8

Differentiate vapour compression and vapour absorption refrigeration system. (min. eight points of difference)

Differences between Vapour Absorption and Vapour Compression refrigeration system

4

What is machine ? Differentiate between a machine and a structure.

8

Explain the construction and working of doubled acting reciprocating compressor with neat sketch.

Double acting reciprocating air compressor is similar to double acting reciprocating pump. It is comprised of following parts: 1) Cylinder 2) Piston and piston rod and connecting rod. 3) Crank and crank case 4) Two suction valves and two delivery valves. 5) One inlet port and one outlet port It uses four bar mechanism. There are 4 valves (2 suction valves and 2 delivery valves) shown at A, B, C, D in figure. There are cooling fans similar to single acting compressors. The crank rotates on electric motor/engine/turbine. In this compressor, compression of air takes place on both side of the piston. When crank rotates, the piston starts reciprocating. When piston comes down and attains, ‘Bottom dead center piston’ the air comes in through port ‘A’ due to vacuum created due to downward movement. When piston starts moving upward, the air starts compressing. When piston attains, ‘Top dead center piston’, the stroke is complete and air is fully compressed which goes out through delivery valve ‘B’ to air receiver. During this upward movement the vacuum is created on other side (Piston rod side) of piston. Suction valve ‘C’ opens and air comes in. When piston starting comes down, this air which came through valve ‘C’, gets compressed and compressed air goes out through delivery valve ‘D’ to air receiver. In this downward movement air comes in through valve ‘A’ and entire cycle repeats.

4

Explain Klein’s construction to determine velocity and acceleration of different links in single slider crank mechanism.

Klein’s construction

a) For velocity of different links

b) For acceleration of different links

8

State two applications each of cotter joint and knuckle joint.

Applications of cotter joint: cotter foundation bolt, big end of the connecting rod of a steam engine, joining piston rod with cross head, joining two rods with a pipe Applications of knuckle joint: link of bicycle chain, tie bar of roof truss, link of suspension bridge, valve mechanism, fulcrum of lever, joint for rail shifting mechanism

4

Explain with neat sketch different types of follower.

4

State the composition of the materials 30 Ni 16 Cr5, 40C8, FeE230 X15Cr25Ni 12

30 Ni 16 Cr5 : alloy steel carbon 0.3% of average, Nickel 16%, chromium 5% 40C8 : Plain carbon steel carbon 0.4% of average, manganese 0.8% FeE230 : Steel with yield strength of 230N/mm2

X15Cr25Ni12 : high alloy steel carbon 0.15% of average, chromium 25%, Nickel 12%,

4

List any four pollutants in exhaust gases of I.C. engine with their effects.

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

The crank and connecting rod of steam engine are 0.5m and 2m long respectively. The crank makes 180r.p.m. in clockwise direction. When it has turned through 45° from I.D.C. Find the velocity of piston and angular velocity of connecting rod by relative velocity method.

4

Draw symbols of: (i) Oil reservoir (ii) Oil filter (iii) Heat exchanger (iv) Unidirectional fixed displacement pump.

4

Compare cross belt drive and open belt drive on the basis of - (i) Velocity ratio (ii) Direction of driven pulley (iii) Application (iv) Length of belt drive

4

Explain the principle of regenerative circuit.

Principle of regenerative circuit is recovering the energy available with returning oil by using regeneration technique. The concept of re-generative circuit is explained from following figure. Consider the double acting cylinder. Pressurized oil from pump is admitting in cylinder cavity through port (A). Due to pressure force piston is moving from right to left. During this movement, the oil present on piston rod side of piston starts coming out through port (B). This oil will return to the oil reservoir via DC valve. It is clear from figure that, returning oil will enter in pressure pipe through pipe ‘P’ During exit of oil through port (B), some energy is still there with oil on piston rod side. This energy is otherwise wasted if this oil directly goes to oil reservoir. To avoid wastage of this energy, pipe ‘P’ is connected so that, the pressurized oil gets more energy and it will create more pressure force while entering through port (A).

4

State the applications of : (i) Band brake (ii) Disc brake (iii) Internal expanding shoe brake (iv) External shoe brake

4

Explain why bolts of uniform strength are preferred. Draw sketches of two different types of bolts of uniform strength

bolts of uniform strength: if a shank dia.is reduced to a core dia.as shown in fig. the stress become same through out the length of the bolt. Hence impact energy is distributed uniformly throughout the bolt length, thus relieving the threaded portion of high stress. The bolt in this way becomes stronger and lighter. This type of bolt is known as bolt of uniform strength.Another method of obtaining the bolt of uniform strength is shown in fig.in this method, instead of reducing the shank dia.an axial hole is drilled through the head down to

the threaded portion such that the cross sectional area of the shank becomes equal to the area of the threaded portion If bolts of uniform strength are not used a large portion of impact energy will be absorbed in the threaded portion and relatively a small portion of energy is absorbed by a shank. This uneven distribution of impact energy may lead to the fracture of the bolt in threaded portion .hence bolts of uniform strength are preferred.

