Technology & Engineering
Fluid Power Pumps and Motors
Fluid power pumps and motors are essential components in hydraulic systems, providing the means to convert mechanical energy into fluid power. Pumps are used to generate fluid flow and create hydraulic pressure, while motors convert hydraulic energy back into mechanical energy. These devices play a crucial role in various applications, including construction equipment, manufacturing machinery, and aerospace systems.
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10 Key excerpts on "Fluid Power Pumps and Motors"
- Wayne Kilcollins(Author)
- 2012(Publication Date)
- Cengage Learning EMEA(Publisher)
A basic fluid-power system comprises a fluid, power source, control system, and actuator. This basic system may be used to lift heavy components such as the boom on an excavator, to apply clamping force to a disc brake assem-bly, or to move the control surfaces of an aircraft wing. The brute force or finesse of the system depends on the size and control of the system components chosen. The purpose of discussions in this chapter is to further develop a technician’s Fluid Power 5 CHAPTER Copyright 2012 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 92 Chapter 5 Fluid Power covers liquids and gases. Typical fluid-power systems use a hydraulic fluid that comprises oil or a mixture of water and glycol along with additives that were mentioned in Chapter 4 on lubricants. The purpose of the hydraulic fluid is multifold. It is used to transfer power through a combination of flow and pressure, lubricate system components, and transfer heat generated by friction in the system. Fluid-power systems that use gases such as air are considered pneumatic . The major difference between the systems is the nature of the fluid. Hydraulic fluids such as oil, water, glycol, and other liquid types are virtually incompressible. Incompressible means you can pressurize the fluid and there will be virtually no change in the volume. Gases used in pneumatic systems are considered compressible . Compressing a volume of gas will FIGURE 5-1 Examples of fluid-power applications for construction and wind power © Cengage Learning 2013 and a W. Kilcollins photograph © Cengage Learning 2013 and a W.
eBook - PDF- Olga Moreira(Author)
- 2019(Publication Date)
- Arcler Press(Publisher)
FLUID POWER CHAPTER 14 CONTENTS 14.1. Introduction .................................................................................. 290 14.2. Definitions, Coefficient, And Power Calculations .......................... 291 14.3. Properties Of Fluids In Hydraulics ................................................ 295 14.4. Elements Of Power Hydraulics ...................................................... 296 Theory and Problems of Fluid Dynamics 290 14.1. INTRODUCTION In this chapter, we study the utilization of fluid to generate, control, and transmit power. Many regard this to be a separate branch of fluid mechanics. Some categorize it as hydraulics and pneumatics . Ultimately we study the utilization of fluids to make them more useful towards achieving our own purposes. Some terms, such as density, pressure, discharge, etc., are redefined here for the purpose of refreshing the memory. The definitions should universally remain the same. We deal with Hydraulic- defined as properties, effects, and the power derived from liquids- and Pneumatic- meaning that which encompasses the same traits but from gases; for example, compressible fluids utilized for power conversion. Utilization of fluid for purposes such as transferring energy, lifting objects or similar efforts goes back to 200 BC. The first person known to the world who utilized fluid power is Archimedes. Other historical figures known to have explored and employed the tools and principles of hydraulics are Pascal, Bernoulli, and Euler to name just a few. Definitions: Let us define a fluid. No doubt there are many ways of defining fluid, but in simple terms, it is defined as a mass/matter that flows continuously. A few examples of fluids are water (called as universal fluid), oil, milk, etc. any of such kind. However, air is also a fluid. Is it not different from water or oil? Yes, it is true- fluids are further classified as liquids and gases.
