Influence of Meridian Flow Path and Loading Distribution on the Performance of Turbine Rear Frame

Abstract

The prototype gas turbine has low efficiency and severely deviated outlet flow, thus, the Turbine Rear Frame (TRF) meridian flow path and Outlet Guide Vane (OGV) are redesigned, and the influence of meridian flow path and the different loading distribution on the internal flow field structure is analyzed by CFD calculations. The results show that when the maximum flow area ratio of the blade area is too high, separation will occur. The flow path design with a character that expand first and then contract can suppress the corner separation. The load distribution of OGV will affect the deflection distribution. Moving the maximum deflection position backwards can make the blade suction side turn smoothly, which is beneficial to reduce the axial adverse pressure gradient and relieve the suction surface corner separation. The transition-loaded airfoil can form an endwall bend on the suction side of the blade, reduce the cross flow in the channel, and alleviate the corner separation. After the retrofit design, the turbine efficiency can be increased by 6% or more, and the pressure recovery coefficient of OGV has a rise of more than 0.08, the outlet flow deviation after OGV is less than 3.5º (15.864º for prototype).