Approved

Figure 4 shows that the predicted Mach numbers at the exit of the 1st vane from the VBI run were higher than those from the ADPAC steady run and the design system. The data also show that predicted VBI flow angles from 10% to 60% span were slightly higher. Together, the plots indicate that the flow coming into the 1st rotor for the VBI run had a higher Mach number with higher incidence angle. This difference was enough to cause flow separation on the suction surface of the blade. Additional runs with the design system tools confirmed that this behavior was expected. If the flow angles into the ltt rotor are specified, the design system blade row flow solver does not indicate separation, and the blades were designed using that option. If the Ve velocity component into the 1st rotor is specified, the design system indicated flow separation over the lower and midspan sections of the blade. The 3-D predictions and the design system runs indicated that the flow through the 1st rotor probably would not separate at design conditions, but that there were clear indications that off design conditions could cause flow separation. This flow separation results in a loss in rotor efficiency and stage efficiency.

Figure 5 shows the envelope of unsteady pressures over the surface of the 1st vane at 10%, 50%, and 90% span. At each spanwise location, these plots have the maximum, minimum, and time mean values for instantaneous pressure vs. surface distance at every grid point on the blade surface. For the vane, the maximum, minimum, and time mean were practically equal, except on the suction surface near the trailing edge. The relative Mach number entering the 1st rotor was about 0.14, and the rotor potential field was very weak. Only the suction surface of the vane was affected by the passing of the rotor and the effect was minimal. Figure 6 shows the envelope of unsteady pressure over the surface of the 1st blade at 10%, 50%, and 90% span. There was considerably more unsteadiness on the blade than on the vane, but the levels were still quite low. The principal source of the unsteadiness in the blade was the wake from the vane. For this low Mach number case the flow is nearly incompressible, and the velocity deficit through the wake was the only mechanism for changes in pressure.

VBI3D Calculation: Purdue Turbine Rig 1st Stage VBI3D Calculation: Purdue Turbine Rig 1st Stage VBI3D Calculation: Purdue Turbine Rig 1st Stage

VBI3D Prediction of Vsme Unsteady Pressure 8t 1 'J™ Span VB13D Prediction of Vano Unsteady Ptoseuro at 50% Span VBI3D Production of Vano Uniloady Prof®uro at 9<K4 Span

VBI3D Calculation: Purdue Turbine Rig 1st Stage VBI3D Calculation: Purdue Turbine Rig 1st Stage VBI3D Calculation: Purdue Turbine Rig 1st Stage

VBI3D Prediction of Vsme Unsteady Pressure 8t 1 'J™ Span VB13D Prediction of Vano Unsteady Ptoseuro at 50% Span VBI3D Production of Vano Uniloady Prof®uro at 9<K4 Span

Figure 5. Illustrations of the envelope of the maximum, minimum, and time mean static pressure on the surface of the 1st vane at

Figure 5. Illustrations of the envelope of the maximum, minimum, and time mean static pressure on the surface of the 1st vane at

PROPRIETARY RIGHTS LEGEND This technical data and the information embodied herein is the property of and proprietary to Rolls-Royce Corporation, and shaft not, without prior written permission of Rolls-Royce Corporation, be disclosed In whole or in part to third parties This legend shall be Included on any reproduction of this data in whole or in part. Copyright 2000 - Rolls-Royce Corporation, (unpublished)

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