RPMTurbo
Specialists in Linear Flow Analysis

Wet Steam Test Case

This test case was established by RPMTurbo to examine wet steam effects on flutter analysis. Previously, there was no publicly avaliable experimental data or numerical solutions for unsteady wet steam flow due to harmonically oscillating profiles. The results were published at the 13th ISUAAAT at the University of Tokyo, Japan on 13 September 2012.


Geometry

The two-dimensional turbine geometry from Standard Configuration 11 was used. The chord length for the results shown here was increased by a factor of 3.0 to 0.2334 metres, so that the Reynolds numbers for the flow conditions were similar to those expected in an industrial steam turbine. The chord length for the results shown in the 2012 ISUAAAT paper was 0.0778 metres.


Flow Conditions

The flow conditions used for this test case are similar to the flow conditions at the last stage of a typical industrial steam turbine. The description of the flow conditions is given in the Table below. The first flow condition is pure steam vapour with no condensation, the second flow condition is high subsonic flow with condensation, and the third flow condition is transonic flow with condensation. The incoming turbulence for all conditions was assumed to be zero.

Flow Condition #1 #2 #3
Inlet Total Pressure (kPa) 13.0 13.0 13.0
Inlet Total Temperature (K) 400.0 324.2 324.2
Inlet Inflow Angle (deg) 15.2 15.2 15.2
Inlet Total Quality 1.0 0.9 0.9
Outlet Pressure (kPa) 9.75 9.75 7.5

Steady-State Solutions

A summary of the steady-state solutions are shown in the Table below. The Reynolds number is based on the flow conditions at the outlet. There are differences in the steady-state solutions shown here and those presented in the 2012 ISUAAAT paper. The differences occur on the suction side near the leading edge and are due to different Reynolds numbers.

Flow
Condition
Outlet
Mach Number
Reynolds
Number
Polytropic
Index
Steam Quality
Contours
Mach Number
Contours
Pressure Plot Profile Data
1 0.663 380 000 1.308 [Data]
2 0.658 433 000 1.107 [Data]
3 0.915 469 000 1.109 [Data]

Unsteady Flow

The unsteady flow response due to the blade oscillating in a torsion mode is shown in the Table below. The centre of rotation for the torsion mode is 36.34% along the chord line. The frequency of the vibration for the results shown here is 70.66 Hz and the interblade phase angle is 0 degrees. The frequency was 212.0 for the results presented in the 2012 ISUAAAT paper. The frequency was changed in order to match the reduced frequency of the results presented in the 2012 ISUAAAT paper (shorter chord length). The reduced frequency is calculated based on full chord. The non-dimensional values were calculated using the maximum mode displacement divided by the chord length as the mode amplitude. Again there are differences in the unsteady solutions compared with the results in the 2012 ISUAAAT paper on the suction side near the leading edge because of different Reynolds numbers.

Flow
Condition
Reduced
Frequency
Imag Unsteady
Cp Plot
Local Work
Coefficient
Data
1 0.328 [Data]
2 0.380 [Data]
3 0.278 [Data]