Pdf cavitation in fluid machinery and hydraulic structures. Cavitation is one of the failure and damage in hydraulic machinery and plain bearings. It applies the laws of similitude to the use of physical models to improve hydraulic design and computer programs for the numerical solution of unsteady flow in closed and open channels. Figure 1 shows the erosions in the discharge hole of liujiaxia. Cavitation in chutes and spillways, engineering monograph.
Millions of dollars have been spent to repair structures that were damaged from cavitation erosion. Cavitation related phenomena covered include such diverse examples as erosion of ship propellers, ultrasonic cleaning, detection of high energy particles, fragmentation of biological cells and sonoluminescence. The types of surfaces often encountered in construction are shown and many examples of cavitation damage induced by the irregularities are shown photographically. While there have been several papers dealing with cavitation as a damage producing phenomenon, little has been written on the. Water hammer was exploited before there was even a word for it. Conceptualization of a model for simulation and assessment of the combined damage, therefore, becomes necessary. The extent of damage and the associated disruption to operation of such facilities, and the costs of repairs and loss due to outage, are facts of life in numerous highhead water engineering projects. Hydraulic cavitation is usually an undesirable phenomenon since it can. The three different geometry nozzles were used to evaluate the efficiency of cavitating jets. Hydraulic and structural considerations of dams spillwaya case study of karkheh dam, andimeshk, iran. In general, the damage due to the phenomenon of cavitation in hydraulic structures can be considered as a function of flow rate, flow pressure, consumable materials resistance, boundaries hardness and the rate of air in the flow 6.
The simple enumeration of some types of equipment, structures, or. Cavitation has also become a concern in the renewable energy sector as it may occur on the blade surface of tidal stream turbines. In general, flow around hydraulic structures can be numerically simulated through the use of 2dimensional or 3dimensional models. Solid line is for the 3d lbe simulation, dotted line is a 2d simulation hou. Dec 12, 2009 cavitation damage in hydraulic structures may reduce the useful life of structures, leading to periods of operation interruption. Avoiding cavitation damage to hydraulic structures. Figure i cavitation damage in the spillway tunnel of the yellowtail dam in montana. Introduction cavitation in hydraulic structures is well known. It is often neglected or ignored in the design and construction of hydraulic structures, and the results can be costly. Cavitation damage to hydraulic machinery y iwai et al. The spillway thus became a huge hydraulic structure equipped with six radial gates. Ordinarily, concrete in properly designed, constructed. Rahmeyer cavitation damage can occur to almost any type of hydraulic structure.
Cavitation wear is mechanical in nature and cannot occur without the application of the tensile and compressive stresses. Reduction the risk of cavitation phenomenon in dam spillway. Perhaps the occurrence is, but how well its character. Wear 257 2004 11761184 relationship between cavitation structures and cavitation damage matev. While no official figures exist, it is not misleading to say that in the last five years, cases of pump cavitation have increased markedly. The technique is based on rapid prototyping methods and shows promise for other hydro plant applications. Cavitation damage to concrete structures and its prevention methods cavitation damage to concrete structure surface is most common in case of spillway in dams. This book gives an unparalleled, uptodate, indepth treatment of all kinds of flow phenomena encountered in centrifugal pumps including the complex interactions of fluid flow with vibrations and wear of materials. Incorporates many reallife examples from the authors experience in the design and operation of pipelines.
The book includes a section on cavitation in hydraulic structures and a concise introduction to the physics of cavitation and application to hydraulic structures. The mouth of the seat exhibits smooth wear caused by flashing, but deeper inside you can see the pockmarked surface characteristic of cavitation, where liquid microjets literally blasted away pieces of metal. The flow characteristics such as pressure, velocity and depth through the spillway have been calculated for five different flow rates. Fundamentals of cavitation jeanpierre franc, jeanmarie. Long spillways are as hydraulic structures in which the occurrence of cavitation phenomenon is so probable. Another factor, that can lead to hydraulic pump cavitation damage, but which is often overlooked, is the reaction time of certain open loop variable displacement pumps, typically when applied in closed center load sensing systems with frequent cycling between standby and full flow operation. Determination of the flow distribution around hydraulic structures is an important aspect for their protection and safety. Usually associated with powered, rotating equipment, cavitation also occurs in stationary hydraulic structures involving both small and large scale flows. Interesting facts and myths about cavitation 2012 randall w.
Pdf cavitation in chutes and spillways, engineering monograph. Large scale cavitation structures nte vortex cavitation ntf cloud cavitation ntg attached or sheet cavitation. Mean velocity profiles left, and, in the symmetry plane along the vertical and the horizontal centerlines. Cavitation in hydraulic structures and turbomachinery fed.
Numerical prediction and risk analysis of hydraulic. Design of spillway aeration devices to prevent cavitation damage on chutes and spillways by hubert chanson h. Where boundaries are not deeply submerged, their shape must be exactly correct, irregularities must be very small, and velocities must be moderate. That is why it is important to carefully evaluate every part of an assembly, without jumping into rushed assumptions and taking the parts condition for granted. Downstream of control valves that have high pressure differentials, in the suction chambers of pumps where starved inlet conditions. This book treats cavitation, which is a unique phenomenon in the field of hyd dynamics, although it can occur in any hydraulic machinery such as pumps, propellers, artificial hearts, and so forth. Hydraulic structures an overview sciencedirect topics. Simulation modeling of the combined damage caused by.
