1

INTRODUCTION

A heat engine is a machine, which converts heat energy into mechanical energy. The

combustion of fuel such as coal, petrol, diesel generates heat. This heat is supplied to a working

substance at high temperature. By the expansion of this substance in suitable machines, heat

energy is converted into useful work.

Heat engines can be further divided into two types:

(i) External combustion Engine

(ii) Internal combustion Engine.

In a steam engine the combustion of fuel takes place outside the engine and the steam thus

formed is used to run the engine. Thus, it is known as external combustion engine. In the case

of internal combustion engine, the combustion of fuel takes place inside the engine cylinder

itself.

APPLICATIONS OF IC ENGINE:

I.C. engines have many applications, including:

Road vehicles(e.g. scooter , motorcycle , buses etc.)

Aircraft

Motorboats

Small machines, such as lawn mowers, chainsaws and portable engine-generators

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FUNDAMENTALS OF IC ENGINE

ENGINE CLASSIFICATIONS:

1. Types of Ignition

Spark Ignition (SI).

Compression Ignition (CI).

2. Engine Cycle

Four-Stroke Cycle

Two-Stroke Cycle

3.Types of fuel used

Petrol engine

Diesel engine

Gas engine

4.Number of strokes per cycle

Otto cycle

Diesel cycle

Dual cycle

5. Speed of the engine

Slow speed

Medium speed

High speed

6.Cooling system

Air- cooled

Water cooled

7. Method of fuel injection

Carburetors engine

Air injection engines

8. Number of cylinders

Single cylinder

Multi cylinder

9. Arrangement of cylinders

Horizontal

Vertical

Radial

In-line multi- cylinder

V-type multi- cylinder

Opposite cylinder

Opoosite piston

10. Method of governing

Hit and Miss governed

Quality governed

Quantity governed

11.Valve arrangement

Over Head Valve

L-head type

T-head type

F-head type

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CONSTRUCTIONAL FEATURES & FUNCTIONS OF IC ENGINE :

1. Cylinder :- It is a container fitted with piston, where

the fuel is burnt and power is produced.

2.Cylinder Head/Cylinder Cover:-One end of the

cylinder is closed by means of cylinder head. This

consists of inlet valve for admitting air fuel mixture and

exhaust valve for removing the products of combustion.

3. Piston:- Piston is used to reciprocate inside the

cylinder. It transmits the energy to crankshaft through

connecting rod.

4. Piston Rings:- These are used to maintain a

pressure tight seal between the piston and cylinder

walls and also it transfer the heat from the piston head

to cylinder walls. It is of two types- Compression

rings & Oil control/scrapper rings.

5. Piston /Wrist/Gudgeon pins: It connects the

piston to the end of connecting rod.The pin is retained

in the piston with chips or plugs to prevent cylinder

wall storing & constructed of hardened steel

Fig. Cylinder Block

6.Connecting Rod:- One end of the connecting rod is connected to piston through piston pin while

the other is connected to crank through crank pin. It transmits the reciprocatory motion of piston

to rotary crank.

Fig. Piston & pins Fig. Connecting rod

4

6. Crank:- It is a lever between

connecting rod and crank shaft.

7. Crank Shaft:- The function of

crank shaft is to transform

reciprocating motion in to a rotary

motion.

8. Crank Case:- It supports and

covers the cylinder and the crank

shaft. It is used to store the

lubricating oil.

Fig. Crankshaft

9. Fly wheel:- Fly wheel is a rotating mass used as an

energy storing device It stores energy during power

stroke and returns back the energy during the idle

strokes, providing a uniform rotary motion of flywheel.

The rear surface of the flywheel serves as one of the

pressure surfaces for the clutch plate.

10. Cam Shaft: The shaft that has intake and exhaust

cams for operating the valves. Fig. Camshaft

11.Valves: Minimum two valves per Cylinder

Exhaust Valve: lets the exhaust gases escape the

combustion Chamber. (Diameter is smaller then

Intake valve)

Intake Valve: lets the air or air fuel mixture to enter

the combustion chamber. (Diameter is larger than the

exhaust valve)

Fig. Valves

12. Spark Plug: It provides the means of ignition when the gasoline

engine’s piston is at the end of compression stroke, close to Top Dead

Center(TDC)

Fig. Spark plug

5

Materials used for engine parts:

Sl.

