Internal combustion EngineT Alrayyes

Internal Combustion Engine

Total Credits

3 credits

Course Type

Optional

Name of Instructor

Dr. Taleb BakrAlrayyes

Email:talrayyes@iugaza.edu.ps

Text Book

Pulkrabek, Willard W. Engineering Fundamentals of the Internal Combustion Engine , Prentice Hall

Topics covered

• Operating characteristics

• Engine Standard and real Cycles

• Thermochemistry and fuel

• Intake and exhaust

• Combustion

• Emissions and air pollusion

• Heat transfer in Engines

Engine main strokes

Early history• Huygens (1673) developed piston mechanism, Papin (1695) first to use

steam in piston mechaanism• Lenoir Engine (1860): driving the piston by the expansion of burning

products - first practical engine, 0.5 HP later 4.5 kW engines with mechefficiency up to 5%. several hundred of these engine

• Otto-Langen Engine (1867), Mechanical Efficiency 11%.• Otto was given credit for the first built 4 stroke internal combustion Engine• 1880s the internal combustion engine first appeared.

• Also in this decade the two-stroke cycle engine became practical and wasmanufactured in large numbers.

• Diesel Engine 1892: noisy, large, single cylinder.• 1920s multicylinder engines where introduced

• Daimler/Maybach (1882) Incorporated IC engine in automobile

Single cylinder Otto Engine

Engine parts

• Intake Valve lets the air or air fuel mixture to enter the combustion chamber. (Diameter is larger than the exhaust valve

Valves: Minimum Two Valves pre Cylinder

• Exhaust Valve lets the exhaust gases escape the combustion Chamber. (Diameter is smaller then Intake valve)

• Cam Shaft: The shaft that hasintake and Exhaust cams foroperating the valves

• Cam Lobe: Changes rotarymotion into reciprocatingmotion.

• Valve Springs: Keeps the valvesClosed.

Different arrangements of valve and cam shaft

Valve damage• The valves can be damaged in two ways:

• Bent Valves• The most common failure in valves• result of contact with the piston (The valves contacting the top of a piston is due to

incorrect engine synchronization caused by timing chain/belt breakage and incorrect fitting of new belts and chains.)

• it is crucial not to attempt to start the engine as this may result in more costly damage being caused to the cylinder head, pistons and cylinder bores.

• Burnt valve• Essentially this is caused by combustion gases escaping between the valve and valve seat

when they are not sealing correctly. The hot combustion gases are forced past the valve which starts to burn away the edge of the valve

• It is caused by• Excessive localized heat• Combustion gases escaping past the valve and concentrated at only one point• Irregular valve sealing with cylinder head valve seat. Carbon residues generated by irregular

combustion (poor mixture) will appear at the seat region and will jeopardize the sealing between the valve and its seat

Bent Valves

Burnt Valves

Spark plugs

It provides the means of ignition when the gasoline engine’s piston is at the end of compression stroke, close to Top Dead Center(TDC)

The difference between a"hot" and a "cold" sparkplug is that the ceramic tipis longer on thehotter plug.

Signs of faulty spark plug

• Engine has a rough idle

• Having trouble starting your car

• Your engine misfires

• High fuel consumption

• Lack of acceleration

Engine Block

Foundation of the engine andcontains pistons, crank shaft,cylinders, timing sprockets andsometimes the cam shaft.

Engine crackUsually happened at area where there is thin castingIt can start small then propagate as a result of thermal stress and strain cycles

Cause of Engine crack

1. Engine full of water in very cold weather. The ice will crack the block.

2. Engine has inadequate oil when running. The heat can cause the block to crack.

3. Over heating, due to the lack of coolant of failure of the cooling pump.

Minor causes including

1. Bad bearing in connecting rod causes it to break. This can cause the block to break as the connecting rod goes through it.

2. Broken valve springs can drop a valve into the piston, causing the piston and/or connecting rod to crack the block.

3. Broken cam drive chain can cause the valves to be open at the wrong time and cause the pistons or con rods to break the block

Piston

• A movable part fitted into acylinder, which can receiveand transmit power.Through connecting rod,forces the crank shaft torotate.

