Advanced Statistical Analysis Estimating the Heat Load Issued by Hot Streaks and Turbulence on a High-Pressure Vane in the Context of Adiabatic Large Eddy Simulations

2017 ◽  
Author(s):  
Martin Thomas ◽  
Florent Duchaine ◽  
Laurent Gicquel ◽  
Charlie Koupper
Keyword(s):  
High Pressure ◽  
Large Scale ◽  
Guide Vane ◽  
Large Eddy Simulations ◽  
High Pressure Turbine ◽  
Substantial Impact ◽  
Lean Combustion ◽  
Large Eddy ◽  
Inlet Conditions ◽  
The Impact

The next generation of lean combustion engines promises to further decrease environmental impact and cost of air traffic. Compared to the currently employed Rich Quench Lean (RQL) concept, the flow field at the exit of a lean combustion chamber is characterized by stronger variations of velocity as well as temperature and higher levels of turbulence. These specific features may have a substantial impact on the aerothermal performance of the high-pressure turbine and thereby on the efficiency of the entire engine. Indeed, high levels of turbulence in the Nozzle Guide Vane (NGV) passages locally impact the heat flux and result in globally over dimensioned cooling systems of the NGV. In this study, Large Eddy Simulations (LES) are performed on an engine representative lean combustion simulator geometry to investigate the evolution of turbulence and the migration of hot streaks through the high-pressure turbine. To investigate the impact of non-uniform stator inlet conditions on the estimated thermal stress on the NGVs, adiabatic LES predictions of the lean combustor NGV FACTOR configuration are analyzed through the use of high statistical moments of temperature and two point statistics for the assessment of turbulent quantities. Relations between temperature statistical features and turbulence are evidenced on planes through the NGV passage pointing to the role of mixing and large scale features along with marked wall temperatures that locally can largely differ from obtained mean values.

Large-Scale Simulation of the Clocking Impact of 2D Combustor Profile on a Two Stage High Pressure Turbine

2014 ◽  
Author(s):  
Thomas E. Dyson ◽  
David B. Helmer ◽  
James A. Tallman
Keyword(s):  
High Pressure ◽  
Large Scale ◽  
High Pressure Turbine ◽  
Cfd Simulations ◽  
Two Stage ◽  
Substantial Impact ◽  
Sliding Mesh ◽  
Wall Flow ◽  
End Wall ◽  
Film Flows

This paper presents sliding-mesh unsteady CFD simulations of high-pressure turbine sections of a modern aviation engine in an extension of previously presented work [1]. The simulation included both the first and second stages of a two-stage high-pressure turbine. Half-wheel domains were used, with source terms representing purge and film flows. The end-wall flow-path cavities were incorporated in the domain to a limited extent. The passage-to-passage variation in thermal predictions was compared for a 1D and 2D turbine inlet boundary condition. Substantial impact was observed on both first and second stage vanes despite the mixing from the first stage blade. Qualitative and quantitative differences in surface temperature distributions were observed due to different ratios between airfoil counts in the two domains.

scholarly journals High-resolution large-eddy simulations of sub-kilometer-scale turbulence in the upper troposphere lower stratosphere

2013 ◽  
Vol 13 (12) ◽  
pp. 31891-31932 ◽  
Author(s):  
R. Paoli ◽  
O. Thouron ◽  
J. Escobar ◽  
J. Picot ◽  
D. Cariolle
Keyword(s):  
Large Scale ◽  
Lower Stratosphere ◽  
Atmospheric Model ◽  
Large Eddy Simulations ◽  
Stratified Flows ◽  
Flow Topology ◽  
Upper Troposphere ◽  
Large Eddy ◽  
Scale Turbulence ◽  
The Impact

Abstract. Large-eddy simulations of sub-kilometer-scale turbulence in the upper troposphere lower stratosphere (UTLS) are carried out and analyzed using the mesoscale atmospheric model Méso-NH. Different levels of turbulence are generated using a large-scale stochastic forcing technique that was especially devised to treat atmospheric stratified flows. The study focuses on the analysis of turbulence statistics, including mean quantities and energy spectra, as well as on a detailed description of flow topology. The impact of resolution is also discussed by decreasing the grid spacing to 2 m and increasing the number of grid points to 8×109. Because of atmospheric stratification, turbulence is substantially anisotropic, and large elongated structures form in the horizontal directions, in accordance with theoretical analysis and spectral direct numerical simulations of stably stratified flows. It is also found that the inertial range of horizontal kinetic energy spectrum, generally observed at scales larger than a few kilometers, is prolonged into the sub-kilometric range, down to the Ozmidov scales that obey isotropic Kolmorogov turbulence. The results are in line with observational analysis based on in situ measurements from existing campaigns.

