scholarly journals Scale-Resolving Simulations of Bypass Transition in a High-Pressure Turbine Cascade Using a Spectral Element Discontinuous Galerkin Method

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Anirban Garai ◽  
Laslo T. Diosady ◽  
Scott M. Murman ◽  
Nateri K. Madavan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Guide Vane ◽  
Suction Side ◽  
Spectral Element ◽  
Bypass Transition ◽  
Heat Transfer Characteristics ◽  
High Pressure Turbine ◽  
Computational Capability ◽  
Inflow Turbulence

The application of a new computational capability for accurate and efficient high-fidelity scale-resolving simulations of turbomachinery is presented. The focus is on the prediction of heat transfer and boundary layer characteristics with comparisons to the experiments of Arts et al. (1990, “Aero–Thermal Investigation of a Highly Loaded Transonic Linear Turbine Guide Vane Cascade,” von Karman Institute for Fluid Dynamics, Rhode St. Genese, Belgium, Technical Note No. 174.) for an uncooled, transonic, linear high-pressure turbine (HPT) inlet guide vane cascade that includes the effects of elevated inflow turbulence. The computational capability is based on an entropy-stable, discontinuous Galerkin (DG) spectral element approach that extends to arbitrarily high orders of spatial and temporal accuracy. The suction side of the vane undergoes natural transition for the clean inflow case, while bypass transition mechanisms are observed in the presence of elevated inflow turbulence. The airfoil suction-side boundary layer turbulence characteristics during the transition process thus differ significantly between the two cases. Traditional simulations based on the Reynolds-averaged Navier–Stokes (RANS) fail to predict these transition characteristics. The heat transfer characteristics for the simulations with clean inflow agree well with the experimental data, while the heat transfer characteristics for the bypass transition cases agree well with the experiment when higher inflow turbulence levels are prescribed. The differences between the clean and inflow turbulence cases are also highlighted through a detailed examination of the characteristics of the transitional and turbulent flow fields.

scholarly journals Scale-Resolving Simulations of Bypass Transition in a High-Pressure Turbine Cascade Using a Spectral-Element Discontinuous-Galerkin Method

2017 ◽  
Author(s):  
Anirban Garai ◽  
Laslo T. Diosady ◽  
Scott M. Murman ◽  
Nateri K. Madavan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
High Pressure ◽  
Suction Side ◽  
Spectral Element ◽  
Bypass Transition ◽  
Heat Transfer Characteristics ◽  
High Pressure Turbine ◽  
Computational Capability ◽  
Inflow Turbulence

The application of a new computational capability for accurate and efficient high-fidelity scale-resolving simulations of turbomachinery is presented. The focus is on the prediction of heat transfer and boundary layer characteristics with comparisons to the experiments of Arts et al. for an uncooled, transonic, linear high-pressure turbine (HPT) inlet guide vane cascade that includes the effects of elevated inflow turbulence. The computational capability is based on an entropy-stable, discontinuous-Galerkin spectral-element approach that extends to arbitrarily high orders of spatial and temporal accuracy. The suction side of the vane undergoes natural transition for the clean inflow case, while bypass transition mechanisms are observed in the presence of elevated inflow turbulence. The airfoil suction-side boundary layer turbulence characteristics during the transition process thus differ significantly between the two cases. Traditional simulations based on the Reynolds-averaged Navier Stokes (RANS) fail to predict these transition characteristics. The heat transfer characteristics for the simulations with clean inflow agree well with the experimental data, while the heat transfer characteristics for the bypass transition cases agree well with the experiment when higher inflow turbulence levels are prescribed. The differences between the clean and inflow turbulence cases are also highlighted through a detailed examination of the characteristics of the transitional and turbulent flow fields.

