JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech IV Year TURBO MACHINERY Previous Question Paper (January/February - 2023 - R18)
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
Explain the significance of Mach number in the turbo machines and its importance.
Answer
The Mach number (M = v/a) is the ratio of fluid velocity to the local speed of sound. It is significant in turbo machinery as it dictates the compressibility effects of the working fluid. It determines whether the flow is subsonic, transonic, or supersonic, which fundamentally changes the design of blade profiles and flow passages to avoid shock losses and flow separation.
Discuss the significance of Bernoulli’s equation.
Answer
Bernoulli’s equation represents the principle of conservation of energy for a flowing fluid along a streamline. It relates pressure, velocity, and elevation, allowing for the calculation of pressure changes due to velocity variations in turbo machine components like nozzles and diffusers. It is essential for analyzing energy transfer and efficiency in incompressible flow regimes.
Why do we provide cavitation in axial machines?
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Explain the role of positive suction on the performance of Radial machines.
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Explain the supersonic flow theory.
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Compare and contrast the pre whirl and diffuser.
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How cascade blades will work?
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Explain the working principle of axial flow compressor.
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How do you explain the Zweifels relation?
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Explain the correlations of Soderberg and Hawthrone.
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PART - B
Derive the polytropic compression efficiency through an infinitesimal compression stage with the help of fundamental relationships.
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Explain the concept and derive the general Euler’s expression for flow through variable cross-sectional area in a turbo machine its implications.
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Explain the effect of number of vanes on the velocity triangles and the concept of slip factor on radial machines.
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What are the effects of specific speed and shape number on axial and mixed flow machines and also explain the similarity laws.
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Calculate the pitot pressure of an air stream flowing at 410 m/sec. assume that the blow wave set up ahead of the tube is detached, the centre part being considered as a normal shock. Ambient pressure =1.033 Kgf/cm2 abs., static temperature=21oC.
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Air enters at 27oC and leaves at 105oC in centrifugal compressor. Air compressed to a pressure ratio of 2. Calculate the isentropic efficiency and power requires by the compressor, if 30 kg of air is compressed per minute. Cp=1.0kJ/kg k; Cv=0.716kJ/kg k.
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What is secondary flow in the axial flow turbine and compressor cascades? How does it lead to a loss of energy? How is it estimated? Explain in detail.
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An axial flow compressor has a constant axial velocity of 150 m/s and 50% reaction. The mean diameter of the blade ring is 35 cm and speed is 15,000 RPM and exit angle of the blade is 27o. Calculate the blade angle at inlet and work done per Kg of air.
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Explain the different factors to be considered in the selection of blade materials of axial flow gas turbines. Also explain the concept of variable degree of reaction.
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Explain the concept of external and internal cooling of blades. Also explain the different stresses in the blades and the blade assembling.
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