6

Explain Morse test conducted to find the frictional power of a multi-cylinder petrol engine

Morse Test

Morse test is a method to measure the frictional power of a multicylinder SI engine.

Morse Test – This test carried out on multi cylinder I.C. engine. In this test, first engine is allowed to run at constant speed and brake power of engine is measured when all cylinders are working and developing indicated power. (Considering Four cylinders)

I1+I2+I3+I4 = (BP)engine +(F1+F2+F3+F4)

Where I1, I2, I3 and I4 – Indicated power of four cylinders

(BP)engine – Brake power of engine when all cylinders are working

F1, F2, F3, F4 – Frictional power of all four cylinders

Then the first cylinder is cut off by short circuiting spark plug in case S.I. engine (or cutting fuel supply in case C.I. engine). This causes the speed to drop due to non firing of first cylinder. It should be noted that although first cylinder is not producting power still it is moving up and down so its frictional power must be considered. This speed is once again maintained to its original value by reducing load on the engine

4

A petrol engine has a cylinder of diameter 60 mm and stroke 100 mm. If the mass of charge admitted per cycle is 2×10 – 4 kg. Find volumetric efficiency of the engine.

6

a) Define : i) Stroke ii) Bore iii) Piston speed iv) MEP (Mean Effective Pressure).

a) i) Stroke – Distance travelled by piston from one dead Centre to other dead Centre (Say TDC to BDC). ii) Bore:- The nominal Inner diameter of engine cylinder is called cylinder bore. iii) Piston Speed- Distance traveled by piston in one minute.(= 2LN m/min.) iv) The Mean Effective Pressure (MEP) :-It is a fictitious pressure that, if it operated on the piston during the entire power stroke, would produce the same amount of net work as that produced during the actual cycle. OR The average pressure acting on the piston which will produce the same output as is done by the varying pressure during the cycle

8

The following results were obtained during Morse test on 4-stroke petrol engine. Brake power developed when all cylinders working = 16.2 kW Brake power developed when 1 st cylinder cutoff = 11.5 kW Brake power developed when 2 nd cylinder cutoff = 11.6 kW Brake power developed when 3 rd cylinder cutoff = 11.68 kW Brake power developed when 4 th cylinder cutoff = 11.57 kW Calculate mechanical efficiency and friction power.

4

Define the following w.r.to. I.C. engine. i) Indicated power ii) Brake power iii) Volumetric efficiency iv) BSFC

(i) Indicated Power: The total power developed by combustion of fuel in the combustion chamber is called indicated power.

(ii) Brake Power: The power developed by an engine at the output shaft is called brake power.

(iii) Volumetric efficiency: It is defined as the ratio of the actual volume of the charge admitted into the cylinder to the swept volume of the piston is known as volumetric efficiency.

( iv) Brake specific fuel consumption: It is the mass of fuel consumed per kw developed per hour, and is a criterion of economical

6

What is meant by catalytic converter ? Briefly explain with the help of neat sketch.

Catalytic converter:

harmless gases. Catalytic converter is used in exhaust emission in control system to convert CO, NOx, HC and other harmful gases to harmless gases. A Catalytic converter consists of a cylindrical unit of small size like a small silencer and is installed into the exhaust system of a vehicle. It is placed between the exhaust manifold and the silencer. Inside the cylindrical tube i.e. converter there is a honey comb structure of a ‘ceramic or metal’ which is coated with ‘alumina base’ material and there after a second coating of precious metals ‘platinum, palladium or rhodium’ or combination of the same. This second coating serves as a catalyst. A catalyst is a substance which causes a chemical reaction intro the gases. When the exhaust gases pass over the converter substance, the toxic gases as CO, HC & NOx are converted into harmless gases as CO2, H2 & N2. 

6

Explain in brief, how ‘Morse test’ is carried out ?

First engine is allowed to run at constant speed and brake power of engine is measured when all four cylinder working. (IP1 + IP2 + IP3 + IP4) = (BP) 1234 + (FP) 1234  Where, IP- indicated power. BP – brake power develop. FP – frictional power.

8

Following observations were made during a trial on 4-stroke, single cylinder engine running at 240 rpm having brake wheel diameter 1.5 meter. Duration of trial 30 min. Fuel consumption 6 liter C.V. of fuel 42000 kJ/kg Sp. gravity 0.8 IMEP 550 kPa Brake load 150 kg Spring balance reading 15 kg Cylinder diameter 30 cm Stroke length 45 cm Jacket cooling water 11 kg/min Temp. rise in jacket water 36°C Determine : i) I.P. and B.P. ii) Heat balance sheet on percentage basis.

