Hydraulic Power Principles of Engineering 2012 Project Lead

Hydraulic Power Principles of Engineering © 2012 Project Lead The Way, Inc.

Hydraulic Power • Hydraulic power • Hydraulics vs. pneumatics • Early hydraulic uses • Hydrodynamic systems • Hydrostatic systems • Liquid flow • Mechanical advantage • Bernoulli's principle • Viscosity • Common hydraulic system components • Emerging hydraulic application example

Hydraulic Power Hydraulics – The use of a liquid flowing under pressure to transmit power from one location to another Liquid in a hydraulic system behaves like a solid since it compresses very little

Hydraulic Power

Hydraulics vs. Pneumatics Hydraulic Systems • • • Use a relatively incompressible liquid Have a slower, smoother motion Are generally more precise Lubricate naturally Are not as clean as pneumatics when leakage occurs • Often operate at pressures of 500– 5000 psi • Generally produce more power

Early Hydraulic Uses Water Wheels • Create rotational motion • Descriptions exist as early as 1 st century BC • Several examples in ancient China • Grist mill is pictured

Early Hydraulic Uses Roman Aqueducts • Delivered water to buildings, agricultural fields, and fountains • Used gravity to create flow • Fountains were decorative and used by people to collect water for practical use

Hydrodynamic Systems • Fluid is in motion • Force and energy are transmitted by flow Water Turbine Propeller

Hydrostatic Systems • Fluid does not flow quickly or continuously • Fluid is pressurized • Force and energy transmitted by pressure • Most common in industrial settings National Fluid Power Association & Fluid Power Distributors Association

Hydrostatic Systems Pascal’s Law Pressure exerted by a confined fluid acts undiminished equally in all directions Click the arrows to activate the hydraulic press.

Liquid Flow Rate The volume of fluid that moves through a system in a given period of time Flow Velocity The distance the fluid travels through a system in a given period of time Symbol Definition Q Flow Rate v Flow Velocity A Area Example Units gpm or gal/min in. 3 / min (gallons per minute) fps or ft/s (feet per second) in. 2 in. / min

Liquid Flow Example A flow meter attached to the main line in a hydraulic system measures the flow rate at 15 gpm. The line has an inside diameter of 2 in. What is the flow velocity in the meter? Q = 15 gal/min d = 2 in. v=? Convert 15 gal/min to in. 3 /min Float 1 gal = 231 in. 3 Reprinted with permission from Introduction to Fluid Power, by James L. Johnson. Copyright © 2002 Thomson Delmar Learning.

Liquid Flow Example A flow meter attached to the main line in a hydraulic system measures the flow rate at 15 gpm. The line has an inside diameter of 2 in. What is the flow velocity in the meter? Q = 3465 in. 3/min d = 2 in. v=?

Mechanical Advantage Since F=p*A and p is equal in / out then: MA = Aout / Ain National Fluid Power Association & Fluid Power Distributors Association

Mechanical Advantage- Fluid Power • Since F=p*A and p is equal in / out then we can simplify mechanical advantage to a ratio of areas MA = Aout / Ain

Mechanical Advantage Example A force of 100. lbf is applied to the input cylinder of the hydraulic press seen below. What is the pressure in the system? How much force can the output cylinder lift? What is the mechanical advantage of the system? Fin = 100. lbf din = 4. 0 in. Fin = 100. lbf Fout = ? din = 4. 0 in. dout = 12. 0 in. Ain = ? Aout = ? p=? MA = ? dout = 12. 0 in.

Mechanical Advantage Example Find the area of each cylinder. Fin=100. lb Ain=? Fout=? Aout=? Rin=2. 0 in. p=? MA=? Rout =6. 00 in.

Mechanical Advantage Example Find the pressure in the system. Fin=100. lb Ain=12. 57 in. 2 Fout=? Rin=2. 0 in. Aout=113. 10 in. 2 Rout=6. 00 in. p=? MA=?

Mechanical Advantage Example Find the force that the output cylinder can lift. Fin=100. lb Fout=? Rin=2. 0 in. Ain=12. 57 in. 2 Aout=113. 10 in. 2 Rout =6. 00 in. p=7. 955 lb/in. 2 MA=?

Mechanical Advantage Example Find the mechanical advantage of the system. Fin=100. lb Fout=900. 28 lb Rin=2. 0 in. Ain=12. 57 in. 2 Aout=113. 10 in. 2 Rout =6. 00 in. p=7. 96 lb/in. 2 MA=?

Solve Using Areas • Area In = 12. 57 in 2 • Area Out= 110 in 2 • Ratio = 110/12. 57 – Approx 9

Bernoulli’s Principle Conservation of Energy: An increase in velocity results in a decrease in pressure. Likewise, a decrease in velocity results in an increase in pressure. Pipe Reduction drives an increase in velocity from Q=v. A…. Q remains constant

Viscosity The measure of a fluid’s thickness or resistance to flow Crucial for lubricating a system Measured in slugs/sec-ft (US) or centistokes (metric) – Hydraulic oil is usually around 1. 4 slugs/sec-ft Decreases as temperature increases

Common Hydraulic System Components Cylinder Transmission Lines Directional Control Valve Filter Pump Reservoir National Fluid Power Association & Fluid Power Distributors Association

Common Hydraulic System Components Click the lever on the valve to extend and retract the cylinder. Cylinder Valve Reservoir Pump

Image Resources Johnson, J. L. (2002). Introduction to fluid power. United States: Thomson Learning, Inc. Microsoft, Inc. (2008). Clip Art. Retrieved January 10, 2008, from http: //office. microsoft. com/en-us/clipart/default. aspx National Fluid Power Association. (2008). What is fluid power. Retrieved February 15, 2008, from http: //www. nfpa. com/Our. Industry/Our. Ind_About. FP_What. Is. Fluid. Power. asp National Fluid Power Association & Fluid Power Distributors Association. (n. d. ). Fluid power: The active partner in motion control technology. [Brochure]. Milwaukee, WI: Author.