Lecture-3
Prepared under QIP-CD Cell Project
Internal Combustion Engines
Ujjwal K Saha, Ph.D.
Department of Mechanical Engineering
Indian Institute of Technology Guwahati 1
Background
2
Classifications
1. Engine Cycle Four Stroke Cycle Experiences 4 strokes
of the Piston movements over 2 revolutions of the crankshaft
Two Stroke Cycle Experiences 2 strokes
of the Piston movements over 1 revolution of the crankshaft 3
Classifications – Contd.
2. Fuel Used
Using volatile fuels like gasoline, alcohol, kerosene
Using gaseous fuels like natural gas, biogas
Using solid fuels like charcoal, powdered coke
(converted to gaseous fuel outside the engine in a gas producer)
Using viscous fuels like diesel
Using dual fuel – methanol (suction stroke) + diesel (comp. stroke) – CI Engine – gasoline + alcohol (gasohol) 4
Fuel Used - at a Glance Gasoline Diesel Gas, Natural gas, Methane Liquid Petroleum Gas Alcohol, Methanol Hydrogen Dual Fuel 5
Classifications – Contd.
3. Method of Ignition Spark Ignition: An SI engine starts the combustion process in each cycle by use of a spark plug. In early engine development, before the invention of the electric spark plug, many forms of torch of torch holes were used to initiate combustion form an external flame. Compression Ignition: The combustion process in a CI engine starts when the air-fuel mixture self-ignites due to high temperature in the combustion chamber caused by high compression. 6
Classifications – Contd.
4. Position & Number of Cylinders Single Cylinder Inline Cylinders V Engine Opposed Cylinder Engine W Engine Opposed Piston Engine Radial Engine 7
(b)
(a)
(d)
(c)
(e)
(f)
(g)
8
Cylinder Arrangement Single cylinder: Engine has one cylinder and piston connected to the crankshaft.
In-Line: Cylinders are positioned in a straight line, one behind the other along the length of the crankshaft. Number of cylinders may vary from 2 to 11 or even more. Inline four-cylinder engines are very common for automobiles. In-line engines are also referred to as straight such as straight six or straight eight.
9
V Engine: Two banks of cylinders at an angle with each other along a single crankshaft. The angle between the banks of cylinders is usually within 60-90. V engines have even numbers of cylinders ranging from 2 to 20 or more. V6 and V8 are the common engines with six and eight cylinders respectively.
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Opposed Cylinder Engine: Two banks of cylinders opposite to each other on a single crankshaft. These are mostly used in small aircraft and some automobiles with an even number of cylinders from two to eight or more. These engines are also called flat engines such as flat four.
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W Engine: Similar to that of V engine except with three banks of cylinders on the same crankshaft. This type of arrangement has been used in some racing cars.
Opposed Piston Engine: Two pistons in each cylinder with the combustion chamber located centrally between the pistons. A singlecombustion process causes two power strokes at the same time, with each piston being pushed away from the center and delivering power to a separate crankshaft at each end of the cylinder Engine output is either on two rotating crankshafts or on one crankshaft incorporating a complex mechanic linkage.
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Radial Engine: Engine with pistons positioned in a circular plane around the central crankshaft. The connecting rods of the pistons are connected to the crankshaft through a master rod. A bank of cylinders on a radial engine always has an odd number of cylinders ranging from 3 to 13 or more.
Many medium-and largesize propeller-driven aircraft use radial engines. For large aircraft, two or more banks of cylinders are mounted together, one behind the other on a single crankshaft, making a powerful and smooth engine. 13
Cylinder Arrangement
14
15
Single Cylinder Engine Single-cylinder engine gives one power stroke per crank revolution (360 CA) for 2 stroke, or every two revolutions for 4 stroke. The torque pulses on the crank shaft are widely spaced, and engine vibration and smoothness are significant problems.
4-stroke
2-stroke 0 CA (TC)
180 CA
360 CA (TC)
540 CA
720 CA (TC)
180 CA
Used in small engine applications where engine size is more important 16
Multi-cylinder Engines Multi-cylinder engines spread out the displacement volume amongst multiple smaller cylinders. Increased frequency of power strokes produces smoother torque characteristics. Most common cylinder arrangements are in-line 4 and V-6:
Engine balance (inertia forces associated with accelerating and decelerating piston) better for in-line versus V configuration. 17
V-6 Engine
Inlet runner Air intake manifold
18
Classifications – Contd.
5. Valve Locations Valves in head (overhead valve), also called I-head engine. Valves in block (flat head), also called L-head engine. Some historic engines with valves in block had the intake valve on one side of the cylinder, and the exhaust valve on the other side. These were called T-head engines. One valve in head (usually intake) and one in block, also called F-head engine. 19
(a)
(c)
(b)
(d)
20
Classifications – Contd.
6. Air Intake process Naturally Aspirated: No intake air pressure boost system.
Supercharged: Intake air pressure increased with the compressor driven off the engine crankshaft.
Turbocharged: Intake air pressure increased with the turbine-compressor driven by the engine exhaust gases
Crankcase Compressed: Two-stroke cycle engine that uses the crankcase as the intake air compressor.
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Air Intake
Turbine
Compressor Air Intake
Aftercooler
Exhaust
22
Where the turbocharger is located in the car
Where the turbocharger is located in the car 23
How a turbocharger is plumbed (including the charge air cooler) 24
Roots Blower
Radial compressor
Vane Compressor
Screw Compressor
Axial compressor
25
Classifications – Contd.
7. Method of Fuel supply for SI Engines
Carbureted
Multi Point Fuel Injection - One or more injectors at each cylinder intake.
Throttle Body Fuel Injection - Injectors upstream in intake manifold.
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Inlet Valve
Throttle
Vent Fuel discharge nozzle Float Fuel metering jet lip, h
Fuel from supply Float Chamber
Fuel
Choke Air
Carbureted System 27
Multi Point Fuel Injection System
Throttle Body Injection System 28
Classifications – Contd.
8. Combustion Chamber Design Open chamber (disc, wedge, hemispherical, bowl-in-piston) Divided chamber (small and large auxiliary chambers like swirl chamber, pre-chambers)
29
30
Classifications – Contd.
9. Type of Cooling
Air Cooled
Liquid Cooled/Water Cooled R a d ia to r
C ylin d e r
P isto n
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The cooling system in most cars consists of the radiator and
water pump. Water circulates through passages around the cylinders and then travels through the radiator to cool it off.
32
Classifications – Contd.
10. Applications Car, buses, two-wheelers, trucks Locomotives Stationary Marine Light Aircraft Portable Power Systems Lawnmowers 33
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References Crouse WH, and Anglin DL, 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, (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, YR (1992), Engineering Thermodynamics, Addison 1.
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. 35
Web Resources 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.
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