Diesel engine

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INSTRUCTION MANUAL OF FOUR STROKE FOUR CYLINDER DIESEL ENGINE TEST RIG WITH HYDRAULIC DYNAMOMETER

AIM: TO CONDUCT A TRIAL ON FOUR STROKE PETROL ENGINE WITH ELECTRICAL DYNAMOMETER.

INTRODUCTION AND THEORY:
A heat engine is a device, which performs the chemical energy of a fuel into thermal energy and uses this energy to produce mechanical work. Heat engines are classified into two broad types.
Any type of engine or Machine, which derives heat energy from the combustion of fuel or any other sources and converts this energy into Mechanical work, is termed as heat engine.
1. EXTERNAL COMBUSTION ENGINES &
2. INTERNAL COMBUSTION ENGINES.

INTERNAL COMBUSTION ENGINES:
Internal combustion engine in which the combustion of fuel takes place inside the cylinder is known as I.C. Engine. In an internal combustion engine, the products of combustion are directly the motive fluid.
Diesel engine and petrol engine are the examples of this type, where the working substance is the product of combustion.
Reciprocating Internal combustion Engines offers following Advantages over External Combustion Engines:
Ø Overall Efficiency is High.
Ø Greater Mechanical Simplicity.
Ø General Lower Initial cost.
Ø Easy Starting from Cold conditions.
Ø These Units are Compact and Thus Require less Space.
Ø Weight to Power Ratio is Generally Lower.

I.C. ENGINE CLASSIFICATION

The I.C. engine can be classified on the following basis
Ø WORKING CYCLE
(a) Spark Ignition Engines
(b) Compression Ignition Engines
Ø NO. OF STROKES
(a) Two Stroke Engines
(b) Four Stroke Engines



PARTS COMMON TO BOTH PETROL AND DIESEL ENGINE

1. CYLINDER
2. CYLINDER HEAD
3. PISTON
4. PISTON RINGS
5. GUDGEON PIN
6. CONNECTING ROD
7. CRANKSHAFT
8. CRANK
9. ENGINE BEARING
10. CRANK CASE
11. FLYWHEEL
12. GOVERNOR
13. VALVES AND VALVE OPERATING MACHNIES

PARTS FOR PETROL ENGINES ONLY

1. SPARK PLUGS
2. CARBURETOR
3. FUEL PUMP

PARTS FOR DIESEL ENGINE ONLY

1. FUEL PUMP
2. INJECTOR

CYLINDER: The Cylinder Contains Gas under Pressure and Guides the Piston. It is in direct contact with the Products of Combustion and it must be cooled. It is one of the most important part of the engine in which the piston moves to and fro in order to develop power. Generally, the engine cylinder has to withstand a high-pressure more than 50 kg/cm2 and temperature more than 2000c.The Cylinder is made of hard Grade Cast Iron and is Usually cast in One Piece.
Engine bodies are designed of STEEL ALLOYS or ALLUMINIUM ALLOYS.

CYLINDER HEAD: Head is an arrangement which covers cylinder bore and consists of suction and exhaust valves. Cylinder and Cylinder head are made from same material, usually cast as one piece.
The Main function of Cylinder head is to seal the working ends of the Cylinder and not to Permit entry and exit of Gases on cover head valve engines.

PISTON: Piston is the heart of an engine whose main function is to transmit the force exerted by the burning of charge to connecting rod. A Piston is fitted to each Cylinder as a face to receive gas Pressure and transmit the thrust to the Connecting Rod

PISTON RINGS: Piston rings are housed in the circumferential grooves provided on the outer surface of the piston. Two sets of rings are used generally.
The function of upper ring is to provide airtight seal to prevent leakage of burnt gases in to the lower piston. Similarly, the function of lower ring is to provide effective seal to prevent leakage of the oil ring in to the engine cylinder.
CONNECTING ROD: It is a link between the position and crankshaft.
Function - To Transmit force from the piston to the crack shaft. Reciprocating motion is converted in to circular motion of crack shaft.
A special care is to be taken while designing the crankshaft, as it is subjected to alternatively compressive and tensile stresses, as well as bending stresses. A connecting rod is made of special steel alloys or aluminum alloys.

CRANK SHAFT: Crankshaft is the back of an engine. It consists of one or more eccentric portions called cranks. That part of the crank, to which bigger end of the connecting rod is fitted, with the help of crank pin.The Crank Shafts of an Internal combustion Engine receive via its cranks the Efforts supplied by the Pistons to the connecting Rods. The Shape of the Crankshafts i.e. the mutual arrangements of cranks depends on the numbers and arrangements of Cylinders and the Turning Order of the engine.

