Study of Boundary Layer Development in a Two-Stage Low-Pressure Turbine
Dorney, Daniel J. (Virginia Commonwealth Univ., Richmond, VA United States); Ashpis, David E. (NASA Lewis Research Center, Cleveland,OH United States); Halstead, David E. (General Electric Co., Aircraft Engines Cincinnati, OH United States); Wisler, David C. (General Electric Co., Aircraft Engines Cincinnati, OH United States)
NASA Center for AeroSpace Information (CASI)
NASA/TM-1999-208913
Experimental data from jet-engine tests have indicated that unsteady blade row interactions and separation can have a significant impact on the efficiency of low-pressure turbine stages. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that Reynolds number effects may contribute to the lower efficiencies at cruise conditions. In the current study numerical simulations have been performed to study the boundary layer development in a two-stage low-pressure turbine, and to evaluate the transition models available for low Reynolds number flows in turbomachinery. The results of the simulations have been compared with experimental data, including airfoil loadings and integral boundary layer quantities. The predicted unsteady results display similar trends to the experimental data, but significantly overestimate the amplitude of the unsteadiness. The time-averaged results show close agreement with the experimental data.
No Digital Version Available - Order This Document
Updated/Added to NTRS: 2003-05-08

The Effects of Blade Count on Boundary Layer Development in a Low-Pressure Turbine
Dorney, Daniel J. (Virginia Commonwealth Univ., Dept. of Mechanical Engineering Richmond, VA United States); Flitan, Horia C. (Virginia Commonwealth Univ., Dept. of Mechanical Engineering Richmond, VA United States); Ashpis, David E. (NASA Glenn Research Center, Cleveland, OH United States); Solomon, William J. (Ohio Aerospace Inst., Cleveland, OH United States)
NASA Center for AeroSpace Information (CASI)
NASA/TM-2000-209911
Experimental data from jet-engine tests have indicated that turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Recent studies have shown that Reynolds number effects contribute to the lower efficiencies at cruise conditions. In the current study numerical simulations have been performed to study the boundary layer development in a two-stage low-pressure turbine, and to evaluate the models available for low Reynolds number flows in turbomachinery. In a previous study using the same geometry the predicted time-averaged boundary layer quantities showed excellent agreement with the experimental data, but the predicted unsteady results showed only fair agreement with the experimental data. It was surmised that the blade count approximation used in the numerical simulations generated more unsteadiness than was observed in the experiments. In this study a more accurate blade approximation has been used to model the turbine, and the method of post-processing the boundary layer information has been modified to more closely resemble the process used in the experiments. The predicted results show improved agreement with the unsteady experimental data.
No Digital Version Available - Order This Document
Updated/Added to NTRS: 2003-05-08

Experimental and Numerical Investigation of Losses in Low-Pressure Turbine Blade Rows
Dorney, Daniel J. (NASA Glenn Research Center, Cleveland, OH United States); Lake, James P. (NASA Glenn Research Center, Cleveland, OH United States); King, Paul I. (NASA Glenn Research Center, Cleveland, OH United States); Ashpis, David E. (NASA Glenn Research Center, Cleveland, OH United States)
NASA Center for AeroSpace Information (CASI)
NASA/TM-2000-209910
Experimental data and numerical simulations of low-pressure turbines have shown that unsteady blade row interactions and separation can have a significant impact on the turbine efficiency. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that the performance of low-pressure turbine blades is a strong function of the Reynolds number. In the current investigation, experiments and simulations have been performed to study the behavior of a low-pressure turbine blade at several Reynolds numbers. Both the predicted and experimental results indicate increased cascade losses as the Reynolds number is reduced to the values associated with aircraft cruise conditions. In addition, both sets of data show that tripping the boundary layer helps reduce the losses at lower Reynolds numbers. Overall, the predicted aerodynamic and performance results exhibit fair agreement with experimental data.
No Digital Version Available - Order This Document
Updated/Added to NTRS: 2003-05-08

