| Detailed measurements have been made of the mid-span aerodynamic performance of two transonic turbine cascades at off-design conditions. The cascades investigated were a baseline cascade, designated HS1A, and a cascade with a modified leading edge design, designated HS1B. The measurements were for exit Mach numbers ranging from about 0.5 to about 1.2 and for Reynolds numbers from 4 × 105 to 106. The turbulence intensity in the test section and upstream of the cascade test section was about 4%. The profile losses were measured for the incidence values of −10°, 0.0°, +4.5°, +10.0°, and +14.5° relative to design. To aid in understanding the loss behaviour and to provide other insights into the flow physics, measurements of the blade loading, exit flow angles, trailing-edge base pressures, and the Axial Velocity Density Ratio (AVDR) were also made.; The results showed that the profile losses at transonic Mach numbers can be closely related to the behaviour of the base pressure. The losses were also found to be affected by the AVDR. The AVDRs were found to decrease with increasing positive incidence.; Moreover the results from both cascades showed that the modifications to the leading edge geometry of HS1B cascade were not successful in improving the blade performance at positive off-design incidence.; Comparisons between the present experimental data and the available correlations in the open literature were also made. These comparisons included mid-span losses at design and off-design, and exit flow angles. It was found that further improvements can still be made to the existing correlations. Furthermore, the present experimental data represents a significant contribution to the data base of results available in the open literature for the development of new and improved correlations, particularly at transonic flow conditions, at both design and off-design conditions. |