Cavitation damage is one of the major problems confronting the designers and users of modern highspeed hydrodynamic systems as reported by hammitt 1. In devices such as propellers and pumps, cavitation causes a great deal of noise, damage to components, vibrations, and a loss of efficiency. Irregularities in flow surfaces of hydraulic structures operating at high velocities have been the source of serious damage by cavitation. Design of spillway aeration devices to prevent cavitation.
Therefore, the prevention of cavitation is an important concern for designers of hydraulic machinery. Pdf cavitation in chutes and spillways researchgate. Frequently the risk of erosion is accepted and the damages provoked are minimized with the use of appropriate cavitation resistant materials. Effects of cavitation damage on the hydraulic characteristics. Numerical detection of cavitation damage on dam spillway. Cavitation is a common mode of wear in hydraulic pumps and control valves.
Cavitation is generated not only in water, but also in any kind of fluid, such as liquid hydrogen. Many areas in hydraulic systems are prone to cavitation wear, such as. This comprehensive textreference addresses all hydraulic aspects of pipeline design. Cavitation is the phenomenon in which a fluid evaporates to form vapor bubbles which then subsequently implode. Despite what many people believe, the fluid is not sucked into the pump.
A new method for producing cavitation damage in the laboratory is described in which the test specimen has no mechanical accelerations applied to it in contrast with the conventional magnetostriction device. At first, flow over a spillway was simulated using the computational fluid dynamics method. Energy dissipation may be achieved by a wide range of design techniques. It is a serious problem in hydraulic turbines, pumps, valves, control devices, hydraulic structures, sluices, energy dissipators. Cavitation in fluid machinery and hydraulic structures. Finally occurrence of cavitation damage to the doosti dam spillway was investigated.
Cavitation damage to hydraulic structures william j. Alternative apparatus to evaluate cavitation damage. Cavitation damage in hydraulic structures may reduce the useful life of structures, leading to periods of operation interruption. Pump cavitation and how to avoid it best practices in pump system design white paper august 2015 cavitation is not a new phenomenon that can impact a pump system, but it is an issue that is growing. Relationship between cavitation structures and cavitation damage. Some methods of preventing cavitation damage, other than aeration grooves, are discussed. Cavitation damage often may be avoided by not allowing cavities to form. Incidents and failures of hydraulic structures subject to.
Dissipators are used in places where the excess hydraulic energy could cause damage such as erosion of tailwater channels, abrasion of hydraulic structures, generation of tailwater waves or scouring. Results showed that the spillway may be at the risk of cavitation damage, and the serious damage can occur at ending parts of the structure. Four key hydropower projects of different dam types near the epicenter withstood the most severe tests, sustaining only repairable damage. Cavitation is a phenomenon that occurs at high speeds and causes damage and cavities in the structures. In this experiment, pressure and velocity of the system were adjusted to reach a cavitation index of 0. Understanding the causes behind this phenomenon is the first step in developing solutions to combat its harmful effects. In this chapter, an introduction to cavitation and cavitation erosion is presented. The present paper deals with the numerical detection of cavitation damage level and location on dam spillways. It extensively exists in the contact zone of fluid machinery, pipes, ship propellers, and valves owing to growth and implosion of cavitation bubbles in flow liquids. Brennen academic home, the california institute of technology, for the help in. Whitesides, cpe, pe 2 cavitation can, and often does, occur in any situation where fluid is moving in relation to a solid surface. The scope includes all aspects of hydraulic design, 3dflow phenomena and partload operation, cavitation, numerical flow calculations, hydraulic forces, pressure.
According to statistical data, 70% of discharge structures of large hydraulic projects in china suffer from cavitation erosion and abrasion damage wang et al. Experimental study on the mechanism of the combined action. This volume in the hydraulic machinery book series deals with cavitation and its effects in turbines and pumps. In a matter of days cavitation can damage a structure to the point of failure. Topics covered include basic equations necessary to pipeline design, how to conduct a feasibility study and perform economic analysis, design considerations for pumps and valves, how to suppress. The damage to components more often than not results in severe losses of service life times and flow efficiencies. This paper explores the effects of cavitation damage on the hydraulic performance of a gate valve. Accelerated cavitation damage of steels in liquid metal.
This volume in the hydraulic machinery book series deals with cavitation and its effects in turbines. In a hydraulic system, by increasing the flow rate, the local pressure is reduced and such a reduced pressure may continue down to the fluid vapor pressure limit so that the flow converts to the steam mode. Fatigue is commonly defined as a cumulative damage due to stresses and. Based on cavitation index, five different damage levels from no damage to major damage have been considered. Alternative apparatus to evaluate cavitation damage journal. Cavitation in hydraulic structures and turbomachinery fed, vol 25 r. Hidden cavitation erosion damage insane hydraulics. Cavitation damage is most prominent inside the seat, where almost all the damage is in the form of pitting.
