4 stroke internal combustion engine work

Principle of operation of machines

For a machine to work successfully, it must follow an orderly cycle of operation. The sequence is very rigid and cannot be changed. The working principle of SI and CI engines is described in the following sections. Although both engines have a lot in common there are some basic differences. Nicholas A. How does a 4 stroke internal combustion engine work is credited with inventing the spark-ignition engine. Otto (1876) while the compression-ignition engine was invented by Rudolf Diesel (1892). Hence, they are often referred to as otto engines and diesel engines.

Mechanical components

4-stroke internal combustion engine work

The main components of a cross-section engine of a single-cylinder spark-ignition engine with overhead valves and their functions are briefly described below. How does a 4 stroke internal combustion engine work

Cylinder Block: The cylinder block is the main subsystem

For different components. The cylinders of a multicylinder engine can assembled into a single unit called a cylinder block. The cylinder head and cylinder block are provided with water jacket when water cooled or cooling fins when air cooled. A cylinder head gasket can included between the cylinder block and the cylinder head. The cylinder head can rigidly attached to the cylinder block by a number of bolts or studs.

How does a 4 stroke internal combustion engine work The lower part of the cylinder block can called the crankcase. Attached to the bottom of the crankcase can a cover called the crankcase which becomes the sump for the lubricating oil. The inner surface of the cylinder block can  machined and precisely shaped into a cylindrical shape and can called the bore or face.

How does a 4 stroke internal combustion engine work

4 stroke internal combustion engine work

As the name suggests it is a cylindrical vessel or where the piston does the reciprocating motion. How does a 4 stroke internal combustion engine work During engine operation the various blocks formed in the cylinder can  filled with working fluid and subjected to various thermodynamic processes.

Piston: It is a cylindrical component that fits into the cylinder and forms the moving boundary of the combustion system. It fits perfectly into the cylinder and provides a gas-tight space with piston rings and lubricants.

Combustion Chamber: The space at the top of the cylinder covered by the cylinder head and the top of the piston during the combustion process can called the combustion chamber. Combustion of fuel and release of heat energy creates pressure in this part of the cylinder.

Inlet Manifold: The pipe that connects the intake system to the inlet valves of the engine and through which the air or air-fuel mixture can drawn into the cylinder can called the inlet manifold. How does a 4 stroke internal combustion engine work

Exhaust Manifold: The pipe that connects the exhaust system to the exhaust valve of the engine and through which the combustion products can  released into the atmosphere.

Inlet and Exhaust Valves: Valves can usually mushroom-shaped poppet types. These are provided in the cylinder head or on the side of the cylinder to regulate the charge entering the cylinder (inlet valve) and exhaust the combustion products from the cylinder (exhaust valve).

Spark Plug: This is the component that initiates the combustion process in sparkignition (SI) engines and is usually located in the cylinder head.

Components

 

Connecting Rod: It connects the piston and the crankshaft and transmits the gas forces from the piston to the crankshaft. How does a 4 stroke internal combustion engine work The two ends of the connecting wire can called the small end and the large end (Fig. 1.3). The smaller end can connected to the piston by the gudgeon pin and the larger end can connected to the crankshaft by the crankpin.

Crankshaft: It converts the reciprocating motion of the piston into effective rotary motion of the output shaft. How does a 4 stroke internal combustion engine work The crankshaft of a single cylinder engine consists of a pair of crank arms and balance weights. Balance weights are provided for static and dynamic balance of rotating system. The crankshaft can attached to a crankcase.

Piston Rings: Piston rings fitted in slots around the piston provide a strong seal between the piston and the cylinder wall, preventing leakage of combustion gases (see Figure 1.3).

Gudgeon Pin: It connects the small end of the connecting rod and the piston. How does a 4 stroke internal combustion engine work Camshaft: The camshaft (not shown in the figure) and its associated parts control the opening and closing of the two valves. The parts involved are push rods, rocker arms, valve springs and tappets. This shaft provides the drive to the ignition system. The camshaft can driven by the crankshaft through the timing gear.

Cams: These can formed as an integral part of the camshaft and can designed to open the valves at the right time and hold them open for the required duration (not shown in the figure).

Flywheel:

The net torque supplied to the crankshaft during a full cycle of engine operation causes fluctuations, How does a 4 stroke internal combustion engine work which cause angular changes, in the form of a wheel connected to the output shaft, this wheel can  called a flywheel. (not shown in picture).

