Fluid dynamics of acoustic and hydrodynamic cavitation in hydraulic power systems

Cavitation is the transition from a liquid to a vapour phase, due to a drop in pressure to the level of the vapour tension of the fluid. Two kinds of cavitation have been reviewed here: acoustic cavitation and hydrodynamic cavitation. As acoustic cavitation in engineering systems is related to the propagation of waves through a region subjected to liquid vaporization, the available expressions of the sound speed are discussed. One of the main effects of hydrodynamic cavitation in the nozzles and orifices of hydraulic power systems is a reduction in flow permeability. Different discharge coefficient formulae are analysed in this paper: the Reynolds number and the cavitation number result to be the key fluid dynamical parameters for liquid and cavitating flows, respectively. The latest advances in the characterization of different cavitation regimes in a nozzle, as the cavitation number reduces, are presented. The physical cause of choked flows is explained, and an analogy between cavitation and supersonic aerodynamic flows is proposed. The main approaches to cavitation modelling in hydraulic power systems are also reviewed: these are divided into homogeneous-mixture and two-phase models. The homogeneous-mixture models are further subdivided into barotropic and baroclinic models. The advantages and disadvantages of an implementation of the complete Rayleigh–Plesset equation are examined.

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Artificial Neural Network Solution for Anomalous Operation Detection in Power Systems

10.48011/sbse.v1i1.2158 ◽

2021 ◽

Author(s):

Nathan Elias Maruch Barreto ◽

Ciro Monteiro Baer ◽

Mateus Jaensen Daros ◽

Marlon Alexsandro Fritzen ◽

Guilherme Schneider de Oliveira ◽

...

Keyword(s):

Neural Network ◽

Artificial Neural Network ◽

Power Systems ◽

Power System ◽

Test System ◽

Measurement Unit ◽

Two Phase ◽

Advantages And Disadvantages ◽

Phasor Measurement ◽

Artificial Neural

This paper presents an anomalous operation detection system for power systems using the artificial neural network approach while discussing its advantages and disadvantages. The initial data for the proposed technique is a set of simulated post-fault bus voltages and currents obtained in a sampling rate so as to emulate a phasor measurement unit network. Several types of faults are dealt with, such as three-phase to ground, two-phase, two-phase to ground and single-phase to the ground as well as line and load contingencies. All fault and steady-state simulations were performed on MATLAB using Graham Rogers’ Power System Toolbox. The artificial neural network was designed on MATLAB, using an architecture proper for pattern recognition with supervised learning and obtaining high accuracy predictions within a short amount of time. The test system used in all simulations is the IEEE 39-Bus New England Power System, which presents 10 generation units, 21 loads and three distinct areas alongside transient and sub transient models, with phasor measurement units in 14 buses. Future works are discussed, showing the possibilities for feature engineering in this type of problem, fault type detection and fault location in operation using analogous dataset and neural network structures.

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A Review of Techniques for RSS-Based Radiometric Partial Discharge Localization

Sensors ◽

10.3390/s21030909 ◽

2021 ◽

Vol 21 (3) ◽

pp. 909

Author(s):

David W. Upton ◽

Keyur K. Mistry ◽

Peter J. Mather ◽

Zaharias D. Zaharis ◽

Robert C. Atkinson ◽

...

Keyword(s):

Power Systems ◽

High Voltage ◽

Partial Discharge ◽

Specific Area ◽

Electrical Insulation ◽

Acoustic Detection ◽

Advantages And Disadvantages ◽

Initial Stage ◽

Catastrophic Failures ◽

Radiometric Detection

The lifespan assessment and maintenance planning of high-voltage power systems requires condition monitoring of all the operational equipment in a specific area. Electrical insulation of electrical apparatuses is prone to failure due to high electrical stresses, and thus it is a critical aspect that needs to be monitored. The ageing process of the electrical insulation in high voltage equipment may accelerate due to the occurrence of partial discharge (PD) that may in turn lead to catastrophic failures if the related defects are left untreated at an initial stage. Therefore, there is a requirement to monitor the PD levels so that an unexpected breakdown of high-voltage equipment is avoided. There are several ways of detecting PD, such as acoustic detection, optical detection, chemical detection, and radiometric detection. This paper focuses on reviewing techniques based on radiometric detection of PD, and more specifically, using received signal strength (RSS) for the localization of faults. This paper explores the advantages and disadvantages of radiometric techniques and presents an overview of a radiometric PD detection technique that uses a transistor reset integrator (TRI)-based wireless sensor network (WSN).

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A Neural Network-Based Model Reference Control Architecture for Oscillation Damping in Interconnected Power System

Energies ◽

10.3390/en12193653 ◽

2019 ◽

Vol 12 (19) ◽

pp. 3653

Author(s):

Uddin ◽

Zeb ◽

Ishfaq ◽

Khan ◽

...