4

Explain the term w.r.t. I.C. engine. i) Mean Effective Pressure (MEP) ii) Cut off ratio.

( i ) Mean effective pressure – Defined as the average pressure acting on the piston which will produce the same output as is done by the varying pressure during the cycle.

( ii ) Cut off ratio – Fuel is injected into combustion chamber where only air compressed and is at high temperature. Fuel is injected for a duration of time, say T. The piston would not have reached the bottom dead centre in time T. The fuel is cut off when the volume is, say V2. The clearance volume is V1. The ratio V2/V1 is cut off ratio.

6

A four cylinder engine running at 1200 rpm delivers 20 kW. The average torque when one cylinder was cut is 110 N.m. Find the indicated thermal efficiency if the calorific value of the fuel is 43 MJ/Kg and the engine uses 360 gm. of gasoline (fuel) per kW. hr.

8

A four stroke gas engine has a cylinder diameter of 25 cm and stroke 45 cm. The effective diameter of brake is 1.6 m. The observations made in a test of the engine were as follows. Duration of test = 40 min. Total no. of revolutions = 8080 Total no. of explosions = 3230 Net load on brake = 90 kg Mean effective pressure = 5.8 bar Volume of gas used = 7.5 m3 Pressure of gas = 136 mm of water Atm. temp. = 17°C Calorific value of gas = 19 MJ/m3 at NTP Rise in temp. of jacket cooling water = 45°C Cooling water supplied = 180 kg Draw heat balance sheet and estimate indicated thermal efficiency and brake thermal efficiency. Assume atmospheric pr. as 760 mm of Hg.

4

State the norms of Bharat stage III and IV

Bharat stage III and IV norms :

Petrol Emission Norms (All figures in g/km) Emission Norm CO HC NOx HC+NOx PM BS-III 2.30 0.20 0.15 --- --- BS-IV 1.00 0.10 0.08 --- --- Diesel Emission Norms (All figures in g/km) Emission Norm CO HC NOx HC+NOx PM BS-III 0.64 --- 0.50 0.56 0.05 BS-IV 0.50 --- 0.25 0.30 0.025

CO emissions are Carbon Monoxide emissions are are more evident in Petrol engines. Long Term exposure can prevent oxygen transfer and increase headaches/nausea. HC emissions are Hydrocarbons which are again more prevalent in Petrol engines. Short term exposure can cause headaches, vomiting and disorientation. NOx emissions are Nitrogen Oxide emissions which are more prevalent in Diesel engines. Long Term exposure can cause Nose and eye irritation and damage lung tissue. PM is Particulate matter, again more prevalent in a Diesel engine. Long Term exposure can harm the respiratory tract and reduce lung function.

6

List the additives of lubricant used in S.I engine and state their advantages.

Additives (any six ) (1) Detergents – To keep engine parts, such as piston and piston rings, clean & free from deposits. (2) Dispersants – To suspend & disperse material that could form varnishes, sludge etc that clog the engine. (3) Anti – wear – To give added strength & prevent wear of heavily loaded surfaces such as crank shaft rods & main bearings. (4) Corrosion inhibitors – To fight the rust wear caused by acids moisture. Protect vital steel & iron parts from rust & corrosion. (5) Foam inhibitors – control bubble growth, break them up quickly to prevent frothing & allow the oil pump to circulate oil evenly. (6)Viscosity index improver – added to adjust the viscosity of oil. (7) Pour point depressant - improves an oil ability to flow at very low temperature

6

What is the necessity of I.C. Engine Testing ? What are the different test carried out on I.C. Engines ?

Necessity of I.C. engine testing i) To get information, that is not possible to be determine by calculations. ii) To confirm the validity of data used while designing the engine. iii) To satisfy the customer as to rated power with guarantied fuel consumption. iv) To reduce the cost and to improve the power output and reliability of an engine. v) To know & improve the performance of an engine. Test carried out on I.C. Engine – 1) Commercial Tests 2) Thermodynamic Tests 1) Commercial Tests – These tests are carried out in order to check following a) Rated power out-put with guarantied fuel consumption in kg/kw hr b) Quantity of lubricating oil per kw-hr c) Quantity of cooling water per kw-hr d) Steadiness of engine under varied load conditions e) Overload carrying capacity of the engine 2) Thermodynamic Tests – These tests are carried out for the purpose of comparing actual results with theoretical results by measuring following parameters and then drawing heat balance sheet. i) Indicated power ii) Brake power iii) Frictional power iv) Rate of fuel consumption v) Rate of flow of cooling water and its temperature rise vi) Heat carried by exhaust gas

8

An I.C. Engine uses 6 kg of fuel having calorific value 44000 kJ/kg in one hour. The IP developed is 18 kW. The temperature of 11.5 kg of cooling water was found to rise through 25°C per minute. The temperature of 42 kg of exhaust gas with specific heat 1 kJ/kg°k was found to rise through 220°C. Draw the heat balance sheet for the engine.

4

What are the effects of pollutants on environment ?

The major air pollutants emitted by petrol & diesel engines are CO2, CO, HC, NOx, SO2, smoke & lead vapour. Effect of CO: (1) Carbon monoxide combines with hemoglobin forming carboy hemoglobin ,which reduces oxygen carrying capacity of blood. (2) This leads to laziness, exhaustion of body & headache. (3) Prolong exposure can even leads to death. (4) It also affects cardiovascular system, thereby causing heart problem Effect of CO2: Causes respiratory disorder & suffocation. Effect of NOx: • It causes respiration irritation, headache, bronchitis, pulmonary emphysema, impairment of lung, loss of appetite , & corrosion of teeth to human body. Effect of HC: • It has effect like reduced visibility, eye irritation , peculiar odour & damage to vegetation & acceleration the cracking of rubber products. • It induce cancer, affect DNA & cell growth are know a carcinogens. Effect of SO2: It is toxic & corrosive gas, human respiratory track of animals, plants & crops

6

Write any three pollutants in exhaust gasses of petrol and diesel engine with their effects on environment.

The major air pollutants emitted by petrol & diesel engines are CO2, CO, HC, NOx, SO2, smoke & lead vapour. Effect of CO:  Carbon monoxide combines with hemoglobin forming carboy hemoglobin ,which reduces oxygen carrying capacity of blood.  This leads to laziness, exhaustion of body & headache.  Prolong exposure can even leads to death.  It also affects cardiovascular system, thereby causing heart problem Effect of CO2: Causes respiratory disorder & suffocation. Effect of NOx: It causes respiration irritation, headache, bronchitis, pulmonary emphysema, impairment of lungs, and loss of appetite & corrosion of teeth to human body. Effect of HC: • It has effect like reduced visibility, eye irritation, peculiar odour & damage to vegetation & acceleration the cracking of rubber products. • It induce cancer, affect DNA & cell growth are know a carcinogens. Effect of SO2: It is toxic & corrosive gas, human respiratory track of animals, plants & crops

4

What is catalytic convertor ? Explain two way catalytic convertor with neat sketch

Catalytic converter is a device which converts harmful pollutants to harmless gases. Catalytic converter is used in exhaust emission in control system to convert CO, NOx, HC and other harmful gases to harmless gases. A Catalytic converter consists of a cylindrical unit of small size like a small silencer and is installed into the exhaust system of a vehicle. It is placed between the exhaust manifold and the silencer. Inside the cylindrical tube i.e. converter there is a honey comb structure of a ‘ceramic or metal’ which is coated with ‘alumina base’ material and there after a second coating of precious metals ‘platinum, palladium or rhodium’ or combination of the same. This second coating serves as a catalyst. A catalyst is a substance which causes a chemical reaction intro the gases. When the exhaust gases pass over the converter substance, the toxic gases as CO, HC & NOx are converted into harmless gases as CO2, H2 & N2

4

Define the following related I.C. engine. i) Indicated power ii) Brake power iii) Brake specific fuel consumption iv) Relative efficiency.

i) Indicated Power (ip) is defined as the power developed by combustion of fuel in the cylinder of engine. It is always more than brake power. ii Brake Power:-  The useful power which is available at the crank shaft is called as brake power.  It is denoted by “B.P.”  It has unit kW iii) B.S.F.C: It is the weight of fuel required to develop 1KW of the brake power for period of 1 hour. Unit of B.S.F.C is Kg/KWh. It is defined as the amount of fuel consumed per unit of break power developed per hour.

iv) Relative efficiency is defined as the ratio of indicated / brake thermal efficiency to the air standard efficiency.

6

What do you mean by: 1) frictional power 2) brake thermal efficiency 3) BSFC, w.r.to I.C. engine

1) Friction Power:- The difference between indicated power and brake power.  It is the power lost in friction FP =IP -BP

8

During a trial on 4-stroke gas engine following observations were recorded: Bore = 300 mm ; Speed = 200 rpm Stroke = 400 mm ; Gas used = 11.7 m3/h Number of explosions/min = 90 Gauge pressure of gas = 170 mm of water Barometer reading = 755 mm of Hg Mean effective pressure = 6 bar Calorific value of gas used = 21500 KJ/kg at N.T.P. Net load on brake = 2 KN Brake drum diameter = 1.2 m Ambient temperature = 27°C Calculate: (i) mechanical efficiency (ii0 brake thermal efficiency.

Indicated power – IP = PmepLAN Where Pmep – 6 bar – mean effective pressure - 6 x 100 kN/m2 L – Length of stroke in m

Assuming CV of gas used as 21,500 kj/m3 at NTP instead of 21,500 kJ/kg at NTH Heat supplied by fuel in kJ/sec. = 0.00300 x 21,500

4

Various efficiencies of 4-stroke petrol engine run at full throttle over its speed range are plotted in Fig. No. 2. Label different efficiency curves (indicated by 1, 2, 3, 4). Which conclusion can be drawn from this figure.

6

State different methods of determining frictional power of I.C. engine and explain any one method

Methods to determine the frictional power of I.C. engine are`

1. Willan’s line method 2. Morse test 3. Motoring test 4. Difference between i.p. and b.p.

Explanation of any one method

4

Define :  i) Brake thermal efficiency ii) BSFC related to I.C. Engine.

i) Brake thermal efficiency – It is defined as the ratio of heat equivalent to brake power per unit time to the heat supplied to the engine per unit time Brake thermal efficiency = B.P./ mf x C.V. 

ii) BSFC – It is the mass of fuel required to develop 1 kW brake power for a period of one hour. It is inversely proportional to the brake thermal efficiency. BSFC = Mass of fuel consumed in kg/hr / Brake power in kW

4

State effects of pollutants in exhaust gases of petrol engine.

The major air pollutants emitted by petrol engines are CO2, CO, HC, NOx, SO2, smoke & lead vapour. 

Effect of CO:

Carbon monoxide combines with hemoglobin forming carboy hemoglobin, which reduces oxygen carrying capacity of blood.

1. This leads to laziness, exhaustion of body & headache. 2. Prolong exposure can even leads to death. 3. It also affects cardiovascular system, thereby causing heart problem

Effect of CO2: Causes respiratory disorder & suffocation.

Effect of HC: 1. It has effect like reduced visibility, eye irritation, peculiar odour & damage to vegetation & acceleration the cracking of rubber products. 2. It induce cancer, affect DNA & cell growth are know a carcinogens.

Effect of SO2: It is toxic & corrosive gas, human respiratory track of animals, plants & crops.

4

State advantages of closed cycle gas turbine.

Advantages of closed cycle gas turbine:

(i) It has higher thermal efficiency for the same minimum and maximum temperature limits and for the same pressure ratio.

(ii) Since the heating is external, any kind of fuel even solid fuel having low calorific value may be used.

(iii) There is no corrosion due to circulation of combustion product.

(iv) As the system is a closed one there is no loss of the working fluid.

(v) The size of the turbine will be smaller compared to an open cycle gas turbine of the same output.

(vi) The regulation is more simple.

(vii) The heat transmission coefficient in the exchanger is better due to the increase in suction pressure.

(viii) Loss due to fluid friction is less due to higher Reynolds number.

4

State any four types of sensors used in I.C. engine.

Following sensors are used in ECU:  A permanent magnet inductive signal generator is mounted in close proximity to the flywheel, where it radiates a magnetic field. As the flywheel spins and the pins are rotated in the magnetic field, an alternating (AC) waveform is delivered to the ECM to indicate speed of rotation.

Air Flow Sensor (AFS): The AFS is normally located between the air filter and the throttle body. As air flows through the sensor, it deflects a vane (flap) which wipes a potentiometer resistance track and so varies the resistance of the track and generates a variable voltage signal. Manifold absolute pressure (MAP) sensor: The MAP sensor measures the manifold vacuum or pressure, and uses a transducer to convert the signal to an electrical signal which is returned to the ECM. The unit may be designed as an independent sensor that is located in the engine compartment or integral with the ECM.

Coolant temperature sensor (CTS): The CTS is a two-wire thermistor that measures the coolant temperature. The CTS is immersed in the engine coolant, and contains a variable resistor that usually operates on the NTC principle.

Throttle Position Sensor (TPS): TPS is provided to inform the ECM of idle position, deceleration, rate of acceleration and wide-open throttle (WOT) conditions. The TPS is a potentiometer which varies the resistance and voltage of the signal returned to the ECM.

Oxygen sensor (OS): An oxygen sensor is a ceramic device 'placed in the exhaust manifold on the engine side of the catalytic converter. The oxygen sensor returns a signal to the ECM, which can almost instantaneously (within 50 ms) adjust the injection duration