Internal Combustion Engine

In this episode of the I Can't Sleep Podcast, fall asleep learning about the internal combustion engine. You may think this is an exciting, educational episode, but you're wrong. It's a boring, educational episode. Happy sleeping!

Transcript

Welcome to the I Can't Sleep podcast,

Where I read random articles from across the web to bore you to sleep with my soothing voice.

I'm your host,

Benjamin Bostor.

This episode is from a Wikipedia article titled,

Internal Combustion Engine,

Recommended by Tyson Wilkie from Australia.

An internal combustion engine,

ICE,

Is a heat engine in which the combustion of a fuel occurs with an oxidizer,

Usually air,

In a combustion chamber that is an integral part of the working fluid flow circuit.

In an internal combustion engine,

The expansion of the high temperature and high pressure gases produced by combustion applies direct force to some component of the engine.

The force is applied typically to pistons,

Turbine blades,

A rotor,

Or nozzle.

This force moves the component over a distance,

Transforming chemical energy into useful work.

This replaced the external combustion engine for applications where weight or size of the engine is important.

The first commercially successful internal combustion engine was created by Étienne Lenoir around 1860,

And the first modern internal combustion engine was created in 1876 by Nicolas Otto.

The term internal combustion engine usually refers to an engine in which combustion is intermittent,

Such as the more familiar four-stroke and two-stroke piston engines,

Along with variants such as the six-stroke piston engine and the Wankel rotary engine.

A second class of internal combustion engines use continuous combustion,

Gas turbines,

Jet engines,

And most rocket engines,

Each of which are internal combustion engines on the same principles as previously described.

Firearms are also a form of internal combustion engine,

Though of a type so specialized that they are commonly treated as a separate category.

In contrast,

In external combustion engines such as steam or Stirling engines,

Energy is delivered to a working fluid not consisting of,

Mixed with,

Or contaminated by combustion products.

Steam fluids for external combustion engines include air,

Hot water,

Pressurized water,

Or even liquid sodium,

Heated in a boiler.

ICEs are usually powered by energy-dense fuels such as gasoline or diesel fuel,

Liquids derived from fossil fuels.

While there are many stationary applications,

Most ICEs are used in mobile applications and are the dominant power supply for vehicles such as cars,

Aircraft,

And boats.

ICEs are typically powered by fossil fuels like natural gas or petroleum products such as gasoline,

Diesel fuel,

Or fuel oil.

Renewable fuels like biodiesel are used in compression ignition engines and bioethanol or ETBE produced from bioethanol and spark ignition engines.

Renewable fuels are commonly blended with fossil fuels.

Hydrogen which is rarely used can be obtained from either fossil fuels or renewable energy.

History Various scientists and engineers contributed to the development of internal combustion engines.

In 1791,

John Barber developed the gas turbine.

In 1794,

Thomas Mead patented a gas engine.

Also in 1794,

Robert Street patented an internal combustion engine,

Which was also the first to use liquid fuel and built an engine around that time.

In 1798,

John Stevens built the first American internal combustion engine.

Swiss engineer Francois-Isaac de Rivas invented a hydrogen-based internal combustion engine and powered the engine by electric spark.

In 1808,

De Rivas fitted his invention to a primitive working vehicle,

The world's first internal combustion powered automobile.

In 1823,

Samuel Brown patented the first internal combustion engine to be applied industrially.

In 1854,

In the UK,

The Italian inventors Eugenio Barsanti and Felice Mattucci obtained the certification,

Obtaining motive power by the explosion of gases.

In 1857,

The great seal patent office conceded them patent number 1655 for the invention of an improved apparatus for obtaining motive power from gases.

Barsanti and Mattucci obtained other patents for the same invention in France,

Belgium,

And Piedmont between 1857 and 1859.

In 1860,

Belgian Jean-Joseph Etienne Lenoir produced a gas-fired internal combustion engine.

In 1864,

Nicolas Otto patented the first atmospheric gas engine.

In 1872,

American George Braden invented the first commercial liquid-fueled internal combustion engine.

In 1876,

Nicolas Otto,

Working with Gottlieb Daimler and Wilhelm Maybach,

Patented the compressed-charge four-cycle engine.

In 1879,

Carl Benz patented a reliable two-stroke gasoline engine.