Causes of damages for Piston

• Un complete combustion, damage From Running Unmixed Fuel

• Damage From Debris Getting Through the Air Filter

• Damage From Bearing Failure

• Damage From Detonation, Knock

Connecting (conn.) Rod• Attaches piston (wrist-pin) to

the crank shaft (conn. Rodcaps).

Hydrolock is the main reason for the damage in the connecting rod• It happens when the volume of

liquid that’s entering the combustion chamber (water or fuel) exceeds the chamber’s volume.

• Can happen if coolant leaked to the cylinder either due to engine head crack or driving through a deep water

• Although it’s rare, sometimes a bad ECM/PCM or fuel injector can cause too much fuel to enter a cylinder, causing hydrolocking and resulting in a bent rod.

Piston rings

• Four stroke: Three rings

Top two are compression rings (sealing the compression pressure in the cylinder)and the third is an oil ring (scrapes excessive oil from the cylinder walls)

• Two Stroke: Two Rings

Both the rings are Compression rings.

Common Symptoms of Damaged Piston Rings

The piston rings are damaged for the same reason as piston

Common symptoms are

• White or gray exhaust smoke

• Excessive oil consumption

• Low power for acceleration

• Overall loss of power or poor performance

Cylinder head

• Part that covers and enclosesthe Cylinder.

• It contains cooling fins or waterjackets and the valves.

• Some engines contains the camshaft in the cylinder head.

Damage in the cylinder head

• The following symptom's could be due to either a crack in the cylinder head or failure in the head gasket

• Mix in oil and water

Crank shaft• Converts up and down or reciprocating motion into circular or rotary motion.

Reason for failure or misalignmentvin Crank shaft• Fatigue failure

• Insufficient lubrication:

• Vibration (Loose engine foundation)

• Over Pressurised Cylinder (Hydrolock)

• Crack in the bearing saddle or Loose main bearing bolt leading to damage of main bearing

• Very high bending moment on the crankshaft due to excessive force from piston assembly

Starter motor

Oil pan, oil sump, oil filter and oil pump

Water pump, radiator and thermostat

Water circulation

Engine Classification

1. Type of Ignitiona) Spark Ignition Engine (SI Engines)

• Mixture is uniform (conventional engines), mixture is non-uniform (stratified-charge engines)

• Ignition is by the application of external energy (to spark plug)

b) Compression Ignition (CI Engines).• By compression in conventional engine (Diesel engine),

• Pilot injection of fuel in gas engines (eg, natural gas and diesel fuel – dual fuel engines)

Engine Classification

2. By application • motorcycles, scooters, 0.75 – 70 kW, SI, 2- and 4-stroke

• passenger cars, 15 – 200 kW, SI and CI, 4-stroke

• light commercial vehicles, 35 – 150 kW, SI and CI, 4-stroke

• Heavy commercial vehicles, 120 – 400 kW, Diesel, 4 stroke

• locomotives, 400 – 3 000 kW, CI, 4-stroke

• ships, 3 500 – 22 000 kW, CI, 2- and 4-stroke

• airplanes, 45 – 3 000 kW, SI, 4-stroke

• stationary engines, 10 – 20 000 kW, CI, 2- and 4-stroke

Engine Classification

3. Engine Cycle3. Four-Stroke Cycle.

• A four-stroke cycle experiences four piston movements over two engine revolution for each cycle.

• complete cycle in 720 OCA• naturally aspirated, supercharged, turbocharged

4. Two-Stroke Cycle. • A two-stroke cycle has two piston movements over one

revolution for each cycle.• complete cycle in 360 OCA• supercharged, turbocharged

Engine Classification4. Basic Design

• Reciprocating.

• Rotary . • Wankel engine (Felix Wankel, prototype

in 1929, patented double rotor in 1934).

• Engine is made of a block (stator) built around a large non-concentric rotor and crankshaft. The combustion chambers are built into the nonrotating block.

