0lec1 Pneumatics and Hydraulics Practice.pptx

0lec1 Pneumatics and Hydraulics Practice.pptx

1. Pneumatics and Hydraulics Practice DR. Sherif Al Hosary

2. Learning Outcomes 1. Explore the essential properties of the air and the hydraulic oils basic laws, Be able to apply fluid power principles in the design of circuits 2. Know the construction and operation of fluid power devices and describe and investigate the characteristics, operation and performance of fluid power components and equipment 3. Construct, setup and commission of practical applications of pneumatic and hydraulic systems. 4. Know about the legislation, regulations and safety precautions that apply when working with fluid power systems and Be able to carry out maintenance, inspection, testing and fault-finding on fluid power systems.

3. Week Contents of Lectures Contents of Sections Student Activities Resources 1 Introduction to Principles of Fluid Sheet 1 Discussion Peer to Peer Activity Group Activity Projector & Whiteboard   2   Pascale's law to determine and explore more than one operating variable of system parameters Sheet 1 Discussion Peer to Peer Activity Group Activity Projector & Whiteboard   3 fluid power symbols and Block diagram Sheet 2 Discussion Peer to Peer Activity Group Activity Projector & Whiteboard   4 fluid power symbols and describe the function and operation of a given fluid power circuit diagram   Sheet 2 Discussion Peer to Peer Activity Group Activity Projector & Whiteboard   5 Fluid power symbols and describe the function and operation of a given fluid power circuit diagram. Sheet 2 Discussion Peer to Peer Activity Group Activity Projector & Whiteboard   6 characteristics, operation and performance of fluid power   Sheet 2 Discussion Peer to Peer Activity Group Activity Projector & Whiteboard   7 Assignment1 8 circuit design of pneumatic Systems Training students on practical experiences Discussion Peer to Peer Activity Group Activity LAB (Hydralic) 9 circuit design of hydraulic Systems Training students on practical experiences Discussion Peer to Peer Activity Group Activity LAB (Hydralic)   10 electro-pneumatic or electro-hydraulic circuit for a given industrial application Training students on practical experiences Discussion Peer to Peer Activity Group Activity LAB (Hydralic) 11 electro-pneumatic or electro-hydraulic circuit for a given industrial application Training students on practical experiences Discussion Peer to Peer Activity Group Activity Projector & Whiteboard / LAB (Hydralic) 12 Safety and environmental regulations and concerns related to fluid power Identify hazards and risks Training students on practical experiences Discussion Peer to Peer Activity Group Activity LAB (Hydralic) 13 Assignment2 14 Assignment2 (Resub) 15  

4. Introduction to Hydraulics and Pneumatics Fluid power systems are widely used in manufacturing engineering. Such systems can be pneumatic systems (i.e. pressurised air or gas) or hydraulic systems (i.e. pressurised liquid), and use electrical control devices to make them work. Pneumatic systems are used to operate equipment such as automated assembly machines, packaging machines and devices used for clamping and lifting equipment. Hydraulic systems are used where greater amounts of power are required, e.g. actuators used to move arms on earth moving equipment such as excavators.

5. The Concept of a Fluid

6. Physical Properties of Fluids Density  Specific Weight Relative density Viscosity

7. Density The density of a substance is defined as its mass per unit volume. In other words, it is the number of kilograms that go to make up a cubic metre of a substance. It is denoted by the Greek letter (rho) and its units are kilograms per cubic metre (kgm3). If you know the mass m(kg) of a liquid or a gas and the volume V(m3) in which it is contained, its density can be calculated using the following Formula

8. Specific weight This is closely related to density. It is defined as the weight per cubic metre of a substance and is usually denoted by the symbol (w). Weight (w) is of course the mass multiplied by g, the acceleration due to gravity. Specific weight is given by the formula

9. Relative density The relative density of a substance is the ratio of its density to the density of water. Sometimes, it is also called specific gravity and since it is a ratio, it does not have any unit. You will note from Table 1.1 that the density of water is 1000 kgm-3.

10. Relative density Table 1.1

11. Example 1.1 The cylindrical fuel tank on a lorry is 0.5m in diameter and 1.5m in length. What will be the weight of fuel contained when it is full? The relative density of diesel oil is 0.86. Finding volume of tank:

12. Example 1.1

13. VISCOSITY Viscosity is a consequence of COHESIVE forces in a liquid and to a lesser extent in gases. On its own, it would not be important but when the fluid is in contact with a solid surface we get ADHESION . This makes the fluid stick to the surface. This could be a good thing if we want it to stick to the surface e.g. for protection or to reduce friction by LUBRICATING the surfaces.

14. VISCOSITY LUBRICATION BETWEEN TWO SURFACES

15. VISCOSITY In the following we will only consider the case where a liquid wets the surface. We will derive equations for the forces needed to make a fluid flow and provide a definition for viscosity. The diagram illustrates molecules flowing over a surface. The molecules in contact with the surface stick to it and do not move. The molecules above are pulled back by the forces of attraction but we find that the further you move from the surface, the faster the molecules move.

16. Newtonian Fluids

17. KINEMATIC VISCOSITY ν

18. EXAMPLE 1. 2 A sample of oil has a dynamic viscosity of 15 cP. At a certain point in the fluid the velocity gradient is 0.05 s-1. Calculate the shear stress between the layers at this point.

19. NON-NEWTONIAN FLUIDS

20. Newtonian & Non Newtonian Fluids

21. Newtonian & Non Newtonian Fluids

22. Effect of temperature on viscosity For Gases: In gases momentum exchange is dominant. Therefore, if the temperature of gases is increases, its momentum exchange will increase and hence viscosity will increase For Liquids: In case of liquids, cohesion (molecular attraction is dominant). Therefore, if the temperature of liquid is increased, its cohesion and hence viscosity will decrease.

23. Effect of temperature on viscosity