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Internal Combustion Engines – IC Engines

Pioneering topic of mechanical engineering - A fundamental approach.
Instructor:
J Aatish Rao
30 students enrolled
Good understanding of all the main components of IC engines
Understanding of valve timing diagram & its importance
Actuator indicator diagrams & their importance
Understanding of different type of ignition systems
Additional concepts like supercharging,lubrication,governing & many more

This course covers in details about IC engines,its main components,Valve timing diagrams,4-stroke & 2-stroke engines,Actuator indicator diagrams,Scavenging,Detonation,Fuel ignition system,Injection system & many more.

Prior to be on board, Let’s have a brief description about IC engines …. Please read below.

The internal combustion engine is an engine in which the burning of a fuel occurs in a confined space called a combustion chamber. This exothermic reaction of a fuel with an oxidizer creates gases of high temperature and pressure, which are permitted to expand. The defining feature of an internal combustion engine is that useful work is performed by the expanding hot gases acting directly to cause movement, for example by acting on pistons, rotors, or even by pressing on and moving the entire engine itself.

This contrasts with external combustion engines, such as steam engines, which use the combustion process to heat a separate working fluid, typically water or steam, which then in turn does work, for example by pressing on a steam actuated piston.

The term Internal Combustion Engine (ICE) is almost always used to refer specifically to reciprocating engines, Wankel engines and similar designs in which combustion is intermittent. However, continuous combustion engines, such as Jet engines, most rockets and many gas turbines are also internal combustion engines.

Internal combustion engines are seen mostly in transportation. Several other uses are for any portable situation where you need an non-electric motor. The largest application in this situation would be an Internal combustion engine driving an electric generator. That way, you can use standard electric tools driven by an internal combustion engine.

Being a mechanical or automobile engineer, it requires to have a good grasp over this particular topic. I hope this course lives up to your expectation. HAPPY LEARNING !!

Introduction

1
Introduction to IC engines & their classifications.

Internal Combustion Engines are heat engines in which combustion takes place inside of engine cylinder with an oxidizer (generally air). Internal combustion heat engines work on the principle of the ideal gas law: 

pV=nRT. (Ideal gas law)

An internal combustion engine has a chamber, which has fuel added to it which ignites in order to raise the temperature of the gas.When heat is added to the system, it forces gas inside to expand, this causes the piston to rise, and in case of  a gas turbine, the hot air is forced into the turbine chamber...By attaching the piston or turbine to a camshaft, the engine is able to convert a portion of the energy input to the system into useful work.To compress the piston in an intermittent combustion engine, the engine exhausts the gas. A heat sink is then used to keep the system running at a consistent temperature. A gas turbine, which uses continuous combustion, simply exhausts its gas continuously rather than in a cycle.

The classification of IC engines is covered in this lecture along with basic introduction.

2
Main components of I.C.engine.

What are the components which makes an IC engine.... The answer is hundreds of. Out of these many components, we are going to have a discussion regarding cylinder,cylinder head,piston,piston rings,connecting rod,crankshaft & other major components.A brief description about each of these major components are enlisted below ;

Cylinder - Cylinder is the main body of IC engine. Cylinder is a part in which the intake of fuel, compression of fuel and burning of fuel take place. The main function of cylinder is to guide the piston.

Cylinder head - One end of the cylinder is closed by means of cylinder head. This consists of inlet valve for admitting air fuel mixture and exhaust valve for removing the products of combustion.The inlet valve, exhaust valve, spark plug, injector etc. are bolted on the cylinder head. The main function of cylinder head is to seal the cylinder block and not to permit entry and exit of gases on cover head valve engine.Generally made up of aluminium alloys.

Piston -  It transmits the energy to crankshaft through connecting rod.

Piston rings - These are used to maintain a pressure tight seal between the piston and cylinder walls and also it transfer the heat from the piston head to cylinder walls.These rings are fitted in grooves which have been cut in the piston. They are split at one end so they can expand or slipped over the end of piston.Generally made of highly elastic material or fine grain cast iron.

