Structure Of The Internal Combustion Engine Engineering Essay

Structure Of The Internal Combustion Engine Engineering Essay

The internal burning engine is an engine in which the burning of a fuel ( by and large, fossil fuel ) occurs with an oxidant ( normally air ) in a burning chamber. In an internal burning engine the enlargement of the high temperature and force per unit area gases, which are produced by the burning, straight applies force to a movable constituent of the engine, such as the Pistons or turbine blades and by traveling it over a distance, bring forth utile mechanical energy.

The term internal burning engine normally refers to an engine in which burning is intermittent, such as the more familiar four-stroke and two-stroke Piston engines, along with discrepancies, such as the Wankel rotary engine. A 2nd category of internal burning engines use uninterrupted burning: gas turbines, jet engines and most projectile engines, each of which are internal burning engines on the same rule as antecedently described.

Figure: IC Engine


Engines can be classified in different ways:

By the rhythm of the engine used, the engine layout, beginning of energy, the usage of engine, or by the chilling system employed.

Principles of operation


Two-stroke rhythm

Four-stroke rhythm

Six-stroke engine

Diesel engine

Atkinson rhythm

Section 2

Four Stroke Engine:


Four-stroke rhythm ( or Otto rhythm )


2. Compaction

3. Power

4. Exhaust

Its operation has four basic stairss that repeat with every two revolutions:


Combustible mixtures enter into the burning chamber.


The mixtures are pressurised with Piston.


The mixture is burned immediately due to trip doing rapid enlargement forcing the Piston down and traveling parts of the engine and executing necessary work.


The cooled burning gas escapes into the ambiance.

More than 1 engine overlaps these stairss at one clip ; jet engines do all the stairss at the same time at different parts of the engines.


IC engines depend on exothermic chemical procedure of burning. The reaction of fuel takes topographic point with O from air ( though shooting azotic oxide in order could derive power encouragement and make same thing ) . The end point of burning procedure is production of heat in great measure and besides production of C dioxide and steam and other chemicals at really high temperature ; the maximal temperature is ascertained by chemical make-up of oxidants and the fuel.

Most common modern fuels are made of derived largely from fossil fuels like gasoline, Diesel and besides hydrocarbons. Fossil fuels are gasoline, crude oil gas and Diesel fuel. Rarer use of propane can besides be seen. Except for those fuel constituents, most internal burning engines designed for gasolene use can besides run on liquified gasoline gases and natural gas without many alterations. Large diesel engines run with air mixed in gases and a pilot Diesel fuel ignition injection. Liquefied and gas biofuels like ethyl alcohol and biodiesel ( which is a signifier of Diesel fuel produced from harvests such as soybean oil ) can besides be used. Some engines with disposed alterations can besides be run on H gas.

Internal burning engine requires ignition of the mixture, either by compaction ignition ( CI ) or spark ignition ( SI ) . Before the innovation of dependable electrical methods, fire methods and hot tubing were used. [ 1 ]

Gasoline Ignition Process

Gasoline engine ignition systems normally depends on a combination of an initiation spiral and a lead-acid battery to supply a high-potential electrical flicker for the ignition of the air-fuel mix in the engine ‘s cylinders. This battery is recharged during operation utilizing a device that generates electricity such as a generator or an alternator driven by the engine. Gasoline engine takes in a mixture of gasolene and air and compress it to 12.8 saloon ( 1.28 MPa ) , so uses a flicker stopper to light the mixture when it is compressed by the Piston caput in each cylinder.