4

Name four sensors used in I.C. engine and explain working of any one.

Sensor used in IC engines ( Explanation of any one )

A sensor is an input device that provides variable information on an engine function. Examples of sensors include the airflow sensor (AFS), crank angle sensor (CAS), throttle potentiometer sensor (TPS) etc, and these provide data on load, rpm, temperature, throttle opening etc. This data is signaled to the ECM, which then analyses the results and computes an output signal. The output signal is used to actuate an n output device.

Crank angle sensor: 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. If a pin is intentionally omitted at two points on the flywheel, or by contrast a double pin is used, the signal will vary at these points, and a reference to TDC will be returned to the ECM. The location of the positional signal is not at TDC, but may be some other point fixed by the VM. When used, the CAS provides the primary signal to initiate both ignition and fuelling.

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. 01 03 MAHARASHTRA STATE BOARD OF TECH From the voltage returned, the ECM is able to calculate idle position, full-load and also how quickly the throttle is opened.

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.

4

Draw pilot operated DA cylinder circuit using 4 × 2 DC valve and 3 × 2 pilot valve

4

Explain with neat sketch working principle of epicyclic gear train.

4

Explain the process of combustion in diesel engine.

Combustion in CI Engines :The combustion in CI engines is taking place in following stages as shown in figure 1. Ignition delay period: During this period, some fuel has been admitted but not yet ignited. The delay period is a sort of preparatory phase. It is counted from the start of injection to the point where P-ɵ curve separates from air compression curve. 2. Rapid or uncontrolled combustion : In this stage , the pressure rises rapid because during the delay period the fuel droplets have time to spray and have fresh air around them. This period is counted from end of delay period to the max pressure on indicator diagram. 3. Controlled combustion : uncontrolled combustion is followd by controlled combustion stage. The period of this stage assumed to be at the end of max cycle temperature. 4. After burning : It is expected to end combustion process after third stage. Because of poor distribution of fuel particles combustion still continues during remaining part of expansion stroke. This is after burning .

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.

4

State four examples of ergonomic considerations in the design of a lathe machine.

Ergonomics consideration in the design of Lathe machine Any 4 1) The controls on lathe should be easily accessible and properly positioned. 2) the control operation should involve minimum motions. 3) Height of lathe should be match with worker for operation 4)Lathe machine should make less noise during operation. 5) force& power capacity required in turning the wheel as per operation or human being can apply normally. 6) should get required accuracy in operation.

4

Write the equation with Wahl’s factor, used for design of helical coil spring. State the SI unit of each term in the equation

4

State four important modes of gear failure.

Modes of Gear Failure: ANY 4 modes 1. Bending failure. Every gear tooth acts as a cantilever. If the total repetitive dynamic load acting on the gear tooth is greater than the beam strength of the gear tooth, then the gear tooth will fail in bending, 2. Pitting. It is the surface fatigue failure which occurs due to many repetition of Hertz contactstresses. 3. Scoring. The excessive heat is generated when there is an excessive surface pressure, high speed or supply of lubricant fails. 4. Abrasive wear. The foreign particles in the lubricants such as dirt, dust or burr enter betweenthe tooth and damage the form of tooth. 5. Corrosive wear. The corrosion of the tooth surfaces is mainly caused due to the presence ofcorrosive elements such as additives present in the lubricating oils

4

Draw symbol of: 1) 2 × 2 DC valve 2) Fixed type flow control valve 3) Pressured relief valve. 4) Muffler

4

Describe with neat sketch the working of Oldham’s coupling.

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

Explain the design procedure of shaft on the basis of torsional rigidity. State the equation with SI units. State two applications of this approach.

6

Draw S-N curve. Explain the concept of endurance limit and its need in design of machine elements

Endurance Limit: It is defined as maximum value of the completely reversed bending stress which a polished standard specimen can withstand without failure, for infinite number of cycles (usually 107 cycles).It is known as endurance or fatigue limit (ϭe). Need of Endurance Limit in Machine Design: Endurance limit is used to describe a property of materials: the amplitude (or range) of cyclic stress that can be applied to the material without causing fatigue failure.