Cylinder Bore (D): The nominal internal diameter of the working cylinder can called the cylinder bore and can denoted by the letter D and can usually expressed in millimeters (mm).

Piston Area (A): The area of a circle with a diameter equal to the cylinder bore can  called the piston area and can denoted by the letter A and can usually expressed in square centimeters (cm2).

Stroke (L): The nominal distance that a working piston moves between two consecutive reversals of its direction of motion can called the stroke and can denoted by the letter L and can usually expressed in millimeters (mm). Stroke to Bore Ratio: L/T ratio is an important parameter in sizing an engine. If d < L, it can called a least-squares machine. If d = L, it can  called a square machine. If d > L, it can called an over-square engine.

An over-square engine can run at high speeds due to its large bore and short stroke.

Dead Centre: The position of the working piston and the moving parts mechanically connected to it, How does a 4 stroke internal combustion engine work when the direction of movement of the piston reverses at both ends of the stroke, can  called dead centre. As shown in Figure 1.3, the machine has two dead centers.

Principle of operation of machines

For a machine to work successfully, it must follow an orderly cycle of operation. The sequence can very rigid and cannot can changed. How does a 4 stroke internal combustion engine work The working principle of SI and CI engines can described in the following sections. How does a 4 stroke internal combustion engine work Although both engines have a lot in common there are some basic differences.

Nicholas A. can credited with inventing the spark-ignition engine. Otto (1876) while the compression-ignition engine invented by Rudolf Diesel (1892). Hence, they can often referred to as otto engines and diesel engines.

Four-stroke spark-ignition engine

In a four-stroke engine, the operating cycle can completed in four strokes of the piston or two revolutions of the crankshaft. During the four strokes, five events must can accomplished, namely, absorption, contraction, combustion, expansion and expulsion. How does a 4 stroke internal combustion engine work Each stroke covers 180◦ crankshaft rotation, so a four-stroke cycle can completed by 720◦ crank rotation. The operating cycle of an ideal four-stroke SI engine consists of the following four strokes:

  • suction or intake stroke;
  • (ii) compression stroke;
  • (iii) expansion or power stroke and
  • (iv) exhaust stroke.

Four-stroke compression-ignition engine

A four-stroke CI engine is similar to a four-stroke SI engine but operates at a higher compression ratio. How does a 4 stroke internal combustion engine work The compression ratio of an SI engine is 6 to 10 while that of a CI engine is 16 to 20. During the suction stroke in a CI engine, air can introduced instead of the fuel-air mixture. Due to the high compression ratio used, the temperature at the end of the compression stroke is high enough to cause the fuel injected into the combustion chamber to self-ignite.

In CI engines, a excessive strain fuel pump and an injector are provided to inject the fuel into the combustion chamber. How does a 4 stroke internal combustion engine work The carburettor and ignition system required in SI engines can not required in CI engines.

As shown in  The ideal sequence of operation of a four-stroke CI engine is as follows:

  • Suction stroke:

During the suction stroke only air can added. when

This stroke can  when the inlet valve will open and when the exhaust valve can closed,

  • Compression stroke:

During the suction stroke the entrained air can compressed into the clearance volume. Both valves can closed right now

This stroke, Figure 1.6(b).

  • Expansion stroke:

Fuel injection begins almost at the end of the compression stroke. The injection rate keeps the pressure constant even as the combustion volume increases, despite the movement of the piston on its expansion stroke. Heat can believed to added at consistent pressure. How does a 4 stroke internal combustion engine work After fuel injection is complete (i.e. after cutting) the combustion products expand. Both valves can closed during the expansion stroke,

  • Exhaust stroke:

Piston pushes outwards as it travels from BDC to TDC

Combustion products. During this stroke the exhaust valve canopen and the intake valve can closed,

 

Read More>>>> who invented the internal combustion engine

Four-stroke SI and CI engines

In both SI and CI 4-stroke engines, there may be one power stroke for every  revolutions of the crankshaft. How does a 4 stroke internal combustion engine work There are two non-productive exhaust and intake strokes required to expel the combustion products from the cylinder and fill it with fresh charge respectively. If this objective can accomplished by an alternate arrangement without involving piston movement, one power stroke can obtained for each revolution of the crankshaft increasing the output of the engine.

However, in both SI and CI engines running on a four-stroke cycle, power can only can obtained for every two revolutions of the crankshaft. How does a 4 stroke internal combustion engine work Since both SI and CI engines have a lot in common, it is useful to compare them on important parameters like base cycle, fuel induction, compression ratio etc. Readmore

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