Rotary Engines

http://www.animatedengines.com/wankel.html

Engine classification

Triple rotor engine by MazdaMazda Rx-8250 hp engine

Engine Classification

5. Position and Number of Cylinder:• Single cylinder• In-Line: The cylinders are arranged in a line, in a

single bank. (2 to 11 cylinders, L4 and L6 are the most common ones

• V-Engine: : The cylinders are arranged in two banks, set at an angle to one another. (2 to 20 cylinders more, V6, V8 and V12 are the most common ones)

• Opposed Cylinder Engine (flat engine): The cylinders are arranged in two banks on opposite sides of the engine. Commonly used in small aircrafts and some automotive

Engine classification

Opposed Cylinder Engine (flat engine):

Engine Classification

Engine Classification

Engine classification

Engine Classification

• W Engine: • Same as a V engine except with three banks of cylinders

on the same crankshaft.

• Usually 12 cylinders with about a 60° angle between each bank.

• Opposed Piston Engine: • Two pistons in each cylinder with the combustion

chamber in the centre between the pistons.

• A single-combustion process causes two power strokes at the same time, with each piston being pushed away from the centre and delivering power to a separate crankshaft at each end of the cylinder.

• Engine output is either on two rotating crankshafts oronone crankshaft incorporating complex mechanical linkage

Engine Classification• Radial Engine

• Engine with pistons positioned in a circular plane around the central crankshaft.

• Always has an odd number of cylinders ranging from 3 to 13 or more. Operating on a four-stroke cycle,

• every other cylinder fires and has a power stroke as the crankshaft rotates, giving a smooth operation. Many medium- and large-size 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 one powerful, smooth engine. Very large ship engines exist with up to 54 cylinders, six banks of 9 cylinders each.

Engine Classification

6. Air Intake Process:• Naturally Aspirated.• Supercharged: Intake air pressure increased with the compressor drivenoff of

the engine crankshaft• Turbocharged : Intake air pressure increased with the turbine-compressor

driven by the engine exhaust gases• Crankcase Compressed: Two-stroke cycle engine which uses the crankcase as

the intake air compressor. Limited development work has also been done on design and construction of four-stroke cycle engines with crankcase compression.

Turbocharger with EGR system

Engine Classification7. Fuel used,

• gasoline engines

• diesel engines

• natural gas (CNG and LNG),

• methane,

• LPG engines

• alcohol engines

• Biodiesel

• Dual Fuel. Some, usually large, CI engines use a combination of methaneanddiesel fuel. These are attractive in developing third-world countries because of the high cost of diesel fuel. Combined gasoline-alcohol fuels

Engine Classification8. Type of cooling,

• Air Cooled.

• Liquid Cooled, Water Cooled.

Method of Fuel Input for SI Engines

• (a) Carbureted.

• (b) Multipoint Port Fuel Injection. One or more injectors at each cylinder intake.

• (c) Throttle Body Fuel Injection. Injectors upstream in intake manifold.

ENGINE EMISSIONS AND AIR POLLUTION

• The exhaust of automobiles is one of the major contributors to the world's air pollution problem.

• Recent research and development has made major reductions I engine emissions, but a growing population and a greater number of automobiles means that the problem will exist for many years to come.

• During the first half of the 1900s, automobile emissions were not recognized as a problem, mainly due to the lower number of vehicles. As the number of automobiles grew along with more power plants, home furnaces, and population in general, air pollution became an ever-increasing problem.

Main Pollutants

• Four major emissions produced by internal combustion engines are:

• hydrocarbons (He),

• carbon monoxide (CO),

• oxides of nitrogen (NOx),

• and solid particulates.

Pollution reduction

• Two methods are being used to reduce harmful engine emissions:• One is t improve the technology of engines and fuels so that better

combustion Occurs and fewer emissions are generated.

• The second method is aftertreatment of the exhaust gases. This is done by using thermal converters or catalytic converters that promote hemicalreactions in the exhaust flow. These chemical reactions convert the harmful emissions to acceptable CO2, H20, and N2

Laws and polution

• During the 1940s, the problem was first seen in the Los Angeles area due to the high density of people and automobiles, as well as unique weather conditions. By the 1970s, air pollution was recognized as a major problem in most cities of the United States as well as in many large urban areas around the world.

Euro emissions regulation