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SINGLE-CYLINDER FOUR-STROKE PETROL ENGINE WITH ELECTRICAL DYNAMOMETER

Aim

:

To conduct a performance testing on single cylinder four stroke petrol

engine. Theory : The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an ICE the expansion of the high temperature and pressure gases, which are produced by the combustion , direct applies force to a movable component of the engine by moving it over a distance , generate useful mechanical engineering. All internal combustion engines depend on the exothermic chemical process of combustion. The reaction of a fuel, typically with oxygen from the air. The combustion process typically result in the production of a great quantity of heat, as well as the production of steam and carbon dioxide and other chemical at very high temperature, the temperature reached is determined by the chemical mack up of the fuel and oxidizers. The principle behind any reciprocating ice engine : if you put a tiny amount of a high energy fuel in a small, enclosed space and ignite it ; an incredible amount of a energy is released in the form of expanding gas.

 Classification of a I C Engines :Internal combustion engine may be classified as given below : A. According to cycle of operation :

 Two- stroke engine  Four- stroke engine

B. According to cycle of combustion :  Otto cycle engine  Diesel cycle engine  Dual cycle engine

C. According to the fuel employed and the method of fuel supply to the engine cylinder :  Petrol engine  Diesel engine  Oil , Gas engine

D. According to the method of ignition :  Spark ignition (S.I. ) engine  Compression ignition (C.I.) engine

E. According to method of cooling the cylinder :  Air cooled engine  Water cooled engine

F. According to number of cylinders :  Single- cylinder engine  Multi- cylinder engine  Different parts for I.C engines :

Cylinder , cylinder head, piston, piston rings, gudgeon pin, connecting road, crank-shaft, engine bearing, crank case, flywheel, governor, cam shaft, valves and valve operating mechanism.

 Parts for petrol engine only : Spark plug, Carburetor, Fuel pump  Parts for diesel engine only : Fuel pump, Injector  Four Stroke Petrol-Engine :

The Four-stroke cycles refers to its use in petrol engines, gas engines, light oil engine and heavy oil engines in which the mixture of air fuel are drawn in the engine cylinder. Since ignition in these engine is due to a Spark, there for they are also called as a spark ignition engines.

a. Suction Stroke or Intake Stroke In this stroke the inlet valve opens and proportionate fuel-air mixture is sucked in the engine cylinder. Thus the piston moves from top dead centre (T.D.C) to bottom dead centre (B.D.C). The Exhaust valve remains closed throughout the stroke. b. Compression Stroke In this stroke both the inlet and exhaust valve remains closed during the stroke. The piston moves towards (T.D.C) and compressed the enclosed fuel-air mixture drawn. Just before the end of this stroke operating plug initiate a spark which is ignites the mixture and the combustion takes place at a constant pressure. c. Power Stroke or Expansion Stroke In this stroke both the inlet valve remain closed during the start of this stroke but when the piston just reaches the B.D.C. the exhaust valves opens. When the mixture is ignited by the spark plug the hot gases are produced which drive or throws the piston from T.D.C to B.D.C and thus the work is obtained in this stroke. d. Exhaust Stroke Exhaust Stroke is the last stroke of the cycle. Here the gas from which the work has been collected becomes useless after the competition of the expansion stroke and are made the escape through exhaust valve to atmosphere. This removal of gas is accomplished during this stroke. The piston moves from B.D.C to T.D.C. and the exhaust gases are driven out of the cylinder. This is also called “Scavenging”

Theoretical Diagram of P.V. of Petrol Engine 1.8 Working Principle of Electrical Dynamometer Generators use an armature surrounded by a set of unmoving field coils, likes a DC motor. The field coils are powered and the regulator controls current to the fields to control the output of the generator. As the armature turns, electrical current is induced in its windings. One of the greatest advantages of generator was very clean electrical output, since they produced pure DC. However, all the current had to travel through the brushes and brush leads, this produced a lot of heat, and when the brushes would pass over the bars in the commutator, small electrical arcs would be produced, which shortened the life of brush. To counter this, the brushes were made very hard, which more out the commutator faster. Because all current travelled through the brushes, most generators had maximum output of 50 amps.

Generator also needed a cut-out relay to disengage power to the generator when not charging. This was done so that the generator would not pick up the power and turns into a motor, burning out when not being spun by the engines.

