Lecture PPTs (23) - Lect 25 1 Lect 25 Axial Flow Turbines...

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1 Lect 25
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2 Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay Lect 25 Axial Flow Turbines 3-D Flow theories
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3 Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay Lect 25 It is assumed that radial motion takes place in the blade passage only C r << C a ; C r << C w The stream surface has a cylindrical shape simplified radial equilibrium equation is valid 2 w dp 1 1 = .C ρ r dr r m
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4 Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay Lect 25 Following Three 3-D flow models in axial turbines are often used for design and analysis 1) Free Vortex flow 2) Constant nozzle exit angle, α 2 3) Arbitrary vortex case, C w = r n
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5 Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay Lect 25 1) Free Vortex Flow model C w . r = constant , applied on the rotor flow which normally entails a few assumptions : At turbine rotor entry , dH 02 /dr = 0 ; C w2 .r = constant ; C a2 = const Rotor specific work done : H 02 – H 03 = U (C w2 + C w3 )= ω (r 2 .C w2 - r 3 .C w3 ) = constant With C w3 .r = constant, it follows C a3 = const
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6 Prof. Bhaskar Roy, Prof. A M Pradeep, Department of Aerospace, IIT Bombay Lect 25 Hence, for obtaining various parameters along blade length following may be adopted:
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