* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Design of Hydraulic System - A Review
Survey
Document related concepts
Coandă effect wikipedia , lookup
Flow conditioning wikipedia , lookup
Compressible flow wikipedia , lookup
Navier–Stokes equations wikipedia , lookup
Computational fluid dynamics wikipedia , lookup
Flow measurement wikipedia , lookup
Derivation of the Navier–Stokes equations wikipedia , lookup
Fluid thread breakup wikipedia , lookup
Aerodynamics wikipedia , lookup
Vacuum pump wikipedia , lookup
Hydraulic cylinder wikipedia , lookup
Reynolds number wikipedia , lookup
Hydraulic jumps in rectangular channels wikipedia , lookup
Bernoulli's principle wikipedia , lookup
Fluid dynamics wikipedia , lookup
Transcript
International Journal of Trend in Research and Development, Volume 2(5), ISSN 2394-9333 www.ijtrd.com Design of Hydraulic System - A Review 1 Mr.S.R.Jadhav, 2Mr.Y.P.Ballal and 3Mr. A.R. Mane 1 UG student, 2Asst.Professor, 3Asst.Professor, Department of Mechanical Engineering, Annasaheb Dange College of Engineering & Technology, Ashta, Maharashtra, India. Abstract - Hydraulic components are manufactured to provide the control function required for the operation of a wide range of system and application. This review on hydraulic system design gives an understanding of basic types of hydraulic components, their operational principle and estimation of their performance in various applications. The analytical methods that are used helps to designing the hydraulic components like reservoir, pump, motor, cylinder (actuator), control valves. Keywords- Fluid, Reservoir, Filters, Pumps, Motor, Cylinder, Control Valve. I. INTRODUCTION In the industry we use three methods for transmitting power from one point to another. Mechanical transmission is through shafts, gears, chains, belts, etc. Electrical transmission is through wires, transformers, etc. Hydraulic transmission is through liquids or gas in a confined space. Hydraulics is a type of science and engineering that deals with mechanical properties of liquids and gases. Hydraulics is part of the more general discipline of fluid power. Fluid mechanics provides the foundation for hydraulics, which focuses on engineering uses of fluid and gas properties. Hydraulics means study of water or other fluids at rest or in motion, especially with respect to engineering application. Hydraulics and hydraulic systems can be found almost everywhere. Hydraulics can be found at any construction site. Some machines that use hydraulics are bulldozers, fork lift, and cranes. Hydraulics are used to lift cars so mechanics can work underneath them. Many elevators use the same operating technique. Hydraulics is the science of transmitting force and/or motion through the medium of a confined liquid. In a hydraulic device, power is transmitted by pushing on a confined liquid. The transfer of energy takes place because a quantity of liquid is subject to pressure. To operate liquid-powered systems, the operator should IJTRD | Sep - Oct 2015 Available [email protected] have a knowledge of the basic nature of liquids. This chapter covers the properties of liquids and how they act under different conditions. II. HYDRAULIC PRINCIPLE The basic idea behind any hydraulic system is very simple: force applied at one point is transmitted to another point using and incompressible fluid, which is almost always going to be a type of oil. In some systems, such as brake systems in a car, multiply the process. A major part of hydraulics is Pascal’s principle: Pascal’s principle - the change in pressure on one part of a confined fluid is equal to the change in pressure on any other part of the confined fluid. Following fig. shows the principle of hydraulic. Fig 1: Pascal’s Principle III. COMPONENTS IN HYDRAULIC SYSTEM A hydraulic system consists of a many components for operating the system. Hydraulic systems are power-transmitting assemblies employing pressurized liquid as a fluid for transmitting energy from an energygenerating source to an energy-using point to accomplish useful work. Figure 2 shows a simple circuit of a hydraulic system with basic components. A hydraulic system consist of fluid for system reservoir, filter, pump, motor, pressure regulator, direction control valve, cylinder (actuator), gripper these main parameters. [1] 356 International Journal of Trend in Research and Development, Volume 2(5), ISSN 2394-9333 www.ijtrd.com reservoirs. Compare the two reservoirs item by item and, except for the filters and bypass valve, notice the similarities. Fig 2 Components in Hydraulic System A .FluidHydraulic fluid is the medium of power transfer in hydraulic equipment, it is important to know the properties of hydraulic fluids and its influence on system performance. There are different types of fluids based on their availability, working purpose etc. A hydraulic the fluid is transmitting medium of a hydraulic system. It is, therefore, an essential part of the system and we must know enough about it to ensure that the hydraulic system works efficiently. The most common liquid that is used as a medium in fluid power systems is petroleum-based mineral oil. [7] In order to the suitable for the demand of heat dissipation and air separation, the oil reservoir must be designed be as large as possible. Primarily size of reservoir is decided by the pump delivery flow. By an imperial rule these are taken as Where V=Reservoir size in liter. Factors Influencing the Selection of a Fluid The selection of a hydraulic fluid for a given system is governed by the following factors: 1. Operating pressure of the system. 