Brake Power (B.P.) =

𝑽 ×𝑰 𝟏𝟎𝟎𝟎

×

𝟏 𝜼𝒈

(Kw)

Where, 1. V = Voltmeter Reading 2. I = Ammeter Readings 3. 𝜂𝑔 = Generator Efficiency = 65%

1.9 Exhaust Gas Calorimeter The Exhaust gas calorimeter is a simple heat exchanger in which, part of the heat of the exhaust gases is transferred to the circulating water. This calorimeter helps to determine the mass of exhaust gases coming out of the engine. The arrangement of the exhaust gas calorimeter is shown in fig

Exhaust Gas Calorimeter

The exhaust gases from the engines exhaust are passed through the exhaust gas calorimeter by closing the valve B and opening the valve A. The hot gases are cooled by the water flow rate is adjusted with the help of valve of ‘C’ to give a measurable temperature rise to water circulated. If it is assumed that the calorimeter is well insulated, there is no heat loss except by heat transfer from the exhaust gases to the circulating water.

2.0 Test Rig Control panel Burette

For measuring the fuel consumption per unit time.

Manometer

For measuring the air consumption.

Temperature Indicator

For measuring the temperature at various locations.

2.1 Experimental Procedure 1. Before starting the engine check the fuel supply, lubrication oil, and availability of cooling water. 2. Set the dynamometer to zero load and run the engine till it attain the working temperature and steady state condition. 3. Note down the fuel consumption rate, Engine cooling water flow rate,inlet and outlet temperature of the engine cooling water , Exhaust gases cooling water flow rate, Air flow rate, and Air inlet temperature. 4. Set the dynamometer to 20% of the full load, till it attains the steady stste condition. Note down the fuel consumption rate, Engine cooling water flow rate, inlet and outlet temperature of the engine cooling water, Exhaust gases cooling water flow rate, Air flow rate, and Air inlet temperature. 5. Repeat the experiment at 40%, 60%, and 80% of the full load at constant speed. 6. Disengage the dynamometer and stop the engine. 7. Do the necessary calculation and prepare the heat balance sheet.

Precautions Do not start engine in loaded conditions Do not stop engine in loaded condition Engine should be run at least once a week

2.2 Observation 1. Specifie gravity of petrol

0.739 Kg / m3

2. Calorific value petrol

42000KJ/Kg

3. Diameter of orifice (d)

0.014 m

4. Coefficient of discharge of orificemeter (cd)

0.65

5. Density of Air at room Temperature (Pa)

1.2 Kg/m3

6. Specific heat of exhaust gas (CP g)

1.05 KJ/Kg – 0 K

7. Specific het of water (CP g)

4.184 KJ/Kg – 0K

8. Density of exhaust gas

1 Kg/ m3

9. Density of water (P w)

1000 Kg/ m3

10. Density of petrol (P a)

737.22 Kg/m3

2.3 Single Cylinder Four Strock Petrol Engine Specifications(HONDAGX160)

 Engine Type

Air-cooled 4-strock OHV

 Bore x strock

68 X 45 mm

 Displacement

163 cm3

 Net power output

4.8HP (3.6 kW)@3,6000rpm

 POT shaft Rotation

counter clockwise (from POT shaft side)

 Compression Ratio

9.0:1

 Lamp/charge coil options

25W , 50W / 1A , 3A, 7A –

 Carburettor

Butterfly

 Ignition system

Transistorized magneto

 Starting System

Recoil Starter

 Lubrication System

splash

 Governor system

Centerifugal Mechanical

 Air cleaner

Dual Element

 Oil Capacity

0.61US qt. (0.58 L)

 Fuel Tank Capicity

3.3 U.S .qts. (301 litters)

 Fuel

Unleaded 86 octane or higher

 Dry Weight

33 lbs. (15.1 Kg)

TABULAR COLUMN(PERFOMANCE TEST OF ENGINE): Sr.

Load

No

Speed

Manometer

Time

Temperatures

Voltmeter

(N)

Difference

required for

0

&

RPM

(hw) mm

50 ml fuel

Ammeter

consumption

Readings

C

T1 1.

T2 T3 T4 V

I

Heater 1

2.

Heater 2

3.

Heater 3

4.