No.

Name of the Parts Materials of Construction

1. Cylinder head Cast iron, Cast Aluminium

2. Cylinder liner Cast steel, Cast iron

3. Engine block Cast iron, Cast aluminum, Welded steel

4. Piston Cast iron, Aluminium alloy

5. Piston pin Forged steel, Casehardened steel.

6. Connecting rod Forged steel. Aluminium alloy.

7. Piston rings Cast iron, Pressed steel alloy.

8. Connecting rod bearings Bronze, White metal.

9. Main bearings White metal, Steel backed Babbitt base.

10. Crankshaft Forged steel, Cast steel

11. Camshaft Forged steel, Cast iron, cast steel,

12. Timing gears Cast iron, Fiber, Steel forging.

13. Push rods Forged steel.

14. Engine valves Forged steel, Steel, alloy.

15. Valve springs Carbon spring steel.

16. Manifolds Cast iron, Cast aluminium.

17. Crankcase Cast iron, Welded steel

18. Flywheel Cast iron.

19. Studs and bolts Carbon steel.

20. Gaskets Cork, Copper, Asbestos.

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IC ENGINE – TERMINOLOGY

Cylinder Bore (d) : inner diameter of the working cylinder (mm)

Piston Area (A) : cross section area of bore (cm2)

Stroke(L): The linear distance

along the cylinder axis between

the two limiting positions of the

piston is called stroke(mm)

Stroke to Bore Ratio (L/d)

d<L - under-square Engine

d = L - Square Engine

d>L - Over Square Engine.

Dead center :Position of working

piston at the moment when the

direction of the piston is reversed at the ether end of the stroke

Top Dead Centre (T.D.C) : The top most position of the piston towards cover end side of

the cylinder” is called top dead centre. In case of horizontal engine, it is called as inner

dead centre

Bottom Dead Centre (B.D.C):The lowest position of the piston towards the crank end side

of the cylinder is called bottom dead centre. In case of horizontal engine, it is called outer

dead centre (O.D.C).

Displacement or Swept Volume (VS): Volume swept by the piston when travelling from

one dead center to the other (cc)

Cubic Capacity or Engine Capacity :Displacement volume ×No. of cylinders

Clearance Volume (VC): The volume contained in the cylinder above the top of the piston,

when the piston is at the top dead centre is called clearance volume.

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

Compression ratio (r) = 𝑉𝑇/ 𝑉c

=(𝑉𝐶+𝑉𝑆 )/𝑉𝐶

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SEQUENCE OF OPERATION:

A. Four Stroke Engine:

A four-stroke engine is an internal combustion engine in which the piston completes four separate

strokes which comprise a single thermodynamic cycle. A stroke refers to the full travel of the

piston along the cylinder, in either direction.

1 piston stroke = ½ crankshaft revolution.

4 piston strokes = 2 crankshaft revolutions.

The four separate strokes are termed:

1. SUCCTION: this stroke of the piston begins at top dead center. The piston descends from the top

of the cylinder to the bottom of the cylinder, increasing the volume of the cylinder. A mixture of

fuel and air is forced by atmospheric (or greater) pressure into the cylinder through the intake port.

2. COMPRESSION: with both intake and exhaust valves closed, the piston returns to the top of the

cylinder compressing the air or fuel-air mixture into the cylinder head.

3. POWER: this is the start of the second revolution of the cycle. While the piston is close to Top

Dead Centre (TDC), the compressed air–fuel mixture in a gasoline engine is ignited, by a spark

plug in gasoline engines, or which ignites due to the heat generated by compression in a diesel

engine. The resulting pressure from the combustion of the compressed fuel-air mixture forces the

piston back down toward Bottom Dead Center (BDC).

4. EXHAUST: during the exhaust stroke, the piston once again returns to top dead center while the

exhaust valve is open. This action expels the spent fuel-air mixture through the exhaust valve(s).

8

B. Two Stroke Engine:

In two stroke cycle engines, the suction and exhaust strokes are eliminated.

There are only two remaining

strokes i.e., the compression

stroke and power stroke and

these are usually called upward

stroke and downward stroke

respectively.

Also, instead of valves, there

are inlet and exhaust ports in

two stroke cycle engines.

