scholarly journals Voltage Harmonic Analysis of Typical PWM Strategies in a Dual Inverter with Floating Capacitor in the Partial-Load Condition

2021 ◽  
Author(s):  
Akihito Mizukoshi ◽  
Hitoshi Haga
Keyword(s):  
Harmonic Analysis ◽  
Load Condition ◽  
Partial Load ◽  
Floating Capacitor

Performance of Francis Turbine Operating at Excess Load Condition

2020 ◽  
Author(s):  
Muhannad Altimemy ◽  
Justin Caspar ◽  
Alparslan Oztekin
Keyword(s):  
Flow Field ◽  
Draft Tube ◽  
Turbine Blades ◽  
Pressure Fluctuations ◽  
Load Condition ◽  
Operating Conditions ◽  
Francis Turbine ◽  
Partial Load ◽  
Dynamics Simulations ◽  
Excess Load

Abstract Computational fluid dynamics simulations are conducted to characterize the spatial and temporal characteristics of the flow field inside a Francis turbine operating in the excess load regime. A high-fidelity Large Eddy Simulation (LES) turbulence model is applied to investigate the flow-induced pressure fluctuations in the draft tube of a Francis Turbine. Probes placed alongside the wall and in the center of the draft tube measure the pressure signal in the draft tube, the pressure over the turbine blades, and the power generated to compare against previous studies featuring design point and partial load operating conditions. The excess load is seen during Francis turbines in order to satisfy a spike in the electrical demand. By characterizing the flow field during these conditions, we can find potential problems with running the turbine at excess load and inspire future studies regarding mitigation methods. Our studies found a robust low-pressure region on the edges of turbine blades, which could cause cavitation in the runner region, which would extend through the draft tube, and high magnitude of pressure fluctuations were observed in the center of the draft tube.

Optimal Control of a Wind Turbine for Tradeoff Analysis Between Energy Harvesting and Noise Emission

2013 ◽  
Author(s):  
Mohamed L. Shaltout ◽  
Dongmei Chen
Keyword(s):  
Optimal Control ◽  
Energy Harvesting ◽  
Wind Turbine ◽  
Load Condition ◽  
Noise Emission ◽  
Continuous Growth ◽  
Control Approach ◽  
The Public ◽  
Partial Load ◽  
Blade Pitch Angle

An optimal control approach for a wind turbine drivetrain with the objective of maximizing energy harvesting and minimizing noise emission is presented. One of the major challenges facing the public acceptance for continuous growth of wind turbine installation is its noise emission. However, reducing the noise emission could lead to decreased wind energy harvesting. As a result, a tradeoff arises between power generation and noise emission, especially when a wind turbine operates under the partial-load condition. This paper will show that through controlling the generator electromagnetic torque and/or the blade pitch angle, an optimal tradeoff between wind turbine energy harvesting and noise emission can be obtained. The dynamic model of a wind turbine drivetrain and a noise emission prediction model are also presented. Simulation results of using the proposed control design for different wind speed ranges are analyzed and compared.

Stationary stall phenomenon and pressure fluctuation in a centrifugal pump at partial load condition

2019 ◽  
Vol 55 (8) ◽  
pp. 2277-2288 ◽  
Author(s):  
Xuanming Ren ◽  
Honggang Fan ◽  
Zhifeng Xie ◽  
Bing Liu
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Load Condition ◽  
Partial Load

Numerical study on characteristics of unsteady flow in a centrifugal pump volute at partial load condition

2015 ◽  
Vol 32 (6) ◽  
pp. 1549-1566 ◽  
Author(s):  
Lei Tan ◽  
Baoshan Zhu ◽  
Yuchuan Wang ◽  
Shuliang CAO ◽  
Shaobo Gui
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Numerical Study ◽  
Pressure Fluctuations ◽  
Load Condition ◽  
Dominant Frequency ◽  
Content Type ◽  
Cavitation Effect ◽  
Partial Load ◽  
Large Pressure Gradient

