Flows in an intermediate turbine duct connecting low-pressure turbines and power turbines are very complex, affected by the upstream low-pressure turbine flow structures. Non-uniformities originating from the duct with struts also affect the power turbine inflow conditions, resulting in reduced efficiency. The present investigation is done to clarify the flow and loss mechanisms within the intermediate turbine duct and the power turbine. Steady and unsteady numerical investigations of the flow interaction between low-pressure turbine blade, intermediate turbine duct and power turbine vane were conducted. Effects of upstream low-pressure turbine blade on intermediate turbine duct flow fields and loss characteristics, and that of intermediate turbine duct with big and small struts on power turbine aerodynamics are explored. The generation and propagation of wake and secondary flows through the whole configuration are described. The fast Fourier transformation analyses of the flow in the low-pressure turbine blade, intermediate turbine duct and power turbine vane are also presented. Results from the steady and unsteady investigations show complex flow patterns resulted from blade–strut–vane flow interactions, which are not obtainable from intermediate turbine duct-only or power turbine-only simulations. The intermediate turbine duct has a great amplifying influence on the distorted inflow, and the inlet flow with upstream wakes and secondary flows introduces a high-loss area along the casing at intermediate turbine duct exit. Detailed results are presented and discussed for the flow physics and loss mechanisms as well as the unsteady flow evolution through the low-pressure turbine blade, intermediate turbine duct and power turbine vane.
The Role of Reverse Transcriptase in Intron Gain and Loss Mechanisms