The burnt exhaust gases are forced out through the exhaust port by a fresh charge which

enters the cylinder nearly at the end of the working stroke through the inlet port.

The process of removing burnt exhaust gases from the engine cylinder is known as

scavenging.

COMPARISON BETWEEN TWO STROKE AND FOUR STROKE ENGINES

Four stroke engine Two stroke engine

1. One power stroke for every two revolutions

of the crankshaft.

One power stroke for each revolution of the

crankshaft.

2. There are inlet and exhaust valves in the

engine.

There are inlet and exhaust ports instead of

valves.

3. Crankcase is not fully closed and air tight. Crankcase is fully closed and air tight.

4. Top of the piston compresses the charge. Both sides of the piston compress the charge.

5. Size of the flywheel is comparatively larger. Size of the flywheel is comparatively smaller.

6. Fuel is fully consumed. Fuel is not fully consumed.

7. Weight of engine per hp is high. Weight of engine per hp is comparatively low.

8. Thermal efficiency is high. Thermal efficiency is comparatively low.

9. Removal or exhaust gases easy. Removal of exhaust gases comparatively

difficult.

10. Torque produced is even. Torque produced is less even.

11. For a given weight, engine would give only

half the power of two stroke

For same weight, two stroke engine gives twice

the power that of four stroke engine.

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Otto Cycle:

An Otto cycle is an idealized thermodynamic cycle that

describes the functioning of a typical spark ignition piston

engine. It is the thermodynamic cycle most commonly

found in automobile engines.

The processes are described by:

Process 0–1 a mass of air is drawn into piston/cylinder

arrangement at constant pressure.

Process 1–2 is an adiabatic (isentropic) compression of the air as the piston moves from

bottom dead centre (BDC) to top dead centre (TDC).

Process 2–3 is a constant-volume heat transfer to the

working gas from an external source while the piston

is at top dead centre. This process is intended to

represent the ignition of the fuel-air mixture and the

subsequent rapid burning.

Process 3–4 is an adiabatic (isentropic) expansion

(power stroke).

Process 4–1 completes the cycle by a constant-volume process in which heat is rejected from

the air while the piston is at bottom dead centre.

Process 1–0 the mass of air is released to the atmosphere in a constant pressure process.

The Otto cycle consists of isentropic compression, heat addition at constant volume, isentropic

expansion, and rejection of heat at constant volume. In the case of a four-stroke Otto cycle,

technically there are two additional processes: one for the exhaust of waste heat and combustion

products at constant pressure (isobaric), and one for the intake of cool oxygen-rich air also at

constant pressure;

Efficiency of Otto Cycle

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Diesel Cycle:

The Diesel cycle is a combustion process of a reciprocating internal combustion engine. In

it, fuel is ignited by heat generated during the compression of air in the combustion chamber, into

which fuel is then injected. This is in contrast to igniting the fuel-air mixture with a spark plug as

in the Otto cycle (four-stroke/petrol) engine. Diesel engines are used in

aircraft, automobiles, power generation, diesel-electric locomotives, and both surface ships and

submarines.

The image on the left shows a p-V diagram for the ideal Diesel cycle; where is pressure and V

the volume or the specific volume if the process is placed on a unit mass basis. The ideal Diesel

cycle follows the following four distinct

processes:

Process 1 to 2 is isentropic compression

of the fluid

Process 2 to 3 is reversible constant

pressure heating

Process 3 to 4 is isentropic expansion

Process 4 to 1 is reversible constant

volume cooling

Work in ( ) is done by the piston

compressing the air (system)

Heat in ( ) is done by the combustion of the fuel

Work out ( ) is done by the working fluid expanding and pushing a piston (this

produces usable work)

Heat out ( ) is done by venting the air

Net work produced = -

Thermal efficiency of a Diesel cycle is dependent on the compression ratio and the cut-off ratio.

Where, is the cut-off ratio (ratio between the end and start volume for the

combustion phase)

r is the compression ratio

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Dual Cycle:

The dual combustion cycle (also known as the limited pressure or mixed cycle, Trinkler

cycle, Seiliger cycle or Sabathe cycle) is a thermal cycle that is a combination of the Otto cycle and

the Diesel cycle, first introduced by Russian-German engineer Gustav Trinkler. Heat is added

partly at constant volume and partly at constant pressure.

