UNSTEADY EFFECTS OF A GENERIC NON-AXISYMMETRIC ROTOR ENDWALL CONTOUR ON A 11/2 STAGE TURBINE TEST RIG AT OFF DESIGN CONDITIONS

With the current drive to improve fuel efficiency and reduce emissions, in gas turbine engines various methods have been investigated. Previously it has been shown that a generic rotor endwall contour could improve the efficiency of a 1 1/2 stage test turbine at design conditions. The current investigation looked at the increased and decreased loading conditions to determine if the contour introduces detrimental effects at off design conditions. A previous unsteady analysis of the design condition found that the contoured rotor does have an effect on the flow field, reducing the magnitude of the hub endwall secondary flow region as well as reducing fluctuations in the velocity. Experimental results showed that the increased load case presented with an increase in hub endwall secondary flow structure when compared to the design case. This increase was to be expected due to the increased turning of the flow due to the increased loading operating condition. The contoured rotor had a weaker hub endwall secondary flow system, with the high momentum flow distributed more in the span wise direction. The variation in the velocity was also found to be smaller for the contoured rotor. The decreased loading case showed similar improvements, but the extent of the change was less due to the lower turning of the flow (due to a faster rotor). The numerical results show that the hub endwall secondary flow vortex of the contoured rotor was not as tightly wrapped as that of the annular rotor The rotor outlet flow was thus more uniform due to the more dispersed vortex system. As seen with the experimental results, the extent of the change due to the contoured rotor changes with loading. The differences present in the decreased loading case being relatively insignificant. It was concluded that the generic contour does not introduce any unsteady effects at off design conditions that were not observed in the design case.