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Air compressor
- 1. Air Compressor Active LearningAssessment Elements of Mechanical Engineering(2110006) Semester:1 Made by: Burhanuddin Kapadia Enrollment Number: 170120119026/201719000028 Class: ME H2 Submitted to: Prof. Shubham Sarthi GANDHINAGAR INSTITUTE OF TECHNOLOGY Approved by AICTE and Affiliated to GTU Khatraj - Kalol Road, Vil. MotiBhoyan, Tal.Kalol, Dist. Gandhinagar-382721
- 2. Outline • Introduction • Classification •Reciprocating Compressor i. Single acting • Working i. Compression without clearance ii. Compression with clearance • Power Required • Reciprocating Compressor efficiency • Multi stage reciprocating compressor • Advantages of multi stage reciprocating compressor • Rotary Compressor • Application/Uses • Reference
- 3. Introduction • The machinewhich takes in air at low pressure and compresses it to high pressure with the help of some suitable arrangement are called air compressors. • According to 2nd law of thermodynamics it is only possible when work is done on the system. • Generally, the compressors are driven by electric motors, I.C engine or gas turbine. • A compressor which is used for increasing the pressure of air is called as air compressor.
- 4. Delivery Pressure Methods of compression Pressure Limits Number Of Cylinders VolumeOf air Delivered Fluid to be Compressed Reciprocating Rotary Centrifugal Low Pressure (up to 1.1 bar) Medium Pressure (1.1 – 8 bar) High Pressure (8-10 bar) Very High Pressure (above 10 bar) Positive DisplacementRotodynamic Single Stage (up to 5 bar) Multi Stage ( above 5 bar) Single Multi Fans (1-1.1) Blower ( 1.1-2.5) Compressor ( <2.5) Low Capacity (10 m³/min) Medium Capacity (10 m³/min-300 m³/min) High Capacity (<300 m³/min) Air Gas Vapour • Classification
- 5. Reciprocating Compressor • isa positive-displacement compressor that uses pistons driven by a crankshaft to deliver gases at high pressure. • sizes up to 25 hp. • used for light-duty applications • Has low mass flow rate (kg/s) and high pressure ratio • Applications include oil refineries, gas pipelines, chemical plants, natural gas processing plants and refrigeration plants. Reciprocating Single Cylinder Double Cylinder Single Acting Double Acting
- 6. Piston moves Down Pressure Falls Inlet valve opens Piston moves up Pressure rises Air delivered to container Someair is left in clearance space Fresh Air is sucked from atm Suction stroke Air gets sucked Delivery stroke End of deliver stroke Due to pressure difference Discharge valve opens Suction stroke Repeats the cycle again Reciprocating Single acting compressor
- 7. Working • Generally, anair compressor takes in air at atm, compresses at high pressure then deliver it to storage tank. • From storage tank to gets supplied to different uses through pipe. • Going technical, working for compression is based on two types :- a) Compression without clearance b) Compression with clearance
- 8. Compression without clearance •Consider a single stage reciprocating air compressor without clearance volume delivering air from one side of the piston only. • Let, P1 = Initial pressure of air V1 = Initial volume of air T1 = Initial temperature of air P2, V 2, T2 = Corresponding values for the final r = Pressure ratio (i.e. P 2 / P 1) • Hence the net work done, during adiabatic process will be: swept volume A)𝑊 = 𝛾 γ−1 𝑝1𝑉1 𝑝2 𝑝1 𝛾−1 𝛾 − 1 Isothermal 𝑝𝑉 = 𝐶 adiabatic 𝑝𝑉 𝛾 = 𝐶 Polytrophic 𝑝𝑉 𝑛 = 𝐶 1 p p2 p1 V 4 22’2”3 V1
- 9. Compression without clearance B)Work done if compression is polytrophic, Replacing𝛾 = 𝑛, 𝑊 = 𝑛 𝑛 − 1 𝑝1𝑉1 𝑝2 𝑝1 𝑛−1 𝑛 − 1 C) If compression is isothermal, 𝑊 = 𝑝1𝑉1 log 𝑒 𝑝2 𝑝1 = 𝑝2𝑉2 log 𝑒 𝑝2 𝑝1 = 𝑝𝑉 log 𝑒( 𝑝2 𝑝1 )
- 10. Compression with clearance •Consider a single stage reciprocating air compressor with clearance volume delivering air from one side of the piston only. • Let, P1 = Suction pressure V1 = Initial volume of air T1 = Initial temperature of air P2,V 2, T2 = Delivery change in valve r = Pressure ratio (i.e. P 2 / P 1) P1=P4 & P2=P3 • Work done during adiabatic cycle :- 𝑊 = 𝑛 𝑛 − 1 𝑝1 𝑉1 − 𝑉4 𝑝2 𝑝1 𝑛−1 𝑛 − 1 J cycle Can also be written as 𝑊 = 𝑛 𝑛−1 𝑚𝑎𝑑 𝑅𝑇1 𝑝2 𝑝1 𝑛−1 𝑛 − 1 J cycle