The dual cycle consists of following

operations:

1-2Adiabatic compression

2-3 Addition of heat at

constant volume.

3-4 Addition of heat at

constant pressure.

4-5Adiabatic expansion.

5-1 Rejection of heat at

constant volume.

1)1(

111

1 c

k

c

kcconst

Dualrk

r

rv

2

3

5.2

3 and whereP

Pv

vrc

COMPARISON OF DIESEL ENGINE WITH PETROL ENGINE :

Diesel engine Petrol engine

i) It has got no carburetor, ignition coil and

spark plug.

It has got carburetor, ignition coil & spark

plug.

ii) Its compression ratio varies from 14:1 to

22:1

Its compression ratio varies from 5:1 to 8:1.

iii) It uses diesel oil as fuel. It uses petrol (gasoline) or power kerosine as

fuel.

iv) Only air is sucked in cylinder in suction

stroke.

Mixture of fuel and air is sucked in the

cylinder in suction stroke.

v) It has got ‘fuel injection pump’ and

injector

It has got no fuel injection pump and

injector, instead it has got carburetor and

ignition coil.

vi) Fuel is injected in combustion chamber

where burning of fuel takes places due to

heat of compression.

Air fuel mixture is compressed in the

combustion chamber when it is ignited by

an electric spark.

vii) Thermal efficiency varies from 32 to 38% Thermal efficiency varies from 25 to 32%

viii)Engine weight per horse-power is high. Engine weight per horsepower is

comparatively low.

ix) Operating cost is low. Operating cost is high.

x) Compression pressure inside the cylinder

varies from 35 to 45 kg/cm2 and

temperature is about 500°C.

Compression pressure varies from 6 to 10

kg/cm2 and temperature is above 260°C.

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VALVE TIMING DIAGRAM :

The valve timing of an engine is set to give the best possible performance. This means that

the valves must be opened and closed at very precise times. The traditional way of showing

exactly when the valve opens and closes is by the use of a valve-timing diagram.

As can be seen the valves are opened and closed in relation to the number of degrees of

movement of the crankshaft.

Valve timing diagram of 4- stroke single cylinder diesel engine.

IVO - 25 before TDC

IVC - 30 after BDC

EVO - 45 before BDC

EVC - 15 after TDC

FVO - 15 before TDC

FVC - 25 after TDC

Valve timing diagram of 4- stroke single cylinder petrol engine.(low speed)

IVO - 10 before TDC

IVC - 20after BDC

EVO - 25 before BDC

EVC - 5 after TDC

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Valve timing diagram of 4- stroke single cylinder petrol engine.(high speed)

IVO - 10 before TDC

IVC - 50 after BDC

EVO - 45before BDC

EVC - 20 after TDC

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ENGINE PERFORMANCE PARAMETERS RELATED TO IC ENGINE:

1.Indicated Power- It is defined as the power developed by combustion of fuel in the cylinder of

engine is called (ip). It is always more than brake power. It is given by,

where: is the mean pressure,

is the area of the piston

is the number of cylinders

2.Brake Power- The power developed by an engine and measured at the output shaft is called the

brake power (bp) and is given by,

where: is the torque, in Newton meter (N.m),

is the rotational speed, in minutes,

is the brake power, in watt.

3.Friction Power- Friction power is the difference between indicated power and brake power.

FP = BP-IP

4.Volumetric Efficiency-It is the ratio of actual volume sucked to the displacement volume.

ȵvol = Va/ Vs

5.Mechanical Efficiency- It is defined as ratio of brake power to the indicated power.

ȵmech= BP/IP= BP/(BP+FP)

6.Fuel-Air Ratio-It is the ratio of mass of fuel to mass or volume of air in mixture. It effects the

phenomenon of combustion and used for determining flame propagation velocity, the heat released

in combustion chamber.

For practise always relative air fuel ratio is defined. It is the ratio of actual air -fuel ratio

to that of the stoichiometric air fuel ratio required for burning of fuel which is supplied.