Later in 1886,

Benz began the first commercial production of motor vehicles with the internal combustion engine,

In which a three-wheeled,

Four-cycled engine and chassis formed a single unit.

In 1892,

Rudolf Diesel developed the first compressed-charge compression-ignition engine.

In 1926,

Robert Goddard launched the first liquid-fueled rocket.

In 1939,

The Heinkel He 178 became the world's first jet aircraft.

Etymology At one time,

The word engine meant any piece of machinery,

A sense that persists in expressions such as siege engine.

A motor is any machine that produces mechanical power.

Traditionally,

Electric motors are not referred to as engines.

However,

Combustion engines are often referred to as motors.

An electric engine refers to a locomotive operated by electricity.

In boating,

An internal combustion engine that is installed in the hull is referred to as an engine,

But the engines that sit on the transom are referred to as motors.

Applications Reciprocating piston engines are by far the most common power source for land and water vehicles,

Including automobiles,

Motorcycles,

Ships and,

To a lesser extent,

Locomotives.

Some are electrical,

But most use diesel engines.

Rotary engines of the Winkle design are used in some automobiles,

Aircraft,

And motorcycles.

These are collectively known as internal combustion engine vehicles,

ICEV.

Where high power-to-weight ratios are required,

Internal combustion engines appear in the form of combustion turbines or Winkle engines.

Powered aircraft typically uses an ICE,

Which may be a reciprocating engine.

Engines can instead use jet engines and helicopters can instead employ turbo shafts,

Both of which are types of turbines.

In addition to providing propulsion,

Airliners may employ a separate ICE as an auxiliary power unit.

Winkle engines are fitted to many unmanned aerial vehicles.

ICEs drive large electric generators that power electrical grids.

They are found in the form of combustion turbines with a typical electrical output in the range of some 100 milliwatts.

Combined cycle power plants use the high-temperature exhaust to boil and superheat water steam to run a steam turbine.

Thus,

The efficiency is higher because more energy is extracted from the fuel than what could be extracted by the combustion engine alone.

Combined cycle power plants achieve efficiencies in the range of 50% to 60%.

In a smaller scale,

Stationary engines like gas engine or diesel generators are used for backup or for providing electrical power to areas not connected to an electric grid.

Small engines,

Usually two-stroke gasoline engines,

Are a common power source for lawn mowers,

String trimmers,

Chainsaws,

Leaf blowers,

Pressure washers,

Snowmobiles,

Jet skis,

Outboard motors,

Mopeds,

And motorcycles.

Classification.

There are several possible ways to classify internal combustion engines.

Reciprocating by number of strokes.

Two-stroke engine.

Clerk cycle.

Day cycle.

Four-stroke engine.

Auto cycle.

Six-stroke engine.

By type of ignition.

Compression ignition engine.

Spark ignition engine,

Commonly found as gasoline engines.

By mechanical thermodynamic cycle.

These two cycles do not encompass all reciprocating engines and are infrequently used.

Atkinson cycle.

Miller cycle.

Rotary.

Winkle engine.

Continuous combustion.

Gas turbine engine.

Turbo jet through a propelling nozzle.

Turbo fan through a duct fan.

Turbo prop through an unducted propeller,

Usually with variable pitch.

Turbo shaft,

A gas turbine optimized for producing mechanical torque instead of thrust.

Ram jet.

Similar to a turbo jet but uses vehicle speed to compress ram,

The air,

Instead of a compressor.

Scram jet.

A variant of the ram jet that uses supersonic combustion.

Rocket engine.

Reciprocating engines.

Structure.

The base of a reciprocating internal combustion engine is the engine block,

Which is typically made of cast iron due to its good wear resistance and low cost or aluminum.

In the latter case,

The cylinder liners are made of cast iron or steel.

The engine block contains the cylinders.

In engines with more than one cylinder,

They are usually arranged either in one row,

Straight engine,

Or two rows,

Boxer engine or V engine.

Three rows are occasionally used,

W engine.

In contemporary engines and other engine configurations are possible and have been used.

Single cylinder engines are common for motorcycles and in small engines of machinery.

On the outer side of the cylinder,

Passages that contain cooling fluid cast into the engine block whereas in some heavy duty engines,

The passages are the types of removable cylinder sleeves which can be replaceable.

Water cooled engines contain passages in the engine block where cooling fluid circulates the water jacket.