- Robert W. Fox, Alan T. McDonald, John W. Mitchell(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
• Determine the performance of a propeller or wind turbine. • Use the dimensionless parameters to scale compressor performance between operating conditions. Humans have sought to harness the forces of nature to offset human labor nature since antiquity. The first fluid machines developed were bucket wheels and screw pumps to lift water. The Romans introduced paddle wheels around 70 B.C.E. to obtain energy from streams [1]. Later, windmills were developed to harness wind power, but the low power density of the wind limited output to a few hundred horsepower. Development of waterwheels made it possible to extract thousands of horsepower at a single site. Today we take many fluid machines for granted. On a typical day we draw water pressurized by pumps from the tap, drive a car in which fluid pumps operate the lubrication, cooling, and power steering systems, and work in a comfortable environment provided lights and cooling systems powered by electricity produced by steam or gas turbines. The list could be extended indefinitely. A fluid machine is a device that either performs work on or extracts work from a fluid. This is a very large field of study, so we will limit ourselves mostly to incompressible flows. First the terminology of the field is introduced and machines are classified by operating principle and physical characteristics. We will focus on machines in which energy transfer to or from the fluid is through a rotating element. Basic equations are reviewed and then simplified to forms useful for analysis of fluid machines. Performance characteristics of typical machines are considered. We will use as examples pump and turbine applica- tions in typical systems and then discuss propellers and wind turbines. A discussion of compressible flow machines concludes the chapter. 10.1 Introduction and Classification of Fluid Machines Fluid machines may be broadly classified as either positive displacement or dynamic.
eBook - PDF- John Ward-Smith(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
Fluid machines 13 13.1 INTRODUCTION A fluid machine is a device either for converting the energy held by a fluid into mechanical energy or vice versa. In this chapter the internal workings of a number of different designs of fluid machine are described. We shall not consider here every kind of machine that has been devised, nor describe constructional details or the practical operation of machines. Our concern is simply with the basic principles of mechanics of fluids that are brought into play. The chapter starts by introducing the main categories of fluid machines. 13.1.1 Turbines and pumps A machine in which energy from a fluid is converted directly to the mechan-ical energy of a rotating shaft is known as a turbine (from the Latin turbo , a circular motion). If, however, the initial mechanical movement is a reciproc-ating one the term engine or motor is used. A machine in which the converse process – the transfer of energy from moving parts to the fluid – takes place is given the general title of pump . 13.1.2 Compressors, fans and blowers When the fluid concerned is a gas, other terms may be used. If the primary object is to increase the pressure of the gas, the machine is termed a com-pressor . On the other hand, a machine used primarily for causing the movement of a gas is known as a fan or blower . In this case the change in pressure across the machine is quite small – usually sufficient only to over-come the resistance to the motion – so the variation of density is negligible and the fluid may be regarded as incompressible. 13.1.3 Positive-displacement machines Although a great variety of fluid machines is to be found, any machine may be placed in one of two categories: the positive-displacement group or the rotodynamic group. The functioning of a positive-displacement machine 592 Fluid machines derives essentially from changes of the volume occupied by the fluid within the machine.
eBook - PDF- Xixi Wang(Author)
- 2021(Publication Date)
- Cambridge University Press(Publisher)
5 Hydraulic Machinery 5.1 Overview of Pumps and Turbines 178 5.2 Pumps 180 5.3 Turbines 214 Problems 233 Pumps and turbines, two commonly used hydraulic machines, are important components in water resources engineering systems. Pumps are used to transfer water, whereas turbines are used to har- vest water energy to generate electricity. This chapter discusses the characteristics and selection of these two hydraulic machines from the perspective of hydraulic engineering. The purpose of this chapter is to present the basics for water resources and hydraulic engineers to understand the performance of these machines and how they can be selected to best match a hydraulic engineering system. How these machines are designed is a subject for other disciplines, such as mechanical engineering, and is thus beyond the scope of this book. In addition to the differences and simi- larities between pumps and turbines, this chapter also discusses the selection considerations and characteristics of these two machines. 5.1 Overview of Pumps and Turbines Pumps are devices that lift water by converting mechanical energy into water energy. A pump consumes electronic power to generate rotatory motion, through which the power is transferred into a water system so that the water can be transported from one location to another between which a negative energy gradient exists. Pumps are widely used in water resources and environ- mental engineering, such as in water supply, flood control, irrigation, wastewater treatment, and groundwater exploration. For instance, as illustrated in Figure 5.1, a pump is needed to transfer the water in Reservoir A through a pipeline upward to Reservoir B. The head against by the pump is ∆H = z B −z A , while the head that needs to be added by the pump should be at least h p = ∆H+h L , where h L is the total energy loss, including friction and minor losses (Eq. (2.22)). h p is also called the total head against which the pump operates.
