JNTU
JNTU B.Tech II MECHANICAL TECHNOLOGY Previous Question Paper (September/October - 2023 - R13)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
How the cam size is defined?
Answer
The cam size is primarily defined by the base circle, which is the smallest circle that can be drawn tangent to the cam profile. The size is also influenced by the pressure angle and the required lift of the follower.
Draw and name various types of follower motions.
Answer
The common types of follower motions are:
- Uniform velocity motion
- Simple harmonic motion
- Uniform acceleration and retardation motion
- Cycloidal motion
List the materials used for the construction of flat and V belts.
Answer
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Explain the phenomenon, “creeping of the belt”.
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State law of gearing and represent it graphically.
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Explain the phenomenon of interference in involute gears.
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What are the main differences between 4-stroke and 2-stroke engines?
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What are the basic requirements of an ideal ignition system?
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Why is the clearance volume provided in each reciprocating compressor?
Answer
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Compare reciprocating and rotary compressors.
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Part B
Differentiate between (i) base circle and prime circle, (ii) cam angle and pressure angle and (iii) trace point and pitch point.
Answer
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Explain in detail about steps for cam profile construction.
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A cam operating a knife - edged follower has the following data: a) Follower moves outwards through 40 mm during 60° of cam rotation. b) Follower dwells for the next 45°. c) Follower returns of its original position during next 90°. d) Follower dwells for the rest of the rotation. The displacement of the follower is to take place with simple harmonic motion during both the outward and return strokes. Draw the displacement, velocity and acceleration diagrams for the follower. Also find the maximum acceleration.
Answer
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Derive an expression for power transmission of a belt considering both the initial tension and the centrifugal tension. Also obtain the condition for maximum power transmission.
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Give the classification of chains.
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Two pulleys of diameters 450 mm and 150 mm are mounted on two parallel shafts 2 m apart and are connected by a flat belt drive. Find the power which can be transmitted by the belt when the larger pulley rotates at 180 rpm. The maximum permissible tension in the belt is 1 kN, and the coefficient of friction between the belt and the pulley is 0.25. Also find the length of the cross belt required and the angle of arc of contact between the belt and the pulleys.
Answer
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Prove that the change in centre distance within limits between involute gear wheels does not change the angular velocity ratio but alters the pressure angle.
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Two involute gears of 20° pressure angle are in mesh. The number of teeth on pinion is 20 and the gear ratio is 2. If the pitch expressed in module is 5 mm and the pitch line speed is 1.2 m/s, assuming addendum as standard and equal to one module, find the angle turned through by pinion when one pair of teeth is in mesh.
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Input shaft A and the output shaft B are coincident and are geared together through a parallel counter shaft C. The wheels connecting shafts A and C have a module of 2 mm and those connecting C and B have a module of 3.5 mm. Speed of output shaft has to be less than 1/10 that of shaft A. If the two pinions have each 24 teeth, determine suitable teeth for the other gear wheels, actual velocity ratio, and the corresponding distance of shaft C from A.
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State the purposes of lubrication. With the help of suitable sketch, discuss any one lubrication system.
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Classify IC engines as per cylinder arrangement along with their applications.
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A six-cylinder, four-stroke spark-ignition engine of 10 cm × 12 cm (bore × stroke) with a compression ratio of 6 is tested at 4800 rpm on a dynamometer of arm 55 cm. During a 10 minutes test, the dynamometer reads 45 kg and the engine consumed 5 kg of petrol of calorific value 45 MJ/kg. The carburetor receives air at 9°C and 1 bar at the rate of 10 kg /min. Calculate (a) the brake power, (b) the brake mean effective pressure, (c) the brake specific fuel consumption, (d) the brake specific air consumption, and (e) the brake thermal efficiency.
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Explain with a sketch the working of double-acting reciprocating air compressor.
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Prove that in a reciprocating air compressor, with perfect intercooling, the work done for compressing the air is equal to heat rejected by the air.
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Describe the principle of operation, construction and working of centrifugal compressor.
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Explain the phenomenon of surging and its effects in compressors.
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