Pneumatic Power Principles of Engineering 2012 Project Lead The Way, Inc. Pneumatic Power Pneumatic power Pneumatics vs. hydraulics Early pneumatic uses Properties of gases Pascals Law Perfect gas laws Boyles Law
Charles Law Gay-Lussacs Law Common pneumatic system components Compressor types Future pneumatic possibilities Pneumatic Power Pneumatics The use of a gas flowing under pressure to transmit power from one location to another Gas in a pneumatic system behaves like a spring since it is compressible.
Pneumatics vs. Hydraulics Pneumatic Systems . . . Use a compressible gas Possess a quicker, jumpier motion Are not as precise Require a lubricant Are generally cleaner Often operate at pressures around 100 psi Generally produce less power Early Pneumatic Uses Bellows Tool used by blacksmiths and smelters for working iron and
other metals Early Pneumatic Uses Otto von Guericke Showed that a vacuum can be created Created hemispheres held together by atmospheric pressure Early Pneumatic Uses Americas First Subway Designed by Alfred
Beach Built in New York City Completed in 1870 312 feet long, 8 feet in diameter Closed in 1873 Properties of Gases Gases are affected by 3 variables Temperature (T) Pressure (p) Volume (V) Gases have no definite volume Gases are highly compressible Gases are lighter than liquids
Properties of Gases Absolute Pressure Gauge Pressure: Pressure on a gauge does not account for atmospheric pressure on all sides of the system Absolute Pressure: Atmospheric pressure plus gauge pressure Gauge Pressure + Atmospheric Pressure = Absolute Pressure Properties of Gases Absolute Pressure Pressure (p) is measured in pounds per square inch (lb/in.2 or psi) Standard atmospheric pressure equals 14.7 lb/in. 2 If a gauge reads 120.0 psi, what is the absolute
pressure? 120.0 lb/in.2 + 14.7 lb/in.2 = 134.7 lb/in.2 Properties of Gases Absolute Temperature 0F does not represent a true 0 Absolute Zero = -460.F Absolute Temperature is measured in degrees Rankine (R) R = F + 460. If the temperature of the air in a system is 65 F, what is the absolute temperature? Answer: 65 F + 460. = 525 R
Pascals Law Pressure exerted by a confined fluid acts undiminished equally in all directions. Pressure: The force per unit area exerted by a fluid against a surface F p A Symbol Definition Example Unit
p Pressure lb/in.2 F Force lb A Area
in.2 Pascals Law Example How much pressure can be produced with a 3.00 in. diameter (d) cylinder and 60.0 lb of force (F)? d = 3.00 in. p = ? F = 60.0 lb A = ? Formula Formula Sub / Solve
Sub / Solve * Sub / Solve *Note: This intermediate value has been rounded. The full stored value in your calculator should be utilized when Perfect Gas Laws The perfect gas laws describe the behavior of pneumatic systems Boyles Law Charles Law Gay-Lussacs Law
Boyles Law The volume of a gas at constant temperature varies inversely with the pressure exerted on it. p1 (V1) = p2 (V2) NASA Symbol Definition Example Unit
V Volume in.3 Boyles Law Example A cylinder is filled with 40. in.3 of air at a pressure of 60. psi. The cylinder is compressed to 10. in.3. What is the resulting absolute pressure? p1 = 60. lb/in.2 V1 = 40. in.3 p2 = ? V2 = 10. in.3 Convert p1 to absolute pressure. p1 = 60. lb/in.2 + 14.7 lb/in.2 = 74.7 lb/in.2
Formula p(1 V1 ) p2( V2 ) lb Sub / Solve 74.7 2( 40.in.3 ) p2( 10.in.3 ) in. 2988 in. lb p2 32 10.in. Final p2 3.0 102 lb
in2 Charles Law Volume of gas increases or decreases as the temperature increases or decreases, provided the amount of gas and pressure remain constant. V1 V2 T1 T2 Note: T1 and T2 refer to