Diesel Ignition Process

Diesel engines rely entirely on force per unit area and heat created by the engine in its compaction procedure for ignition of gasolene. The compaction degree that occurs is normally thrice or more than a gasolene engine. Diesel engines takes in air merely, and merely earlier peak compaction, a little measure of Diesel fuel is sprayed into the cylinder via a fuel injector that allows the fuel to immediately light. HCCI type engines takes in both air and fuel but such engines continue to trust on an single-handed auto-combustion procedure, due to heat and higher force per unit areas. This is besides the ground why Diesel and HCCI engines are more vulnerable to cold-starting issues, although they run merely all right in cold conditions once they are started. Light responsibility Diesel engines with indirect injection in light trucks and cars use glow stoppers that pre-heat burning Chamberss merely before they start to cut down no-start conditions in cold conditions. Most diesel engines besides have a battery and bear downing system ; nevertheless, this system is secondary and is added by makers as a luxury for the comfort of get downing, turning fuel on and off ( which can besides be done through a mechanical setup or switch ) , and to run subsidiary electrical constituents and accoutrements. Most new engines rely on electronic and electrical control system to cut down emanations and besides to command the burning procedure to increase efficiency.


Ideal Pressure/volume diagram of the Otto rhythm demoing burning heat input Qp and waste exhaust end product Qo, the compaction shot is the bottom curving line and the power shot is the top curving line.

Engines that are based on the four-stroke ( “ Otto rhythm ” ) have one power shot for every four shots ( up-down-up-down ) and employ flicker stopper ignition. Combustion occurs rapidly, and during burning the volume varies small ( “ changeless volume ” ) . They are used in larger boats, autos, some bikes, and many visible radiation aircraft. They are by and large quieter, more efficient, and larger than their two-stroke opposite numbers. [ 2 ]

The stairss involved here are:

Intake shot: Vaporized fuel and air are sucked in.

Compaction shot: Air and fuel vapor are compressed and ignited.

Combustion stroke: Fuel burns up and Piston is pushed downwards.

Exhaust shot: Exhaust is driven out. During 1st, 2nd, and 4th stroke the Piston is trusting on the power and the impulse generated by the other Pistons. Relatively, a six or eight cylinder engine would be more powerful than four cylinder engine.

Otto Cycle

The first homo to construct a auto with an engine was German applied scientist Nicolaus Otto. That is the ground why the four-stroke rule today is normally known as the Otto rhythm and four-stroke engines that uses flicker stoppers frequently are called Otto engines. The Otto rhythm consists of four stairss that are adiabatic compaction, heat add-on, adiabatic enlargement and rejection of heat at changeless volume.

In modern universe, internal burning engines in trucks, autos, aircrafts, bikes building vehicles, dawdlers and many others cars normally use a four-stroke rhythm. The four shots refer to intake, compaction, burning, and exhaust shots that occur during two crankshaft rotary motions per working rhythm of the Diesel and gasonline engine. A less proficient description of the four-stroke rhythm is, “ Suck, Squeeze, Bang and Blow ”

The rhythm begins at top dead centre, when the Piston is furthest off from the crankshaft axis. A shot refers to the entire travel of the Piston from Top Dead Center ( TDC ) to Bottom Dead Center ( BDC ) .

Stroke 1 of 4 “ Suck ” : After the initiation stroke or consumption of the Piston, the Piston descends from the top of the cylinder to the underside of the cylinder, cut downing the force per unit area inside the cylinder. A mixture of air and fuel is forced by atmospheric force per unit area into the cylinder through the consumption port. The consumption valve ( s ) closes afterwards.

Stroke 2 of 4 “ Squeeze ” : With both exhaust and intake valves closed, the Piston moves to the top of the cylinder and compresses the fuel-air mixture. This is called as the compaction shot.

Stroke 3 of 4 “ Bang ” : While the Piston is at Top Dead Center, the tight air-fuel mixture ignites, normally by a flicker stopper or by the heat and force per unit area of compaction of air-fuel mixture ( for a compaction ignition engine or diesel rhythm ) . The monolithic force per unit area ensuing from the burning of the tight fuel-air mixture shoots down the Piston back toward underside dead centre with enormous force. This is known as power shot, which is the chief beginning of the engine ‘s power and torsion.

Stroke 4 of 4 “ Blow ” : During the exhaust shot, the Piston once more returns to exceed dead centre while the exhaust valve is unfastened. This action empties the merchandise of burning of air-fuel mixture from the cylinder by forcing the exhausted fuel-air mixture through the exhaust valve ( s ) .