4

Discuss the working of Rope brake dynamometer with the help of a neat sketch.

4

Explain the process of balancing of single rotating mass by a single mass rotating in the same plane.

m = Mass attached to shafts,

r = Distance of CG from axis of rotation.

Consider mass ‘m’ is attached to rotating shaft at a radius are then the centrifugal force exerted by mass ‘M’ on the shaft is

F_c = Mw2R Where,

W = Angular velocity of shaft

R = Distance of CG from axis of rotation

M = Mass attached to shaft.

Due to continuous rotation of shaft the centrifugal force developed will be continuously changing its direction. It will cause bending moment on shaft. To counter act the effect of centrifugal force the balance weight may be introduced in same plane of rotation. This balance weight should be attached it will result in exactly equal but opposite centrifugal force to that of disturbing weight ‘M’.

The balanced centrifugal force is given by F_b = mbw2Rb For balancing the shaft – Mw²R = mbw²R_b.

8

Explain with neat sketch construction and working of ice plant.

Working of Ice plant: The main cycle used for ice plant is vapor compression cycle with ammonia as the refrigerant in primary circuit and brine solution in secondary circuit. Brine solution takes heat from water in secondary circuit and delivers the heat to ammonia in primary circuit. Thus, the indirect method of cooling is used in ice plant. In secondary circuit brine is cooled in evaporator and then it is circulated around the can which contains water. The heat is extracted from the water in the can and is given to the brine. The brine is contentiously circulated around the can with the help of brine pump till entire water in the can is converted into ice at -6 0 C. Ammonia vapor coming out of evaporator is compressed to high pressure and then these vapors are condensed in the condenser. High pressure liquid ammonia is collected in the receiver and it is passed through the expansion valve to reduce its pressure and temperature as per requirement. The throttle liquid ammonia at low temperature & low pressure enters in evaporator, which are the coils dipped in brine tank. The liquid ammonia absorbs heat from brine and gets converted into vapors, which are drawn by suction line of compressor.

8

Draw symbol of any three types of Hydraulic motors.

8

Design a helical compression spring with ground ends. The spring index is 12. Maximum load on the spring is 100N and deflection under maximum load is 15 mm. Allowable shear stress of the material is 100 MPa and modulus of rigidity is 4 MPa. Find wire and spring diameters, number of coils and stiffness of spring.

8

A single cylinder reciprocating compressor has a bore of 120 mm and a stroke of 150 mm. and is driven at a speed of 1200 rpm. It is compressing CO2 gas from a pressure of 120 Kpa and temp. of 20°C to a temp. of 215°C. Assuming polytropic compression with n = 1.3, no clearance and volumetric efficiency of 100% calculate (i) pressure ratio, (ii) Indicated power, (iii) shaft power with mech. efficiency 80%, (iv) mass flow rate

8

Explain working of directly operated (Poppet type) check valve with neat sketch.

When oil under pressure is supplied to port A, the oil exerts pressure on the ball against the spring force, hence the ball will be lifted off from its seat and creates a passage for

oil to flow. Hence oil can flow from port A to port B. when under pressure is supplied in opposite direction that is to port B, the oil force the ball to sit firmly in its seat, hence the passage is closed by ball. The oil cannot flow port B to port A.

8

8

State two engineering applications of each of Acme and Buttress thread profiles with neat sketches.

Engg. Application of ACME Thread profiles : 1)screw cutting lathes,2) brass valves,3) cocks and 4) bench vices.

4

Derive strength equation for parallel fillet weld subjected to tensile load.

Derivation of strength equation for parallel fillet weld subjected to tensile load The parallel fillet welded joints are designed for shear strength. Consider a double parallel fillet welded joint as shown in Fig.

4

Define the following terms as applied to cam with neat sketch. (1) Pitch circle (2) Pressure angle (3) Stroke of follower (4) Module

(1) Pitch circle- Circle drawn from centre of cam through pitch points.

(2) Pressure angle- Angle between direction of follower motion and normal to pitch curve.

(3) Stroke- Maximum travel of follower from its lowest position to top most position.

(4) Module –(Gears) – Ratio of pitch circle diameter in mm to No. of teeth on gear.

4

State two applications of leaf spring. Draw neat sketch of leaf spring

Application of Leaf spring Bus/truck/Car suspension springs, diving board, Sketch of Leaf Spring of semi elliptical Type

Given Data: D=250 mm , P=1.5 N/mm2 , n =12 Nos. ,σt = 30 Mpa

4

Compare meter in circuit and meter out circuit

4

A steam engine cylinder has effective diameter of 250 mm. It is subjected to maximum steam pressure of 1.5 MPa. The cylinder cover is fixed to the cylinder with the help of 12 bolts. The pitch circle diameter of bolts is 400 mm. Permissible tensile stress of the bolt material is 30 MPa. Determine nominal diameter of the bolts.

