Reaction Number or RN In Turbine

What is the context? What kind of turbine in what service? Are you talking about the number of reaction blades? Reaction blade rows? Reaction force (thrust load)? Is it a gas turbine, or a steam turbine? If a gas turbine is it land based or aircraft?

The context follows:

Axial turbines can be freely designed for different numbers
•RN =0.5: 50% expansion in the stator, 50% expansion in the rotor
•RN <=0.05: impulse turbine

Radial turbines feature a degree of of reaction around 0.5
lower degrees of reaction are not possible due to the centrifuga centrifugal l
flow field.

I get the following definition from:

The Design of High-Efficiency Turbomachinery and Gas Turbines, David Gordon Wilson & Theodosios Korakinaitis, 1998, Prentice Hall, page 220

The stage Reaction (of a turbine stage) -

"The strict definition of reaction is the ratio of the change in static enthalpy to the change in stagnation enthalpy on the flow passing through the rotor."

You can use Google and search "turbine degree of reaction".

I got the following hit from this search:

http://books.google.com/books?id=v6EvNjtOJcoC&pg=RA1-PA147&lpg=RA1-PA147&dq=turbine+degree+of+reaction&source=web&ots=7evElGMyxG&sig=SgENWVoeML-0khSsHLOymfT0puU#PRA1-PA149,M1

This link gives page 149 of Fluid Dynamics and Heat Transfer of Turbomachinery by Budugur Lakshminarayana and it showsthe change in blade shape (blade angles) of the rotor and nozzle for the various degrees of reaction.

I believe that this is speaking to the ratio of reaction stages and impulse stages. On a large steam turbine it is not unusual to have both impluse and reaction blading.

"Could somebody explain RN to me?"

What kind of turbine is under consideration? Air (windmill)?, Steam? Water?

Reynolds Number This should give you a head start.