Study of Low Reynolds Number Effects on the Losses in Low-Pressure Turbine Blade Rows
Ashpis, David E. (NASA Lewis Research Center, Cleveland, OH United States); Dorney, Daniel J. (General Motors Inst., Engineering and Management Inst. Flint, MI United States)
NASA Center for AeroSpace Information (CASI)
NASA/TM-1998-207919
Experimental data from jet-engine tests have indicated that unsteady blade row interactions and separation can have a significant impact on the efficiency of low-pressure turbine stages. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that Reynolds number effects may contribute to the lower efficiencies at cruise conditions. In the current study numerical experiments have been performed to study the models available for low Reynolds number flows, and to quantify the Reynolds number dependence of low-pressure turbine cascades and stages. The predicted aerodynamic results exhibit good agreement with design data.
No Digital Version Available - Order This Document
Updated/Added to NTRS: 2003-05-08

Study of Boundary Layer Development in a Two-Stage Low-Pressure Turbine
Dorney, Daniel J. (Virginia Commonwealth Univ., Richmond, VA United States); Ashpis, David E. (NASA Lewis Research Center, Cleveland, OH United States); Halstead, David E. (General Electric Co., Aircraft Engines Cincinnati, OH United States); Wisler, David C. (General Electric Co., Aircraft Engines Cincinnati, OH United States)
NASA Center for AeroSpace Information (CASI)
1998
Experimental data from jet-engine tests have indicated that unsteady blade row (wake) interactions and separation can have a significant impact on the efficiency of turbine stages. The effects of these interactions can be intensified in low-pressure turbine stages because of the low Reynolds number operating environment. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Thus, during the last decade a significant amount of effort has been put into determining the effects of transition and turbulence on the performance of low pressure turbine stages. Experimental investigations have been performed, for example, by Hodson et al. and Halstead et al. These investigations have helped identify/clarify the roles that factors such as the Reynolds number, free stream turbulence intensity, pressure gradient and curvature have in the generation of losses. In parallel to the experimental investigations, there have been significant analytical efforts to improve the modeling of transition. Examples of such efforts include the works of Mayle and Gostelow et al. These newer models show promise of providing accurate transition predictions over a wide range of flow conditions, although they have yet to be implemented into the numerical flow analyses used by the turbine design community. Some recent computational investigations of interest include the works of Chernobrovkin and Lakshminarayana and Eulitz and Engel. The focus of the current effort has been to -use a viscous, unsteady quasi-three-dimensional Navier-Stokes analysis to study boundary layer development in a two-stage low-pressure turbine. A two-layer algebraic turbulence model, along with a natural transition model and a bubble transition model, have been used, The geometry used in the simulations has been the subject of extensive experiments. The predicted results have been compared with experimental data, including airfoil loadings and time-averaged/unsteady integral boundary layer quantities.
No Digital Version Available - Order

Study of Low Reynolds Number Effects on the Losses in Low-Pressure Turbine Blade Rows
Dorney, Daniel J. (General Motors Inst., Engineering and Management Inst. Flint, MI United States); Ashpis, David E. (NASA Lewis Research Center, Cleveland, OH United States)
NASA Center for AeroSpace Information (CASI)
AIAA Paper 98-3575 , 1998
Experimental data from jet-engine tests have indicated that unsteady blade row interactions and separation can have a significant impact on the efficiency of low-pressure turbine stages. Measured turbine efficiencies at takeoff can be as much as two points higher than those at cruise conditions. Several recent studies have revealed that Reynolds number effects may contribute to the lower efficiencies at cruise conditions. In the current study numerical experiments have been performed to study the models available for low Reynolds number flows, and to quantify the Reynolds number dependence of low-pressure turbine cascades and stages. The predicted aerodynamic results exhibit good agreement with design data.
No Digital Version Available - Order This Document
Updated/Added to NTRS: 2003-05-08