Numerical Predictions of Turbine Cascade Secondary Flows and Heat Transfer With Inflow Turbulence

2020 ◽  
Author(s):  
Yousef Kanani ◽  
Sumanta Acharya ◽  
Forrest Ames
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Leading Edge ◽  
Suction Side ◽  
Lateral Spreading ◽  
Secondary Flows ◽  
Pressure Side ◽  
Initial Flow ◽  
Numerical Predictions ◽  
Inflow Turbulence

Abstract Turbine passage secondary flows are studied for a large rounded leading edge airfoil geometry considered in the experimental investigation of Varty et al. (J. Turbomach. 140(2):021010) using high resolution Large Eddy Simulation (LES). The complex nature of secondary flow formation and evolution are affected by the approach boundary layer characteristics, components of pressure gradients tangent and normal to the passage flow, surface curvature, and inflow turbulence. This paper presents a detailed description of the secondary flows and heat transfer in a linear vane cascade at exit chord Reynolds number of 5 × 105 at low and high inflow turbulence. Initial flow turning at the leading edge of the inlet boundary layer leads to a pair of counter-rotating flow circulation in each half of the cross-plane that drive the evolution of the pressure-side and suction side of the near-wall vortices such as the horseshoe and leading edge corner vortex. The passage vortex for the current large leading-edge vane is formed by the amplification of the initially formed circulation closer to the pressure side (PPC) which strengthens and merges with other vortex systems while moving toward the suction side. The predicted suction surface heat transfer shows good agreement with the measurements and properly captures the augmented heat transfer due to the formation and lateral spreading of the secondary flows towards the vane midspan downstream of the vane passage. Effects of various components of the secondary flows on the endwall and vane heat transfer are discussed in detail.

Large Eddy Simulation of Bypass Transition in Vane Passage With Freestream Turbulence

2020 ◽  
Vol 142 (6) ◽  
Author(s):  
Yousef Kanani ◽  
Sumanta Acharya ◽  
Forrest Ames
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Bypass Transition ◽  
Freestream Turbulence ◽  
Turbulent Spot ◽  
Suction Surface ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Inflow Turbulence

Abstract High Reynolds flow over a nozzle guide-vane with elevated inflow turbulence was simulated using wall-resolved large eddy simulation (LES). The simulations were undertaken at an exit Reynolds number of 0.5 × 106 and inflow turbulence levels of 0.7% and 7.9% and for uniform heat-flux boundary conditions corresponding to the measurements of Varty and Ames (2016, “Experimental Heat Transfer Distributions Over an Aft Loaded Vane With a Large Leading Edge at Very High Turbulence Levels,” ASME Paper No. IMECE2016-67029). The predicted heat transfer distribution over the vane is in excellent agreement with measurements. At higher freestream turbulence, the simulations accurately capture the laminar heat transfer augmentation on the pressure surface and the transition to turbulence on the suction surface. The bypass transition on the suction surface is preceded by boundary layer streaks formed under the external forcing of freestream disturbances which breakdown to turbulence through inner-mode secondary instabilities. Underneath the locally formed turbulent spot, heat transfer coefficient spikes and generally follows the same pattern as the turbulent spot. The details of the flow and temperature fields on the suction side are characterized, and first- and second-order statistics are documented. The turbulent Prandtl number in the boundary layer is generally in the range of 0.7–1, but decays rapidly near the wall.

The Influence of the Boundary Layer State and Reynolds Number on Film Cooling and Heat Transfer on a Cooled Nozzle Guide Vane

2000 ◽  
Author(s):  
Hans Reiss ◽  
Albin Bölcs
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Film Cooling ◽  
Guide Vane ◽  
Suction Side ◽  
Flow Conditions ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nozzle Guide Vane ◽  
Nozzle Guide

Film cooling and heat transfer measurements were carried out on a cooled nozzle guide vane in a linear cascade, using a transient liquid crystal technique. Three flow conditions were realized: the nominal operating condition of the vane with an exit Reynolds number of 1.47e6, as well as two lower flow conditions: Re2L = 1.0e6 and 7.5e5. The vane model was equipped with a single row of inclined round film cooling holes with compound angle orientation on the suction side. Blowing ratios ranging form 0.3 to 1.5 were covered, all using foreign gas injection (CO2) yielding an engine-representative density ratio of 1.6. Two distinct states of the incoming boundary layer onto the injection station were compared, an undisturbed laminar boundary layer as it forms naturally on the suction side, and a fully turbulent boundary layer which was triggered with a trip wire upstream of injection. The aerodynamic flow field is characterized in terms of profile Mach number distribution, and the associated heat transfer coefficients around the uncooled airfoil are presented. Both detailed and spanwise averaged results of film cooling effectiveness and heat transfer coefficients are shown on the suction side, which indicate considerable influence of the state of the incoming boundary layer on the performance of a film cooling row. The influence of the mainstream flow condition on the film cooling behavior at constant blowing ratio is discussed for three chosen injection regimes.