4

Draw the hydraulic circuit for shaping machine. Explain its working

Parts of shaper machine: Fixed DA cylinder, spool type DC valve, spool shaft stroke adjusting lever, pump, pressure relief valve, return line with filter, oil reservoir. Working: Forward stroke: As shown in fig ,the pump is supplying oil to DA cylinder through DC valve and through port B. Hence piston will move from right to left with force and this is a cutting stroke. Backward Stroke: When lever touches the stopper, then spool shifts to right and flow directions in DC valve change. The oil is entering through port A of DA cylinder and piston will move from left to right. During this stroke, the tool post slightly lift with ideal stroke.

4

Differentiate between sliding contact and rolling contact type bearings.

4

Explain the principle of Ram jet with neat sketch

Ram jet – (Fig – 2 marks ; explanation –2 marks) - Ram jet is also called as ‘Athodyd or flying stove pipe’. - It is a steady combustion or continuous flow engine & has the simplest construction of any propulsion engine. - Consist of inlet diffuser, combustion chamber & exit nozzle. - Air entering into ram jet with supersonic speed is slowed down to sonic speed in supersonic diffuser, increasing air pressure. - The air pressure is further increased in the subsonic diffuser. - The fuel injected into the combustion chamber is burned with the help of flame stabilizers. The high temp & high pressure gases are passed through the nozzle converting the pressure energy into kinetic energy. - It is not self operating at zero flight velocity. It requires launching rockets.

4

A taper roller bearing has a dynamic load capacity of 26 kN. The desired life for 90% of the bearing is 8000 hr. and speed is 300 rpm. Calculate equivalent radial load that the bearing can carry

4

Write the equations for air standard efficiency of otto cycle and diesel cycle and state various terms involved in it.

4

 Define : i) Compression ratio (Rc) ii) Swept volume (vs) iii) Cut off ratio iv) Clearance volume (vc)

4

Write uses of compressed air.

 Uses of compressed air:- 1. Cleaning automobiles 2. Pneumatic tools 3. Supercharging in I.C. engines 4. Cooling of large building 5. Construction of bridges, roads etc. 6. Spraying points 7. Spraying fuel in high speed diesel engine 8. Starting of I.C. engines

4

Draw a neat sketch of vane compressor and label the different parts.

2

State four applications of flywheel.

Applications of flywheel : Used in Internal combustion engines, press machines, mills, punching machines.

2

Why is balancing of rotating parts necessary for high speed engines ?

The high speed of engines and other machines is a common phenomenon now-a-days. It is, therefore, very essential that all the rotating and reciprocating parts should be completely balanced as far as possible. If these parts are not properly balanced, the dynamic forces are set up.

These forces not only increase the loads on bearings and stresses in the various members, but also produce unpleasant and even dangerous vibrations. The balancing of unbalanced forces is caused by rotating masses, in order to minimize pressure on the main bearings when an engine is running.

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

6

Explain the procedure for conducting Morse test.

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

Explain with neat sketch working principle of Oldham’s coupling.

When the driving shaft A is rotated, the flange C (link 1) causes the intermediate piece (link 4) to rotate at the same angle through which the flange has rotated, and it further rotates the flange D (link 3) at the same angle and thus the shaft B rotates. Hence links 1, 3 and 4 have the same angular velocity at every instant. A little consideration will show that there is a sliding motion between the link 4 and each of the other links 1 and 3.

4

Define linear velocity, angular velocity, absolute velocity and state the relation between linear velocity and angular velocity.

4

Describe stepwise procedure for determination of velocity and acceleration by Klein’s construction with suitable data.

Steps in Klein’s construction :

 Klein’s construction is a simpler construction to get velocity and acceleration diagrams. For example : for reciprocating engine mechanism OPC. draw a circle with PC as diameter as shown. and obtain velocity diagram OCM ie. produce PC to cut perpendicular to line of stroke in ‘M’ . Draw another circle with ‘C’ as center and “CM” as radius cutting the first circle in points K and L. Join “KL” which is the chord common to both the circles. Let it cuts PC and OP in “Q” and “N” respectively. Then “OCQN” is the required quadrilateral which is similar to acceleration diagram.

