Advanced Manufacturing Processes And Materials Engineering Essay

Crankshaft, linking rod and Piston assembly are the primary parts of internal burning engine. In internal burning engines reciprocating gesture of a Piston is converted into rotary gesture of a grouch. [ 1 ]

As shown in the figure1.1 above one terminal of the connecting rod is connected to the grouch and other terminal is connected to the Piston with the aid of goby pin. Figure 1.2 illustrates the operation of 4 shot engine. These four shots are known as recess shot, compaction shot, and power shot and exhaust shot. During inlet stroke piston moves from top dead Centre to bottom dead Centre. This creates vacuity at the top resulting into gap of recess valve. As recess valve opens, fresh sum of air is fed into the burning chamber of cylinder. During compaction stroke air and fuel mixture is compressed by the upward motion of the Piston as it reciprocates inside the cylinder. At the terminal of compaction stroke a charge is ignited to fire the mixture. High temperature and pressurised gases are generated. These gases push piston down during power shot and reciprocating gesture of Piston is converted into the rotary gesture of a crankshaft. The heat energy generated is used for mechanical work. Exhaust valve opens at the terminal of power shot and exhaust gases issue from port when Piston travels once more from bottom dead Centre to exceed dead Centre. Stroke is defined as the distance travelled by Piston from TDC to BDC. [ 6 ]

Fig 1.2 Working of four shot engine [ 2 ]

The lone difference between 2 shot and 4 shot engine is that, 2 shot engine has ports alternatively of valves and it performs twice every bit many of power shots per cylinder per revolution. [ 2 ]

FUNCTION OF PISTON ASSEMBLY, CONNECTING ROD AND CRANKSHAFT

2.1 PISTON ASSEMBLY

Piston assembly consists of a Piston, Piston rings and Piston pin known as goby pin. Functions of Piston assembly are given below:

It transmits gas force generated during burning to the connecting rod and crankshaft.

As Piston is connected to little terminal of the linking rod with the aid of goby pin. It guides the connecting rod when gas force is transmitted.

Air/fuel mixture is compressed by Piston.

Piston rings restrict the flow of hot gases into the crankcase. This is besides referred as blow by control.

Piston rings lubricate the cylinder wall.

Piston rings restrict the sum of oil from crankcase into the spread between Piston and cylinder caput.

Heat is transferred to the cylinder wall from Piston by Piston rings. [ 4 ]

Fig 2.1 Piston building [ 2 ]

Fig 2.1 illustrates the building of a Piston. Piston top is the portion of burning chamber. Top part can be a level or bowl is provided as per the burning demand. Grooves are provided in the ring belt country to suit Piston rings. The heat flows from Crown, out of the ring belt. Heat is transferred to the cylinder walls through Piston rings and so little part is transferred to the skirt. Some sum of heat is besides taken by the lubricator. [ 1 ]

Piston rings

There are two types of Piston rings: compaction and oil control ring. Piston rings are by and large made up of rectangular subdivision. To forestall sticking of pealing into the channel, their inner and outer borders are chamfered. Compression rings are subjected straight to gas force per unit area. [ 2 ]

Gudgeon Pin or Piston pin

Gudgeon pin is the chief burden transporting portion in Piston assembly. Small terminal of the connecting rod is connected to piston with the aid of goby pin as shown in fig 2.2.It consists of aluminium tablets are placed at the terminals ; these will non damage the cylinder. In order to keep a right tantrum between Piston and connexion rod, external surfaces of goby pins are finished to a high grade of truth. [ 1 ]

2.2 CONNECTING Rod

The chief map of a connecting rod is to organize a nexus between a Piston and crankshaft. A little terminal of the connecting rod is connected to the Piston with goby pin and large terminal is separated into two parts for easiness of assembly with crankpin. The two parts of the large terminal are bearing cap and large terminal lodging. Both are being bolted together. This is done for easiness of assembly of linking rod with crankpin. To provide oil to the large terminal, the oil hole is drilled from large terminal. A typical agreement of linking rod is given below: [ 1 ]

Fig 2.2 Construction of a connecting rod [ 2 ]

2.3 CRANKSHAFT

Crankshaft is the concluding nexus in the skidder grouch mechanism. The additive gesture of a Piston is converted into rotary gesture of a crankshaft. The energy is generated into the burning chamber by transforming the reciprocating gesture of a Piston into rotary gesture of a crankshaft. Crankshaft consists of two chief bearings at the other side of the it, made up in to two half line drives. Crankshaft, crankshaft oil seals, chief bearings, block and quiver damper are parts of crankshaft assembly. [ 4 ]

Fig 2.3: Crankshaft and chief bearings [ 2 ]

IN SERVICE CONDITIONS OF PISTON ASSEMBLY, CONNECTING ROD AND CRANKSHAFT

3.1 PISTON ASSEMBLY

Walter pistons are subjected to mechanical burden, thermic burden and side burden. During burning stroke high pressurised gases are formed. Mechanical burden is due to these high pressurised gases and the reaction from the pin and cylinder wall. Thermal burden is due to the temperature and heat transportation conditions in the cylinder. Heat flux is a step of thermic burden. Articulation of the linking rod consequences in a side burden.