Some small engines are air cooled and instead of having a water jacket,

The cylinder block has fins protruding away from it to cool by directly transferring heat to the air.

The cylinder walls are usually finished by honing to obtaining a cross hatch which is better able to retain the oil.

A too rough surface would quickly harm the engine by excessive wear on the piston.

The pistons are short cylindrical parts which seal one end of the cylinder from the high pressure of the compressed air and combustion products and slide continuously within it while the engine is in operation.

In smaller engines,

The pistons are made of aluminum while they are made of cast iron in larger engines.

The top wall of the piston is termed its crown and is typically flat or concave.

Some two stroke engines use pistons with the deflector head.

Pistons are open at the bottom and hollow except for an integral reinforcement structure,

The piston web.

When an engine is working,

The gas pressure in the combustion chamber exerts a force on the piston crown which is transferred through its web to a gudgeon pin.

Each piston has rings fitted around its circumference that mostly prevent the gases from leaking into the crankcase or the oil into the combustion chamber.

A ventilation system drives a small amount of gas that escapes past the piston during normal operation to blow by gases.

It is the result of the crankcase so that it does not accumulate,

Contaminating the oil and creating corrosion.

In two stroke gasoline engines,

The crankcase is part of the air fuel path and due to the continuous flow of it,

You do not need a separate crankcase ventilation system.

The cylinder head is attached to the engine block by numerous bolts or studs.

It has several functions.

The cylinder head seals the cylinders on the side opposite to the pistons.

It contains short ducts,

The ports,

For intake and exhaust and the associated intake valves that open to let the cylinder be filled with fresh air and exhaust valves that open to allow the combustion gases to escape.

However,

Two stroke crankcase scavenged engines connect the gas ports directly to the cylinder wall without poppet valves.

The piston controls are opening and occlusion instead.

The cylinder head also holds the spark plug in the case of spark ignition engines and the injector for engines that use direct injection.

All CI engines use fuel injection,

Usually directed injection,

Usually direct injection,

But some engines instead use indirect injection.

SI engines can use a carburetor or fuel injection as port injection or direct injection.

Most SI engines have a single spark plug per cylinder,

But some have two.

A head gasket prevents the gas from leaking between the cylinder head and the engine block.

The opening and closing of the valves is controlled by one or several cram shafts and springs or in some engines a dysmodromic mechanism that uses no springs.

The cram shaft may press directly the stem of the valve or may act upon a rocker arm,

Again either directly or through a push rod.

The crankcase is sealed at the bottom with a sump that collects the falling oil during normal operation to be cycled again.

The cavity created between the cylinder block and the sump houses a crankshaft that converts the reciprocating motion of the pistons to rotational motion.

The crankshaft is held in place relative to the engine block by main bearings which allow it to rotate.

Bulkheads in the crankcase form a half of every main bearing.

The other half is a detachable cap.

In some cases a single main bearing deck is used rather than several smaller caps.

A connecting rod is connected to offset sections of the crankshaft,

The crank pins,

In one end and to the piston in the other end through the gudgeon pin and thus transfers the force and translates the reciprocating motion of the pistons to the circular motion of the crankshaft.

The end of the connecting rod attached to the gudgeon pin is called its small end and the other end where it is connected to the crankshaft,

The big end.

The big end has a detachable half to allow assembly around the crankshaft.

It is kept together to the connecting rod by removable bolts.

The cylinder head has an intake manifold and an exhaust manifold attached to the corresponding ports.

The intake manifold connects to the air filter directly or to a carburetor when one is present which is then connected to the air filter.

It distributes the air incoming from these devices to the individual cylinders.

The exhaust manifold is the first component in the exhaust system.

It collects the exhaust gases from the cylinders and drives it to the following component in the path.

The exhaust system of an ICE may also include a catalytic converter and muffler.

The final section in the path of the exhaust gases is the tailpipe.

Four stroke engines The top dead center TDC of a piston is the position where it is nearest to the valves.

Bottom dead center BDC is the opposite position where it is furthest from them.

A stroke is the movement of a piston from TDC to BDC or vice versa together with the associated process.

While an engine is in operation,

The crankshaft rotates continuously at a nearly constant speed.

In a four stroke ICE,

Each piston experiences two strokes per crankshaft revolution in the following order.

