15819 03-classification of engines

8/3/2019 15819 03-Classification of Engines

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Background


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Classifications

1. Engine Cycle

Four Stroke Cycle Experiences 4 strokesof the Piston movements over 2 revolutionsof the crankshaft

Two Stroke Cycle Experiences 2 strokes

of the Piston movements over 1 revolutionof the crankshaft


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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)

Classifications Contd.2. Fuel Used


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Fuel Used - at a Glance

Gasoline

Diesel

Gas, Natural gas, Methane

Liquid Petroleum Gas

Alcohol, Methanol

Hydrogen

Dual Fuel


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Classifications Contd.3. Method of Ignition

Spark Ignition: An SI engine starts thecombustion process in each cycle by use of aspark plug. In early engine development,before the invention of the electric spark plug,

many forms of torch of torch holes were used toinitiate combustion form an external flame.

Compression Ignition: The combustion

process in a CI engine starts when the air-fuelmixture self-ignites due to high temperature inthe combustion chamber caused by high

compression.


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Classifications Contd.

4. Position & Number of Cylinders

Single Cylinder Inline Cylinders

V Engine

Opposed Cylinder Engine

W Engine

Opposed Piston Engine

Radial Engine


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(a) (b) (c)

(d) (e)

(f) (g)


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Single cylinder: Engine has one cylinder andpiston connected to the crankshaft.

In-Line: Cylinders arepositioned in a straight line, onebehind the other along thelength of the crankshaft.Number of cylinders may varyfrom 2 to 11 or even more. In-line four-cylinder engines are

very common for automobiles.In-line engines are also referredto as straight such as straight sixor straight eight.

Cylinder Arrangement


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V Engine: Two banks of cylinders at an anglewith each other along a single crankshaft. Theangle between the banks of cylinders is usuallywithin 60-90. V engines have even numbers ofcylinders ranging from 2 to 20 or more. V6 and V8are the common engines with six and eightcylinders respectively.


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Opposed Cylinder Engine: Two banks ofcylinders opposite to each other on a singlecrankshaft. These are mostly used in small aircraftand some automobiles with an even number of

cylinders from two to eight or more. Theseengines are also called flat engines such as flatfour.


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W Engine: Similar to that of V engine exceptwith three banks of cylinders on the samecrankshaft. This type of arrangement has beenused in some racing cars.

Opposed Piston Engine: Two pistons in eachcylinder with the combustion chamber locatedcentrally between the pistons. A single-combustion process causes two power strokes atthe same time, with each piston being pushedaway from the center and delivering power to a

separate crankshaft at each end of the cylinderEngine output is either on two rotating crankshaftsor on one crankshaft incorporating a complexmechanic linkage.


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Radial Engine: Engine with pistons positioned ina circular plane around the central crankshaft.The connecting rods of the pistons are connectedto the crankshaft through a master rod. A bank of

cylinders on a radial engine always has an oddnumber of cylinders ranging from 3 to 13 or more.

Many medium-and large-

size propeller-driven aircraftuse radial engines. For largeaircraft, two or more banksof cylinders are mounted

together, one behind theother on a single crankshaft,making a powerful andsmooth engine.


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Cylinder Arrangement


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Multi-cylinder Engines

Multi-cylinder engines spread out the displacement volumeamongst multiple smaller cylinders. Increased frequency of powerstrokes produces smoother torque characteristics.

Most common cylinder arrangements are in-line 4 and V-6:

Engine balance (inertia forces associated with accelerating anddecelerating piston) better for in-line versus V configuration.


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V-6 Engine

Air intake

manifold

Inletrunner


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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 inblock had the intake valve on one side of thecylinder, 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.


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(a)(b)

(c) (d)


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6. Air Intake process

Naturally Aspirated: No intake air pressure

boost system. Supercharged: Intake air pressure increasedwith the compressor driven off the engine

crankshaft. Turbocharged: Intake air pressure increasedwith the turbine-compressor driven by the engineexhaust gases

Crankcase Compressed: Two-stroke cycleengine that uses the crankcase as the intake aircompressor.


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Air Intake

Aftercooler

Turbine Compressor

Air Intake

Exhaust


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Where the turbocharger is located in the car

Where the turbocharger is located in the car


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How a turbocharger is plumbed (including the

charge air cooler)


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Roots Blower Vane CompressorScrew Compressor

Axial compressorRadial compressor


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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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Fuel

Float

Vent

Float

Chamber

Throttle

Fuel dischargenozzle

Fuel meteringjet lip, h

Choke

Air

Inlet

Valve

Fuelfromsupply

Carbureted System


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Multi Point Fuel Injection System

Throttle Body Injection System


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8. Combustion Chamber Design

Open chamber (disc, wedge, hemispherical,

bowl-in-piston) Divided chamber (small and large auxiliarychambers like swirl chamber, pre-chambers)


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9. Type of Cooling

Air Cooled

Liquid Cooled/Water Cooled

Radiator

Cylinder

Piston


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The cooling system in most cars consists of the radiator and

water pump. Water circulates through passages around thecylinders and then travels through the radiator to cool it off.


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10. Applications

Car, buses, two-wheelers, trucks Locomotives

Stationary

Marine

Light Aircraft

Portable Power Systems

Lawnmowers


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15819 03-classification of engines

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