4

The central distance between two shaft is 4 m having two pulleys with diameter having 500 mm and 700 mm respectively. Find length of belt required (i) for open belt drive (ii) for cross belt drive

4

Draw actual valve timing diagram for 4-stroke petrol engine.

4

Explain turb charging with a neat sketch.

4

Explain three way catalytic convertor.

4

Explain with a neat sketch turbo propeller w.r.to Jet propulsion

4

Explain the concept of super heating and sub cooling with the help of P-h and T-s charts

4

What are the causes of detonation in I.C. engine ?

The loud pulsating noise heard within the engine cylinder is known as detonation. The following are the certain factors which causes detonation. (1) The shape of the combustion chamber. (2) The relative position of the sparking plugs in case of petrol engines. (3) The chemical nature of the fuel. (4) The initial temp & pressure of fuel (5) The rate of combustion of that portion of fuel which is the first to ignite. This portion of fuel in heating up , compresses the remaining unburnt fuel, thus producing the condition for auto ignition to occur.

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

Explain with neat sketch turning moment diagram for a four-stroke engine.

4

What are the methods to improve thermal efficiency of gas turbine ? Explain any one method.

4

What is jet propulsion ? Give the classification of jet propulsion system.

Jet Propulsion: This is done by expanding the gas which is at high temperature & pressure through the nozzle so that the gas with very high velocity leaves the nozzle giving thrust in opposite direction. - Principle is based on Newton’s Second & third law of motion. Jet propulsion – Classification (1) Atmospheric jet engines (breathing engine) -Turbojet engine - Turbo prop engines - Ram jet (2) Rocket engine (Non - breathing engine)

4

Three masses 10 kg, 20 kg and 15 kg are attached at a point at radii of 20 cm, 25 cm and 15 cm respectively. If the angle between successive masses is 60° and 90°. Determine analytically the balancing mass to be attached at radius of 30 cm.

8

Differentiate between reciprocating and rotary compressors

8

Construct a cam profile with knife edge follower having an offset of 10 mm for the following data : Outstroke = 60° with SHM Dwell = 30° Return = 60° with uniform velocity and remaining is dwell period. Minimum radius of cam = 50 mm Lift of follower = 25 mm Consider the rotation of cam in clockwise direction.

8

Draw a neat sketch of vapour compression refrigeration cycle. Describe its working

Vapour compression refrigeration cycle Vapour compression refrigeration cycle consist of four different processes 1) Compression 2) Condensation 3) Expansion 4) Evaporation Components and its functions 1) Compressor – The low pressure & temperature refrigerant from evaporator is drawn into compressor. It is compressed to a high pressure & high temp. vapour refrigerant is discharged into condenser. 2) Condenser – High pressure & temperature vapour refrigerant is cooled and condensed by using air or water & form liquid vapour refrigerant. Heat is rejected 3) Expansion valve – to control flow of refrigerant and reducing it pressure and temperature 4) Evaporator – liquid vapour refrigerant at low pressure and low temperature is evaporated by absorbing heat from system or substance and change into vapour refrigerant.

4

What is MPFI ? Explain any one MPFI system with neat sketch.

The MPFI means multi point injection system. In this system each cylinder has number of injector to supply/ spray fuel in cylinder as compared to one injector located centrally to supply and spray fuel in case of single point injection system

4

(i) Define ‘Gear Train’. State its purpose and types of gear train.  

Definition: When two or more gears are made to mesh with each other to transmit power from one shaft to another. Such a combination is called gear train

Purpose: The purpose of the train used is

To obtain correct & required velocity ratio between driver & driven shafts.

To decide upon the relative position of the axes of shafts.

To decide upon amount of power to be transmitted between shafts

Types: Following are the different types of gear trains, depending upon the arrangement of wheels :

1. Simple gear train,

2. Compound gear train,

3. Reverted gear train, and

4. Epicyclic gear train.

8

A simple band brake is operated by lever 40 cm long. The brake drum diameter is 40 cm and brake band embrance 5/8 of its circumference. One end of band is attached to a fulcrum of lever while other end attached to pin 8 cm from fulcrum. The coefficient of friction 0.25. The effort applied at the end of lever is 500 N. Find braking torque applied if drum rotates anticlockwise and acts downwards.

8

An engine of a car has a single plate clutch developed maximum torque 147 N-m. External diameter of clutch plate is 1.2 times its internal diameter. Determine the dimension of clutch plate and axial force provided by the spring. The maximum pressure intensity of the clutch facing 98 kN/m2 and coefficient of friction is 0.3. Assume uniform wear condition.

4

Explain the working of window air conditioner with neat sketch.