Heater 4

5. 6.

 Flow of Water from exhaust gases calorimeter (1Litter=0.98kg) Thermocouple Locations  T1= Exhaust Gas inlet Temp.  T2= Exhaust Gas outlet Temp.  T3= Water inlet Temp. to exhaust gas calorimeter  T4= Water outlet Temp. From exhaust gas calorimeter

-……… (Kg/s)

2.2 CALCULATION 1. Fuel consumption (Kg/s) Fuel consumption (Mf) =

50ml ×10−6 × 𝜌 𝑡

(Kg/s)

Where, 1. Ρ = Density of Petrol = 737.22 (Kg/m3) 2. Here, 1ml = 10-3 litters 1000 litters = 1 m3 So, 1 ml = 10-3 m3 3. t = time required for 50 ml fuel consumption (s)

2. Brake Power (Kw) Break Power (B.P.) =

𝑉 ×𝐼 1000

×

𝐼 𝜂𝑔

(Kw)

Where, 4. V = Voltmeter Reading 5. I = Ammeter Reading 6. 𝜂𝑔 = Generator Efficiency = 65%

3. Break Thermal Efficiency (%) Break Thermal efficiency (𝜂𝐵𝑡ℎ ) =

𝐵.𝑃. 𝑀𝑓 ×𝐶.𝑉.

× 100 %

Where, 1. C.V. = Calorific value of Petrol = 42000(kJ/kg) 2. Mf = Fuel Consumption =……….. (Kg/s) 3. B.P. = Break Power = …………. (Kw)

4. Heat energy available from the fuel brunt (KJ/hr)

Qs = Mf × C.V. × 3600 (KJ/hr)

5. Heat energy equivalent to output break power (KJ/hr)

QB.P. = B.P. × 3600 (KJ/hr)

6. Heat energy lost to engine cooling water (KJ/hr)

QCW = mw × Cpw (t6-t5) × 3600 (KJ/hr)

Where 1. Mw = Mass of water (Kg/s) 2. Cpw = Specific Heat of water = 4.184 (KJ/Kg- 0K) 3. T4 = Outlet Temperature fro Exhaust gas calorimeter = 0C + 273 =……… (K) 4. T3 = Inlet Temperature from exhaust gas calorimeter = 0C + 273 =………. (K)

7. Heat energy carried away by the exhaust gases (KJ/hr) QEG = mw × Cpw × (t4 – t3) ×3600 (KJ/hr) Where, 1. mw = Mf + Mair (Fuel consumption + mass of air) (Kg/s) 2. Cpw = Specific heat of water = 4.184 (KJ/Kg – 0K) 3. 𝑡4 = Outlet Temperature from Exhaust gas Calorimeter =0 C + 273 =……… (K) 4. 𝑡3 = Inlet temperature from Exhaust gas calorimeter = 0C + 273 =………. (K) 8. Mass of Air (Kg/s)

Mair = Cd × Ao × √2𝑔ℎ𝑤 (𝜌𝑤 /𝜌𝑎 ) (Kg/m) Where, 1. Cd = Coefficient of Orifice meter = 0.6 2. Ao = Area of Orifice meter = 1.539 × 10-4 (m2) 3. ℎ𝑤 = Manometer Difference =…………(m) 4. 𝜌𝑤 = Density of water = 1000 Kg/m3 5. 𝜌𝑎 = Density of Air = 1.2 Kg/m3

9. Unaccounted heat energy loss (KJ/hr) 𝑄𝑢𝑛𝑎𝑐𝑐𝑜𝑢𝑛𝑡𝑒𝑑 = Qs – {QBP + QCW + QEG} (KJ/hr)

2.7 Heat Balance Sheet

Heat

KJ/hr

%

Heat Energy

Energy

Consumed

Supplied

(Distribution)

Heat

100%

a) Heat

KJ/hr

energy

Energy

Equivalent

available

output

from

power. (QBP)

the

fuel burnt

to break

b) Heat energy lost

(Qs)

to

engine

cooling

water.

(QCW) c) Heat

energy

carried away by exhaust

gases.

(QEG) d) Unaccounted heat

Energy

loss. (𝑸𝐮𝐧𝐚𝐜𝐜𝐨𝐮𝐧𝐭𝐞𝐝 ) Total

100%

Total

%