2. Operating temperature of the system and its variation. 3. Material of the system and its compatibility with oil used 4. Speed of operation. 5. Availability of replacement fluid. 6. Cost of transmission lines. 7. Contamination possibilities. 8. Environmental condition (fire proneness, extreme atmosphere like in mining, etc.). 9. Lubricity. 10. Safety to operator. 11. Expected service life. [7] B. RESERVIORThe hydraulic reservoir is a container for holding the fluid required to supply the system, including areserve to cover any losses from minor leakage and evaporation. The reservoir can be designed to provide space for fluid expansion, permit air entrained in the fluid to escape, and to help cool the fluid. Fig. No. 3 shows two typical IJTRD | Sep - Oct 2015 Available [email protected] Fig 3. Cut Section of Reservoir V=3.5 for stationery installation V=1*Q………….For mobile installation Q=Pump delivery flow in liter per minute. C. FILTERSContamination of hydraulic fluid is one of the common causes of hydraulic system troubles. Installing filter units in the pressure and return lines of a hydraulic system allows contamination to be removed from the fluid before it reaches the various operating components. Filters of this type are referred to as line filters. Filtering Material and Elements: The general classes of filter materials are mechanical absorbent, inactive and absorbent active. 1. Mechanical filters contain closely woven metal screens or discs. They generally remove only fairly coarse particles. 2. Absorbent inactive filters, such as cotton, wood pulp, yarn, cloth, or resin, remove much smaller particles; some remove water and water-soluble contaminants. The elements often are treated to make them sticky to attract the contaminants found in hydraulic oil. 3. Absorbent active materials, such as charcoal and Fuller's Earth (a claylike material of very fine 357 International Journal of Trend in Research and Development, Volume 2(5), ISSN 2394-9333 www.ijtrd.com particles used in the purification of mineral or vegetablebase oils), are not recommended for hydraulic systems. [1] Let, D= Outside diameter of gear teeth in mm. d= Inside diameter of gear teeth in mm. D. PUMPA hydraulic pump is a heart of hydraulic system. Its function is to convert mechanical energy into hydraulic energy by pushing the hydraulic fluid into the system. Hydraulic pumps convert mechanical energy from a prime mover (engine or electric motor) into hydraulic (pressure) energy. The pressure energy is used then to operate an actuator .Pumps push on a hydraulic fluid and create flow. L= Width of gear teeth in mm. N= Speed of pump in rpm. V= Displacement of pump in m/rev M= Module of gear. z= Number of teeth. Volume Displacement, Gear pumpA fixed positive displacement external gear pump has been selected in this system with maximum flow rate of 36 lit./min and volume displacement of24 cm3/rev. Technical data of this pump is summarized in Table No. 1 Table No.1Technical Data of Hydraulic Pump Sr. No. 1 2 3 4 Name of Component Maximum flow rate at speed 1500 rpm Displacement Continuous maximum pressure Maximum Speed Specification V=π/4(𝐷 2 − 𝑑2 )L Theoretical discharge, Q= V*N If the gear is specified by it’s module and number of teeth, then the theoretical discharge can be found by Q= 2 πL𝑚2 N[z+(1+(π2 𝑐𝑜𝑠 2 α/12 ) )] 36 lit/min 24 cm3/rev 220 bar 3000 rpm Selection of pump can be based on following points: a) Safe and maximum system working pressure b) Allowable pump speeds c) System flow requirement d) Leakage loss e) Drive type and mounting f) Hydraulic oil characteristics g) Heat, noise and vibration generation h) Power-to-weight ratio i) Initial and running cost Following steps can be adopted while selecting hydraulic pump: Fig. No. 4 External Gear Pump a) b) c) d) Select the actuator and its size Select the system operating pressure Determine the pump speed Select the pump type [4] Design of External Gear Pump: The flow rate of an external gear pump is depends on the volume displacement and theoretical discharge. The flow rate of an external gear pump can be calculated as follows: IJTRD | Sep - Oct 2015 Available [email protected] E. MOTORHydraulic