The low pressure and low temperature refrigerant vapour from evaporator is sucked by compressor. The compressor compresses the vapour to high pressure and high temperature and discharges to the condenser. On the condenser the refrigerant vapour condenses by dissipating heat to the cooling medium (air) the liquid refrigerant coming out of condenser passes through filter, dryer into capillary tube where it is again throated back to the evaporated pressure. The low pressure low temp liquid refrigerant then flows to evaporator which it boil off by extracting heat from air to be circuited to the conditioned space.

4

State any four industrial uses of compressed air.

1) To drive air motors in coal mines. 2) To inject fuel in air injection diesel engines. 3) To operate pneumatic drills, hammers, hoists, sand blasters. 4) For cleaning purposes. 5) To cool large buildings. 6) In the processing of food and farm maintenance. 7) For spray painting in paint industry. 8) In automobile & railway braking systems. 9) To operate air tools like air guns. 10) To hold & index cutting tools on machines like milling / cnc machines.

4

What is pre-ignition ? State any two factors responsible for pre-ignition.

In S.I. engine, the spark is timed to occur at a definite point just before the end of the compression stroke. If the ignition starts, due to any other reason, when the piston is still doing its compression stroke, it is known as pre – ignition.  Following factors are responsible for Pre – ignition 1) High compression ratio 2) Overheated spark plug 3) Incandescent carbon deposit in cylinder wall 4) Overheated exhaust valve 5) It may occur due to faulty timing of spark production

4

Differentiate between Knuckle joint and Cotter joint. (any four points of difference)

2

Define slip and creep in the belt.

Slip : When the frictional grip becomes insufficient. This may cause some forward motion of the driver without carrying the belt with it. This may also cause some forward motion of the belt without carrying the driven pulley with it. This is called slip of the belt and is generally expressed as a percentage. Creep : When the belt passes from the slack side to the tight side, a certain portion of the belt extends and it contracts again when the belt passes from the tight side to slack side. Due to these changes of length, there is a relative motion between the belt and the pulley surfaces. This relative motion is termed as creep.

2

State any two advantages of V belt drive over flat belt drive.

Advantages -1. The V-belt drive gives compactness due to the small distance between the centres of pulleys.

2. The drive is positive, because the slip between the belt and the pulley groove is negligible.

3. Since the V-belts are made endless and there is no joint trouble, therefore the drive is smooth.

4. It provides longer life of 3 to 5 years.

5. It can be easily installed and removed.

6. The operation of the belt and pulley is quiet.

7. The belts have the ability to cushion the shock when machines are started.

8. The high velocity ratio (maximum 10) may be obtained.

9. The wedging action of the belt in the groove gives high value of limiting ratio of tensions. Therefore the power transmitted by V-belts is more than flat belts for the same coefficient of friction, arc of contact and allowable tension in the belts.

10. The V-belt may be operated in either direction with tight side of the belt at the top or bottom. The centre line may be horizontal, vertical or inclined.

4

What are the steps involved in general design procedure? Explain.

1. Recognition of need. First of all, make a complete statement of the problem, indicating the need, aim or purpose for which the machine is to be designed. 2. Synthesis (Mechanisms). Select the possible mechanism or group of mechanisms which will give the desired motion. 3. Analysis of forces. Find the forces acting on each member of the machine and the energy transmitted by each member. 4. Material selection. Select the material best suited for each member of the machine. 5. Design of elements (Size and Stresses). Find the size of each member of the machine by considering the force acting on the member and the permissible stresses for the material used. It should be kept in mind that each member should not deflect or deform than the permissible limit. 6. Modification. Modify the size of the member to agree with the past experience and judgment to facilitate manufacture. The modification may also be necessary by consideration of manufacturing to reduce overall cost. 7. Detailed drawing. Draw the detailed drawing of each component and the assembly of the machine with complete specification for the manufacturing processes suggested. Prepare assembly drawing giving part numbers, overall dimensions and part list. The component drawing is supplied to the shop flow for manufacturing purpose, while assembly drawing is supplied to the assembly shop 8. Production. The component, as per the drawing, is manufactured in the workshop

2

State the function of flywheel in IC engine.

A flywheel controls the speed variations caused by the fluctuation of the engine turning moment during each cycle of operation.

A flywheel used in machines serves as a reservoir, which stores energy during the period when the supply of energy is more than the requirement, and releases it during the period when the requirement of energy is more than the supply.

2

Compare brakes and dynamometers (two points).

Brakes : A brake is a device by means of which artificial frictional resistance is applied to a moving machine member, in order to retard or stop the motion of a machine.