Figure 2: Starting Position Figure 3: Consumption Stroke

Figure 4: Compaction Stroke Figure 5: Ignition of Fuel

Figure 6: Power Stroke Figure 7: Exhaust Stroke

Energy balance

Otto rhythm engines are about 34 % efficient. 34 % of the energy generated in the engine by burning is converted into valuable rotational energy at the end product shaft of the engine, while the staying appears as waste heat. By contrast, a six-stroke engine which is still under research and development may perchance change over more than 50 % of the energy of burning into valuable rotational energy.

Modern engines are frequently intentionally built to be somewhat less efficient than they otherwise be. This is necessary to command emanations such as catalytic convertors that cut down smog and other atmospheric pollutants and fumes gas recirculation. Efficiency decrease may be countered with an engine control unit by utilizing thin burn techniques.

Diesel rhythm

P-v Diagram for the Ideal Diesel rhythm.

The image above shows P-v diagram of ideal diesel rhythm ; where V is specific volume and P is force per unit area. Below are the 4 distinguishable stairss that follow ideal Diesel rhythm:

1 to 2 is isentropic compaction

2 to 3 is reversible changeless force per unit area warming

3 to 4 is isentropic enlargement

4 to 1 is reversible changeless volume chilling

The Diesel is a heat engine which converts heat energy into work.

Work ( Win ) is done by the compaction of the working fluid by Piston.

Heat ( Qin ) is done by the fuel burning

Work out ( Wout ) is done by the working fluid spread outing on to the Piston, this produces torsion for motion of parts

Heat out ( Qout ) is done by venting the air out

Most automotive Diesel engines and trucks use a rhythm evocative of a four-stroke rhythm, but with a compaction heating ignition system, than in demand of a separate ignition system. This difference is called the Diesel rhythm. In the Diesel rhythm, Diesel fuel is injected straight into the cylinder so that burning occurs at changeless force per unit area, as the Piston moves.


Engine Partss

Most of the constituents of the compaction ignition ( CI ) and spark ignition ( SI ) engines are the same. The of import constituents of the engine are: Pistons, crankshaft, cylinders, cylinder block, linking rod and crankcase. This is one of the two parts depicting all of import constituents.

There are two chief types of internal burning engines. The spark ignition is besides called the gasoline engine, and compaction ignition is besides called the Diesel engine. Almost all the constituents of both the engines are same, but merely their fuel combustion procedure differs. In CI engines the combustion of fuel occurs by its compaction to high force per unit areas but in SI engines the combustion of fuel occurs by the flicker generated by the flicker stopper while. [ 3 ]

Here are the of import constituents of the IC engines:

1. Cylinder block: Cylinder block is the chief organic structure of the engine, this construction supports all the other constituents of the engine. In this instance of the individual cylinder engine the cylinder block stocks the cylinder while in the instance of multi-cylinder engine, figure of cylinders are arranged in a row together to organize the cylinder block. The cylinder caput is mounted at the uppermost portion of the cylinder block.

When the vehicle runs, big sums of heat is generated inside the cylinder block. To take the heat the cylinder caput and the cylinder block are cooled down by H2O that is fluxing through the H2O jackets inside the larger engines that are found in autos and trucks. For smaller vehicles like bikes, fives are rendered on the cylinder caput and on the cylinder block to chill them. The bottom part of the cylinder block is called crankcase. Inside the crankcase is lubricating oil, which is used for lubricating assorted traveling parts of the engine stored.

2. Cylinder: As the name says, it is a cylindrical molded vas that is fitted in the cylinder block. This cylinder can be removed from the cylinder block and machined whenever required. It is besides called a line drive or arm. Inside the cylinder the Piston moves up and down, which is called the reciprocating gesture of the Piston. Burning of fuel occurs at the top of the cylinder, due to which the reciprocating gesture of the Piston is produced. The surface of the cylinder is finished to a high coating, so that there is minimum clash between the Piston and the cylinder.

