Q5. The nozzle angle of a two row Curtis wheel is 25° to the plane of rotation. The isentropic specific enthalpy drop in the nozzle is 312.5 kJ/kg and the isentropic efficiency is 90%.
The first row of moving blades has symmetrical blades.
The outlet angle of the fixed blades is half the inlet angle.
The second row of moving blades has an outlet angle designed so that the absolute velocity at stage exit is in axial direction.
All the blades have a friction coefficient of 0.95 and the mean blade need 200 m/s.
(a) Calculate the absolute velocity of the steam leaving the nozzle. (2)
(b) Draw the moving blade velocity diagrams to a scale of 1 mm = 5 m/s (6)
(c) Determine EACH of the following:
(i) the fixed and moving blade angles; (2)
(ii) the power output for a steam flow of I kg/s; (3)
(iii) the axial thrust for a steam flow of 1 kg/s (3)
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