Degree of reaction
![Figure 1. Enthalpy vs. Entropy diagram for stage flow in turbine](/Images/godic/202501/08/Enthalpy_vs._Entropy_diagram_for_stage_flow_in_turbine.3848.jpg")
![Figure 2. Velocity Triangle for fluid flow in turbine](/Images/godic/202501/08/Velocity_Triangle3848.jpg")
![Figure 3. Influence of reaction on total-to-static efficiency with fixed value of stage loading factor](/Images/godic/202501/08/Influence_of_reaction_on_total_to_static_efficiency.3848.jpg")
![Figure 4. Velocity triangle for Degree of Reaction = 1/2 in a turbine](/Images/godic/202501/08/Velocity_triangle_for_Degree_of_Reaction_=_1⁄2_in_a_turbine3848.jpg")
Degree of reaction or reaction ratio (R) is defined as the ratio of static pressure drop in the rotor to the static pressure drop in the stage or as the ratio of static enthalpy drop in the rotor to the static enthalpy drop in the stage.
Degree of reaction (R) is an important factor in designing the blades of a turbine, compressors, pumps and other turbo-machinery. It also tells about the efficiency of machine and is used proper selection of machine for the required purpose.