Keyword(s):

Neural Network ◽

Power Systems ◽

Power System ◽

Performance Indicator ◽

Stable Condition ◽

External Perturbation ◽

Absolute Error ◽

Unified Power Flow Controller ◽

Two Phase ◽

Model Reference

In this paper, a model reference controller (MRC) based on a neural network (NN) is proposed for damping oscillations in electric power systems. Variation in reactive load, internal or external perturbation/faults, and asynchronization of the connected machine cause oscillations in power systems. If the oscillation is not damped properly, it will lead to a complete collapse of the power system. An MRC base unified power flow controller (UPFC) is proposed to mitigate the oscillations in 2-area, 4-machine interconnected power systems. The MRC controller is using the NN for training, as well as for plant identification. The proposed NN-based MRC controller is capable of damping power oscillations; hence, the system acquires a stable condition. The response of the proposed MRC is compared with the traditionally used proportional integral (PI) controller to validate its performance. The key performance indicator integral square error (ISE) and integral absolute error (IAE) of both controllers is calculated for single phase, two phase, and three phase faults. MATLAB/Simulink is used to implement and simulate the 2-area, 4-machine power system.

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Assessment of Tandem Venturi on Enhancement of Cavitational Chemical Reaction

Journal of Fluids Engineering ◽

10.1115/1.3026731 ◽

2008 ◽

Vol 131 (1) ◽

Cited By ~ 5

Author(s):

Hoseyn Sayyaadi

Keyword(s):

Chemical Reaction ◽

Oxidation Process ◽

Flow Characteristics ◽

Chemical Oxidation ◽

Cavitation Number ◽

Cavitating Flow ◽

Hydrodynamic Cavitation ◽

Operating Pressure ◽

Local Pressures ◽

Second Category

The collapsing phenomenon of cavitation bubbles generates extremely high local pressures and temperatures that can be utilized for the chemical oxidation process. This process is carried out in cavitation reactors. A Venturi tube is one of the most common forms of hydrodynamic cavitation reactors, which is suitable for industrial scale applications. In this work, the hydraulic performance and efficiency in chemical reaction of a new form of hydrodynamic cavitation reactors, which is called “tandem Venturi,” were studied and compared with the conventional type of the single Venturi. The tandem Venturi is used for enhancement of the chemical reaction of hydrodynamic cavitating flow. The reaction enhancement is useful especially for the reaction of aqueous solutions not containing volatile organic compounds (VOCs). The operating pressure, inlet pressure, flow rate, and consequently the cavitation number were controlled and systematically varied for both single and tandem Venturis. Moreover, a specified amount of H2O2 was injected into the flow as required. The effects of operating pressure and the cavitation number on cavitating flow characteristics for single and tandem Venturis were experimentally observed and the results were compared. In addition, the performance of the tandem-Venturi reactor for degradation of non-VOC contaminants (2-chlorophenol) was studied. Its performance was compared with the performance of a conventional Venturi reactor. Two different categories were conducted for the experiments. In the first category, the effect of the net cavitating flow on degradation of non-VOC for the single and tandem Venturis was compared. In the second category, the effect of H2O2 injection into the cavitating flow on degradation of non-VOC (“cavitation-oxidation” process) was studied. The performance of the single and tandem Venturis for the cavitation-oxidation process was compared. Further investigation was performed to assess the advantage of utilizing the tandem Venturi from the viewpoint of efficiency of the oxidation process. The results of the energy efficiency were compared with the corresponding efficiency of the single Venturi. Finally, the relationship between the main parameters of cavitation reaction flow with the chemical performance was discussed.

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Second Life as a research environment: avatar-based focus groups (AFG)

Qualitative Market Research An International Journal ◽

10.1108/qmr-08-2015-0070 ◽

2016 ◽

Vol 19 (1) ◽

pp. 101-114 ◽

Cited By ~ 4

Author(s):

Eman Gadalla ◽

Ibrahim Abosag ◽

Kathy Keeling

Keyword(s):