In smaller vehicles like bikes there is merely one cylinder. In larger more powerful vehicles like high milliliter bikes, trucks, autos, etc. , there is more than one cylinder in the engine. These engines are called multi-cylinder engines. The figure of cylinders in these engines can be 2, 3, 4, 6, 8. In really big engines such as those of ships and pigboats, the figure of cylinders can be 12 to 16. The displacement volume of engine entirely depends on the size of the cylinder.

3. Piston: The Piston is a circular cylindrical constituent that performs a mutual gesture in the cylinder. The Piston has to suit absolutely inside the cylinder. Piston rings are fitted over and on the Piston. The spread between the cylinder and the Piston is filled by the lubricating oil and Piston rings. The Piston is by and large made up of aluminum.

4. Piston rings: These are thin rings fitted in the slots made along the surface of the Piston. They provide a tight seal between the cylinder walls and the Piston that prevents leaking of the burning gases from one side to the other. This ensures that the gesture of the Piston produces every bit near as to the power generated from inside of the cylinder.

5. Combustion chamber: It is inside the burning chamber where the existent combustion of fuel takes topographic point. It is the uppermost part of the cylinder which is enclosed by the Piston and the cylinder caput. When the fuel is burnt, much thermal energy is produced which generates overly high force per unit areas doing the reciprocating gesture of the Piston to force down with intense force.

6. Inlet manifold: Through the recess manifold air-fuel mixture or the air is drawn into the cylinder.

7. Exhaust manifold: All the exhaust gases generated inside the cylinder after fuel combustion are discharged through the exhaust manifold into the ambiance.

8. Inlet and exhaust valves: The recess and the exhaust valves are placed at the top portion of the cylinder in the cylinder caput. The recess valves allow the consumption of fuel during suction stoke of the Piston and to shut thenceforth. During the exhaust stoke of the Piston the fumes valves open to the full leting the fumes gases to let go of into the ambiance. Both these valves allow the flow of gases and fuel in individual way merely.

9. Spark stopper: The flicker stopper is a device that produces a flicker which causes the instant combustion of the pressurized fuel.

10. Connecting rod: It is the linking nexus between the crankshaft and the Piston that performs the rotary gesture. There are two terminals of the connecting rod called the large terminal and little terminal. The large terminal is connected to crankshaft by grouch pin while the little terminal of the connecting rod is connected to the Piston by goby pin.

11. Crankshaft: The crankshaft performs the revolving gesture. It is connected to the axle of the wheels which moves as the crankshaft rotate. The reciprocating gesture of the Piston is converted into rotational gesture of the crankshaft with the aid of the connecting rod. The crankshaft in the crankcase rotates in the bushings.

The above are the of import constituents of the IC engine. Automotive companies have mastered in the art of fabricating the precise constituents of the IC engine ; therefore engine lifetimes have been increased over the old ages. Major alterations have been carried out in the designing of the engines toA addition fuel efficiency and entire power end product of the vehicle.

These yearss the engines are besides designed to work on different type of fuels. Therefore you can run your vehicle either on gasolene fuel or LPG.


Oxidants and Fuels


In future, internal burning engines could finally be replaced by Hydrogen fuels. Alternate fuel cell engineering will slowly replace bing internal burning engines.

Although there are many ways of bring forthing free H, all those methods require change overing burning molecules into devouring electric energy or H. The energy produced for the above procedure should be from renewable beginning to avoid energy crisis. Often storage of H is a major issue. Liquid H has really low denseness ( 14 times lower than that of H2O ) and requires extended insulation-whilst gaseous H requires heavy tankage. Hydrogen has higher specific energy even after liquification, nevertheless the volumetric energetic storage is five times lower than gasoline. However the energy denseness of H is significantly higher than electric batteries, doing it a strong campaigner as an energy bearer to replace fossil fuels. The ‘Hydrogen on Demand ‘ procedure creates H as needed, but has many other issues such as production of extremely priced Na borohydride which is the natural stuff.


As air is abundant on the surface of the Earth, the oxidant is atmospheric O need non be stored within the vehicle, increasing the power to volume ratios and power-to-weight. There are other stuffs used for particular intents, normally to increase end product power or to let operation in infinite or under H2O.

