Question 7.9: single-stage axial flow gas turbine has the following data M......
single-stage axial flow gas turbine has the following data
Mean blade speed 340 m/s
Nozzle exit angle 15°
Axial velocity (constant) 105 m/s
Turbine inlet temperature 900°C
Turbine outlet temperature 670°C
Degree of reaction 50%
Calculate the enthalpy drop per stage and number of stages required.
At 50%,
α_2 = β_3
α_3 = β_2
C_2 = \frac{U} {\cos 15°} = \frac{340} {\cos 15°} = 351.99 m/s
Heat drop in blade moving row = \frac{C^2_2 – C_3^2}{2C_p} = \frac{(351.99)^2 – (105)^2} {(2)(1147)}
= \frac{123896.96 – 11025} {(2)(1147)}
= 49.2 K
Therefore heat drop in a stage = (2)(49.2) = 98.41 K
Number of stages = \frac{1173 – 943} {98.41} = \frac{230} {98.4} = 2