Connecting Rods - One end of the connecting rod is connected to piston through piston pin while the other is connected to crank through crank pin.It transmits the reciprocatory motion of piston to rotary crank."Big end of the connecting rod is connected to the crankshaft and the small end is connected to the piston by using piston pin".Generally made of low carbon steels.

Crank - A lever between connecting rod and crank shaft.

Crank Shaft - The function of crank shaft is to transform reciprocating motion in to a rotary motion.The crankshaft of an internal combustion engine receives the efforts or thrust supplied by piston to the connecting rod and converts the reciprocating motion of piston into rotary motion of crankshaft.The crankshaft mounts in bearing so it can rotate freely."The shape and size of crankshaft depends on the number and arrangement of cylinders." 


3
Valve timing diagrams.

A valve timing diagram is a graphical representation of the opening and closing of the inlet (Intake) and outlet (Exhaust)  valve of the engine, The opening and closing of the valves of the engine depend upon the movement of piston from TDC (Top Dead Center) to BDC (Bottom Dead Center). Encapsulating the crank revolution corresponding to the relevant movement of the piston, valve timing diagrams are made.

The valve timing diagram comprises of a  360 degree figure which represents the movement of the piston from TDC to BDC in all the strokes of the engine cycle, Which is measured in degrees and the opening and closing of the valves is controlled according to these degrees. 

What is the need for Valve Timing Diagram ?

A normal engine works such that it completes approximately 1,00,000+ cycles per minute. Hence it is mandatory to monitor & supervise a system which can enable :-

  • Providing engine with a mixer of air and fuel or simply pure air in case of diesel engine when required ( at the time of suction) which is the necessity of the engine.

  • Complete seizure of the combustion chamber at the instant at which the combustion of air-fuel mixture takes place as the leakage can cause damage to the engine and can be hazardous as well.

  • Synchronization between  the steps of a cycle of the engine from intake of air-fuel ratio to the exhaust of combustion residual (Burnt gases).

  • Ideal timing for the opening and closing of the inlet and outlet valve which in turn protect the engine from defects like knocking or detonation.

  • A high compression ratio required to ignite the fuel especially in case of diesel engine by overlapping the closing of the valve (Valve overlapping).

  • The study of the details of the combustion that is required for the modification of the power of the engine.

  • The cleaning of engine cylinder which in turn maintain the quality of combustion and decreases wear and tear inside the cylinder.

Hence for these many reasons, engines (whether they are 2 or 4 stroke) are designed keeping valve timing diagram meticulous & accordingly. So that the movement of piston from TDC to BDC is provided with the ideal timing of opening and closing of the intake and exhaust valves respectively.

This lecture covers the basics of making & understanding the theoretical valve timing diagram of two & four stroke cycle internal combustion engines

4
Sequence of operation.

Each stroke in IC engines forms a sequence of operations in one cycle of an IC Engines i.e suction stroke, compression stroke, expansion stroke, and exhaust stroke.

When an engine is working continuously, we can consider a cycle starting from any stroke. We know that when the engine returns back to the stroke where it started, we say that one cycle has completed. The following sequence of operation in a cycle is widely used.

  1. Suction stroke :- In this stroke, the fuel vapor in correct proportion, is supplied to the engine cylinder.


  2. Compression stroke :- In this stroke, the fuel vapor is compressed in the engine cylinder.


  3. Expansion or working stroke :- In this stroke, the fuel vapor is fired just before the compression is complete. It results in the sudden rise of pressure, due to expansion of the combustion products in the engine cylinder. This sudden rise of pressure pushes the piston with a great force and rotates the crankshaft. The crankshaft, in turn, drives the machine connected to it.


  4. Exhaust stroke :- In this stroke, the burnt gases (or combustion products) are exhausted from the engine cylinder, so as to make space available for the fresh fuel vapor.

Four stroke cycle IC engines

1
Four stroke cycle petrol engine.

The power generation process in a SI engine is divided into four parts, each part known as the piston stroke.  In an engine, stroke is refer to the maximum distance travel by the piston in a single direction. The piston is free to move only in upward and downward direction. In four stroke engine the piston moves two time up and down and the crankshaft moves two complete revolution to complete four piston stroke. These strokes are Suction stroke, compression stroke, expansion stroke and exhaust stroke.

