In this article we will discuss about:- 1. Introduction to Internal Combustion (IC) Engine 2. Classification of Internal Combustion (IC) Engine 3. Components.
Introduction to Internal Combustion (IC) Engine:
Unlike external combustion engines, wherein the combustion of fuel takes place outside the engine, in internal combustion (IC) engines, the fuel used undergoes combustion inside the engine in the presence of air. The product produced by the combustion becomes the working fluid of the engine.
Internal combustion engines have higher efficiency and are lighter in weight in comparison to the power developed. They have become very much suitable for mobile applications. With all these advantages, IC engines have become universal means of power generation and very much popular.
Classification of Internal Combustion (IC) Engine:
Internal combustion engines may be classified on the basis of:
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Thermodynamic cycle used – Otto cycle, diesel cycle, and dual cycle engine
Fuel used – Petrol engine, diesel engine, gas engine, and kerosene oil engine
Number of strokes for completion of cycle – Four-stroke engine and two-stroke engine
Types of fuel ignition – Spark ignition (SI) and compression ignition (CI)
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Number of cylinders – Single cylinder engine and multi-cylinder engine
Position of cylinders – Horizontal, vertical, V-engine, and radial engine
Method of cooling engines – Air-cooled engine and water-cooled engine
Components of Internal Combustion (IC) Engine:
An assembled diagram with various parts of an IC engine is shown in Figs. 4.25 and 4.26.
i. Engine Cylinder:
It is a cylindrical vessel in which the fuel is burnt and the product of combustion gets expanded to develop power. Inside the cylinder, there is a sleeve fitted called the cylinder liner of hard metal. A piston makes reciprocating motion inside the cylinder.
ii. Cylinder Head:
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It is fitted at the top of cylinder to cover the cylinder. The cover provides the accommodation of inlet valve, exhaust valve, and spark plug (in SI engine) or injector (in CI engine).
iii. Piston:
Piston is a tightly fitted block generally known as trunk piston which receives the gas pressure inside the engine cylinder. The gas pressure is transmitted to the crankshaft through the connecting rod (Fig. 4.27).
Piston Rings:
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There are two types of rings fitted on the circumferential groove provided on the outer surface of piston (Fig. 4.28):
Compression Ring:
Compression rings maintain a gas tight contact between cylinder and the piston.
Oil Scraper Ring:
Lubrication is required in the cylinder sleeve surface to reduce frictional forces. However, the excess oil needs to be removed. Thus, the ring will have a groove which removes this excess lubricating oil from the sleeve of the cylinder into the crank case.
Connecting Rod:
Connecting rod transmits the force from piston to crankshaft. It helps in converting the reciprocating motion to rotary motion. It has two ends—small end and big end. The small end is connected with piston with a gudgeon pin. The big end is connected with crankshaft (Fig. 4.29).
Crank and Crankshaft:
It converts the reciprocating motion of the piston to rotary motion of the shaft. The crankshaft is enclosed inside a crank case [Figs. 4.30(a) – 4.30(c)].
Valves:
These valves are also called poppet valves.
There are two types of valves:
i. Suction valve and
ii. Exhaust valve.
i. Suction Valve:
This valve controls the mixture of petrol vapors and air in SI engines and only air in CI engines.
ii. Exhaust Valve:
It controls the flow of exhaust gas from the cylinder. The product of combustion is to be expelled out by opening this valve for starting fresh cycle.
The valves are operated by cam mechanism with the help of rocker arms in a single cylinder engine and by camshaft in a multi cylinder engine [Figs. 4.31(a) and 4.31(b)]. In four-stroke engines, the rotation of the camshaft is half of rotation of the crankshaft.
Fly Wheel:
Fly wheel is a heavy wheel mounted on engine shaft. It has large moment of inertia and, hence, absorbs energy during operation and supplies back the energy to the engine when required. Thus, this removes the cyclic fluctuation and maintains uniform rotation of the crankshaft. A single cylinder engine will have a large fly wheel, whereas a multi cylinder engine will have a smaller fly wheel.
Crank Case:
It is fitted in the lower part of the engine cylinder to cover crankshaft and also to store the lubricating oil known as oil sump.