Large Eddy Simulation of Bypass Transition in Vane Passage With Freestream Turbulence

2019 ◽  
Author(s):  
Yousef Kanani ◽  
Sumanta Acharya ◽  
Forrest Ames
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Large Eddy Simulation ◽  
Bypass Transition ◽  
Freestream Turbulence ◽  
Turbulent Spot ◽  
Suction Surface ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Inflow Turbulence

Abstract High Reynolds flow over a nozzle guide-vane with elevated inflow turbulence was simulated using wall-resolved large eddy simulation (LES). The simulations were undertaken at an exit Reynolds number of 0.5×106 and inflow turbulence levels of 0.7% and 7.9% and for uniform heat-flux boundary conditions corresponding to the measurements of (Varty, J. W., and Ames, F. E., 2016, ASME Paper No. IMECE2016-67029). The predicted heat transfer distribution over the vane is in excellent agreement with measurements. At higher freestream turbulence, the simulations accurately capture the laminar heat transfer augmentation on the pressure surface and the transition to turbulence on the suction surface. The bypass transition on the suction surface is preceded by boundary layer streaks formed under the external forcing of freestream disturbances which breakdown to turbulence through inner mode secondary instabilities. Underneath the locally formed turbulent spot, heat transfer coefficient spikes and generally follows the same pattern as the turbulent spot. The details of the flow and temperature fields on the suction side are characterized and first and second order statistics are documented. The turbulent Prandtl number in the boundary layer is generally in the range of 0.7–1, but decays rapidly near the wall.

Numerical Predictions of Turbine Cascade Secondary Flows and Heat Transfer With Inflow Turbulence

2021 ◽  
pp. 1-34
Author(s):  
Yousef Kanani ◽  
Sumanta Acharya ◽  
Forrest Ames
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Leading Edge ◽  
Suction Side ◽  
Lateral Spreading ◽  
Secondary Flows ◽  
Pressure Side ◽  
Initial Flow ◽  
Numerical Predictions ◽  
Inflow Turbulence

Abstract Turbine passage secondary flows are studied for a large rounded leading edge airfoil geometry considered in the experimental investigation of Varty et al. (J. Turbomach. 140(2):021010) using high resolution Large Eddy Simulation. The complex nature of secondary flow formation and evolution are affected by the approach boundary layer characteristics, components of pressure gradients tangent and normal to the passage flow, surface curvature, and inflow turbulence. This paper presents a detailed description of the secondary flows and heat transfer in a linear vane cascade at exit chord Reynolds number of 500,000 at low and high inflow turbulence. Initial flow turning at the leading edge of the inlet boundary layer leads to a pair of counter-rotating flow circulation in each half of the cross-plane that drive the evolution of the pressure-side and suction side of the near-wall vortices such as the horseshoe and leading edge corner vortex. The passage vortex for the current large leading-edge vane is formed by the amplification of the initially formed circulation closer to the pressure side which strengthens and merges with other vortex systems while moving toward the suction side. The predicted suction surface heat transfer shows good agreement with the measurements and properly captures the augmented heat transfer due to the formation and lateral spreading of the secondary flows towards the vane midspan downstream of the vane passage. Effects of various components of the secondary flows on the endwall and vane heat transfer are discussed in detail.

Numerical investigations of unsteady passing wake effects on turbine blade tip aerothermal performance with different tip clearances

2019 ◽  
Vol 30 (2) ◽  
pp. 792-817
Author(s):  
Bo Zhang ◽  
Xiaoqing Qiang ◽  
Shaopeng Lu ◽  
Jinfang Teng
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Rotor Blade ◽  
Guide Vane ◽  
Heat Transfer Characteristics ◽  
High Pressure Turbine ◽  
Content Type ◽  
Blade Tip

