ◽  
Simplec Algorithm ◽  
Distribution Uniformity ◽  
Free Plane

Two small flap valves arranged in parallel for each pump were used as flow-cutoff device in certain large-scale axial flow pumping station where the pressurized tank was designed as outlet structure. The flap valves of side-set pump had the poorest performance on flow-cutoff in the pumping station. The flow field in the pressurized tank was shown based on numerical simulation in order to improve the flow-cutoff performance of flap valves. The standard k-ε turbulence model and momentum equations were solved in the SIMPLEC algorithm with the assumption that the free water surface remained flat as a stress-free plane of symmetry. The velocity distribution and free outflow were prescribed on inlet and outlet boundary respectively. Numerical simulation on the flow field in pressurized tank was done at three typical moments chosen in the basis of the flow variation in the process of shutdown of flap valves. The reason that two flap valves of side-set pump could not close simultaneously and the late closing flap valve had a huge force on the wall was analyzed based on the comparison of flow field for side-set pump and middle-set pump. The result from numerical simulation proves that the division pier with appropriate size which helps to improve the flow distribution uniformity is valid for the two flap valves of side-set pump to close simultaneously.

Blade Surface Pressure Measurements on a Low Pressure Rise Axial Flow Fan

2020 ◽  
Author(s):  
Johannes Rohwer ◽  
Sybrand J. van der Spuy ◽  
Theodor W. von Backström ◽  
Francois G. Louw
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Surface Pressure ◽  
Static Pressure ◽  
Axial Flow ◽  
Pressure Rise ◽  
Test Facility ◽  
Pressure Measurements ◽  
Blade Surface ◽  
Axial Flow Fan

Abstract Fan performance characteristic tests of axial flow fans provide information on the global flow field, based on stable inlet flow field distribution. More information is often required on the local flow distribution existing in the vicinity of the fan blades under installed conditions. A 1.542 m diameter scale model of an axial flow fan, termed the M-Fan is tested in an ISO 5801, type A, test facility. The M-fan was specifically designed for low-pressure, high flow rate application in air-cooled or hybrid condensers. The scaled version of the M-fan was designed to have a fan static pressure rise of 116.7 Pa at a flow rate of 14.2 m3/s. Two specially constructed M-Fan blades are manufactured to conduct blade surface pressure measurements on the blades. The fan blades are equipped with 2 mm diameter tubes that run down the length of the fan blades in order to convey the measured pressure. Piezo-resistive pressure transducers, located on the hub of the fan, measure the static pressure distribution on the blades and the data is transferred to a stationary computer using a wireless telemetry setup. The blade pressure measurement setup is re-commissioned from a previous research project and its performance is qualified by testing and comparing to experimental results obtained on the B2a-fan. Excellent correlation to previous results is obtained. The experimental M-fan results are compared against results from a periodic numerical CFD model of a fan blade modelled in an ISO 5801, Type A test facility configuration. The experimental tests and numerical model correlate well with each other. The experimental blade surface pressure measurements have a minimum Pearson correlation to the numerically determined values of 0.932 (maximum 0.971).

scholarly journals The Effect of Root Clearance on Mechanical Energy Dissipation for Axial Flow Pump Device Based on Entropy Production

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1506
Author(s):  
Yanjun Li ◽  
Yunhao Zheng ◽  
Fan Meng ◽  
Majeed Koranteng Osman
Keyword(s):  
Energy Dissipation ◽  
Entropy Production ◽  
Dissipation Rate ◽  
Mechanical Energy ◽  
Axial Flow ◽  
Leakage Flow ◽  
Blade Surface ◽  
Mechanical Energy Dissipation ◽  
Axial Flow Pump ◽  
Flow Pump

The axial flow pump is a low head, high discharge pump usually applicable in drainage and irrigation facilities. A certain gap should be reserved between the impeller blade root and the impeller hub to ensure the blade adjustability to broaden the high-efficiency area. The pressure difference between its blade surface induces leakage flow in the root clearance region, which decreases hydraulic performance and operational stability. Therefore, this study was carried out to investigate the effect of root clearance on mechanical energy dissipation using numerical simulation and entropy production methods. The numerical model was validated with an external characteristics test, and unsteady flow simulations were conducted on the axial flow pump under four different root clearance radii. The maximum reductions of 15.5% and 6.8% for head and hydraulic efficiency are obtained for the largest root clearance of 8 mm, respectively. The dissipation based on entropy theory consists of indirect dissipation and neglectable direct dissipation. The leakage flow in the root clearance led to the distortion of the impeller’s flow pattern, and the indirect dissipation rate and overall dissipation of the impeller increased with increasing root clearance radius. The inflow pattern in the diffuser was also distorted by leakage flow. The diffuser’s overall dissipation, indirect dissipation rate on the blade surface, and indirect dissipation rate near inlet increased with increasing root clearance radius. The research could serve as a theoretical reference for the axial flow pump’s root clearance design for performance improvement and operational stability.