The generation of cavitation can cause severe damage in hydraulic machinery. Dynamic pressure of the liquid is by the virtue of flow velocity and the other component, static pressure, is the actual fluid pressure which the fluid applies and which is acted upon it. This paper discusses the different types, causes, and. This phenomenon commonly occurs when a valve closes suddenly at an end of a pipeline system, and a pressure wave propagates in the pipe. Cavitation damage is often one of the more serious problems in operating a hydraulic structure. Energy dissipation in hydraulic structures hubert chanson. Part of the nato asi series book series nsse, volume 124.
Hydraulic machinery and cavitation pp 594603 cite as. Cavitation damaqe in hydraulic structures is abstract a function of the cavitation potential, the duration of the operation, the boundary roughness and alignment, and the strength of the materials from which the boundary is constructed, a method of locating sites of cavitation damage in spillways is presented. Through the use of the model, an aeration device was developed to ventilate the jet and prevent cavitation damage. Numerical prediction and risk analysis of hydraulic cavitation. It is often neglected or ignored in the design and construction of hydraulic structures, and the results can be. Cavitation damaqe in hydraulic structures is abstract a function of the cavitation potential, the duration of the operation, the boundary roughness and alignment, and the strength of the materials from which the boundary is constructed, a method of locating sites of cavitation damage in spillways. Cavitation damage to concrete structures and its prevention. Cavitation damage mbeh mechanism of cavitation damage mbex cavitation noise mbei cavitating pump performance. Reduction the risk of cavitation phenomenon in dam. Other types of concrete deterioration are outside the scope of this report. Glen canyon dam, left tunnel spillwaydamage at station 760. When hydraulic fluid is pumped from a reservoir, pressure drops in the suction line to the pump. Hydraulic structures, including hydraulic gates, are assets for the organization that owns them. This is the fourth edition of the wellknown book from.
The model helped to define undesirable hydraulic conditions that have caused cavitation damage in the prototype structure. Rather, it is pushed into the pump by atmospheric pressure as shown in the lefthand illustration. Cavitation damage can occur to almost any type of hydraulic structure. The types of surfaces often encountered in construction are shown and many examples of cavitation damage induced by the irregularities are shown. Using rapid prototyping methods to repair runner cavitation damage a new technique developed by ontario power generation allows for accurate, quick repair of cavitation damage on a runner blade.
Cavitation of hydraulic machinery series on hydraulic. Jan 22, 2006 cavitation is generated not only in water, but also in any kind of fluid, such as liquid hydrogen. Cavitation of hydraulic machinery series on hydraulic machinery. Topics covered include basic equations necessary to pipeline design, how to conduct a feasibility study and perform economic analysis, design considerations for pumps and valves, how to suppress cavitation, hydraulic transients, trapped air, and methods of numerical solution of governing equations including applications to complex piping systems.
The liquid enters hydraulic turbines at high pressure. Some types of wear or damage, which is especially the case with cavitation erosion, can be concealed and require additional attention to be found. Water vapour pressure hydraulic structure cavitation number aerate zone equivalent flow. Combined damage caused by cavitation and abrasion is a serious problem concerning hydraulic structures and machinery operating in hyperconcentrated sedimentladen rivers. Design of spillway aeration devices to prevent cavitation damage. When cavitation free design is not possible, damage may be avoided or mitigated by a inventing a. Topics covered include basic equations necessary to pipeline design, how to conduct a feasibility study and perform economic analysis, design considerations for pumps and valves. Cavitation from surface irregularities in high velocity. Therefore, it is very important to prevent the occurrence of hydraulic cavitation by optimizing the structure and installing a protection device 11.
The paper discusses cavitation in a high head gated outlet works, not simply as a casestudy but a rare opportunity to compare results from major instrumentation programs in both model studies and the field installation. Cavitation involves the development of various types of vapor structures such as attached cavities, travelling bubbles, vortical cavities, bubble clouds in liquid flow due to a drop in the local pressure below a critical value usually close to the vapor pressure. This leads to cracks on the concrete surface which further increases the risk of damage to concrete by means of sulfate attack, freezethaw, alkalisilica reaction and other means. Cavitation is the formation and collapse of air cavities in liquid. At the hydraulic structure, the flood waters rush as an open channel flow or freefalling jet, and it is essential to dissipate a very significant part of the flow kinetic energy to avoid damage to the hydraulic structure and its surroundings. Cavitation and the centrifugal pump download ebook pdf. The authors of this book are among the initiators of this working group. The monograph discusses basic concepts, cavitation damage, practical. In consequence, a credible simulation and prediction of hydraulic cavitation is necessary in the design stage to protect the spillway from cavitation damage. Pdf the purpose of the monograph is to give the designer of hydraulic structures both an understanding of cavitation. This site is like a library, use search box in the widget to get ebook that you want. Obviously, ones education is not complete without an understanding of the possibilities offered by cavitation in its various forms. Cavitation is, in many cases, an undesirable occurrence. The flow conditions which dictate the various cavitation preventat i on.
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