Question

In an impulse reaction turbine stage, the heat drop in fixed and moving blades are 20 kJ/kg and 30 kJ/kg respectively. The degree of reaction for this stage will be

1. \(\frac{3}{5} \)
2. \(\frac{5}{3}\)
3. \(\frac{2}{5}\)
4. \(\frac{5}{2}\)

Answer 1

Correct Answer - Option 1 : \(\frac{3}{5} \)

Concept: 

Degree of Reaction

\(R = \frac{{enthalpy\;drop\;in\;moving\;blade}}{{Total\;enthalpy\;drop}}\)

It indicates how much enthalpy drop is taking place in the rotor of the turbine.

Calculation:

Given:

Enthalpy drop in moving blade = 30 kJ/kg,

Enthalpy drop in fixed blade = 20 kJ/kg,

Total Enthalpy drop = Enthalpy drop in moving blade + Enthalpy drop in fixed blade = 50 kJ/kg

\(R = \frac {30}{30+20} = \frac{3}{5}\)