2
Actual indicator diagram of 4 stroke cycle petrol engine.

An indicator diagram is a map of cylinder pressure plotted against stroke or degrees of rotation for the power stroke or complete cycle of an engine. ... Indicator diagrams used to be drawn by a mechanical apparatus called an indicator, which is why they still have this name. 

In this lecture we shall be covering about the actual indicator diagram for a 4 stroke cycle petrol engine.

3
Valve timing diagram of 4 stroke cycle petrol engine.

A valve timing diagram is a graphical representation of the opening and closing of the inlet (Intake) and outlet (Exhaust)  valve of the engine, The opening and closing of the valves of the engine depend upon the movement of piston from TDC (Top Dead Center) to BDC (Bottom Dead Center). Encapsulating the crank revolution corresponding to the relevant movement of the piston, valve timing diagrams are made.

In this lecture we will be covering about valve timing diagram of a 4 stroke cycle petrol engine.

4
Four stroke cycle diesel engine.

The power generation process in four stroke diesel engine is also divided into four parts. Each part is known as piston stroke. In IC engine, stroke is referred to the maximum distance travel by the piston in a single direction. The piston is free to move only in upward and downward direction. In four stroke engine the piston move two time up and down and the crankshaft move two complete revolution to complete four piston cycle. These are suction stroke, compression stroke, expansion stroke and exhaust stroke.

The most important point by which a diesel engine differs from a petrol engine is the way fuel is ignited in engine cylinder.

5
Actual indicator diagram of 4 stroke cycle diesel engine.

An indicator diagram is a map of cylinder pressure plotted against stroke or degrees of rotation for the power stroke or complete cycle of an engine. ... Indicator diagrams used to be drawn by a mechanical apparatus called an indicator, which is why they still have this name. 

In this lecture we shall be covering about the actual indicator diagram for a 4 stroke cycle diesel engine.

6
Valve timing diagram of 4 stroke cycle diesel engine.

A valve timing diagram is a graphical representation of the opening and closing of the inlet (Intake) and outlet (Exhaust)  valve of the engine, The opening and closing of the valves of the engine depend upon the movement of piston from TDC (Top Dead Center) to BDC (Bottom Dead Center). Encapsulating the crank revolution corresponding to the relevant movement of the piston, valve timing diagrams are made.

In this lecture we will be covering about valve timing diagram of a 4 stroke cycle diesel engine.

7
Comparison of Petrol & Diesel engines.

In this lecture we will discuss about difference between petrol and diesel engine. The classification of petrol and diesel engine is done on the basis of the fuel used in these engines.

Two stroke cycle IC engines.

1
Two stroke cycle petrol engine.

As its designation implies, the two-stroke petrol engine completes its working cycle in only two strokes of the piston, so that a combustible charge is ignited at every revolution of the crankshaft. 

2
Actual indicator diagram of 2 stroke cycle petrol engine.

An indicator diagram is a map of cylinder pressure plotted against stroke or degrees of rotation for the power stroke or complete cycle of an engine. ... Indicator diagrams used to be drawn by a mechanical apparatus called an indicator, which is why they still have this name. 

In this lecture we shall be covering about the actual indicator diagram for a 2 stroke cycle petrol engine.

3
Valve timing diagram of 2 stroke cycle petrol engine.

A valve timing diagram is a graphical representation of the opening and closing of the inlet (Intake) and outlet (Exhaust)  valve of the engine, The opening and closing of the valves of the engine depend upon the movement of piston from TDC (Top Dead Center) to BDC (Bottom Dead Center). Encapsulating the crank revolution corresponding to the relevant movement of the piston, valve timing diagrams are made.

In this lecture we will be covering about valve timing diagram of a 2 stroke cycle petrol engine.

4
Two stroke cycle diesel engines.

In a two-stroke engine, the four "cycles" of internal combustion engine theory (intake, compression, ignition, exhaust) occur in one revolution, 360 mechanical degrees, whereas in a four-stroke engine these occur in two complete revolutions,i.e. 720 mechanical degrees.

