engine construction videos

                                 engine construction 3D

                        

                                  engine construction 3D

                                    engine construction 3D

types of engine

4 types of engine

4 cylinder i type

radial 5 cylinder

types of engine

parts of engine

inline 4 cylinder engine

opposed(flat)engine

opposed engine

radial engine

radial engine 7 cylinder

rotary engine

rotary engine

rotary engine 3D

v type engine

w type 12 cylinder engine

Internal Combustion Engine

Internal combustion engines are one of the building blocks of modern civilization. In an internal combustion engine, the combustion takes place inside a confined chamber. All internal combustion engines burn a mixture of air & fuel. The fuel can be gasoline, diesel, methane, propane etc.

The piston is the heart of an internal combustion engine..The concept of the piston engine is that a supply of air-and-fuel mixture is fed to the inside of the cylinder where it is compressed and then burnt. This internal combustion releases heat energy which is then converted into useful mechanical work as the high gas pressures generated force the piston to move along its stroke in the cylinder. It can be said, therefore, that a heat-engine is merely an energy transformer.

To enable the piston movement to be harnessed, the driving thrust on the piston is transmitted by means of a connecting-rod to a crankshaft whose function is to convert the linear piston motion in the cylinder to a rotary crankshaft movement (Fig. 1.1-1). The piston can thus be made to repeat its movement to and fro, due to the constraints of the crankshaft crankpin’s circular path and the guiding cylinder.

The backward-and-forward displacement of the piston is generally referred to as the reciprocating motion of the piston, so these power units are also known as reciprocating engines.

another defination

Animation of two-stroke engine in operation, with a tuned pipe exhaust

An automobile engine partly opened and colored to show components.

The internal combustion engine is an engine in which the combustion of a fuel (normally a fossil fuel) occurs with an oxidizer (usually air) in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine. This force is applied typically to pistons, turbine blades, or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy. The first functioning internal combustion engine was created by Étienne Lenoir.^[1]
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 principle as previously described.^[1]
The internal combustion engine (or ICE) is quite different from external combustion engines, such as steam or Stirling engines, in which the energy is delivered to a working fluid not consisting of, mixed with, or contaminated by combustion products. Working fluids can be air, hot water, pressurized water or even liquid sodium, heated in some kind of boiler.
A large number of different designs for ICEs have been developed and built, with a variety of different strengths and weaknesses. Powered by an energy-dense fuel (which is very frequently gasoline, a liquid derived from fossil fuels). While there have been and still are many stationary applications, the real strength of internal combustion engines is in mobile applications and they dominate as a power supply for cars, aircraft, and boats.

Comparison of SI and CI Engine

 

Comparison of S.I. and C.I. engines is made from various aspects is made below:

Fuel economy 

The chief comparison to be made between the two types of engine is how effectively each engine can convert the liquid fuel into work energy. Different engines are compared by their thermal efficiencies. Thermal efficiency is the ratio of the useful work produced to the total energy supplied. Petrol engines can have thermal efficiencies ranging between 20% and 30%. The corresponding diesel engines generally have improved efficiencies, between 30% and 40%. Both sets of efficiency values are considerably influenced by the chosen compression-ratio and design.

Power and torque 

The petrol engine is usually designed with a shorter stroke and operates over a much larger crankshaft-speed range than the diesel engine. This enables more power to be developed towards the upper speed range in the petrol engine, which is necessary for high road speeds; however, a long-stroke diesel engine has improved pulling torque over a relatively narrow speed range, this being essential for the haulage of heavy commercial vehicles.

At the time of writing, there was a trend to incorporate diesel engines into cars. This new generation of engines has different design parameters and therefore does not conform to the above observations.

Reliability

  Due to their particular process of combustion, diesel engines are built sturdier, tend to run cooler, and have only half the speed range of most petrol engines. These factors make the diesel engine more reliable and considerably extend engine life relative to the petrol engine.

Pollution

  Diesel engines tend to become noisy and to vibrate on their mountings as the operating load is reduced. The combustion process is quieter in the petrol engine and it runs smoother than the diesel engine. There is no noisy injection equipment used on the petrol engine, unlike that necessary on the diesel engine. The products of combustion coming out of the exhaust system are more noticeable with diesel engines, particularly if any of the injection equipment components are out of tune. It is questionable which are the more harmful: the relatively invisible exhaust gases from the petrol engine, which include nitrogen dioxide, or the visible smoky diesel exhaust gases.

Safety 

Unlike petrol, diesel fuels are not flammable at normal operating temperature, so they are not a handling hazard and fire risks due to accidents are minimized.

Cost 

Due to their heavy construction and injection equipment, diesel engines are more expensive than petrol engines.