Types : Hydraulic brakes

1.Electric brakes  2.Mechanical brakes.

The brake absorbs either kinetic energy of the moving member or potential energy given up by objects being lowered by hoists, elevators etc.

The energy absorbed by brakes is dissipated in the form of heat.

This heat is dissipated in the surrounding air (or water which is circulated through the passages in the brake drum) so that excessive heating of the brake lining does not take place.

Dynamometers : A dynamometer is a brake but in addition it has a device to measure the frictional resistance.

Knowing the frictional resistance, we may obtain the torque transmitted and hence the power of the engine.

Types : 1. Absorption dynamometers, and 2. Transmission dynamometers

6

A petrol engine working on otto cycle has compression ratio 8 and consumes 1 kg of air per minute. If maximum temperature during the cycle is 2001 k and minimum temperature is 299 k. Find power developed by engine.

2

Draw neat labeled sketch of crank and slotted lever mechanism. Label all parts.

2

What is the necessity of clutch? State its types.

Necessity: A clutch is necessary for the transmission of power of shafts and machines which must be started and stopped frequently. Its application is also found in cases in which power is to be delivered to machines partially or fully loaded. The force of friction is used to start the driven shaft from rest and gradually brings it up to the proper speed without excessive slipping of the friction surfaces.

In automobiles, friction clutch is used to connect the engine to the driven shaft. It may be noted that -

1. The contact surfaces should develop a frictional force that may pick up and hold the load with reasonably low pressure between the contact surfaces.

2. The heat of friction should be rapidly dissipated and tendency to grab should be at a minimum.

3. The surfaces should be backed by a material stiff enough to ensure a reasonably uniform distribution of pressure.

Types :

1. Disc or plate clutches (single disc or multiple disc clutch),

2. Cone clutches, and

3. Centrifugal clutches.

8

Explain the design procedure of handlever with neat sketch.

4

State and explain various types of constrained motions with suitable examples.

Types of Constrained Motions :

Following are the three types of constrained motions:

1. Completely constrained motion: When the motion between a pair is limited to a definite direction irrespective of the direction of force applied, then the motion is said to be a completely constrained motion. For example, the piston and cylinder (in a steam engine) form a pair and the motion of the piston is limited to a definite direction (i.e. it will only reciprocate) relative to the cylinder irrespective of the direction of motion of the crank.

2. Incompletely constrained motion: When the motion between a pair can take place in more than one direction, then the motion is called an incompletely constrained motion. The change in the direction of impressed force may alter the direction of relative motion between the pair. A circular bar or shaft in a circular hole is an example of an incompletely constrained motion as it may either rotate or slide in a hole. These both motions have no relationship with the other.

3. Successfully constrained motion: When the motion between the elements, forming a pair, is such that the constrained motion is not completed by itself, but by some other means, then the motion is said to be successfully constrained motion. Consider a shaft in a foot-step bearing. The shaft may rotate in a bearing or it may move upwards. This is a case of incompletely constrained motion. But if the load is placed on the shaft to prevent axial upward movement of the shaft, then the motion of the pair is said to be successfully constrained motion.

8

Explain sensible heating and cooling with dehumidification by sketching it on outline diagram of psychrometric chart

Heating with Dehumidification process : By this process, specific humidity of air decreases and its dry bulb temperature increases. This type of process is suitable for industrial air conditioning where low relative humidity is required. This process is achieved by passing a stream of air over chemicals which have an affinity for water. The process is shown in figure. 

  Cooling with Dehumidification process : This process is used when atmospheric condition is hot and humid. To decrease the humidity of air it is passed over a cooling coil whose temperature is less than dew point temperature of air. As the air passes over the cooling coil, the moisture in air condenses and its temperature is also decreased

4

Define the terms linear velocity, relative velocity, angular velocity and angular acceleration.

8

Explain with neat sketch the stress-strain diagram for ductile material.