- 11. Power Required • Powerrequired to compress air is called indicated power(IP) ∴ 𝑰𝑷 = (𝑾𝒐𝒓𝒌 𝒅𝒐𝒏𝒆)/𝒎𝒊𝒏 𝟔𝟎∗𝟏𝟎𝟎𝟎 𝒌𝑾 or ∴ 𝑰𝑷 = 𝑷𝒎𝑳𝑨𝒏 𝟔𝟎𝟎𝟎𝟎 𝒌𝑾 • Power required to drive the compressor is called brake power(BP) ∴ 𝑩𝑷 = 𝟐𝝅𝑵𝑻 𝟔𝟎𝟎𝟎𝟎 (BP>IP) • Mean effective pressure of compressor (𝑃𝑚) ∴ 𝑷𝒎 = 𝒏 𝒏 − 𝟏 𝒑𝟏 𝑽𝟏 − 𝑽𝟒 ∗ 𝒑𝟐 𝒑𝟏 𝒏−𝟏 𝒏 − 𝟏
- 12. Reciprocating compressor efficiency •The ratio of indicated power to brake power gives mechanical efficiency 𝜂 𝑚 = 𝐼𝑃 𝐵𝑃 • The ratio of isothermal work to indicated work gives isothermal efficiency 𝜂𝑖𝑠𝑜 = 𝑝1𝑉1log 𝑒( 𝑝2 𝑝1 ) 𝑛 𝑛 − 1 𝑝1𝑉1 𝑝2 𝑝1 𝑛−1 𝑛 − 1 • The ratio of swept effective volume to swept volume of cylinder is called volumetric efficiency 𝜂 𝑣 = 1 − 𝐶 𝑝2 𝑝1 1 𝑛 − 1
- 13. Multistage Reciprocating Compressor •High delivery pressure=high temperature, leads to more volume of air • Temperature increases reduces the density of air hence mass flow decreases • High temperature will need heavy working parts hence more cost and less work • To overcome this problems of single stage , multistage cylinder came into use • Multi-stage compressors feature a series of cylinders, each of a different diameter. • In a two-stage compressor, air is forced into chamber where it is pressurized to the required extent. • In a three-stage compressor, an cycle of compression and cooling occurs before this.
- 14. Multistage Reciprocating Compressor •An intercooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged. • When air is compressed, its temperature increases. • Between each compression stage, the air passes through a heat exchanger, where it is cooled.
- 15. Advantages of multistageCompressor • By intercooling , more work done in less input • Volumetric efficiency is increased • Less working temperature , hence better fuel consumptions • Better mechanical balance and smoother torque angle is obtained
- 16. Rotary Compressor • Arotary-screw compressor is positive-displacement mechanism. • Air enters a sealed chamber where it is trapped between two contra-rotating rotors. • they reduce the volume of trapped air and deliver it compressed to the proper pressure level. • high mass rate but low pressure ratio.
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- 18. Rotary Compressor • Positivedisplacement compressors draw in and capture a volume of air in a chamber, then reduce the volume of the chamber to compress the air. • Axial compressors use a series of turbine blades, similar in appearance to a jet engine, to force air into a smaller and smaller area. • Centrifugal compressors are often used in sizes ranging from about 150 hp up to over 10,000 hp. • Rotary screw compressors in sizes from small (in cars) up to 500-600 hp are very popular because of their high reliability and low maintenance requirements. • Centrifugal compressors draw in air to the center of an impeller, and then accelerate it outward toward its perimeter. • Centrifugal compressors used for manufacturing are water-cooled and use two or three stages of compression
- 19. Applications • Small &medium size business • Industrial use • Agricultural/Farming • Manufacturing • Dry cleaning • Pharmaceuticals • Food/Beverages • Commercial use
- 20. Uses • Manufacturing ofacids& chemicals • Food processing • Spraying paints & insecticides • Construction • Operating air brakes • Operating elevators& also in doors • Glass blowing
- 21. Reference • https://en.wikipedia.org/wiki/Air_compressor • http://www.popularmechanics.com/home/how-to/a151/how-air-compressors- work/ •Basic of Mechanical Engineering – Pravin Kumar • http://www.tpub.com/fireman/102.htm • http://www.brighthubengineering.com/hvac/64884-different-types-of-air- compressors/ • Elements Of Mechanical Engineering - Dr. N.M Bhatt • https://www.quincycompressor.com/products/2-and-3-stage-air-compressors/ • https://www.google.co.in/search?q=application+of+an+air+compressor&source=l nms&tbm=isch&sa=X&ved=0ahUKEwil9IaXtLfXAhWBOo8KHTJhDiEQ_AUICygC&bi w=1366&bih=651
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