scholarly journals Rotational Speed Fluctuation and Internal Flow in a Variable-filling Fluid Coupling

1981 ◽  
Vol 24 (187) ◽  
pp. 109-116
Author(s):  
Kyohichi UCHIYAMA ◽  
Takeo TAKAGI ◽  
Tsutomu OKAZAKI
Keyword(s):  
Rotational Speed ◽  
Internal Flow ◽  
Speed Fluctuation ◽  
Fluid Coupling

scholarly journals Three-Dimensional CFD Simulations of Start-Up Processes of a Pump-Turbine Considering Governor Regulation

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8507
Author(s):  
Zhiyan Yang ◽  
Yongguang Cheng ◽  
Ke Liu ◽  
Xiaoxia Hou ◽  
Xiaoxi Zhang ◽  
...  
Keyword(s):  
Rotational Speed ◽  
Three Dimensional ◽  
Load Condition ◽  
Internal Flow ◽  
Pump Turbine ◽  
Characteristic Region ◽  
Start Up ◽  
Speed Fluctuation ◽  
Pumped Storage ◽  
Cfd Method

The pumped-storage power station is an efficient stability regulator of the power grid. However, due to the instability of the pump-turbine in the S-shaped characteristic region, rotational speed fluctuation is easy to occur in the speed no-load condition, making synchronization with and connection to the grid difficult. To investigate the key factors of these difficult grid connections, the start-up processes of a practical pump-turbine under the lowest head condition were simulated by using the three-dimensional CFD method, in which the governor regulating equations with different regulating parameters were integrated successfully. The results show that the working points oscillate with the fluctuations of rotational speed, discharge, and torque, and different regulating parameters have a significant influence on the dynamic histories. In addition, the internal flow patterns, especially the backflows at the runner inlet, keep apparent values at the middle span (0.5 span) but have regular transitions near the shroud side (0.7–0.8 span). The faster the guide vanes adjust, the faster the backflows change, and the larger the macro parameters fluctuate. Overall, the instability of the start-up is the result of the periodical evolutions of backflows at the runner inlet, because the trend and period of the radial velocities at different inlet span locations are consistent with those of the discharge.

scholarly journals Computational Analysis on Numerical Simulation of Internal Flow Physics for Pump as Turbine in Renewable Small Hydro Energy Generation

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Du Jianguo ◽  
Daniel Adu ◽  
Emmanuel Acheaw ◽  
Shakir Hafeez ◽  
Eric Ofosu Antw
Keyword(s):  
Flow Rate ◽  
Rotational Speed ◽  
Human Life ◽  
Three Dimensional ◽  
Internal Flow ◽  
Hydroelectric Power ◽  
Small Hydropower ◽  
Speed Increase ◽  
Blade Thickness ◽  
The Impact

Energy contributes significantly in almost all aspects of human life as well as economic activities and plays a crucial role in the infrastructural development of a county to alleviate poverty. Generating energy from a renewable source such as small hydropower through the application of pump operating as a turbine mode called Pump as Turbine is one of the best alternatives to provide clean and inexpensive energy. Using Pump as Turbine helps in generating reasonably priced hydroelectric power for communities in underdeveloped counties. This study investigates the effects of internal flow behaviour and performance of Pump as Turbine under different rotational speed and flow rate. The rotational speed is an essential physical parameter as it affects the Pump as Turbine operation. A model-specific speed centrifugal pump model with head 32 (m), flow rate of 12.5 (m3/h) and the rotational speed of 2900 rpm, has been selected for the study. Numerical simulations have been conducted using the k-ω turbulence model to solve three-dimensional (3D) equations. The pump mode experimental data were used to confirm the results for better analysis. The results predicted that vortex and turbulent kinetic energy increase per rotational speed increase. Also, at the higher rotational speed, very high recirculation of flow is detected at the blade suction chamber, although the pressure side has a smooth flow. This study provides beneficial information which will serve as a reference to help improve PAT performance along with selecting PAT for a small hydropower site. Future works will consider the impact of blade thickness and cavitation in Pump as Turbine.

Dynamic Interactions Between the Rolling Element and the Cage in Rolling Bearing Under Rotational Speed Fluctuation Conditions

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Wenbing Tu ◽  
Ya Luo ◽  
Wennian Yu
Keyword(s):  
Dynamic Model ◽  
Rotational Speed ◽  
Rolling Bearing ◽  
Nonlinear Dynamic Model ◽  
Dynamic Interactions ◽  
Interaction Forces ◽  
Rolling Element ◽  
Speed Fluctuation ◽  
Rolling Elements ◽  
Fluctuation Frequency

Abstract A nonlinear dynamic model is proposed to investigate the dynamic interactions between the rolling element and cage under rotational speed fluctuation conditions. Discontinuous Hertz contact between the rolling element and the cage and lubrication and interactions between rolling elements and raceways are considered. The dynamic model is verified by comparing simulation result with the published experimental data. Based on this model, the interaction forces and the contact positions between the rolling element and the cage with and without the rotational speed fluctuation are analyzed. The effects of fluctuation amplitude, fluctuation frequency, and cage pocket clearance on the interaction forces between the rolling element and the cage are also investigated. The results show that the fluctuation of the rotational speed and the cage pocket clearance significantly affects the interaction forces between the rolling element and the cage.

