1) The steam from the nozzles of a single wheel impulse turbine discharges with a velocity of 600 m/s at an angle of 20 degrees. The blade wheel rotates at 3000 rev/min and the mean blade radius is 590 mm. The axial velocity of the stream at the exit from the blades is 164 m/s and the blades are symmetrical.
Sketch the annotated velocity triangles and calculate:
a) the blade inlet angle
b) the diagram specific work
c) the diagram efficiency
d) the blade velocity coefficient
e) Show that for symmetrical blading and no friction n_rot = 4(U/V_1)(cos(alpha_1) - (U/V_1)) and determine the optimum blade speed ratio and efficiency. Make a sketch of your results.
Notations and assumptions:
[ ]* = total features (like p*, T*)
cp = specific heat at constant pressure (for superheated steam we will take cp ...
This complete solution provides details and formated step-by-step calculations and answers in the attached Word document. The student will be able to clearly see how formulas are derived and answers are calculated for each part (a) through (e). The solution provides an illustration of the geometry of the velocities pattern. (e) also includes an illustration of the velocities pattern for maximum rotor efficiency.
Turbomachinery: Impulse and Reaction Turbines
1. An impulse air turbine rotor with a blade speed (U) of 300 m/s is measured to have a relative rotor inlet velocity (W_1) of 750 m/s at an angle of 69 degrees and an outlet relative velocity (W_2) of 660 m/s. Th temperature and pressure in the rotor are 375 K, 0.83 bar. Calculate the rotor efficiency, rotational speed and power output if it has a mean blade diameter of 220 mm, a blade length of 16,, and if it has 360 degrees of full length nozzles.
At the inlet to a reaction air turbine nozzle, the total pressure and total temperature are 7,39 bar, 1240 K.
a) If the nozzle has an efficiency of 87% and if the nozzle exit/rotor inlet pressure is 4,1 bar, calculate the nozzle exit velocity (C_1).
b) If the nozzle exit angle is 65 degrees and if the rotor speed is 390 m/s, calculate the relative rotor inlet velocity (W_1).
c) If the rotor has an efficiency of 84% and an exit pressure of 1,9 bar, calculate the rotor exit relative velocity (W_2).
d) Sketch the complete velocity diagrams with approximate blade shapes.