Different runing conditions of a Piston are given below:

Max runing force per unit area: Up to 80 to 110 bars in instance of of course aspirated engines, 130 to 180 saloon in instance of supercharged Diesel engines.

Max runing temperature: Peak gas temperature is between 300 to 400 & A ; Acirc ; & A ; deg ; C

Walter pistons are besides subjected to mechanical and thermic emphasiss. Temperature distribution on the top of the Piston is uneven. These tonss and emphasiss are repeated every rhythm and can change with velocity. This induces fatigue emphasis into Piston and goby pin.

Piston rings are subjected to inertia force, gas force per unit area from all sides of the ring and clash force as pealing hang-up against cylinder walls. Fig 3.1 represents the force per unit area distribution and forces moving on Piston ring. [ 4 ]

Fig3.1Temperature distribution across Piston [ 7 ] Fig3.2 Forces moving on a Piston pealing [ 5 ]

Gudgeon pin is subjected to inertia force of the Piston and gas force per unit area. It is aslo subjected with flexing emphasis and shear emphasis due to the perpendicular constituent and normal constituent of force moving on the Piston. Because of the temperature fluctuations pin may deform. [ 4 ]

3.2 CONNECTING Rod

Connecting rod is subjected to lade due to,

Gas force per unit area on a Piston.

Reciprocating parts and Piston.

linking rod weight itself.

Clash between Piston rings and Piston.

Clash of goby pin bearing and crankpin bearing which increase the compressive emphasis on the connecting rod.

Bending emphasis and tensile emphasis is developed due to inertia burden.

Small terminal bearings may subject to corrosion because of the debasement of engine oil at elevated temperatures. That weakens the bearing construction.

3.3 CRANKSHAFT

Crankshaft is subjected to ;

Gas forces and mass action.

Centrifugal force of revolving parts of linking rod mass Acts of the Apostless on a grouch pin.

Bending emphasis.

Shear emphasis produced due to torsional minute on the shaft.

Fracture because of repeatative bending and torsional emphasiss.

Direct compressive emphasis due to radial force moving on it.

May topic to gyroscopic consequence produced because of misalignment in chief bearing, quiver damper lever arm and weight force.

OPERATING REQUIREMENTS OF PISTON ASSEMBLY, CONNECTING ROD AND CRANKSHAFT

4.1 PISTON ASSEMBLY

a ) As inactiveness force is increases with the square of the engine velocity, it is desirable to maintain weight of Piston, Piston pin and Piston rings every bit low as possible in high velocity engines.

B ) The heat of burning should scatter rapidly to the cylinder walls.

degree Celsius ) Reciprocating action should be without noise.

vitamin D ) Gas and oil waterproofing must be effectual.

4.2 CONNECTING Rod

a ) Noiseless operation of the little terminal and large terminal bearings of linking rod.

B ) Alliance of bearing cap with linking rod should be proper.

degree Celsius ) Connecting rod should non clasp during operation.

vitamin D ) Highly stiff.

vitamin E ) Location of oil provender hole should be considered carefully in order to provide equal measure of lubricating oil.

4.3 CRANKSHAFT

a ) Smoother running.

B ) Weight of the crankshaft should be every bit less as possible.

degree Celsius ) Minimum quiver of crankshaft while in operation.

vitamin D ) Alliance of bearing with crankshaft axis should be proper.

vitamin E )

MATERIAL CHARACTERISTICS OF PISTON ASSEMBLY, CONNECTING ROD AND CRANKSHAFT

5.1 PISTON ASSEMBLY

Material of a Piston should,

Have higher coefficent of thermic enlargement.

Have high UTS and fatigue strength.

Have high thermic conduction.

Have resistant to have on.

Have opposition to corrosion.

Sustain temperatures between 300 & A ; Acirc ; & A ; deg ; C to 400 & A ; Acirc ; & A ; deg ; C.

Material of Piston rings should,

Have resistant to have on.

Have mule opposition coatings.

Material of goby pin should,

Have maximal stiffness.

Have lower denseness.

Have ductileness and tensile strength.

Have resistant to have on.

5.2 CONNECTING Rod

Material of a Piston should,

Have maximal stiffness.

Have maximal break stamina.

Have high weariness stength.

Have high tensile emphasis.

Connecting rod bearing stuff should

Have opposition to draging and wear.

Have opposition to draging and wear.

Have opposition to draging and wear.

5.3 CRANKSHAFT

Material of a crankshaft should,

Have high hysterisis for muffling.

Have low dnsity.

Have high tensile strength and weariness opposition.

Have good thermal lading charactristics to back up diary.

Crankshaft bearing stuff should

Adequate endurance strength.

Have opposition to corrosion.

Have opposition to have on.

Have opposition to ictus.