Computational Analysis and Experimental Verification of Reverse Flow in a Low Pressure Steam Turbine under the Low Load Operation

The three-dimensional flow behavior in a low pressure steam turbine under the low load operation was analyzed numerically by applying the Modified FLIC (Fluid In Cell) method to the quasi three-dimensional flow computation. And it was also measured by using the five-hole Pitot probe in the scale-model turbine with the last stage. By comparing the calculated flow angles with the measured ones at the inlet and exit of the rotor, it is shown that the present computation method is a useful skill to predict an occurrence of the reverse flow in the last stage under the low load operation. Both calculated and experimental results show that the reverse flow occurs at the root of the rotor, if the axial exhaust Mach number becomes smaller than 0.3 even though the stator works well.