Point A: Proportional limit Point B: Elastic limit Point c: Upper yield point Point D: Lower yield point Point E: Ultimate tensile stress point Point F: Breaking Stress point. 1. Proportional limit. We see from the diagram that from point O to A is a straight line, which represents that the stress is proportional to strain. Beyond point A, the curve slightly deviates from the straight line. It is thus obvious, that Hooke's law holds good up to point A and it is known as proportional limit. It is defined as that stress at which the stress-strain curve begins to deviate from the straight line. 2. Elastic limit. It may be noted that even if the load is increased beyond point A upto the point B, the material will regain its shape and size when the load is removed. This means that the material has elastic properties up to the point B. This point is known as elastic limit. It is defined as the stress developed in the material without any permanent set. 3. Yield point. If the material is stressed beyond point B, the plastic stage will reach i.e. on the the load, the material will not be able to recover its original size and shape. A little consideration will show that beyond point B, the strain increases at a faster rate with any increase in the stress until the point C is reached. At this point, the material yields before the load and there is an appreciable strain without any increase in stress. In case of mild steel, it will be seen that a small load drops to D, immediately after yielding commences. Hence there are two yield points C and D. The points C and D are called the upper and lower yield points respectively. The stress corresponding to yield point is known as yield point stress. 4. Ultimate stress. At D, the specimen regains some strength and higher values of stresses are required for higher strains, than those between A and D. The stress (or load) goes on increasing till the point E is reached. The gradual increase in the strain (or length) of the specimen is followed with the uniform reduction of its cross-sectional area. The work done, during stretching the specimen, is transformed largely into heat and the specimen becomes hot. At E, the stress, which attains its maximum value is known as ultimate stress. Itis defined as the largest stress obtained by dividing the largest value of the load reached in a test to the original cross-sectional area of the test piece. 5. Breaking stress. After the specimen has reached the ultimate stress, a neck is formed, which decreases the cross-sectional area ofthe specimen, as shown in Fig. The stress is, therefore, reduced until the the specimen breaks away at point F. The stress corresponding to point F is known as breaking stress.

4

For a single slider crank mechanism , state the formulae to calculate by analytical method – Also state the meaning of each term.

i) Velocity of slider:

                                Vp = w.r [sinθ + sin2θ/2n ]

              where,

                  Vp - velocity of slider

w- angular velocity

θ – angle of crank to line of stroke ‘PO’

n- l/r = ratio of length of connecting rod to crank radius.

ii) Acceleration of slider:

               fp = w2 r(cos θ + cos2θ/n)

                 where, fp – acceleration of slider

iii) Angular velocity of connecting rod.:

            wpc = w cos θ / ( n2 – sin2θ)1/2

Where, wpc is angular velocity of connecting rod

iv) Angular acceleration of connecting rod.:

           αpc =  -w2sinθ (n2 -1)/ ( n2 -sin2θ) 3/2

Where, αpc is angular acceleration of connecting rod.

4

A casting weighing 9 kN hangs freely from a rope which makes 2.5 turns round a drum of 300 mm diameter revolving at 20 rpm. The other end of the rope is pulled by a man. Taking μ = 0.25, determine (i) the force required by the man (ii) the power to raise the casting.  

Given: W= T1= 9 kN =9000N, d= 0.3 m, N = 20 rpm , µ= 0.25

(i) Force reqd. by a man 

T2- force reqd. by man

As rope makes 2.5 turns,

Therefore angle of contact ,

θ =2.5x2π = 5 π rad.

We know that,

2.3 log {T1/T2} = µ θ = 0.25 x 5 π = 3.9275

log {T1/T2} = 3.9275/2.3 = 1.71 or T1/T2 = 51

T2 = 9000/51 = 176.47 N

(ii) Power to raise casting : 

As velocity of rope, v = πdN/60 = 3.14x0.3x20/60 = 0.3142 m/s

Power to raise casting = (T1-T2) x v = (9000-176.47) x 0.3142

                                     = 2.772 kW.

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

Describe the method to measure indicated power of I.C. engine.

Method to measure Indicated power :

4

Draw constant pressure closed cycle gas turbine on P.V and T-S planes. Name the various processes involved and give its efficiency equation with meaning of each term.

4

Draw and explain simple vapour absorption refrigeration system

A Simple Vapor absorption system consists of evaporator, absorber, generator, condenser, expansion valve, pump & reducing valve. In this system ammonia is used as refrigerant and solution is used is aqua ammonia. Strong solution of aqua ammonia contains as much as ammonia as it can and weak solution contains less ammonia. The compressor of vapor compressor system is replaced by an absorber, generator, reducing valve and pump. The heat flow in the system at generator, and work is supplied to pump. Ammonia vapors coming out of evaporator are drawn in absorber. The weak solution containing very little ammonia is spread in absorber. The weak solution absorbs ammonia and gets converted into strong solution. This strong solution from absorber is pumped into generator. The addition of heat liberates ammonia vapor and solution gets converted into weak solution. The released vapor is passed to condenser and weak solution to absorber through a reducing valve. Thus, the function of a compressor is done by absorber, a generator, pump and reducing valve. The simple vapor compressor system is used where there is scarcity of electricity and it is very useful at partial and full load.