Numerical Study of Purge and Secondary Flows in a Low-Pressure Turbine

The secondary flow increases the loss and changes the flow incidence in the downstream blade row. To prevent hot gases from entering disk cavities, purge flows are injected into the mainstream in a real aero-engine. The interaction between purge flows and the mainstream usually induces aerodynamic losses. The endwall loss is also affected by shedding wakes and secondary flow from upstream rows. Using a series of eddy-resolving simulations, this paper aims to improve the understanding of the interaction between purge flows, incoming secondary flows along with shedding wakes and mainstream flows on the endwall within a stator passage. It is found that for a blade with an aspect ratio of 2.2, a purge flow with a 1% leakage rate increases loss generation within the blade passage by around 10%. The incoming wakes and secondary flows increase the loss generation further by around 20%. The purge flow pushes the passage vortex further away from the endwall and increases the exit flow angle deviation. However, the maximum exit flow angle deviation is reduced after introducing incoming wakes and secondary flows. The loss generation rate is calculated using the mean flow kinetic energy equation. Two regions with high loss generation rate are identified within the blade passage: the corner region and the region where passage vortex interacts with the boundary layer on the suction surface. Loss generation rate increases dramatically after the separated boundary layer transitions. Since the endwall flow energizes the boundary layer and triggers

[1]  V. N. Rao,et al.  Numerical investigation of secondary flows in a high-lift low pressure turbine , 2017 .

[2]  Jonathan Corpus Ong,et al.  The Effect of Coolant Injection on the Endwall Flow of a High Pressure Turbine , 2012 .

[3]  Stuart E. Rogers,et al.  Steady and unsteady solutions of the incompressible Navier-Stokes equations , 1991 .

[4]  P. Moin,et al.  Large-eddy simulation analysis of mechanisms for viscous losses in a turbomachinery tip-clearance flow , 2007, Journal of Fluid Mechanics.

[5]  Parviz Moin,et al.  Computational Methodology for Large-Eddy Simulation of Tip-Clearance Flows , 2004 .

[6]  John D. Denton,et al.  The Interaction of Turbine Inter-Platform Leakage Flow With the Mainstream Flow , 2005 .

[7]  Paul G. Tucker,et al.  Numerical Investigation of Contrasting Flow Physics in Different Zones of a High-Lift Low Pressure Turbine Blade , 2015 .

[8]  Richard D. Sandberg,et al.  Compressible Direct Numerical Simulation of Low-Pressure Turbines—Part I: Methodology , 2015 .

[9]  S. Harrison,et al.  Secondary Loss Generation in a Linear Cascade of High-Turning Turbine Blades , 1989 .

[10]  Graham Pullan.  Secondary Flows and Loss Caused by Blade Row Interaction in a Turbine Stage , 2004 .

[11]  Richard D. Sandberg,et al.  Compressible direct numerical simulation of low-pressure turbines: part I - methodology , 2014 .

[12]  C. Tan,et al.  Turbine Hub and Shroud Sealing Flow Loss Mechanisms , 2012 .

[13]  John D. Denton,et al.  A Numerical Investigation Into the Sources of Endwall Loss in Axial Flow Turbines , 2012 .

[14]  R. G. Jacobs,et al.  Simulation of boundary layer transition induced by periodically passing wakes , 1999, Journal of Fluid Mechanics.

[15]  Paul G. Tucker,et al.  The influence of geometry on jet plume development , 2012 .

[16]  H. Hodson,et al.  Experimental Investigation of Unsteady Transition Processes on High-Lift T106A Turbine Blades , 2008 .

[17]  John D. Denton,et al.  The 1993 IGTI Scholar Lecture: Loss Mechanisms in Turbomachines , 1993 .

[18]  T. J. Praisner,et al.  Measurements of Losses and Reynolds Stresses in the Secondary Flow Downstream of a Low-Speed Linear Turbine Cascade , 2010 .

[19]  W. Rodi,et al.  Direct numerical simulation of flow and heat transfer in a turbine cascade with incoming wakes , 2006, Journal of Fluid Mechanics.