Calculation of heat transfer in separation zones with the use of local flow parameters at the boundary of the wall boundary layer

1971 ◽  
Vol 21 (1) ◽  
pp. 835-837 ◽  
Author(s):  
B. E. Luzhanskii ◽  
V. P. Solntsev ◽  
V. G. Limonov
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Local Flow ◽  
Wall Boundary Layer ◽  
Flow Parameters ◽  
Wall Boundary ◽  
Separation Zones

Modeling of Rough Wall Boundary Layer Transition and Heat Transfer on Turbine Airfoils

2006 ◽  
Author(s):  
M. Stripf ◽  
A. Schulz ◽  
H.-J. Bauer
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Boundary Layer Transition ◽  
Rough Wall ◽  
New Model ◽  
Free Stream Turbulence ◽  
Wall Boundary Layer ◽  
Wall Boundary ◽  
Turbine Airfoils

A new model for predicting heat transfer in the transitional boundary layer of rough turbine airfoils is presented. The new model makes use of extensive experimental work recently published by the current authors. For the computation of the turbulent boundary layer a discrete element roughness model is combined with a two-layer model of turbulence. The transition region is modeled using an intermittency equation that blends between the laminar and turbulent boundary layer. Several intermittency functions are evaluated in respect of their applicability to rough-wall transition. To predict the onset of transition a new correlation is presented, accounting for the influence of free-stream turbulence and surface roughness. Finally the new model is tested against transitional rough-wall boundary layer flows on high-pressure and low-pressure turbine airfoils.

Effects of Inlet Turbulence and End-Wall Boundary Layer on Aero-Thermal Performance of a Transonic Turbine Blade Tip

2013 ◽  
Author(s):  
Q. Zhang ◽  
L. He ◽  
A. Rawlinson
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Freestream Turbulence ◽  
Suction Surface ◽  
Wall Boundary Layer ◽  
Wall Boundary ◽  
Passage Vortex ◽  
Blade Tip ◽  
Transonic Turbine ◽  
End Wall

Most of previous researches of inlet turbulence effects on blade tip have been carried out for low speed situations. Recent work has indicated that for a transonic turbine tip, turbulent diffusion tends to have distinctively different impact on tip heat transfer than for its subsonic counterpart. It is hence of interest to examine how inlet turbulence flow conditioning would affect heat transfer characteristics for a transonic tip. This present work is aimed to identify and understand the effects of both inlet freestream turbulence and end-wall boundary layer on a transonic turbine blade tip aero-thermal performance. Spatially-resolved heat transfer data are obtained at aerodynamic conditions representative of a high-pressure turbine, using the transient infrared thermography technique with the Oxford High-Speed Linear Cascade research facility. With and without turbulence grids, the turbulence levels achieved are 7–9% and 1% respectively. On the blade tip surface, no apparent change in heat transfer was observed with high and low turbulence intensity levels investigated. On the blade suction surface, however, substantially different local heat transfer for the suction side near tip surface have been observed, indicating a strong local dependence of the local vortical flow on the freestream turbulence. These experimentally observed trends have also been confirmed by CFD predictions using Rolls-Royce HYDRA. Further CFD analysis suggests that the level of inflow turbulence alters the balance between the passage vortex associated secondary flow and the OverTL flow. Consequently, enhanced inertia of near wall fluid at a higher inflow turbulence weakens the cross-passage flow. As such, the weaker passage vortex leads the tip leakage vortex to move further into the mid passage, with the less spanwise coverage on the suction surface, as consistently indicated by the heat transfer signature. Different inlet end-wall boundary layer profiles are employed in the HYDRA numerical study. All CFD results indicate the inlet boundary layer thickness has little impact on the heat transfer over the tip surface as well as the pressure side near-tip surface. However, noticeable changes in heat transfer are observed for the suction side near-tip surface. Similar to the freestream turbulence effect, such changes are attributed to the interaction between the passage vortex and the OTL flow.

Modeling of Rough-Wall Boundary Layer Transition and Heat Transfer on Turbine Airfoils

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
M. Stripf ◽  
A. Schulz ◽  
H.-J. Bauer
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Boundary Layer Transition ◽  
Rough Wall ◽  
Layer Transition ◽  
New Model ◽  
Wall Boundary Layer ◽  
Wall Boundary ◽  
Turbine Airfoils

A new model for predicting heat transfer in the transitional boundary layer of rough turbine airfoils is presented. The new model makes use of extensive experimental work recently published by the current authors. For the computation of the turbulent boundary layer, a discrete element roughness model is combined with a two-layer model of turbulence. The transition region is modeled using an intermittency equation that blends between the laminar and turbulent boundary layer. Several intermittency functions are evaluated in respect of their applicability to rough-wall transition. To predict the onset of transition, a new correlation is presented, accounting for the influence of freestream turbulence and surface roughness. Finally, the new model is tested against transitional rough-wall boundary layer flows on high-pressure and low-pressure turbine airfoils.

Effects of Inlet Turbulence and End-Wall Boundary Layer on Aerothermal Performance of a Transonic Turbine Blade Tip

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Q. Zhang ◽  
L. He ◽  
A. Rawlinson
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Suction Side ◽  
Suction Surface ◽  
Wall Boundary Layer ◽  
Wall Boundary ◽  
Passage Vortex ◽  
Blade Tip ◽  
Transonic Turbine ◽  
End Wall

Most of the previous researches of inlet turbulence effects on blade tip have been carried out for low speed situations. Recent work has indicated that for a transonic turbine tip, turbulent diffusion tends to have a distinctively different impact on tip heat transfer than for its subsonic counterpart. It is hence of interest to examine how inlet turbulence flow conditioning would affect heat transfer characteristics for a transonic tip. The present work is aimed to identify and understand the effects of both inlet freestream turbulence and end wall boundary layer on a transonic turbine blade tip aerothermal performance. Spatially-resolved heat transfer data are obtained at aerodynamic conditions representative of a high-pressure turbine, using the transient infrared thermography technique with the Oxford High-Speed Linear Cascade research facility. With and without turbulence grids, the turbulence levels achieved are 7%–9% and 1%, respectively. On the blade tip surface, no apparent change in heat transfer was observed with high and low inlet turbulence intensity levels investigated. On the blade suction surface, however, substantially different local heat transfer distributions for the suction side near tip surface have been observed, indicating a strong local dependence of the local vortical flow structure on the freestream turbulence. These experimentally observed trends have also been confirmed by CFD examinations using the Rolls-Royce HYDRA. A further CFD analysis suggests that the level of inflow turbulence alters the balance between the passage vortex associated secondary flow and the over tip leakage (OTL) flow. Consequently, an enhanced inertia of near wall fluid at a higher inflow turbulence weakens the cross-passage flow. As such, the weaker passage vortex leads the tip leakage vortex to move further into the mid passage, with the less spanwise coverage on the suction surface, as consistently indicated by the heat transfer signature. Different inlet end wall boundary layer profiles are employed in the computational study with HYDRA. All CFD results indicate the inlet boundary layer thickness has little impact on the heat transfer over the tip surface as well as the pressure side near-tip surface. However, noticeable changes in heat transfer are observed for the suction side near-tip surface. Similar to the inlet turbulence effect, such changes can be attributed to the interaction between the passage vortex and the OTL flow.

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