Inlet Skew and the Growth of Secondary Losses and Vorticity in a Turbine Cascade

1990 ◽  
Vol 112 (4) ◽  
pp. 633-642 ◽  
Author(s):  
J. A. Walsh ◽  
D. G. Gregory-Smith
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Large Scale ◽  
Transverse Velocity ◽  
Axial Flow ◽  
Turbine Cascade ◽  
Streamwise Vorticity ◽  
Loss Prediction

This paper presents results of an experimental investigation into the effects of inlet skew on the flow field of a large-scale axial flow turbine cascade. The results are presented in terms of the development of the streamwise vorticity since, in classical terms, the streamwise vorticity generates the transverse velocity components that cause the generation of the secondary losses. Inlet skew is shown to have a profound effect on the distribution and magnitude of the generated losses. A number of correlations for the secondary losses are compared with the measured values and it is shown that the correlations are not adequate for accurate loss prediction purposes.

Large-Eddy Simulation of Turbine Rim Seal Flow

2018 ◽  
Author(s):  
Alexej Pogorelov ◽  
Matthias Meinke ◽  
Wolfgang Schröder
Keyword(s):  
Flow Field ◽  
Large Eddy Simulation ◽  
Level Set ◽  
Large Scale ◽  
Stokes Equations ◽  
Axial Flow ◽  
Dominant Mode ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Impact

The flow field in a complete one-stage axial-flow turbine with 30 stator and 62 rotor blades is investigated by large-eddy simulation (LES). To solve the compressible Navier-Stokes equations, a massively parallelized finite-volume flow solver based on an efficient Cartesian cut-cell/level-set approach, which ensures a strict conservation of mass, momentum and energy, is used. This numerical method contains two adaptive Cartesian meshes, one mesh to track the embedded surface boundaries and a second mesh to resolve the fluid domain and to solve the conservation equations. The overall approach allows large scale simulations of turbomachinery applications with multiple relatively moving boundaries in a single frame of reference. The relative motion of the geometries is described by a kinematic motion level-set interface method. The focus of the numerical analysis is on the flow inside the cavity between the stator and the rotor disks. Full 360° computations of the turbine stage with a single lip rim seal geometry are conducted. First, the impact of the mesh resolution on the LES results is analyzed. Second, the LES results are compared to experimental data, followed by a detailed analysis of the flow field inside the rotor-stator wheel space. A dominant mode unrelated to the rotor frequency and its harmonics is identified, which shows a major impact on the ingress of the hot gas into the rotor-stator wheel space.

Research and Develop on Static Frequency Converter of Pumped Storage Power Plant

2012 ◽  
Vol 608-609 ◽  
pp. 1120-1126 ◽  
Author(s):  
De Shun Wang ◽  
Bo Yang ◽  
Lian Tao Ji
Keyword(s):  
Power Plant ◽  
Control Strategy ◽  
Large Scale ◽  
Frequency Converter ◽  
Position Estimation ◽  
Position Sensor ◽  
Storage Unit ◽  
Rotor Position ◽  
Start Up ◽  
Pumped Storage

A static frequency converter start-up control strategy for pumped-storage power unit is presented. And rotor position detecting without position sensor is realized according to voltage and magnetism equations of ideal synchronous motor mathematics model. The mechanism and implementation method of initial rotor position determination and rotor position estimation under low frequency without position sensor are expounded and validated by simulations. Based on the mentioned control strategy, first set of a static frequency converter start-up device in China for large-scale pumped-storage unit is developed, which is applied to start-up control test in the 90 MW generator/motor of Panjiakou Pumped-storage Power Plant. Test results show that rotor position detecting, pulse commutation, natural commutation, and unit synchronous procedure control of static start-up are all proved. The outcomes have been applied in running equipment, which proves the feasibility of mentioned method.

scholarly journals Influence of wall roughness on cavitation performance of centrifugal pump

2021 ◽  
Vol 43 (6) ◽  
Author(s):  
Weihui Xu ◽  
Xiaoke He ◽  
Xiao Hou ◽  
Zhihao Huang ◽  
Weishu Wang
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Internal Flow ◽  
Wall Roughness ◽  
Blade Surface ◽  
Centrifugal Pumps ◽  
Three Dimensional Model ◽  
Cavitation Inception ◽  
Cavitation Performance ◽  
Critical Cavitation

AbstractCavitation is a phenomenon that occurs easily during rotation of fluid machinery and can decrease the performance of a pump, thereby resulting in damage to flow passage components. To study the influence of wall roughness on the cavitation performance of a centrifugal pump, a three-dimensional model of internal flow field of a centrifugal pump was constructed and a numerical simulation of cavitation in the flow field was conducted with ANSYS CFX software based on the Reynolds normalization group k-epsilon turbulence model and Zwart cavitation model. The cavitation can be further divided into four stages: cavitation inception, cavitation development, critical cavitation, and fracture cavitation. Influencing laws of wall roughness of the blade surface on the cavitation performance of a centrifugal pump were analyzed. Research results demonstrate that in the design process of centrifugal pumps, decreasing the wall roughness appropriately during the cavitation development and critical cavitation is important to effectively improve the cavitation performance of pumps. Moreover, a number of nucleation sites on the blade surface increase with the increase in wall roughness, thereby expanding the low-pressure area of the blade. Research conclusions can provide theoretical references to improve cavitation performance and optimize the structural design of the pump.

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