JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II MECHANICAL TECHNOLOGY Previous Question Paper (February - 2024 - R13)
Question paper consists of Part A, Part B. Part A is compulsory, which carries 25 marks. In Part A, answer all questions. 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
What is a cam? What is its use?
Answer
A cam is a rotating or sliding machine element that imparts a specific motion to a follower by direct contact. Its primary use is to convert rotary motion into reciprocating or oscillating motion for tasks such as operating valves in internal combustion engines or controlling automated machinery.
What are the methods for reducing pressure angle of a cam?
Answer
- Increase the base circle diameter of the cam.
- Increase the offset of the follower.
- Increase the length of the follower stroke (if permissible) or adjust the cam profile geometry to provide a more gradual rise.
Enumerate the parameters for selection of belt drive.
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What is the effect of centrifugal tension on power transmission of belts?
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Draw the involute tooth profile of two mating gears.
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Define all three different ways of expressing pitch of a gear.
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List the advantages of internal combustion engine over external combustion engine.
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Discuss the types of cooling systems for an IC engine.
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State the main parts of reciprocating air compressor.
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Classify rotary compressors.
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Part B
With neat sketches, classify cams according to shape.
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Construct a tangent cam and mention the important terminologies on it.
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Draw the displacement, velocity and acceleration diagrams for a follower when it moves with uniform acceleration and retardation. Derive the expression for velocity and acceleration during out-stroke and return stroke of the follower.
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Derive the expression for ratio of belt tensions for a flat belt. How this equations needs to be modified to account for the V-Belts.
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A chain drive is used for reduction of speed from 300 to 150 rpm. The number of teeth on the driving sprocket is 25. The pitch circle diameter of the driven sprocket is 500 mm. Determine the number of teeth on the driven sprocket and the pitch.
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An open belt running over two pulleys 300 mm and 600 mm diameter connects two parallel shafts 3 metres apart and transmits 4 kW from the smaller pulley that rotates at 300 rpm. Coefficient of friction between the belt and the pulley is 0.3 and the safe working tension is 10 N per mm width. Determine minimum width of the belt, initial belt tension, and length of the belt required.
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A pinion with 20 teeth is in mesh with a gear with 60 teeth. The pressure angle is 200 and addendum of 7 mm. Determine the number of pairs of teeth in contact and the angle of rotation of the larger wheel for one pair of teeth in contact. Also calculate sliding velocity at teeth engagement, disengagement and at pitch point. The pitch line velocity is 1.4 m/sec.
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Derive an expression for minimum number of teeth on pinion to avoid interference.
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Explain epicyclic gear train. What are its merits and demerits as compared to reverted gear trains and compound gear trains?
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Explain with suitable sketches the working of a four-stroke Otto engine.
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Compare the p-v diagram for 4-stroke petrol engine with 2-stroke petrol engine.
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Enumerate important requirements of a spark ignition system. Draw and explain Battery ignition system for multi-cylinder engines.
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An engine is required to develop 100 kW, the mechanical efficiency of the engine is 86% and the engine uses 55 kg/h of fuel. Due to improvement in the design and operating conditions, there is reduction in engine friction to the extent of 4.8 kW. If the indicated thermal efficiency remains the same, determine the saving in fuel in kg/h.
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Draw and explain the indicator diagram for two-stage compressor.
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Define volumetric efficiency. How is it affected by pressure ratio, speed of compressor, and throttling across the valves?
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Explain construction and working of a roots blower. Draw the p-v diagram. Also write the expressions for the workdone and efficiency.
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Write a short note on the application of compressed air in mining industry.
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