CRANK CASE: It holds the cylinder and crankshaft of an engine. It also serves as a sump for the lubricating oil.

FLYWHEEL: A wheel mounted on the crankshaft, whose function is to maintain its speed constant. It is done by storing excess energy during the power stroke, which is returned during other strokes.
The weight of the Flywheel depends on the Nature of variation of the Pressure.

TESTING OF I.C. ENGINE:
An internal combustion engine is put to the thermodynamic tests, to determine the following quantities.

1) POWER AND MECHANICAL EFFICIENCY:
The main purpose of running an engine is mechanical power. Power is defined as the rate of doing work and linear velocity or the products of torque and angular velocity. Thus, the measurement of power involves the measurement of force (Torque) as well as speed. The first is done with the help of dynamometer, and latter by a tachometer or by some other suitable device.
The power developed by an engine at the out shaft is called the brake power (B.P.) and is given by -

B.P. = 2הּ N T

Where,
T is torque Nm
N is rotational speed in rev / sec.
T = W x R.
Where,
W = 9.81 x Net mass in kg applied.
R = Radius in m.
The total power developed by combustion of fuel in the combustion chamber is however more than the B.P. and is called indicated power. Some is consumed is overcoming friction between moving parts, some in the processes of inducting the air and exhausting the products of combustion from the engine combustion chamber.
Indicated power is the power developed in the cylinder and thus forms the basis of evolution of combustion efficiency or the heat release in the cylinder.
The difference between I.P. and B.P. is the induction of the power lost in the mechanical components of the engine and forms the basis of mechanical efficiency, which is defined as follows and given on the next page.

1) MECHANICAL EFFICIENCY: - B.P. / IP.
The difference between I.P. & B.P. is called friction power (F.P.)
F.P. = I.P. - B.P.
Mechanical Efficiency -B.P. / (B.P. + F.P.)

2) VOLUMETRIC EFFICIENCY:
It is defined as the ratio of the mass of air inducted in to the engine cylinder during the suction stroke to the mass of air corresponding to the swept volume of the engine at atmospheric temperature and pressure.
Alternatively, it can be defined as the ratio of the actual volume inhaled during suction stroke measured at intake conditions to the swept volume of the piston.

3) FUEL - AIR RATIO (F/A):
Fuel air ratio is the ratio of the mass of air in the fuel air mixture. Air fuel ratio is the reciprocal of the fuel air ratio.

4) SPECIFIC FUEL CONSUMPTION - (S F C) :
Specific fuel consumption is defined as the amount of fuel consumed per unit of power developed per hour.
S. F. C. = FUEL CONSUMED IN GRAMS PER HOURHORSE POWER DEVELOPED

5) BRAKE SPECIFIC FUAL CONSUMPTION (BSFC):
BSFC is determined based on brake out put of the engine while indicated specific fuel consumption (ISPC) is determined based on indicated out put of the engine.

6) THERMAL EFFICIENCY:
Thermal efficiency of an engine is defined as the ratio of the out put to that of the chemical energy input in the from of fuel supply. It may be based on brake or indicated out put.

7) HEAT BALANCE:
The energy in put to the engine goes out in various forms, a part is in the form of brake out put, a part goes in to exhaust and the rest is taken by cooling water, and lubricating oil. The brake up of the total energy in put in to these different parts is called the heat balance.

DETAILED SPECIFICATION OF TEST RIG :

A) ENGINE

1) MAKE – TATA Engine
2) SPEED – 800- 6000 RPM.

B) HYDRAULIC DYNAMOMETER -

An Hydraulic Dynamometer is coupled to engine.

C) AIR INTAKE MEASUREMENT:
Intake tank fitted with orifice and water manometer.

D) FUEL INTAKE MEASUREMENT:
Calibrated Burette arrangement fitted on the control panel to measure the fuel consumption with 2 Nos. Ball valves to control and measure the quantity of fuel consumed.
E) EXHAUST GAS CALORIMETER:
Water-cooled exhaust gas calorimeter, shell and coil type to study the heat lost to exhaust gases. Water flows inside the copper tubes and exhaust Gases flows in the shell.

F) MULTI CHANNEL TEMPERATURE INDICATOR :
For measuring inlet and out let temperature of exhausts gases and water from Engine Cooling Jacket and Calorimeter with Cr-Al Thermocouples.
1. Water Inlet Temp. to Engine and calorimeter.
2. water Outlet Temp. to Engine
3. Water Outlet Temp. to Calorimeter.
4. Exhaust Gas inlet Temp. to Calorimeter.
5. Exhaust Gas Outlet Temp. to Calorimeter.
6. Ambient Temp.

