Question 6.31: In a reaction turbine, the fixed blades and moving blades ar...
In a reaction turbine, the fixed blades and moving blades are of the same shape but reversed in direction. The angles of the receiving tips are 35° and of the discharging tips 20°. Find the power developed per pair of blades for a steam consumption of 2.5 kg/s, when the blade speed is 50 m/s. If the heat drop per pair is 10.04 kJ/kg, find the efficiency of the pair.
Angles of receiving tips, θ = β = 35°
Angles of discharging tips, α = φ = 20°
Steam consumption, \dot{m}_{s} = 2.5 kg/s
Blade speed, C_{bl} = 50 m/s
Heat drop per pair, h_{d} = 10.04 kJ/kg
Power developed per pair of blades :
Refer Fig. 46.
NS = PQ = 152 m/s
Work done per pair per kg of steam
= ( C_{ w_1} + C_{w_0} ) C_{bl} = 152 × 50 = 7600 Nm/kg of steam.
Power/pair = \frac{\dot{m}_{s} ( C_{ w_1} + C_{w_0} ) C_{bl}}{1000} = \frac{2.5 × 7600}{1000} = 19 KW.
Efficiency of the pair :
Efficiency = \frac{Work done per pair per kg of steam}{ h_{d}}
= \frac{7600}{10.04 × 1000} = 0.757 = 75.7%.