Compressed air has been normally used in gunmans. Compressed O and some tight air were used in the Nipponese Type 93 gunman. Certain pigboats are specifically designed to transport pure O. Rockets frequently use liquid O.

To increase power and control burning Nitro methane is used to some racing and theoretical account fuels.

Azotic oxide has been used with gasoline mixture in tactical aircraft and in specially equipt autos that allows short explosions of power added from engines that otherwise runs on air and gasolene. It is besides used in projectile ballistic capsule.

Hydrogen peroxide power was under development for pigboats in 1943 and may hold been used in some non-nuclear pigboats. It was besides used in some projectile engines like Black Arrow and Me-163 projectile plane.

Other chemicals like Cl and F have been used by experimentation but were n’t found to be utile practically.


Engine Problems

There are few cardinal grounds for the failure of the engine early forenoon particularly during winter. They are

Bad fuel mix

Lack of compaction

Lack of flicker

Beyond that, there are few more minor causes that might make jobs apart from those large three. Based on the simple engine, below are the inside informations how those jobs affects the engine.

Bad fuel mix – A bad fuel mix can happen due to several grounds:

When the engine is out of gas, which makes it to fire merely air.

Clogging of air intake making instability between fuel and air

Excessively small or excessively much fuel supply to the tuel system mix taking to improper burning.

There might be an dross in the fuel ( like H2O in your gas armored combat vehicle ) that makes the fuel non fire [ 4 ] .

Lack of compaction – If the charge of fuel and air can non be compressed appropriately, the burning procedure does n’t work like it should. Miss of compaction might happen for the below grounds:

When Piston rings are worn ( leting fuel/air leak past the Piston during compaction ) .

The consumption or exhaust valves are non sealed decently, once more leting the leak during compaction procedure.

When a hole is formed in the cylinder.

The most common “ hole ” in a cylinder occurs where top of the cylinder ( keeping the flicker stopper and valves besides called as the cylinder caput ) attaches to the cylinder itself. By and large, the cylinder caput bolt and the cylinder keep together with a thin gasket pressed between them to guarantee a good seal. If the gasket breaks down, little holes develop between the cylinder caput and the cylinder, and these holes can do leaks.

Figure 8: Care Work

Regular engine care can assist avoid frequent fixs.

Lack of flicker – The flicker might be weak or non-existent for a figure of grounds:

If the flicker stopper or the wire taking to it is worn out, the flicker will be excessively weak.

If the system that sends a flicker down the wire is non working decently or If the wire is cut or losing, there will be no flicker.

If the flicker occurs either excessively late or excessively early in the rhythm ( i.e. if the ignition timing is off ) , the fuel will non light at the right clip, and this can do many jobs.

Many other things can travel incorrect. For illustration:

If the battery is dead, engine can non be started.

If the bearing that allows the crankshaft to turn freely are worn out, the crankshaft can non turn on, so the engine can non run.

If the valves do non shut and open at the right clip, air can non acquire in and wash up can non acquire out, so the engine ca n’t run.

If the tailpipe is blocked due to legion grounds, fumes can non go out the cylinder so the engine will non run.

If you run out of oil, the Piston can non travel up and down freely in the cylinder, and the engine will prehend [ 5 ] .

In a properly running engine, all of these factors are within tolerance.


Volumetric Efficiency

Performance: The public presentation of an Otto rhythm can be assessed under changing volumetric efficiency. Finite clip thermodynamics is used to derive dealingss between thermic efficiency and power end product at different volumetric efficiency and compaction ratio for an air-standard Otto Cycle. The consequence of volumetric efficiency on the irreversible rhythm public presentation is of import. The consequence of volumetric efficiency on rhythm public presentation is obvious, and pattern rhythm analysis should be considered.

Section 6


In this study we have covered so far the history of IC engine, types of engine rhythms and their jobs. This being the mid-semester study has described everything briefly. For the concluding study I will cover the designing and analysis of engine and its parts and how efficiency differs by changing the length and cross sectional country of engine cylinders.