motors are installed in hydraulic systems to use hydraulic pressure in obtaining powered rotation. A hydraulic motor does just the opposite of what a power-driven pump does. A pump receives relative force from an engine or other driving unit and converts it 358 International Journal of Trend in Research and Development, Volume 2(5), ISSN 2394-9333 www.ijtrd.com into hydraulic pressure. A hydraulic motor receives hydraulic fluid pressure and converts it into relative force. Fig No. 6 Hydraulic Cylinder Fig. No.5 Hydraulic Motor Selection of motor depends on following factorTheoretical Torque, Power, and Flow rate DESIGN OF CYLINDER- For designing the hydraulic cylinder following parameters are to be consider 1. Force 2. Piston rod velocity 3. Power developed during extension and retraction stroke Theoretical TorqueThe torque generated by a frictional hydraulic motor is known as theoretical torque. Theoretical Torque (T) T= (p*V)/2π P = Pressure in N/m^2 V = Volumetric displacement in m^3/rev PowerThe power generated by a frictional hydraulic motor is known as theoretical power. Power P =T*ω ω = Seed of motor in rad/sec Flow RateThe flow rate hydraulic motor would consume if there were no leakage is known as theoretical flow rate. Flow Rate Q= V * n n = speed of motor in rev/s [7] F. CYLINDER (ACTUATOR)A basic actuating cylinder consists of cylinder housing, one or more pistons and piston rods, and one or more seals. The cylinder housing contains a polished bore in which the piston operates and one or more ports through which fluid enters and leaves the bore. IJTRD | Sep - Oct 2015 Available [email protected] Force and velocity during extension Velocity v = Q/A Q= Flow rate of fluid A= Circular piston area Force F = p * A p = Pressure in N/m^2 Force and velocity during extension Velocity v = Q/(A-a) Q= Flow rate of fluid A= Circular piston area a = Area of piston rod Force F = p * (A - a) Power developed during extension and retraction P=p*Q p = pressure in N/m^2 Q= Flow rate in [7] G. CONTROL VALVESValves are used in hydraulic systems to control the operation of the actuators. Valves regulate pressure by creating special pressure conditions and by controlling how much oil will flow in portions of a circuit and where it will go. The three categories of hydraulic valves are pressure-control, flow- (volume-) control, and directionalcontrol valves have multiple functions, placing them into more than one category. Valves are rated by their size, pressure capabilities, and pressure drop per flow. Pressure Control ValveA pressure-control valve may limit or regulate pressure, create a particular pressure condition required 359 International Journal of Trend in Research and Development, Volume 2(5), ISSN 2394-9333 www.ijtrd.com for control, or cause actuators to operate in a specific order. All pure pressure-control valves operate in a condition approaching hydraulic balance. Usually the balance is very simple: pressure is effective on one side or end of a ball, poppet, or spool and is opposed by a spring. In operation, a valve takes a position where hydraulic pressure balances a spring force. Directional Control ValveA DCV is mainly required for the following purposes: 1.To start, stop, accelerate, decelerate and change the direction of motion of a hydraulic actuator. 2, To permit the free flow from the pump to the reservoir at low pressure when the pump’s delivery is not needed into the system. 3. To vent the relief valve by either electrical or mechanical control. 4. To isolate certain branch of a circuit. [7] [3] En Li, Zize Liang; “Design of hydraulic cylinder pressure based”; March 2011 [4] X. S. Li; “Research on variable pump based system” ; June 2012 [5]. N. Harris, McClaroch; “A end effector of an electro hydraulically controlled robot; Oct 1984 [6]. S. A. Ahmed, A. J. Ishak; “Design of Gripper” ; Dec 2012. [7]. “Fluid Power Generation Transmission and Control”; Jagadeesha T., Thammaiah Gowda; 2013; page no. 42 to 287. Flow Control ValveFlow control valve achieve their primary function of regulating the fluid flow by varying the area of an orifice. Flow through control orifice is usually considered to be turbulent and the quantity of the fluid flowing given by, q =KA ∆𝑝 Where q =Flow rate through the valve A=Orifice area ∆𝑝 =Pressure drop across the orifice CONCLUSION Studying the various components used in hydraulic system it helps to know the selection of proper component used for any hydraulic system. In this study a co-relation and co-ordination of different types of hydraulic fluid, filter, reservoir, pump, motor, cylinders, valves, power pack, end effectors is help to design of hydraulic system. References [1] D. J. Dunn; “Basic hydraulic system and component”; September 1994 [2] Chen Huanming; “Research on features of hydraulic oil for hydraulic pump”: June 2012 IJTRD | Sep - Oct 2015 Available [email protected] 360