Ic Engine by sastra university author

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BASICS

Parts of IC engines

Terms connected withIC engines

Working cycles

Indicator diagram

Comparison of 4stroke and 2 stroke

engines Comparison of SI and

CI engines

Classification ofengines

AIR STANDARD CYCLES

Air standard efficiency

of Otto cycle Air standard efficiency

of diesel cycle

Air standard efficiencyof dual cycle

Comparison of Otto ,

diesel and dual cycle

PERFORPARAMETE

Fuels

Fuel prope Effects of f

properties

Engine parand perfor


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Any device that converts the chemical energy of a fuel into h

energy by combustion and then uses that heat energy to

mechanical work is known as an Engine.

ENGINES

INTERNAL

COMBUSTIONENGINES

EXTERNALCOMBUSTION

ENGINES


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Combustion of fuel takes place outside the cylinder.

The heat of combustion is employed to generate

steam which is used to move piston in the cylinder.

Eg : Steam Engines , Hot air Turbines.

They are generally used in driving locomotives ,

ships , generation of thermal electric power.


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Combustion of fuel takes place within the cylinder

of the engine.

Internal combustion engines can be classified as CI

and SI engines based on the working cycles and

Fuels used.


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1. Overall Efficiency is high.

2. Weight to power ratio is low.

3. Low initial cost.

4. Easy starting in cold conditions.

5. Compact and require less space.


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1. Starting torque will be very high.

2. Cheaper fuels can be used.

3. Flexibility in arrangement.

4. Mechanical Simplicity.


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Cylinder

Cylinder Head

Piston

Piston Rings

Gudgeon Pin

Connecting Rod

Crank Shaft

Crank Case

Flywheel

Valves and Valve Operating M


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PARTS FOR PETROL

ENGINES ONLY

Spark Plugs

Carburettor

Fuel Pump

PARTS FOR D

ENGINES O

Injector

Fuel Pump


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BORE

The inside diameter of the cylinder is called bore.

STROKE

The linear distance between two limiting positions along the cylinder axis is know the stroke

TOP DEAD CENTER

The top most position of the piston is known as TDC or Top Dead Center.

BOTTOM DEAD CENTER

The bottom most position of the piston is known as BDC or Bottom Dead Center.

CLEARANCE VOLUME

The volume above the piston when the piston is at TDC is known as the clearance volume.


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SWEPT VOLUME

The volume swept through by the piston when it moves from TDC to BDC or BDC to TD

as the swept volume.

Hence Total Volume = Swept Volume + Clearance Volume.

COMPRESSION RATIO

It is the ratio of total volume of the cylinder to the clearance volume.

Compression Ratio = Total Volume(Vt) / Clearance Volume

= ( Vs

+ Vc

) / Vc

AIR FUEL RATIO

The mass of air to mass of fuel input to the engine.


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Ideal PV Diagram Actual PV Diagram


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Completion of Cycle

Flywheel

Power/Size

Cooling and Lubrication

Valve and Valve Mechanism

Initial Cost

Volumetric Efficiency

Thermal and Part Load

Efficiency

Applications


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Thermodynamic Cycle

Fuel Used

A/F Ratio

Compression Ratio

Combustion

Fuel Supply

Operating Pressure

Operating Speed

Maintenance

Two Stroke Operation

Power

Distribution

Starting

Noise and Vibration


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Engines can be classified on the basis of

Cycle of Operation

Cycle of Combustion

Arrangement of cylinder

Applications

Speed of Engine

Method of Ignition

Method of Cooling

Valve Arrangement

Method of air induction

Number of cylinders

Fuel Employed

Fuel input method


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The important variable factors which are used as the basis for comparison

are compression ratio, peak pressure, heat addition, heat rejection and th

this section, a comparison of these three cycles is made for the same com

same heat addition, constant maximum pressure and temperature, same

and net work output. This analysis will show which cycle is more efficient

of operating conditions.


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Figures 4 7 3 (a) and (b) show the Otto cycle 1 2 3 4 and


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Figures 4.7.3 (a) and (b) show the Otto cycle 1-2-3-4 and

cycle 1-2'-3-4 on p-V and T-s coordinates, where the

pressure and temperature and the amount of heat reject

the same.

Where, Qs in the area under the curve 2-3 in Fig.4.7.3 (

evident from Fig.4.7.3 that Qs < Qs.

Therefore, the Diesel cycle efficiency is greater than th

cycle efficiency when both engines are built to withsta

same thermal and mechanical stresses.

F i d h t i t th


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For same maximum pressure and heat input, th

4-1) and Diesel cycle

(1-2'-3'-4'-1) are shown on p-V and T-s diagram

(b) respectively. It

is evident from the figure that the heat rejectio

1-5-6-4 on T-s

diagram) is more than the heat rejected in Dies

Hence Diesel cycle is more efficient than Otto c

of same maximum pressure and heat input.


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The following factors are to be considered in evaluating the performanc

Maximum power or torque available at each speed within the u

speed.

Brake Specific Fuel Consumption at each operating Condition wit

range of operation.

Reliability and durability of the engine for the given range of operatio


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Air Standard Efficiency - Thermodynamic Efficiency

Indicated Thermal Efficiency - I.P/(mfX C.V)

Brake Thermal Efficiency - B.P/(mfX C.V)

Mechanical Efficiency - B.P/I.P

Relative Efficiency - Brake Thermal Efficiency / Air Standard Effic

Volumetric Efficiency - Actual Mass of air / Theoretical Mass of Air

Combustion Efficiency - Heat Liberated / Theoretical Heat


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Combustion Rate and Spark Timing

Air Fuel Ratio

Compression Ratio

Engine Speed

Mass of inducted Charge


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IC

EN

GINEFUELS

SOLIDLIQUID

GAS


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Energy Content or Calorific Value

Flash Point

Fire Point

Viscosity

Density

Specific Gravity

Volatility

Specific Heat

Latent Heat of Vapourisation

Pour Point

Sulphur Content

Carbon Residue

Ash and Water Content


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SI ENGINE FUEL

Octane number of the fuel is defined as the percentage by volume of iso octane in a mixtur

heptane, which exactly matches the knocking intensity of the fuel in a standard engine under a set of

conditions.

CI ENGINE FUEL

Cetane number is defined as the percentage by volume of normal Cetane in a mixture of no

Heptamethylnonane(HMN) which has the same knocking characteristics as the test fuels under a set

conditions.


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Parts of IC engines

Terms connected with IC engines

Working cycles

Indicator diagram

Comparison of 4 stroke and 2 stroke engines

Comparison of SI and CI engines

Classification of engines

BASICS

Air standard efficiency of Otto cycle

Air standard efficiency of diesel cycle

Air standard efficiency of dual cycle

Comparison of Otto , diesel and dual cycle

AIR STANDARD CYCLES

Fuels

Fuel properties

Effects of fuel properties

Engine parameters and performance

PERFORMANCE PARAMETERS & FUELS

Documents

Ic Engine by sastra university author