Starting the description at TDC,

These are one,

Intake,

Induction,

Or suction.

The intake valves are open as a result of the cam lobe pressing down on the valve stem.

The piston moves downward,

Increasing the volume of the combustion chamber,

And allowing air to enter in the case of a CI engine or an air fuel mix in the case of SI engines that do not use direct injection.

The air or air fuel mixture is called the charge in any case.

Two,

Compression In this stroke,

Both valves are closed and the piston moves upward,

Reducing the combustion chamber volume,

Which reaches its minimum when the piston is at TDC.

The piston performs work on the charge as it is being compressed.

As a result,

Its pressure,

Temperature,

And density increase,

And approximation to this behavior is provided by the ideal gas law.

Just before the piston reaches TDC,

Ignition begins.

In the case of a SI engine,

The spark plug receives a high voltage pulse that generates the spark,

Which gives it its name and ignites the charge.

In the case of a CI engine,

The fuel injector quickly injects fuel into the combustion chamber as a spray.

The fuel ignites due to the high temperature.

Three,

Power or working stroke The pressure of the combustion gases pushes the piston downward,

Generating more work than it required to compress the charge.

Complementary to the compression stroke,

The combustion gases expand and as a result their temperature,

Pressure,

And density decreases.

When the piston is near to BDC,

The exhaust valve opens.

The combustion gases expand irreversibly due to the leftover pressure,

In excess of back pressure,

The gauge pressure on the exhaust port.

This is called the blowdown.

Four,

Exhaust The exhaust valve remains open while the piston moves upward,

Expelling the combustion gases.

For naturally aspirated engines,

A small part of the combustion gases may remain in the cylinder during normal operation,

Because the piston does not close the combustion chamber completely.

These gases dissolve in the next charge.

At the end of this stroke,

The exhaust valve closes.

The intake valve may open before the exhaust valve closes to allow better scavenging.

Two stroke engines The defining characteristic of this kind of engine is that each piston completes a cycle every crankshaft revolution.

The four processes of intake,

Compression,

Power,

And exhaust take place in only two strokes so that it is not possible to dedicate a stroke exclusively for each of them.

Starting at TDC,

The cycle consists of one power.

While the piston is descending,

The combustion gases perform work on it,

As in a four stroke engine.

The same thermodynamic considerations about the expansion apply.

Two,

Scavenging Around 75 degrees of crankshaft rotation before BDC,

The exhaust valve or port opens and blowdown occurs.

Shortly thereafter,

The intake valve or transfer port opens.

The incoming charge displaces the remaining combustion gases to the exhaust system,

And a part of the charge may enter the exhaust system as well.

The piston reaches BDC and reverses direction.

After the piston has traveled a short distance upwards into the cylinder,

The exhaust valve or port closes.

Shortly the intake valve or transfer port closes as well.

Three,

Compression With both intake and exhaust closed,

The piston continues moving upwards,

Compressing the charge and performing a work on it.

As in the case of a four stroke engine,

Ignition starts just before the piston reaches TDC,

And the same consideration on the thermodynamics of the compression on the charge.

While a four stroke engine uses the piston as a positive displacement pump to accomplish scavenging taking two of the four strokes,

A two stroke engine uses the last part of the power stroke and the first part of the compression stroke for combined intake and exhaust.

The work required to displace the charge and exhaust gases comes from either the crank case or a separate blower.

Before scavenging,

Expulsion of burned gases and entry of fresh mix,

Two main approaches are described,

Loop scavenging and uniflow scavenging.

SAE News published in the 2010s that loop scavenging is better under any circumstance than uniflow scavenging.

Crank Case Scavenged Some SI engines are crank case scavenged and do not use poppet valves.

Instead,

The crank case and the part of the cylinder below the piston is used as a pump.

The intake port is connected to the crank case through a reed valve or a rotary disk valve driven by the engine.

For each cylinder,

A transfer port connects in one end to the crank case and in the other end to the cylinder wall.

The exhaust port is connected directly to the cylinder wall.

The transfer and exhaust port are opened and closed by the piston.

The reed valve opens when the crank case pressure is slightly below intake pressure to let it be filled with a new charge.

This happens when the piston is moving upwards.

When the piston is moving downwards,

The pressure in the crank case increases and the reed valve closes promptly.

When the charge in the crank case is compressed.

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