Purpose The purpose of this paper is to numerically investigate the effect of guide vane unsteady passing wake on the rotor blade tip aerothermal performance with different tip clearances. Design/methodology/approach The geometry and flow conditions of the first stage of GE-E3 high-pressure turbine have been used to obtain the blade tip three-dimensional heat transfer characteristics. The first stage of GE-E3 high-pressure turbine has 46 guide vanes and 76 rotor blades, and the ratio of the vane to the blade is simplified to 38:76 to compromise the computational resources and accuracy. Namely, each computational domain comprises of one guide vane passage and two rotor blade passages. The investigations are conducted at three different tip gaps of 1.0, 1.5 and 2.0 per cent of the average blade span. Findings The results show that the overall discrepancy of the heat transfer coefficient between steady results and unsteady time-averaged results is quite small, but the dramatic growth of the instantaneous heat transfer coefficient along the pressure side is in excess of 20 per cent. The change of the aerothermal performance is mainly driven by turbulence-level fluctuations of the unsteady flow field within gap regions. In addition, the gap size expansion has a marginal impact on the variation ratio of tip unsteady aerothermal performances, even though it has a huge influence on the leakage flow state within the tip region. Originality/value This paper emphasizes the change ratio of unsteady instantaneous heat transfer characteristics and detailed the mechanism of blade tip unsteady heat transfer coefficient fluctuations, which provide some guidance for the future blade tip design and optimization.

Numerical Simulation of Turbine Blade Boundary Layer and Heat Transfer and Assessment of Turbulence Models

1997 ◽  
Vol 119 (4) ◽  
pp. 794-801 ◽  
Author(s):  
J. Luo ◽  
B. Lakshminarayana
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Navier Stokes ◽  
Bypass Transition ◽  
Boundary Layer Development ◽  
Low Reynolds ◽  
Layer Development

The boundary layer development and convective heat transfer on transonic turbine nozzle vanes are investigated using a compressible Navier–Stokes code with three low-Reynolds-number k–ε models. The mean-flow and turbulence transport equations are integrated by a four-stage Runge–Kutta scheme. Numerical predictions are compared with the experimental data acquired at Allison Engine Company. An assessment of the performance of various turbulence models is carried out. The two modes of transition, bypass transition and separation-induced transition, are studied comparatively. Effects of blade surface pressure gradients, free-stream turbulence level, and Reynolds number on the blade boundary layer development, particularly transition onset, are examined. Predictions from a parabolic boundary layer code are included for comparison with those from the elliptic Navier–Stokes code. The present study indicates that the turbine external heat transfer, under real engine conditions, can be predicted well by the Navier–Stokes procedure with the low-Reynolds-number k–ε models employed.

High-Fidelity Simulations of a High-Pressure Turbine Stage: Effects of Reynolds Number and Inlet Turbulence

2021 ◽  
Author(s):  
Yaomin Zhao ◽  
Richard D. Sandberg
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Suction Side ◽  
Rotor Blades ◽  
High Fidelity ◽  
Mean Flow ◽  
High Pressure Turbine ◽  
Flow Shear ◽  
Phase Lock ◽  
The Mean

Abstract We present the first wall-resolved high-fidelity simulations of high-pressure turbine (HPT) stages at engine-relevant conditions. A series of cases have been performed to investigate the effects of varying Reynolds numbers and inlet turbulence on the aerothermal behavior of the stage. While all of the cases have similar mean pressure distribution, the cases with higher Reynolds number show larger amplitude wall shear stress and enhanced heat fluxes around the vane and rotor blades. Moreover, higher-amplitude turbulence fluctuations at the inlet enhance heat transfer on the pressure-side and induce early transition on the suction-side of the vane, although the rotor blade boundary layers are not significantly affected. In addition to the time-averaged results, phase-lock averaged statistics are also collected to characterize the evolution of the stator wakes in the rotor passages. It is shown that the stretching and deformation of the stator wakes is dominated by the mean flow shear, and their interactions with the rotor blades can significantly intensify the heat transfer on the suction side. For the first time, the recently proposed entropy analysis has been applied to phase-lock averaged flow fields, which enables a quantitative characterization of the different mechanisms responsible for the unsteady losses of the stages. The results indicate that the losses related to the evolution of the stator wakes is mainly caused by the turbulence production, i.e. the direct interaction between the wake fluctuations and the mean flow shear through the rotor passages.

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