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Basis of this is the balance of pressure and centrifugal forces under the following assumptions:
•the flow is rotationally symmetric
•friction is neglected
•the streamlines are axisparallel and have no inclination
The radial balance equation is given here for a section behind an impeller [pump, compressor, fan] and before a rotor [turbine] respectively:
The definition of total pressure in section 2 differentiated with respect to r plus above equation yield:
With the blade work according to Euler the equation becomes:
With the following boundary conditions and a given cu2(r)specification the solution of the differential equation gives a cm2(r)distribution and therefore the complete velocity triangles at every span.
From the velocity triangles the degree of reaction can be determined by the following equation: