Q5. The first stage of an impulse turbine is velocity compounded with two rows of moving blades. The isentropic enthalpy drop in the nozzles is 373.56 kJ/kg and the isentropic efficiency is 90%.
The steam leaves the nozzles at an angle of 30° to the plane of blade rotation and the mean blade speed is 200 m/s.
The first row of moving blades and the fixed blades are symmetrical.
The exit angle on the second row of moving blades is designed such that the absolute velocity of the steam at stage exit is in the axial direction.
A blade velocity coefficient of 0. 9 may be assumed for all the blade rows.
(a) Draw the steam velocity vector diagram to a scale of 1 mm = 5 m/s (6)
(b) Determine EACH of the following:
(i) the blade angles for each row of moving blades; (2)
(ii) the blade angle for the fixed blades; (2)
(iii) the diagram power output for 1 kg/s of steam flow; (3)
(iv) the axial thrust for 1 kg/s of steam flow. (3)
Please buy a membership plan and login via our app to view answers.
Download our App
