Engr Help

Analysis of Radial Flow Reaction Turbines (continued)

Summary: (Continued)

Key concept: The principle of conservation of energy can be used to determine the change in

pressure between the entrance to the vane (station 1) and the exit from the vane (station 2).

Conservation of Energy

p₁/ρg + V₁² /2g + z₁ + h_s = p₂/ρg + V₂² /2g + z₂ + h_L (ft or m)

where h_s is negative for a turbine (extracts energy from the fluid)

h_L is the head loss associated with the turbine

For an ideal turbine the head loss is zero.

Change in elevation is generally negligible. i.e z₁ ≈ z₂

Key Points:

The turbine extracts energy from the fluid. The energy at the entrance to the leading edge of the

vane minus the energy extracted from the fluid equals the energy at the trailing edge of the

vane plus any head loss due to friction.

Each of the speeds (magnitude of velocities) in conservation of mass, of angular momentum, and

of energy are absolute values as measured in an inertial frame.

As the impeller rotates, fluid is discharged through the eye of the casing.

The external shaft torque developed by the turbine results from change in angular momentum

of the fluid in the turbine as it rotates. (ω)

The head loss due to friction from the entrance of fluid at the leading edge of the vane to the exit

at the trailing edge of the vane is considered negligible for an "ideal" turbine.

Vector plots showing the tangential components of the fluid velocity, V_t1, at the entrance and

V_t2, at the exit are essential in calculating the shaft torque developed by the turbine.