7.Brake specific fuel consumption(bsfc)-It is defined as the amount of fuel consumed for each

unit of brake power per hour . It indicates the efficiency with which the engine develops the power

from fuel. it is used to compare performance of different engines. Bsfc = mf/ BP

8. Indicated Thermal Efficiency(ȵith)- It is the ratio of Indicated Power to energy supplied to the

cylinder.

ȵith = IP/ (mf * CV) where, mf= mass flow rate

CV= Calorific Value of fuel

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9.Brake Thermal Efficiency(ȵbth)- It is the ratio of Indicated Power to energy supplied to the

cylinder.

ȵbth = BP/ (mf * CV) where, mf= mass flow rate

CV= Calorific Value of fuel

10.Relative Efficiency(ȵrel)- It is the ratio of Actual thermal efficiency to Air- standard

efficiency.

ȵrel = ȵact / ȵair- std

CHARACTERISTICS CURVES OF VARIOUS PERFORMANCE PARAMETERS:

1.Brake Specific Fuel Consumption vs Size

• BSFC decreases with engine size due to

reduced heat losses

from gas to cylinder wall.

• Note: cylinder surface to volume ratio

increases with bore diameter.

• rLr

rL

volumecylinder

areasurfacecylinder 12

2

2. Brake Specific Fuel Consumption vs Speed

There is a minimum in the bsfc versus engine

speed curve

At high speeds the bsfc increases due to

increased friction

At lower speeds the bsfc increases due to

increased time for heat losses from the gas

to the cylinder and piston wall

Bsfc increases with compression ratio due

to higher thermal efficiency

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3. Performance Maps

Performance map is used to display the

bsfc over the engines full load and speed

range. Using a dynamometer to measure

the torque and fuel

mass flow rate you can calculate:

bmep = 2 T nR / Vd Pb = 2 N T

FUEL-AIR CYCLE & THEIR ANALYSIS

By air-standard cycle analysis, it is understood how the efficiency is improved by increasing

the compression ratio. However, analysis cannot bring out the effect of air-fuel ratio on the thermal

efficiency because the working medium was assumed to be air.

The fuel-air cycle analysis takes into account the following:

(i) The actual composition of the cylinder gases: The cylinder gases contains fuel, air, water

vapour and residual gas. The fuel-air ratio changes during the operation of the engine which

changes the relative amounts of CO2 , water vapour, etc.

(ii) The variation in the specific heat with temperature: Specific heats increase with temperature

except for mono-atomic gases. Therefore, the value of also changes with temperature.

(iii) The effect of dissociation: The fuel and air do not completely combine chemically at high

temperatures (above 1600 K) and this leads to the presence of CO, H2 , H and O2 at equilibrium

conditions.

(iv)The variation in the number of molecules: The number of molecules present after combustion

depend upon fuel-air ratio and upon the pressure and temperature after the combustion.

Fig. Effect of Variation of Specific Heats Fig. Effect of Dissociation on Power

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Fig. Effect of Dissociation on Power

ACTUAL INDICATOR DIAGRAM

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V.C.R ENGINE SPECIFICATIONS

Product Research Engine test setup 1 cylinder, 4 stroke, Multifuel VCR

with open ECU for petrol mode (Computerized)

Product code 240PE

Engine Type 1 cylinder, 4 stroke, water cooled, stroke 110 mm, bore 87.5

mm. Capacity 661 cc. Diesel mode: Power 3.5 KW, Speed 1500

rpm, CR range 12:1-18:1. Injection variation:0- 25 Deg BTDC

ECU Petrol mode: Power 4.5 KW @ 1800 rpm, Speed range

1200-1800 rpm, CR range 6:1-10:1

Dynamometer Type eddy current, water cooled, with loading unit

Propeller shaft With universal joints

Air box M S fabricated with orifice meter and manometer

Fuel tank Capacity 15 lit, Type: Duel compartment, with fuel metering pipe

of glass

Calorimeter Type Pipe in pipe

Piezo sensor Combustion: Range 5000 PSI, with low noise cable Diesel line:

Range 5000 PSI, with low noise cable

Crank angle sensor Resolution 1 Deg, Speed 5500 RPM with TDC pulse.

Data acquisition

device

NI USB-6210, 16-bit, 250kS/s

Piezo powering unit. Make-Apex, Model AX-409

Engine control unit. PE3 series ECU, full build potted enclosure

Sensors for ECU Air temp, coolant temp, Throttle position and trigger.

Engine

Controlhardware

Fuel injector, Fuel pump, ignition coil, idle air

Digital voltmeter Range 0-20V, panel mounted

Temperature sensor Type RTD, PT100 and Thermocouple, Type K

Temperature

transmitter

Type two wire, Input RTD PT100, Range 0–100 Deg C, Output 4–

20 mA and Type two wire, Input Thermocouple, Range 0–1200

Deg C, Output 4–20 mA

Load indicator Digital, Range 0-50 Kg, Supply 230VAC

Load sensor Load cell, type strain gauge, range 0-50 Kg

Fuel flow transmitter DP transmitter, Range 0-500 mm WC

Air flow transmitter Pressure transmitter, Range (-) 250 mm WC

Software “Enginesoft” Engine performance analysis software

ECU software peMonitor & peViewer software.

Rotameter Engine cooling 40-400 LPH;

Calorimeter 25-250 LPH Pump Type Monoblock

Overall dimensions W 2000 x D 2500 x H 1500 mm

Shipping details: Gross volume 1.33m3, Gross weight 796kg, Net weight 639kg

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DESCRIPTION

The setup consists of single cylinder, four stroke, Multi-fuel, research engine connected to eddy

current type dynamometer for loading. The operation mode of the engine can be changed from

diesel to ECU Petrol or from ECU Petrol to Diesel mode by following some procedural steps. In

both modes the compression ratio can be varied without stopping the engine and without altering

the combustion chamber geometry by specially designed tilting cylinder block arrangement. In

Diesel mode fuel injection point and pressure can be manipulated for research tests. In Petrol mode

fuel injection time, fuel injection angle, ignition angle can be programmed with open ECU at each

operating point based on RPM and throttle position. It helps in optimizing engine performance

throughout its operating range. Air temp, coolant temp, Throttle position and trigger sensor are

connected to Open ECU which control ignition coil, fuel injector, fuel pump and idle air. Set up is

provided with necessary instruments for combustion pressure, Diesel line pressure and crank-angle

measurements. These signals are interfaced with computer for pressure crank-angle diagrams.

Instruments are provided to interface airflow, fuel flow, temperatures and load measurements. The

set up has stand-alone panel box consisting of air box, two fuel tanks for duel fuel test, manometer,

fuel measuring unit, transmitters for air and fuel flow measurements, process indicator and

hardware interface. Rotameters are provided for cooling water and calorimeter water flow

measurement. A battery, starter and battery charger is provided for engine electric start

arrangement.

The setup enables study of VCR engine performance for brake power, indicated power,

frictional power, BMEP, IMEP, brake thermal efficiency, indicated thermal efficiency,

Mechanical efficiency, volumetric efficiency, specific fuel consumption, A/F ratio, heat balance

and combustion analysis. Labview based Engine Performance Analysis software package

“Enginesoft” is provided for on line engine performance evaluation.

20

FUTURE WORKS & DISCUSSION

The compression ratio strongly affects the working process and provides an exceptional degree of

control over engine performance. By the VCR Engine we can easily get Engine performance

parameters.

And also we can compare the theoretical & experimental characteristics of PV plot, IP,

Heat release ,Max power test ,BSFC and brake thermal efficiency, brake mean effective pressure

at different compression ratio(CR) at certain engine speed.

We also studyValve timing diagram ,Open ECU Experimentation which includes 1) Fuel Quantity,

2) Fuel angle 3) Ignition angle 4) Coolant temp .

VCR Engine measure Emission Parameter i.e. Carbon Monoxide (CO) Emission, Hydrocarbon

(HC) Emission, NOX Emission at different Compression ratio.

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CONCLUSION

A VCR engine offers the potential to increase combustion efficiency and decrease emissions under

varying load and speed conditions. High CR increases theoretical thermal efficiency, but decreases

mechanical efficiency. The maximal pressure within a cylinder, and mechanical loses, increases

with an increase of both engine load and CR.

After performing this project work under supervision and guidance of Dr. Dipak Kumar

Mondal(HOD, Mechanical Engg. Dept.) , we have gained the ideas about the various features of

this research engine setup & what are the things that can be done by this engine.

So, We think that this research engine project is immensely beneficial to our educational as

well as industrial career in future.