The Rotating Cavitation Performance of a Centrifugal Pump with a Splitter-Bladed Inducer under Different Rotational Speed

2015 ◽  
Vol 32 (3) ◽  
Author(s):  
XiaoMei Guo ◽  
ZuChao Zhu ◽  
BaoLing Cui ◽  
Yi Li
Keyword(s):  
Centrifugal Pump ◽  
Rotational Speed ◽  
High Speed ◽  
Internal Flow ◽  
Centrifugal Pumps ◽  
Cavitation Flow ◽  
Operation Condition ◽  
Cavitation Performance ◽  
Cavitation Behavior ◽  
Suction Performance

AbstractDesigning inducer is one of the effective ways to improve the suction performance of high-speed centrifugal pumps. The operation condition including rotational speeds can affect the internal flow and external performance of high-speed centrifugal pumps with an inducer. In order to clarify the rotating cavitation performance of a centrifugal pump with a splitter-bladed inducer under different rotational speed, a centrifugal pump with a splitter-bladed inducer is investigated in the work. By using Rayleigh–Plesset equations and Mixture model, the cavitation flow of centrifugal pump is numerically simulated, as well as the external performance experimental test is carried out. It is found that the cavitation area increases with the rotational speeds. The location of the passage where cavitation is easy to appear is explored. Asymmetric cavitation behavior is observed. That, the trail of the inducer is easy to take cavitation when the rotational speed is increased to a degree, is also observed. The trend of

scholarly journals Method for assessing the technical condition of marine diesel engine driving the synchronous generator

2019 ◽  
Vol 177 (2) ◽  
pp. 139-144
Author(s):  
Tomasz KNIAZIEWICZ ◽  
Marcin ZACHAREWICZ
Keyword(s):  
Diesel Engine ◽  
Rotational Speed ◽  
Synchronous Generator ◽  
Technical Condition ◽  
Marine Diesel Engine ◽  
Phase Voltage ◽  
Working Process ◽  
Working Cycle ◽  
Marine Diesel ◽  
Speed Fluctuation

The paper presents an innovative method for assessing technical condition of a marine diesel engine that drives synchronous generator. It is based on the measurement and analysis of generators phase-to-phase voltage. Additionally, it requires the measurement of a pseudoperiodic signal [3] with a period equal to duration of engines working cycle. The basis for developing method was the assumption that rotational speed fluctuations of an engines crankshaft (and also the generator) depend on a course of a working process carried out in it. The generators phase-to-phase voltage is directly dependent on a rotational speed fluctuation of its rotor. It must therefore be possible to assess a course of a working process of an engine based on a voltage waveform of a synchronous generator that cooperates ogether.

Reduction of rotational speed fluctuation in motors using the repetitive control.

1987 ◽  
Vol 107 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Fuminori Kobayashi ◽  
Shinji Hara ◽  
Hirotomo Tanaka ◽  
Michio Nakano
Keyword(s):  
Rotational Speed ◽  
Repetitive Control ◽  
Speed Fluctuation

Research on LED multi-sector stable display model in variable rotational speed

2021 ◽  
pp. 1-11
Author(s):  
Luhong Lang ◽  
Dong Ma ◽  
Jun Dong ◽  
Junming He ◽  
Panpan Xu ◽  
...  
Keyword(s):  
Rotational Speed ◽  
Linear Array ◽  
Noise Pollution ◽  
Frequency Measurement ◽  
Stepping Motor ◽  
Term Operation ◽  
Speed Fluctuation ◽  
Precision Frequency ◽  
The Relationship

To solve the display distortion caused by the motor rotational speed changes in the long-term operation of the rotating LED multi-sector display system，the model for LED multi-sector stable display (MSSD) in variable rotational speed is proposed based on the principle of visual persistence. The stepping motor subdivision driving technology is applied to the rotating LED multi-sector display, and the equal precision frequency measurement method is used for accurate rotational speed measurement. Then the innovation adaptive kalman filter (IAKF) is researched to further enhance the robustness to eliminate noise pollution, and the relationship between the modification value caused by rotational speed and the LED linear array minimum refresh time is analysed. The rotating LED MSSD system based on LED linear array rotated by stepping motor is provided. The test results reveal the relationship between rotational speed and the LED linear array minimum refresh time, and show that the lighting position of the LED can be synchronized with the lighting state during the rotational speed fluctuation, and the error can be controlled to a low level via LED linear array minimum refresh time correction．The designed model can effectively eliminate the distortion of the rotating LED multi-sector display screen caused by the changes of the motor rotational speed, and has a very stable display effect.

scholarly journals Control Performance Improvement of Hydro-Viscous Clutch Based on Fuzzy-PID Controller

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8282
Author(s):  
Xiangping Liao ◽  
Shuai Yang ◽  
Dong Hu ◽  
Guofang Gong ◽  
Xiongbin Peng
Keyword(s):  
Control System ◽  
Pid Control ◽  
Rotational Speed ◽  
Pid Controller ◽  
Water Pressure ◽  
Fuzzy Pid ◽  
Fuzzy Pid Control ◽  
Relief Valve ◽  
Fuzzy Pid Controller ◽  
Speed Fluctuation

As a rotational speed controller, a hydro-viscous clutch (HVC) is usually used in the constant pressure water supply system to maintain the needed water pressure constant. However, when the hydro-viscous clutch is working, it often suffers from the problem of output rotational speed fluctuation since the spool of proportional relief valve can easily get stuck. Consequently, water pressure will fluctuate too. A special pump control system of HVC was proposed based on the Fuzzy-PID controller for the purpose of reducing the fluctuation rate. The MATLAB simulation was carried out according to the mathematical model and the results show that the Fuzzy-PID control strategy is superior to traditional PID control. The corresponding experiment was performed and the result indicate that through applying the Fuzzy-PID controller based pump control system, the rotational output speed fluctuation of HVC can be inhibited from ±60π to ±6π rad/min, and the water pressure fluctuation is dropped from ±0.1 to ±0.002 MPa.

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