absolute temperature. NASA Charles' Law Example An expandable container is filled with 28 in.3 of air and is sitting in ice water that is 32F. The container is removed from the icy water and is heated to 200.F. What is the resulting volume? V1 = 28in.3 V2 = ? T1 = 32F
T2 = 200.F Convert T to absolute temperature. T1 = 32F + 460.F =492R T2 = 200.F + 460.F =660R Charles' Law Example An expandable container is filled with 28 in.3 of air V1 V2 and is sitting in ice water Formula T1 T2 that is 32F. The container is removed from the icy 3
V2 28 in. water and is heated to Sub / Solve 492 R 660. R 200F. What is the 3 18480 in R resulting volume? V V1 = 28in.3
492 R V2 = ? T1 = 32F T2 = 200.F Convert T to absolute temperature T1 = 32F + 460.F = 492R T = 200F + 460.F = 660R Final V2 38 in.3 2
Gay-Lussacs Law Absolute pressure of a gas increases or decreases as the temperature increases or decreases, provided the amount of gas and the volume remain constant. p1 p2 T1 T2 Note: T1 and T2 refer to absolute temperature. p1 and p2 refer to absolute pressure.
Gay-Lussacs Law Example A 300. in.3 sealed air tank is sitting outside. In the morning the temperature inside the tank is 62F, and the pressure gauge reads 120. lb/in.2. By afternoon the temperature inside the tank is expected to be close to 90.F. What will the absolute pressure be at that point? V = 300. in.3 T1 = 62F p1 = 120. lb/in.2 T2 = 90.F p2 = ? Formula p1 p2 T1 T2
p2 134.7lb / in.2 Sub / Solve 522 R 550. R Convert p to absolute pressure. 2 74085 lb / in R 2 2
p1= 120. lb/in. + 14.7 lb/in. p2 522 R = 134.7 lb/in.2 Convert T to absolute temperature. T1 = 62F + 460.F = 522R Final p2 140 lb / in.2 Gay-Lussacs Law Example A 300 in.3 sealed air tank is sitting outside. In the morning the temperature inside the tank is 62F, and the pressure gauge reads 120 lb/in2. By afternoon the temperature inside
the tank is expected to be closer to 90F. What will the absolute pressure be at that point? Final p2 141.9 lb / in.2 If the absolute pressure is 141.9 lb/in.2, what is the pressure reading at the gauge? 141.9 lb/in.2 14.7 lb/in.2 = 127.2 lb/in.2 = 130 lb/in.2 Common Pneumatic System Components Transmission Lines
Regulator Filter Drain Receiver Tank Directional Control Valve Cylinder Pressure Relief Valve Compressor
National Fluid Power Association & Fluid Power Distributors Association Compressor Types Compair Reciprocating Piston Compressor Compressor Types Compair Rotary Screw Compressor Compressor Types
Compair Rotary Vane Future Pneumatic Possibilities What possibilities may be on the horizon for pneumatic power? Could it be human transport? zapatopi.net Image Resources Compair. (2008). Compressed air explained: The three types of compressors. Retrieved March 5, 2008, from http://www.compair.com/About_Us/Compressed_Air Explained-03The_three_types_of_compressors.aspx 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 Aeronautics and Space Administration. (2008). Boyles law. Retrieved February 3, 2008, from http://www.grc.nasa.gov/ National Fluid Power Association. (2008). What is fluid power. Retrieved February 15, 2008, from http://www.nfpa.com/OurIndustry/OurInd_AboutFP WhatIsFluidPower.asp National Fluid Power Association & Fluid Power Distributors Association. (n.d.). Fluid power: The active partner in motion control technology. [Brochure]. Milwaukee, WI: Author. Zapato, L. (n.d.) The inteli-tube pneumatic transportation system. Retrieved February 29, 2008, from http://zapatopi.net/inteli-tube/