PROCEDURE

Ø Adjust the flow rate of water for calorimeter and Engine jacket.
Ø Now adjust the flow rate of water for Electrical Dynamometer.
Ø Start the engine - To start the engine start the ignition switch that turn the flywheel.
Ø First, measure the speed of the engine with the Help of Tachometer (Not supplied along with this Unit)
Ø Then measure the time required for consumption of Fuel.
Ø Measure the flow of cooling water from calorimeter from engine jacket with the Help of measuring Flask and stopwatch.
Ø Then take the reading of Manometer and Temp indicator.
Ø Than take all these reading by increasing load.
Ø Note Down all the readings in the Observation Table.

OBSERVATIONS


1) Specific gravity of fuel (c) - 0.76
2) Calorific value of fuel - 42500 KJ / kg.
3) Dia of Orifice - 32.0 mm.
4) Coefficient of discharge of orifice meter (Cd) - 0.62.
5) Density of air (Pa) - 1.207 kg/m3
6) Specific heat of water - 4.2 kJ/Kg0k
7) Specific heat of exhaust gas - 1 KJ/kg/ 0k
8) Water ambient temp.= __________0 C
9) Air ambient temp.= _________ 0C


OBSERVATION TABLE
S.NO.
Manometer
Difference
H1-H2
(Metesrs)
Fuel
Consumption
For
50 ml
Water
Flow rate
Engine
Jacket
(Kg/Sec.)
Water Flow rate
Calorimeter
(Kg/Sec.)

1.










S.NO.
T1
0C

T2
0C
T3
0C
T4
0C
T5
0C

T6
0C

1.















CALCULATIONS

1. BRAKE POWER: -

W x N
B.P = -----------------------
2,000

= ____________ KW
2. TOTAL FUEL CONSUMPTION: - KG/SEC.
FINAL READING – INITIAL READING SP.GRAVITY
TFC = ------------------------------------------------------ x --------------------
TIME 1000

Where,
TIME IS IN SECOND

SP GRAVITY OF FUEL = 0.76

C C (ml) Sp Gravity
TFC = --------------- x ----------------- KG/S
Time 1000

3. BREAK SPECIFIC FUEL CONSUMPTION
TFC
= ----------- x 3600 Kg/ Kw. Hr.
BP


Where,
TFC IN Kg/Hr
BP IN KW.


4. BRAKE THERMAL EFFICIENCY: -
BP
= ---------------- x 100
TFC x CV

BP IN KW
TFC IN Kg/SEC
CV= 42500 KJ /Kg

5. AIR FUEL RATIO
MASS OF AIR CONSUMED IN UNIT TIME Ma
= ------------------------------------------------------------ = -------
MASS OF FUEL CONSUMED IN UNIT TIME Mf

MASS OF AIR Ma = Q x pa
Q = Cd A √2g ha

WHERE Cd = 0.62

A = AREA OF ORIFICE METER M2
g = 9.81
DIA. OF ORIFICE = 32 mm

pw x Hw
ha = ----------------- m
pa

HW = H1 - H2

WHERE

pw = DENSITY OF WATER = 1000

Hw = MANOMETER READING (mtrs)

pa = DENSITY OF AIR = 1.178

MASS OF AIR Ma = Q x pa

9. HEAT BALANCE

(A)Total heat input (H i/p) = TFC x C.V = ___________KW
Where,
TFC in Kg/sec
CV in KJ/Kg = 42500 for Petrol

(B)Heat Carried Away by Cooling Water(In Engine Cooling Jacket )
= Hwat. (in KJ/sec) = mw x Cpw x (Tw2-Tw1)
Where,
Tw2 - Tw1 = Difference in temperature (in 0C)
mw = Cooling water flow rate (Kgs/Sec)
Cpg = Sp heat of water 4.187 KJ/Kg0C
(C)Heat Converted to BP (Hbp)
2πNT
BP = -----------
60

(D) Heat Carried Away by Exhaust Gases.(KJ/Sec)=
(Heat gained by water in exhaust gas calorimeter from exhaust gases) + (Heat in exhaust gases at exit from exhaust gas Calorimeter above Room Temperature)
= mw x Cpw x (Tw3-Tw1) + mg x Cpg x (T5-Tr)

where,
mg = Mass of Exhaust Gases formed per minute
= Fuel Supplied/Sec. x (Air Fuel Ratio + 1)Kg/sec
Cpg = Specific Heat of Exhaust Gases =1.05Kj/Kg K


(E)Heat Unaccounted = {Total Heat Input } – {Heat converted to B.P + Heat carried by exhaust gases + Heat carried away by Cooling Water)
















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