- Steven Vogel(Author)
- 2009(Publication Date)
- Princeton University Press(Publisher)
Among our industrial products, only electric motors may exceed them in range of sizes, applica-tions, and designs. When choosing among their diversity of pumps, engi-neers worry about such things as power expenditure, operating condi-tions, and efficiency. We biologists have only occasionally done the same in analyzing and classifying nature’s pumps, and we ought to take full advantage of all that technological attention. [In part, this chapter takes the same viewpoint as did a predecessor (Vogel 1995a), one that a reviewer rightly noted didn’t turn out quite as satisfactorily as the author had hoped. I’ll, of course, have to reiterate some of the points of that paper.] Pumping Fluids through Conduits • 185 The Relevant Variables An insect, most famously an ant, can lift many times its own body weight— but it cannot lift it far. Similarly, a tree can draw sap upward with pres-sures of tens of atmospheres, millions of pascals—but it does so very slowly. We may be overly impressed by the spectacularly high forces and pressures that organisms can produce and insufficiently mindful of con-straints on distances and volume flows. Whether lifting weights or forc-ing fluids through pipes, doing work involves three variables, and these operate over a wide range of combinations. Force, distance, and power define a lifting task, with power the product of force and rate of change of distance. Similarly, pressure, volume flow, and power define the task of a pump, with the last again the product of the first two. A bivalve mol-lusk can pump its own volume of water in, across its gills, and out again every few seconds, but it does so against only a few pascals of pressure— its volume flow should impress us as much as the pressure generated by a sap-lifting tree. The particular graphic representation of pump performance shown in figure 10.1 has enjoyed long usage in engineering.
eBook - PDF- William Graebel(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
533 chapter 11 Hydraulic Machinery Chapter Overview and Goals Hydraulic machinery is an important engineering application of the material we have covered in earlier chapters. In studying the behavior of hydraulic machines, we first present the suitable dimensionless parameters needed to describe the machines, and select those suitable for a given application. Descriptions of several types of pumps are then presented, along with a discussion of turbines used for electric power generation. Other issues involved in the design of a pumping system are discussed in Appendix G. 1. Pump Classification and Selection The use and design of hydraulic machinery is important to many engineering tasks. Hydraulic machinery can be broadly divided into two classes: pumps and turbines. A pump converts mechanical or electrical energy from an outside source into hydraulic energy, often in the form of a pressure rise. Many hydraulic machines used in engineering applications are centrifugal machines, where an essential part of the machine is a rotating member. This member is called an impeller, or a rotor, or a runner, depending on the type of machine. The pressure rise across the pump is due to the kinetic energy imparted to the fluid by the rotation. Positive displacement pumps on the other hand use pistons or rotary vanes to increase the pressure by compressing the fluid. In a sense a turbine is a pump running backward, in that it converts hydraulic energy into mechanical energy. Most turbines are centrifugal machines. There are many varieties of pumps available, each satisfying different needs or a different range of operating conditions. They may be divided two main classifications of pumps, the positive displacement pump and the turbomachine pump. a. Positive displacement pumps A positive displacement pump is used when it is necessary to develop high heads or create a suction lift.
eBook - PDF- Arthur Akers, Max Gassman, Richard Smith(Authors)
- 2006(Publication Date)
- CRC Press(Publisher)
In this chapter, pumps and motors are generally discussed as if there were no difference between the two functions. This lack of discrimination is generally true and pumps may often be substituted for motors and vice versa . It is NOT universally true. For example, a gerotor pump is simpler than a gerotor motor, for reasons that will be explained when discussing that specific geometry. Manufacturers design pumps and motors for specific purposes and it is always advisable to consult with the manufacturer should the intended role of a piece of equipment be changed. The common patterns of positive displacement pumps employed in fluid power systems are displayed in Figure 8.1 to 8.8. It will be observed that all the patterns shown have some means of connecting the expanding chamber to an inlet port and the contracting chamber to a discharge port. Achieving a graceful transition is not trivial. Excess leakage vs. excess pressure rise must be balanced. We shall discuss this topic later for the axial piston pump in Chapter 9. Both pumps and motors are generally ranked in the order: CAVITY CONTRACTION REGION CAVITY EXPANSION REGION FLUID IS CARRIED AROUND THE PERIMETER Figure 8.1 : Spur gear pump. Chapter 8 211 SPUR GEAR INTERNAL GEAR GEROTOR VANE RADIAL PISTON AXIAL PISTON (SWASH PLATE & BENT AXIS) SCREW The initial pumps in the ranking are relatively lower in cost, limited in pres-sure capability, and lower in efficiency. In addition to pressure capability and efficiency, piston pumps are relatively easily modified to incorporate au-tomatic volume displacement reduction as pressure rises above a set value. Furthermore piston pumps and motors can have their displacement varied during normal operation. This characteristic is made use of in a hydrostatic transmission where motor speed must be varied smoothly (i.e. steplessly) over a wide range. Spur gear : A spur gear pump is shown in Figure 8.1. The fluid is car-ried around the perimeter of the gear.