Focus Groups ◽

Data Quality ◽

Virtual Worlds ◽

Second Life ◽

Three Dimensional ◽

Marketing Research ◽

Two Phase ◽

Content Type ◽

Face To Face ◽

Advantages And Disadvantages

Purpose – This study aims to examine the nature and the potential use of avatar-based focus groups (AFGs) (i.e. focus groups conducted in three-dimensional [3D] virtual worlds [VWs]) as compared to face-to-face and online focus groups (OFGs), motivated by the ability of VWs to stimulate the realism of physical places. Over the past decade, there has been a rapid increase in using 3D VWs as a research tool. Design/methodology/approach – Using a two-phase reflective approach, data were collected first by using traditional face-to-face focus groups, followed by AFGs. In Phase 2, an online, semi-structured survey provided comparison data and experiences in AFGs, two-dimensional OFGs and traditional face-to-face focus groups. Findings – The findings identify the advantages and disadvantages of AFGs for marketing research. There is no evident difference in data quality between the results of AFGs and face-to-face focus groups. AFG compensates for some of the serious limitations associated with OFGs. Practical implications – The paper reflects on three issues, data quality, conduct of AFGs (including the moderator reflection) and participant experience, that together inform one’s understanding of the characteristics, advantages and limitations of AFG. Originality/value – This is the first paper to compare between AFGs, traditional face-to-face focus groups and OFGs. AFG holds many advantages over OFGs and even, sometimes, over face-to-face focus groups, providing a suitable environment for researchers to collect data.

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A Review on Fault Current Limiting Devices to Enhance the Fault Ride-Through Capability of the Doubly-Fed Induction Generator Based Wind Turbine

Applied Sciences ◽

10.3390/app8112059 ◽

2018 ◽

Vol 8 (11) ◽

pp. 2059 ◽

Cited By ~ 11

Author(s):

Seyed Naderi ◽

Pooya Davari ◽

Dao Zhou ◽

Michael Negnevitsky ◽

Frede Blaabjerg

Keyword(s):

Power Systems ◽

Wind Turbine ◽

Induction Generator ◽

Fault Current ◽

Doubly Fed Induction Generator ◽

Advantages And Disadvantages ◽

Fault Ride Through ◽

Current Limiting ◽

Two Factors ◽

Doubly Fed

The doubly-fed induction generator has significant features compared to the fixed speed wind turbine, which has popularised its application in power systems. Due to partial rated back-to-back converters in the doubly-fed induction generator, fault ride-through capability improvement is one of the important subjects in relation to new grid code requirements. To enhance the fault ride-through capability of the doubly-fed induction generator, many studies have been carried out. Fault current limiting devices are one of the techniques utilised to limit the current level and protect the switches, of the back-to-back converter, from over-current damage. In this paper, a review is carried out based on the fault current limiting characteristic of fault current limiting devices, utilised in the doubly-fed induction generator. Accordingly, fault current limiters and series dynamic braking resistors are mainly considered. Operation of all configurations, including their advantages and disadvantages, is explained. Impedance type and the location of the fault current limiting devices are two important factors, which significantly affect the behaviour of the doubly-fed induction generator in the fault condition. These two factors are studied by way of simulation, basically, and their effects on the key parameters of the doubly-fed induction generator are investigated. Finally, future works, in respect to the application of the fault current limiter for the improvement of the fault ride-through of the doubly-fed induction generator, have also been discussed in the conclusion section.

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Development of the Trilateral Flash Cycle System: Part 1: Fundamental Considerations

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1243/pime_proc_1993_207_032_02 ◽

1993 ◽

Vol 207 (3) ◽

pp. 179-194 ◽

Cited By ~ 51

Author(s):

I K Smith

Keyword(s):

Power Systems ◽

Power Plants ◽

Rankine Cycle ◽

World Market ◽

Low Grade ◽

Heat Sources ◽

Two Phase ◽

Cycle System ◽

Cycle Systems ◽

Power Recovery

The world market for systems for power recovery from low-grade heat sources is of the order of £1 billion per annum. Many of these sources are hot liquids or gases from which conventional power systems convert less than 2.5 per cent of the available heat into useful power when the fluid is initially at a temperature of 100° C rising to 8–9 per cent at an initial temperature of 200°C. Consideration of the maximum work recoverable from such single-phase heat sources leads to the concept of an ideal trilateral cycle as the optimum means of power recovery. The trilateral flash cycle (TFC) system is one means of approaching this ideal which involves liquid heating only and two-phase expansion of vapour. Previous work related to this is reviewed and details of analytical studies are given which compare such a system with various types of simple Rankine cycle. It is shown that provided two-phase expanders can be made to attain adiabatic efficiencies of more than 75 per cent, the TFC system can produce outputs of up to 80 per cent more than simple Rankine cycle systems in the recovery of power from hot liquid streams in the 100–200°C temperature range. The estimated cost per unit net output is approximately equal to that of Rankine cycle systems. The preferred working fluids for TFC power plants are light hydrocarbons.