5
Actual indicator diagram of 2 stroke cycle diesel engine.

An indicator diagram is a map of cylinder pressure plotted against stroke or degrees of rotation for the power stroke or complete cycle of an engine. ... Indicator diagrams used to be drawn by a mechanical apparatus called an indicator, which is why they still have this name. 

In this lecture we shall be covering about the actual indicator diagram for a 2 stroke cycle diesel engine.

6
Valve timing diagram of 2 stroke cycle diesel engine.

A valve timing diagram is a graphical representation of the opening and closing of the inlet (Intake) and outlet (Exhaust)  valve of the engine, The opening and closing of the valves of the engine depend upon the movement of piston from TDC (Top Dead Center) to BDC (Bottom Dead Center). Encapsulating the crank revolution corresponding to the relevant movement of the piston, valve timing diagrams are made.

In this lecture we will be covering about valve timing diagram of a 2 stroke cycle diesel engine.

Important processes,features & more.

1
Scavenging

During the end of exhaust stroke, certain residual of burnt gases still remains in the combustion chamber. Scavenging is that process by which these remnants can be removed out of the engine cylinder prior to suction stroke of next cycle.

2
Detonation

Detonation is when part of the unburned /partially burned fuel air mixture reaches a critical pressure and temperature and transitions from a normal burning process to an explosive detonation that progresses at near the speed of sound. This lecture covers the fundamentals of detonation. Feel free to ask any queries in Q and A section. HAPPY LEARNING !!

3
Ignition system in petrol engines.

An ignition system generates a spark or heats an electrode to a high temperature to ignite a fuel-air mixture in spark ignition internal combustion engines.. In this lecture we are briefly discussing about the two types of ignition system in IC engines. Coil & Magneto ignition. 

  • Coil Ignition Systems

These ignition systems consist of a 6 or 12-volt battery, resistance, ignition switch, ammeter.It also consists high tension coil, contact breaker, condenser, high tension distributor and spark plug.The high tension coil consists of a waterproof casing containing a few turns of heavy wire forming a primary winding.

It is surrounded by about 20000 turns of fine wire forming a secondary winding.Both windings being wound over a laminated soft iron core and insulated from each other.One end of the secondary winding is earthed. While the other end connected through a heavily insulated wire into the center of the distributor cap.A carbon contact carries the current to the rotor arm.This is made of bronze which revolves and distributes the current to the various cylinders through spark plug leads

  • Magneto Ignition Systems

This system consists of a switch, a magneto, contact breaker, condenser, high tension distributor and spark plugs.The magneto consists of a fixed armature having a primary and secondary winding.It has also a rotating magnetic assembly driven from the engine.The electromotive force induced in the secondary is insufficient to produce a spark.Consequently, it is transformed into the high voltage by the contact breaker in the primary circuit.

"The voltage induced may be more than 10000 volts."

4
Fuel injection system in diesel engines

The purpose of the fuel injection system is to deliver fuel into the engine cylinders, while precisely controlling the injection timing, fuel atomization, and other parameters. The main types of injection systems include pump-line-nozzle, unit injector, and common rail. Modern injection systems reach very high injection pressures, and utilize sophisticated electronic control methods. 

5
Cooling system in IC engines.

All internal combustion engines are equipped with some  type  of  cooling  system because  of  the  high temperatures  they  generate  during  operation.The temperature in the combustion chamber during the burning of fuel is much higher than the melting point of iron.Therefore, if nothing is available to cool the engine during operation, valves burn and warp, lubricating oil breaks  down,  and  bearings  and  pistons overheat resulting in engine seizure. At the same time, the engine must not be allowed to run too cold. An engine running cold does not burn all the fuel taken into the combustion chamber,  causing  carbon  deposits  to  form  that  reduce fuel  mileage,increase wear and reduce engine  power.

In this final lecture,we are about to learn the ins & outs of cooling system in IC engines.Remember you can always come back & revise any portion you want since Udemy provides lifetime access to this course."Please provide your valuable review"

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Thank you so much.

J.Aatish Rao

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