Purpose – The purpose of this paper is to elucidate the detailed flow field and cavitation effect in the centrifugal pump volute at partial load condition. Design/methodology/approach – Unsteady flows in a centrifugal pump volute at non-cavitation and cavitation conditions are investigated by using a computation fluid dynamics framework combining the re-normalization group k-e turbulence model and the mass transport cavitation model. Findings – The flow field in pump volute is very complicated at part load condition with large pressure gradient and intensive vortex movement. Under cavitation conditions, the dominant frequency for most of the monitoring points in volute transit from the blade passing frequency to a lower frequency. Generally, the maximum amplitudes of pressure fluctuations in volute at serious cavitation condition is twice than that at non-cavitation condition because of the violent disturbances caused by cavitation shedding and explosion. Originality/value – The detailed flow field and cavitation effect in the centrifugal pump volute at partial load condition are revealed and analysed.

scholarly journals Power Matching and Energy Efficiency Improvement of Hydraulic Excavator Driven with Speed and Displacement Variable Power Source

2019 ◽  
Vol 32 (1) ◽  
Author(s):  
Lei Ge ◽  
Long Quan ◽  
Xiaogang Zhang ◽  
Zhixin Dong ◽  
Jing Yang
Keyword(s):  
Energy Efficiency ◽  
Dynamic Performance ◽  
Load Condition ◽  
Power Source ◽  
Test System ◽  
Hydraulic Excavator ◽  
Idle Period ◽  
Partial Load ◽  
Variable Power ◽  
Working Performance

AbstractMobile machinery energy efficiency and emission pollution are the national and worldwide issues. This paper contributes in solving these problems by applying a speed variable power source. Unfortunately, almost all of the speed variable systems have the dynamic response problem when the motor starts with full load or heavy load. To address this problem, a hydraulic accumulator is used to balance the load of the power source for assisting starting of the motor and a matching method combined with speed and displacement control of the pump is proposed to improve the energy efficiency and dynamic performance simultaneously under different working conditions. Also, the power source/valve combined control strategy of an independent metering system is designed to realize flow matching of the whole system. Firstly, a test system is established to study the dynamic performance and energy efficiency of the speed variable power source with an auxiliary accumulator. Working performance and energy consumption of the power source under different rotating speeds and different loads are studied. And then, the hydraulic excavator test rig with the proposed system is constructed. Furthermore, the working performance of the excavator with the speed-fixed and speed-variable strategy are studied comparatively. Results show that, compared with fixed-speed strategy, the electric power consumption during the idle period and partial load condition can be reduced about 2.05 kW and 1.37 kW. The energy efficiency of speed variable power source is about 40%‒71%, which is higher than that of the fixed-speed power source by 3%–10%.

Study of Efficiency Improvements in a Fuel-Cell-Powered Vehicle Using Water Electrolysis by Recovering Regeneration Energy and Avoiding Partial Load Operation

2005 ◽  
Vol 2 (3) ◽  
pp. 202-207 ◽  
Author(s):  
S. Obara ◽  
K. Kudo
Keyword(s):  
Energy Efficiency ◽  
Fuel Cell ◽  
Load Condition ◽  
Water Electrolysis ◽  
Maximum Output ◽  
Storage Mechanism ◽  
Vehicle Operation ◽  
Partial Load ◽  
Drive Motor ◽  
Low Efficiency

Improvements in efficiency of a fuel-cell-powered vehicle have been studied using water electrolysis as the energy storage mechanism. Three methods are proposed for this purpose: 1. The reformer and fuel cell are divided into two or more units, and the maximum output of each unit is set to be small, which reduces the partial load operation, 2. all the fuel cell units are operated above the low efficiency partial load condition and excess electricity is supplied to another fuel cell unit to generate hydrogen and oxygen by water electrolysis, and these gases are compressed and stored, and arbitrary fuel cell units are supplied and they generate electricity, 3. deceleration periods perform water electrolysis of the fuel cell units using the electric power generated by the drive motor, and both gases are compressed and they store in each cylinder. The LA4 cycle (EPA urban dynamometer schedule) was introduced for the vehicle operation. The energy saving effects of the abovementioned methods were studied and were shown to increase the energy efficiency by 1.23 to 1.72 times compared to that for the conventional method.

