Internal Combustion Engines

Transcription

1 Lecture-27 Prepared under QIP-CD Cell Project Internal Combustion Engines Ujjwal K Saha, Ph.D. Department of Mechanical Engineering Indian Institute of Technology Guwahati 1

2 What Causes Air Pollution Today? Stationary Sources Combustion of fuels for power and heat Other burning such as incineration or forest fires Industrial/commercial processes Solvents and aerosols Mobile Sources Highway vehicles: cars, trucks, buses and motorcycles Off-highway vehicles such as aircraft, boats, locomotives, farm equipment, construction machinery & lawn mowers 2

3 Primary Types of Air Pollutants Carbon Monoxide (CO) Volatile Organic Compounds (VOCs) Oxides of Nitrogen (NOx) Sulfur Dioxide (SO2) Particulate Matter (PM10) Lead (Pb) 3

4 Carbon Monoxide (CO) Odorless, colorless gas Caused by incomplete combustion of fuel and air Most of it comes from motor vehicles Reduces the transport of oxygen through the blood stream Affects mental functions and visual acuity, even at low levels Improvements are being made but there are still problems in some urban areas 4

5 Volatile Organic Compounds (VOCs) 1. General term for a wide range of hydrocarbon compounds 2. VOCs result from combustion processes and evaporation of gasoline vapors, solvents, etc. 3. They contribute to Global Warming 4. In sunlight, they combine with NOx to form ozone (smog) 5. Ozone irritates eyes, aggravates respiratory ills, damages crops 6. The ozone problem is the one affecting the most people today 5

6 Oxides of Nitrogen (NOx) Nitrogen dioxide is the prominent one (it's the yellow-brown color in smog) NOx results from high temperature combustion processes, e.g. cars and utilities They affect the respiratory system They play a major role in atmospheric reactions Overall levels unchanged but transportation sources are cleaner 6

7 Lead (Pb) Long known as one of the worst toxics in common use Emitted from gasoline additives, battery factories and non-ferrous smelters Affects various organs and can cause sterility and neurological impairment, e.g. retardation and behavioral disorders Infants and children especially susceptible Control of mobile sources has been exceptionally successful 7

8 Particulate Matter (PM10) PM10 is a general term for tiny airborne particles (under ten microns), e.g., dust, soot, smoke Primary sources are fuel-burning plants and other industrial/ commercial processes Some are formed in the air They irritate the respiratory system and may also carry metals, sulfates, nitrates, etc. Some overall decreases seen but trends may be masked by meteorological changes 8

9 Sulfur Dioxide (SO2) This term is used for a number of compounds containing sulfur Primarily caused by burning of coal, oil and various industrial processes They can affect the respiratory system They react in the atmosphere to form acids, sulfates and sulfites Substantial reductions due to controls at the sources and through use of low sulfur fuels 9

10 Other Air Pollutants Carbon dioxide Chlorofluorocarbons Formaldehyde Benzene Asbestos Manganese Dioxins Cadmium Still others which are yet to be fully characterized 10

11 Global Warming Certain gases in the troposphere absorb some of the infrared radiation reflected from the earth Carbon Dioxide is the major one (50%). Others include methane (18%) and CFCs (14%). CFCs also are responsible for destroying the stratospheric ozone layer The United States produces over 20% of the world's "greenhouse" gases 11

12 The Combustion Process (theoretical) Gasoline Air C H + 10 O + 39 N Energy!! 7 CO H O + 39N Carbon Water Dioxide (Steam) Nitrogen 12

13 The Combustion Process (actual) Today's Air Real Fuel Exhaust: Nitrogen Water (steam) Carbon Dioxide Pollutants Pollutants: Unburned Hydrocarbons Carbon Monoxide Oxides of Nitrogen Other elements or compounds 13

14 Other Emissions from Motor Vehicles Refueling Losses (displaced vapors) Evaporative Emissions (diurnal, running losses, hot soak) Miscellaneous Emissions (due to other evaporation and wear of brakes, tires, etc.) Crankcase Losses (due to "blowby") 14

15 The Motor Vehicle as a Source of Air Pollution Refueling Losses Evaporative Emissions Exhaust Emissions Crankcase Losses, etc. 15

16 How Emissions are Formed In the engine - incomplete combustion -"wall quench" - high pressure and temp -"Blowby" Due to evaporation of fuel -"breathing" - hot engine and fuel - displacement of vapors 16

17 The Effect of Air-Fuel Ratio Higher Fuel Economy NOx HC Lower Rich (too much fuel) CO Stoichiometric (14.7 to 1) Lean (too much air) 17

18 Typical Emission Control Devices Positive Crankcase Ventilation (PCV) Valve Air Pump Evaporative Emissions Canister Exhaust Gas Recirculation (EGR) Valve Catalytic Converter 18

19 Efficiency of the Three-way Catalyst 100% 90% 80% 50% The "Window" HC NOx CO 0% Rich (too much fuel) Stoichiometric (14.7 to 1) Lean (too much air) 19

20 Catalytic Converter A catalytic converter is a device that uses a catalyst to convert three harmful compounds in car exhaust into harmless compounds. The three harmful compounds are: Hydrocarbons (in the form of unburned gasoline) Carbon monoxide (formed by the combustion of gasoline) Nitrogen oxides (created when the heat in the engine forces nitrogen in the air to combine with oxygen) 20

21 Catalytic Converter In a catalytic converter, the catalyst (in the form of platinum and palladium) is coated onto a ceramic honeycomb or ceramic beads that are housed in a mufflerlike package attached to the exhaust pipe. The catalyst helps to convert carbon monoxide into carbon dioxide. It converts the hydrocarbons into carbon dioxide and water. It also converts the nitrogen oxides back into nitrogen and oxygen. 21

22 Catalytic Converter 22

23 References 1. Crouse WH, and Anglin DL, (1985), Automotive Engines, Tata McGraw Hill. 2. Eastop TD, and McConkey A, (1993), Applied Thermodynamics for Engg. Technologists, Addison Wisley. 3. Fergusan CR, and Kirkpatrick AT, (2001), Internal Combustion Engines, John Wiley & Sons. 4. Ganesan V, V (2003), Internal Combustion Engines, Tata McGraw Hill. 5. Gill PW, Smith JH, and Ziurys EJ, (1959), Fundamentals of I. C. Engines, Oxford and IBH Pub Ltd. 6. Heisler H, (1999), Vehicle and Engine Technology, Arnold Publishers. 7. Heywood JB, (1989), Internal Combustion Engine Fundamentals, McGraw Hill. 8. Heywood JB, and Sher E, (1999), The Two-Stroke Cycle Engine, Taylor & Francis. 9. Joel R, (1996), Basic Engineering Thermodynamics, Addison-Wesley. 10. Mathur ML, and Sharma RP, (1994), A Course in Internal Combustion Engines, Dhanpat Rai & Sons, New Delhi. 11. Pulkrabek WW, (1997), Engineering Fundamentals of the I. C. Engine, Prentice Hall. 12. Rogers GFC, and Mayhew YR, (1992), Engineering Thermodynamics, Addison Wisley. 13. Srinivasan S, (2001), Automotive Engines, Tata McGraw Hill. 14. Stone R, (1992), Internal Combustion Engines, The Macmillan Press Limited, London. 15. Taylor CF, (1985), The Internal-Combustion Engine in Theory and Practice, Vol. 1 & 2, The MIT Press, Cambridge, Massachusetts. 23

24 Web Resources me429/lecture-air-cyc-web%5b1%5d.ppt ppt/ secondary/powerpoint/sge-parts.ppt