Effects of Subgrid Scale Modeling on the Deterministic and Stochastic Turbulent Energetic Distribution in Large-Eddy Simulations of a High-Pressure Turbine Stage

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Dimitrios Papadogiannis ◽  
Florent Duchaine ◽  
Laurent Gicquel ◽  
Gaofeng Wang ◽  
Stéphane Moreau
Keyword(s):  
High Pressure ◽  
Decomposition Analysis ◽  
Large Eddy Simulations ◽  
Reference Frequency ◽  
Subgrid Scale ◽  
High Pressure Turbine ◽  
Pressure Profiles ◽  
Radial Profiles ◽  
Large Eddy ◽  
Flow Features

This study focuses on the engine-representative MT1 transonic high-pressure turbine. Simulated by use of wall-modeled large-eddy simulations (LES) with three different subgrid scale (SGS) closures, mean pressure profiles across the blades as well as mean radial profiles at the rotor exit are found to be in good agreement with experimental data with only local differences between models. Unsteady flow features, inherently present in LES, are however affected by SGS modeling. This is evidenced by the relative energetic content of the deterministic to stochastic turbulent contributions evaluated, thanks to the triple decomposition analysis of the simulations. Origins of such differences are found to impact the entire radial distribution of the flow and activity, with deterministic and chaotic contributions distributed differently depending on the SGS model and reference frequency used to extract the deterministic signal. Such flow responses can be attributed to the different SGS capacities to satisfy basic turbulent flow features that translate in different dissipative and turbulent diffusive contributions of the three SGS models.

Evaluation of the Numerical Modelling of a High Pressure Turbine Test Rig

2019 ◽  
Author(s):  
David Luquet ◽  
Francois Julienne ◽  
Aurélien Arntz ◽  
Eric Lippinois
Keyword(s):  
High Pressure ◽  
Infrared Imaging ◽  
Guide Vane ◽  
Fuel Efficiency ◽  
Temporal Variations ◽  
Test Rig ◽  
High Pressure Turbine ◽  
Lean Burn ◽  
Multi Stage ◽  
The Impact

Abstract To improve the fuel efficiency demanded by airlines and regulations, the turbomachinery industry is required to steadily enhance engine performances and numerical prediction capabilities. One of the solutions is the lean burn combustor which dramatically reduces NOx levels compared to rich one. However, one drawback of this technology is its impact on the High-pressure turbine due to large swirl and reduced cooling airflow, inducing large spatial and temporal variations in the turbine inlet condition. This can drastically change the operation of the turbine and our ability to model it using standard practice, usually RANS computation. To investigate this combustor-turbine interaction, the European Commission-funded project FACTOR (Full Aerothermal Combustor-Turbine interactiOns Research) was launched several years ago. A test rig of a combustor simulator coupled with a 1.5 stage turbine was built at a DLR facility. An extensive test campaign comprising 5 holes probes and infrared imaging was performed. These produced an array of aerodynamic quantities at different points of interest along the machine axis. With this project reaching its term by the end of 2017, results have been disseminated to the partners. This allows a comparison of measurements with RANS modeling on this configuration. The present paper deals with this analysis using several RANS computations and the results of the test campaign. First, single row computation of the Nozzle Guide Vane and rotor blade were performed. To impose the boundary conditions, the experimental map were azimuthally averaged to obtain profiles of total temperature, total pressure and flow angles. Second, the impact of some geometrical features was investigated. This was done using the recent addition of unstructured mesh capability in the elsA solver. Finally, multi-stage computations, both steady (mixing plane) and unsteady (sliding mesh) give an insight on the relative accuracy of these interstage models. All these computations were then used to investigate the behavior of this particular turbine. In addition to classical analysis using profiles of averaged data, the loss sources were identified by computing the viscous and thermal entropy production. This paves the way for a better understanding of the possibilities and limitations of our simulation capabilities.

Large-Eddy Simulation of a High-Pressure Turbine Vane With Inlet Turbulence

2016 ◽  
Author(s):  
Solkeun Jee ◽  
Jongwook Joo ◽  
Gorazd Medic
Keyword(s):  
Boundary Layer ◽  
High Pressure ◽  
Large Eddy Simulation ◽  
Turbulence Intensity ◽  
The State ◽  
High Pressure Turbine ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbine Vane ◽  
The Impact

It is important to be able to predict the state of the boundary layer on a high-pressure turbine vane with incoming turbulence. The laminar-to-turbulent transition significantly changes the heat transfer on the blade, which impacts the turbine performance and durability assessment. In this study, an experimental cascade with a high-pressure turbine vane was simulated with large-eddy simulation (LES). To incorporate the impact of turbulence from the freestream on the boundary layer, appropriate turbulence data sets were generated in separate direct-numerical simulation and fed into the LES inlet. The state of the boundary layer is reasonably well predicted for the test condition of the turbulence intensity of Tu=4%. Streamwise vortical structures and spanwise two-dimensional waves are observed in the transitional boundary layer. Discrepancy for the case with the higher turbulence intensity Tu=6% is discussed with the focus on the need for more detailed information about the freestream disturbances.