Difference b/w 2 & 4 stroke petrol engine

Difference Between Two & Four Stroke Cycle Petrol Engines

The differences between two- and four-stroke-cycle petrol engines regarding the effectiveness of both engine cycles are given below:

a) The two-stroke engine completes one cycle of events for every revolution of the crankshaft, compared with the two revolutions required for the four-stroke engine cycle.

b) Theoretically, the two-stroke engine should develop twice the power compared to a four-stroke engine of the same cylinder capacity.

c) In practice, the two-stroke engine's expelling of the exhaust gases and filling of the cylinder with fresh mixture brought in through the crankcase is far less effective than having separate exhaust and induction strokes. Thus the mean effective cylinder pressures in two-stroke units are far lower than in equivalent four-stroke engines.

d) With a power stroke every revolution instead of every second revolution, the two-stroke engine will run smoother than the four-stroke power unit for the same size of flywheel.

e) Unlike the four-stroke engine, the two-stroke engine does not have the luxury of separate exhaust and induction strokes to cool both the cylinder and the piston between power strokes. There is therefore a tendency for the piston and small-end to overheat under heavy driving conditions.

f) Due to its inferior scavenging process, the two-stroke engine can suffer from the following:

i) inadequate transfer of fresh mixture into the cylinder,

ii) excessively large amounts of residual exhaust gas remaining in the cylinder,

iii) direct expulsion of fresh charge through the exhaust port. These undesirable conditions may occur under different speed and load situations, which greatly influences both power and fuel consumption.

g) Far less maintenance is expected with the two-stroke engine compared with the four-stroke engine, but there can be a problem with the products of combustion carburizing at the inlet, transfer, and exhaust ports.

h) Lubrication of the two-stroke engine is achieved by mixing small quantities of oil with petrol in proportions anywhere between 1:16 and 1:24 so that, when crankcase induction takes place, the various rotating and reciprocating components will be lubricated by a petrol-mixture mist. Clearly a continuous proportion of oil will be burnt in the cylinder and expelled into the atmosphere to add to unwanted exhaust emission.

i) There are fewer working parts in a two-stroke engine than in a four-stroke engine, so two-stroke engines are generally cheaper to manufacture.

 

valve timing diagram

Valve timing diagram of a four stroke engine gives a clear idea about the actual position of the piston during the opening & closing of inlet & exhaust valves. In practice, the events of the four-stroke cycle do not start and finish exactly at the two ends of the strokes - to improve the breathing and exhausting, the inlet valve is arranged to open before TDC and to close after BDC and the exhaust valve opens before BDC and closes after TDC. These early and late opening and closing events can be shown on a valve timing diagram such as Fig. 1.1-4.

Valve lead This is where a valve opens so many degrees of crankshaft rotation before either TDC or BDC.

Valve lag This is where a valve closes so many degrees of crankshaft rotation after TDC or BDC.

Valve overlap This is the condition when both the inlet and the exhaust valves are open at the same time during so many degrees of crankshaft rotation.

compression ratio

Compression-ratio is a very important parameter for measuring engine performance.The compression-ratio may be defined as the ratio of the maximum cylinder volume when the piston is at its outermost position (BDC) to the minimum cylinder volume (the clearance volume) with the piston at its innermost position (TDC) - that is, the sum of the swept and clearance volumes divided by the clearance volume,

Vs þVc i:e: CR ¼ Vc

where CR ¼ compression ratio

Vs ¼ swept volume (cm3) Vc ¼ clearance volume (cm3)

Petrol engines have compression-ratios of the order of 7:1 to 10:1; but, to produce self-ignition of the charge, diesel engines usually double these figures and may have values of between 14:1 and 24:1 for naturally aspirated (depression-induced filling) types, depending on the design.

In an engine cylinder, the gas molecules are moving about at considerable speed in the space occupied by the gas, colliding with other molecules and the boundary surfaces of the cylinder head, the cylinder walls, and the piston crown. The rapid succession of impacts of many millions of molecules on the boundary walls produces a steady continuous force per unit surface which is known as pressure (Fig. 1.1-12).

When the gas is compressed into a much smaller space, the molecules are brought closer to one another. This raises the temperature and greatly increases the speed of the molecules and hence their kinetic energy, so more violent impulses will impinge on the piston crown. This increased activity of the molecules is experienced as increased opposition to movement of the piston towards the cylinder head.

The process of compressing a constant mass of gas into a much smaller space enables many more molecules to impinge per unit area on to the piston. When burning of the gas occurs, the chemical energy of combustion is rapidly transformed into heat energy which considerably increases the kinetic energy of the closely packed gas molecules. Therefore the extremely large number of molecules squeezed together will thus bombard the piston crown at much higher speeds. This then means that a very large number of repeated blows of considerable magnitude will strike the piston and so push it towards ODC.

This description of compression, burning, and expansion of the gas charge shows the importance of utilising a high degree of compression before burning takes place, to improve the efficiency of combustion. The amount of compression employed in the cylinder is measured by the reduction in volume when the piston moves from BDC to TDC, the actual proportional change in volume being expressed as the compression-ratio.