eBook - PDF- Andrew Parr(Author)
- 1999(Publication Date)
- Butterworth-Heinemann(Publisher)
I Fundamental principles Industrial prime movers Most industrial processes require objects or substances to be moved from one location to another, or a force to be applied to hold, shape or compress a product. Such activities are performed by Prime Movers; the workhorses of manufacturing industries. In many locations all prime movers are electrical. Rotary motions can be provided by simple motors, and linear motion can be obtained from rotary motion by devices such as screw jacks or rack and pinions. Where a pure force or a short linear stroke is required a solenoid may be used (although there are limits to the force that can be obtained by this means). Electrical devices are not, however, the only means of providing prime movers. Enclosed fluids (both liquids and gases) can also be used to convey energy from one location to another and, conse- quently, to produce rotary or linear motion or apply a force. Fluid- based systems using liquids as transmission media are called hydraulic systems (from the Greek words hydra for water and aulos for a pipe; descriptions which imply fluids are water although oils are more commonly used). Gas-based systems are called Pneumatic systems (from the Greek pneumn for wind or breath). The most common gas is simply compressed air. although nitrogen is occa- sionally used. The main advantages and disadvantages of pneumatic or hydraulic systems both arise out of the different characteristics of low density compressible gases and (relatively) high density 2 Hydraulics and Pneumatics incompressible liquids. A pneumatic system, for example, tends to have a 'softer' action than a hydraulic system which can be prone to producing noisy and wear inducing shocks in the piping. A liquid-based hydraulic system, however, can operate at far higher pressures than a pneumatic system and, consequently, can be used to provide very large forces.
- George E. Totten, Victor J. De Negri(Authors)
- 2011(Publication Date)
- CRC Press(Publisher)
The extra fluid needed by the pump (P) is supplied by its left-hand inlet non-return valve, which is an integral part of the pump. When the pump control moves the pump over A V3 V2 V1 M P C F R FIGURE 1.12 Half-closed-loop circuit diagram. Fundamentals of Hydraulic Systems and Components 15 the center, the flow from the pump (P) is reversed and the cylinder (A) begins to retract. During retraction, the larger area of the cylinder piston causes a higher flow rate than needed at the inlet of the pump (P). This excess flow is directed to the reservoir (R) through the unloading valve (V3). The unloaded fluid is filtered and cooled prior to its return to the reservoir. In this way, a portion of the closed-loop fluid is filtered (by F) and cooled (by C) in an open-loop circuit each time the cylinder (A) is cycled. In this case, the fluid volume and reservoir size reductions are not as significant as in the closed-loop scenario. As can be seen in the above examples, each hydraulic component has a basic function, but it is the circuit itself that determines the hydraulic system behavior. Hence, for a designer to conceive a hydraulic system he/she needs to have an understanding of the functional and behavioral charac-teristics of the components which, in turn, are dependent on the fluid-mechanical interaction inside the component. 1.4 HYDRAULIC COMPONENTS 1.4.1 H YDROSTATIC M ACHINES : P UMPS AND M OTORS The energy conversion functions in a hydraulic system are performed by pumps and actuators (basi-cally motors and cylinders). The pumps perform the primary conversion, transforming mechani-cal energy into hydraulic energy. The actuators retransform the hydraulic energy into mechanical energy to be used by the machine or the equipment. There are two classes of hydraulic machines: hydrodynamic and hydrostatic machines. They dif-fer in the way the internal energy is transformed and, consequently, in their form of construction [1].
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