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Development of Electromobility in Terms of Freight Transport

LOGI – Scientific Journal on Transport and Logistics ◽

10.2478/logi-2019-0012 ◽

2019 ◽

Vol 10 (2) ◽

pp. 23-32 ◽

Cited By ~ 1

Author(s):

Václav Cempírek ◽

Iwona Rybicka ◽

Ivica Ljubaj

Keyword(s):

Power Systems ◽

Current System ◽

Freight Transport ◽

Future Research ◽

Advantages And Disadvantages ◽

Traction Motors ◽

Fundamental Information ◽

Road Freight ◽

Battery Packs ◽

Adequate Evaluation

Abstract The paper deals with specific aspects regarding the current development trends of electromobility in the context of road freight transport. The current system of electric vehicles for road freight transport and the relevant investigations are based on the experience with operating trolleybuses, which have the same power supply of traction motors from the overhead traction line by means of traction pantographs. As for the future, it has not been decided yet which electromobility-related power system will be used in practice, whether the supply of electric motors from traction lines or battery packs. In the introductory chapters, the manuscript discusses the fundamental information regarding the electromobility, current projects dealing with this issue, individual aspects and attributes related to these existing power systems, and their advantages and disadvantages in terms of their usage. In the most important part of the manuscript, the adequate evaluation is performed, as well as very recommendations for future research in a given topic are proposed.

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Relay protection and automation of electric power systems

10.12737/1048841 ◽

2021 ◽

Author(s):

Sergey Goremykin

Keyword(s):

Power Systems ◽

Electric Power ◽

Transmission Lines ◽

Power Supply ◽

Power Transmission ◽

Relay Protection ◽

Electrical Equipment ◽

Electric Power Systems ◽

Federal State ◽

Advantages And Disadvantages

The textbook describes the main issues of the theory of relay protection and automation of electric power systems. The structure and functional purpose of protection devices and automation of power transmission lines of various configurations, synchronous generators, power transformers, electric motors and individual electrical installations are considered. For each of the types of protection of the above objects, the structure, the principle of operation, the order of selection of settings are given, the advantages and disadvantages are evaluated, indicating the scope of application. The manual includes material on complete devices based on semiconductor and microprocessor element bases. The progressive use of such devices (protection of the third and fourth generations) is appropriate and effective due to their significant advantages. Meets the requirements of the federal state educational standards of higher education of the latest generation. It is intended for students in the areas of training 13.03.02 "Electric power and electrical engineering" (profile "Power supply", discipline "Relay protection and automation of electric power systems") and 35.03.06 "Agroengineering" (profile "Power supply and electrical equipment of agricultural enterprises", discipline "Relay protection of electrical equipment of agricultural objects"), as well as for graduate students and specialists engaged in the field of electrification and automation of industrial and agrotechnical objects.

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Application of Fast Synchrotron X-ray Imaging in Velocimetry of Cavitating Flows

10.5957/tos-2021-15 ◽

2021 ◽

Author(s):

Mingming Ge ◽

Guangjian Zhang ◽

Navid Nematikourabbasloo ◽

Kamel Fezzaa ◽

Olivier Coutier-Delgosha

Keyword(s):

Phase Contrast ◽

Two Phase Flow ◽

Motion Blur ◽

Hydrodynamic Cavitation ◽

Phase Flow ◽

Two Phase ◽

X Ray ◽

Sheet Cavitation ◽

Contraction Ratio ◽

Wide Range

Hydrodynamic cavitation is a complex two-phase flow phenomenon involving mass and heat transfer between liquid and vapor. It occurs in many widely-used hydraulic machines, such as pumps and marine propellers, and often leads to undesired effects like material erosion, noise, and vibration. To control these detrimental effects, the visualization of two-phase flow morphology inside the opaque cavity is a crucial point to improve the physical and numerical models of cavitation. The major challenge in experimental measurements of cavitating flow fields is the fact that multiple scattering and a direct reflection of visible light from phase boundaries make the flow optically opaque. In recent years, unlike traditional local measurements using various probes, the development of the third-generation synchrotron radiation sources promotes the application of Xray phase-contrast imaging, which enables clear visualization of boundaries between phases with different refractive indices. In this study, the partial cavity is formed in a convergent-divergent (Venturi) channel with a small contraction ratio where the relatively stable cavitation regime can be sustained in a wide range of cavitation numbers. The experiment performed at Advanced Photon Source (APS) of Argonne uses the short high-flux X-ray pulses emitted from synchrotron sources to capture fast dynamic events and minimize motion blur. The internal two-phase structures and bubble development dynamics inside the quasi-stable sheet cavitation can be identified. Aside from the detailed illustration of two-phase morphology, X-ray phase-contrast images were also used to perform velocimetry by tracking either seeded particles or phase interfaces inside the opaque regions. Through appropriate postprocessing to the recorded X-ray images of cavitation, the time resolved velocity and void fraction fields are obtained simultaneously. These unprecedented experimental data will be further explored in understanding fluid mechanics underneath the cavity, estimating slip velocity between fluid-vapor interactions, and reconstructing pressure fields for compressible flows.

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