scholarly journals High-resolution large-eddy simulations of stably stratified flows: application to subkilometer-scale turbulence in the upper troposphere–lower stratosphere

2014 ◽  
Vol 14 (10) ◽  
pp. 5037-5055 ◽  
Author(s):  
R. Paoli ◽  
O. Thouron ◽  
J. Escobar ◽  
J. Picot ◽  
D. Cariolle
Keyword(s):  
Large Scale ◽  
Lower Stratosphere ◽  
Large Eddy Simulations ◽  
Stratified Flows ◽  
Flow Topology ◽  
Upper Troposphere ◽  
Stably Stratified Flows ◽  
Large Eddy ◽  
Scale Turbulence ◽  
The Impact

Abstract. Large-eddy simulations of stably stratified flows are carried out and analyzed using the mesoscale atmospheric model Méso-NH for applications to kilometer- and subkilometer-scale turbulence in the in the upper troposphere–lower stratosphere. Different levels of turbulence are generated using a large-scale stochastic forcing technique that was especially devised to treat atmospheric stratified flows. The study focuses on the analysis of turbulence statistics, including mean quantities and energy spectra, as well as on a detailed description of flow topology. The impact of resolution is also discussed by decreasing the grid spacing to 2 m and increasing the number of grid points to 8 × 109. Because of atmospheric stratification, turbulence is substantially anisotropic, and large elongated structures form in the horizontal directions, in accordance with theoretical analysis and spectral, direct numerical simulations of stably stratified flows. It is also found that the inertial range of horizontal kinetic energy spectrum, generally observed at scales larger than a few kilometers, is prolonged into the subkilometric range, down to the Ozmidov scales that obey isotropic Kolmogorov turbulence. This study shows the capability of atmospheric models like Méso-NH to represent the turbulence at subkilometer scales.

Design of an Intermediate Turbine Duct Downstream of a High Pressure Turbine

2016 ◽  
Author(s):  
Chaoshan Hou ◽  
Hu Wu
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Low Pressure ◽  
Aerodynamic Load ◽  
Duct Flow ◽  
Original Design ◽  
High Pressure Turbine ◽  
Intermediate Turbine Duct ◽  
Low Pressure Turbine ◽  
Inlet Conditions

The flow leaving the high pressure turbine should be guided to the low pressure turbine by an annular diffuser, which is called as the intermediate turbine duct. Flow separation, which would result in secondary flow and cause great flow loss, is easily induced by the negative pressure gradient inside the duct. And such non-uniform flow field would also affect the inlet conditions of the low pressure turbine, resulting in efficiency reduction of low pressure turbine. Highly efficient intermediate turbine duct cannot be designed without considering the effects of the rotating row of the high pressure turbine. A typical turbine model is simulated by commercial computational fluid dynamics method. This model is used to validate the accuracy and reliability of the selected numerical method by comparing the numerical results with the experimental results. An intermediate turbine duct with eight struts has been designed initially downstream of an existing high pressure turbine. On the basis of the original design, the main purpose of this paper is to reduce the net aerodynamic load on the strut surface and thus minimize the overall duct loss. Full three-dimensional inverse method is applied to the redesign of the struts. It is revealed that the duct with new struts after inverse design has an improved performance as compared with the original one.

Prediction of liquid-liquid flow in an SMX static mixer using large eddy simulations

2010 ◽  
Vol 64 (2) ◽  
Author(s):  
Paulina Pianko-Oprych ◽  
Zdzisław Jaworski
Keyword(s):  
Centrifugal Force ◽  
Liquid Flow ◽  
Concentration Distribution ◽  
Large Eddy Simulations ◽  
Dispersed Phase ◽  
Static Mixer ◽  
Phase Concentration ◽  
Large Eddy ◽  
Smx Static Mixer ◽  
The Impact

AbstractThe main purpose of the paper is to apply the large eddy simulations (LES) technique and to verify its use as a predicting tool for turbulent liquid-liquid flow in an SMX static mixer. LES modeling was carried out using the Smagorinsky-Lilly model of the turbulent subgrid viscosity for the Reynolds number of 5000 and 10000. The continuous phase was water and the dispersed phase was silicon oil. The investigation covers the effects of the density ratio between the phases. Three different cases of liquid densities were considered. The dispersed phase concentration distribution in the mixer cross-sections was compared with the corresponding time averaged results obtained formerly for the same configuration in a steady-state simulation using the standard RANS approach with the k-ɛ model. The dependency of the standard deviation of the dispersed phase concentration on the distance from the mixer inlet and the impact of the centrifugal force on the phase concentration distribution were investigated. The presented results for the SMX static mixer confirm conclusions of previous studies by Jaworski et al. (2006) obtained for a Kenics static mixer and show less a pronounced influence of the centrifugal force on the phase concentration distribution of the LES results in comparison to the RANS case.

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