Numerical investigation of rotor–stator interaction for canned motor pump under partial load condition

2019 ◽  
Vol 34 (03) ◽  
pp. 2050039 ◽  
Author(s):  
Xiangyuan Zhu ◽  
Saeed A. El Shahat ◽  
Fen Lai ◽  
Wei Jiang ◽  
Guojun Li
Keyword(s):  
Radial Velocity ◽  
Static Pressure ◽  
Load Condition ◽  
Suction Side ◽  
Separation Flow ◽  
Pressure Side ◽  
Partial Load ◽  
Impeller Outlet ◽  
Rotor Stator Interaction ◽  
Canned Motor

Numerical simulations of a canned motor pump at partial load condition have been conducted for studying the strong rotor–stator interaction. SST [Formula: see text] turbulence model with wall function was adopted for solving three-dimensional (3D) unsteady Reynolds-averaged Naiver–Stokes (URANS) equations. The inner flow field for four typical rotor positions, where the head changes significantly, was explored. It has been shown that when blade approached tongue region, the radial velocity decreased where the pressure at suction side was bigger than pressure side. As a result, a negative work was exerted on the fluid which led to minimum work done by the impeller. At this condition, maximum work was resulted in due to the upstream blade. The fluid from balance hole affected the main flow near hub region which caused a vortex near channel pressure side. Due to impeller channel rotation through tongue, the vortex was enlarged which contributed separation flow at impeller inlet region. The separated flow caused pressure reduction in the channel. Static pressure at impeller outlet near shroud side was always greater than at near hub side which resulted in negative radial velocity at impeller outlet near shroud side. Due to the blade accession to the tongue, the static pressure at impeller channel increased meanwhile the area characterized by negative radial velocity enlarged.

scholarly journals Vibration of Shaft System in the Mixed-Flow Pump Induced by the Rotor-Stator Interaction under Partial Load Conditions

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Wei Li ◽  
Leilei Ji ◽  
Weidong Shi ◽  
Yulu Wang ◽  
Ling Zhou ◽  
...  
Keyword(s):  
Load Condition ◽  
Exciting Force ◽  
Mixed Flow ◽  
Shaft System ◽  
Partial Load ◽  
Axis Orbit ◽  
Rotor Stator Interaction ◽  
Shaft Vibration ◽  
Load Conditions ◽  
Flow Pump

In order to reveal the relationship between rotor-stator interaction-induced unsteady flow and the shaft vibration of the mixed-flow pump, PIV (particle image velocimetry) and axis orbit experiments were carried out synchronously in a mixed-flow pump under designed flow rate (1.0Qdes) and the partial load conditions (0.4Qdes and 0.2Qdes). The distribution of the relative velocity and the vorticity in the rotor-stator interaction region at a certain position of the mixed-flow pump impeller was captured; the axis orbit diagram and the time-domain diagram of shaft system were acquired as well. Besides, the waterfall diagrams of the frequency spectrum under different flow rate conditions were compared. The results show that the backflow and the flow separation phenomenon appear in the rotor-stator interaction flow field under the partial load condition, indicating the flow instability. The medium-frequency exciting force and high-frequency exciting force induced by these unstable flows resulting from the rotor-stator interaction are the main factors to intensify the shaft vibration at the power frequency. The rotor-stator interaction under partial load condition is the main reason for the deterioration of shaft system vibration. The 2X frequency also affects the axis orbit in a low level, while other frequencies have less influence on the shaft vibration. The research results can provide the reference and theory instruction for revealing the operating characteristic of mixed-flow pump when it operates under partial load conditions and to reduce or to prevent the deterioration of vibration of shaft system.

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