these simulation numerique et modelisation de l'ecoulement autour ...

More documents

Recommendations

Info

al. 30 The present paper details the methodology developed for post-processing the reference act geometry for film cooling studies. However, generating this type of data experimentally is very challenging: the operating conditions in the combustion chambers (high temperature and high pressure) are difficult to reproduce in test rigs and experimental techniques are rarely adapted to such conditions. Moreover, the characteristic size of the micro-jets being sub-millimetric, the main flow features are out of reach of current measurements techniques. This explains the lack of detailed measurements in realistic operating conditions: accurate information about the velocity field in FCFC configurations is available only on large-scale isothermal plates. 16–18 When experiments are performed on plates at real scale, only wall parameters, 19–22 like the heat transfer coefficient or the adiabatic cooling efficiency, or integrated data like the discharge coefficient 23,24 are provided and very often, only small temperature differences between the hot and the cold streams are investigated. An alternative is to use direct simulations to generate the requested data. However requirements in computational power are huge due to the configuration: in FCFC, the perforated plate contains hundreds or thousands of holes and resolving the flow in each of these holes would be very expensive. Hence, only Reynolds-Averaged Navier–Stokes (RANS) computations were performed with a large number of cooling rows. 25,26 However, using RANS results as reference data for modeling is questionable, as they already result from the modeling of the whole turbulent part of the flow. On the other hand, owing to the moderate Reynolds number in the perforations, Large-Eddy Simulations (LES) 6,27,28 and Direct Numerical Simulations (DNS) 29 can be used, but until now they only deal with a very small number of holes, typical of turbine blades film cooling. As existing small-scale computations do not directly deal with FCFC configurations, it has been decided to perform specific smallscale wall-resolved LES relevant to FCFC configurations. The underlying methodology and the corresponding results obtained in an isothermal configuration are described in Mendez et isothermal data obtained by LES and proposes a homogeneous model that accounts for the major flow characteristics near a perforated wall. In this model, the injection and the aspiration sides are coupled: a law for the discharge coefficient in the holes relates the pressure drop to the mass flow rate through the plate. The inputs are the pressure drop across the plate and the geometrical characteristics (porosity, aperture angle). A priori testing is first performed, the fluxes provided by this homogeneous model being compared to the reference simulations. 30 As an a posteriori validation, the model is implemented in a LES code in order to reproduce an experimental set-up where two channels are separated by a perforated plate. Numerical results are compared with experimental measurements performed in an isothermal large-scale configuration. 18 Section II is dedicated to the description of the code used to perform the Large-Eddy 5 of 26
Simulations. The small-scale LES results presented by Mendez et al. 30 are related to the experimental test rig of Miron. 18 The model proposed in this study is also tested using this experimental setup. This experiment is thus described in section II. An analysis of small-scale LES results 30 is then provided in section III, in order to estimate the fluxes at the perforated plate: two adiabatic models for effusion cooling are constructed from this analysis. Section IV details the validating simulations. Comparisons with the experimental database are shown. II. Presentation of the experimental configuration and of the LES code A. Presentation of the LES Code All simulations are carried out with the LES code developed at CERFACS, named AVBP (www.cerfacs.fr/cfd/avbp code.php). It is a cell-vertex/finite element code, explicit in time, which solves the compressible Navier–Stokes equations on unstructured meshes for the conservative variables (mass density, momentum and total energy). AVBP is dedicated to LES and DNS and has been widely used and validated in the past years in all kinds of configurations, 31–33 and notably in jets in cross-flow cases. 34,35 Several numerical schemes and sub-grid models are available in AVBP: the most adequate numerical parameters have been chosen, depending on the objectives of each simulation. Two different types of simulations are presented in this paper. First, fine-scale computations are analyzed. They aim at providing detailed data of the flow around a multi-perforated plate. They are based on the WALE sub-grid model. 36 The numerical scheme is the TTGC scheme: 37 this essentially non dissipative scheme was specifically developed to handle unsteady turbulent flows. It is third order accurate in both space and time. Large-scale computations are also shown: they deal with a case where the flow near the perforated wall is not well resolved. A coarse mesh is used in conjunction with the crudest numerical parameters available in AVBP: the sub-grid model is the classical Smagorinsky 38 model (with a constant fixed at C S = 0.1) and the numerical scheme for the large-scale simulations is the Lax-Wendroff scheme 31 (second order accurate in space and time). B. The Experimental Configuration All the calculations presented in this paper are related with a reference experiment named ‘LARA’ 18 and performed at Turbomeca. The experimental set up allows to study the effusion process in the case of a large-scale isothermal configuration. The experimental test rig is divided into two channels: the first one, denoted by ‘1’, represents the combustion chamber 6 of 26
Page 1:
UNIVERSITE MONTPELLIER II SCIENCES
Page 5 and 6:
Table des matières Remerciements 7
Page 7 and 8:
Remerciements Cette thèse a été
Page 9 and 10:
Liste des symboles Lettres romaines
Page 11 and 12:
Introduction générale La volonté
Page 13 and 14:
Chapitre 1 Contexte industriel et s
Page 15 and 16:
1.1 Les turbines à gaz pour les tu
Page 17 and 18:
1.1 Les turbines à gaz a) b) GAZ C
Page 19 and 20:
1.2 La simulation numérique des é
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
1.3 Objectifs et plan de la thèse
Page 29 and 30:
Chapitre 2 L’écoulement autour d
Page 31 and 32:
2.1 Présentation de la configurati
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
2.2 Perte de charge au passage d’
Page 39 and 40:
2.3 La multi-perforation : aspects
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
2.4 Caractérisation aérodynamique
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
2.5 Modélisation de la multi-perfo
Page 69 and 70:
Chapitre 3 Simulations des grandes
Page 71 and 72:
3.2 Simulations des Grandes Echelle
Page 73 and 74:
3.3 Le code de calcul AVBP 3.3.1 As
Page 75 and 76:
3.3 Le code de calcul AVBP dans le
Page 77 and 78:
3.3 Le code de calcul AVBP de sa st
Page 79 and 80:
Chapitre 4 Simulations numériques
Page 81 and 82:
4.1 Quelles simulations pour la mod
Page 83 and 84:
4.2 Choix de la méthode de simulat
Page 85 and 86:
4.2 Choix de la méthode de simulat
Page 87 and 88:
4.3 Sensibilité des simulations au
Page 89 and 90:
4.3 Sensibilité des simulations au
Page 91 and 92: 4.3 Sensibilité des simulations au
Page 97 and 98: Chapitre 5 Simulations numériques
Page 99 and 100: 2 S. Mendez and F. Nicoud COMBUSTIO
Page 101 and 102: 4 S. Mendez and F. Nicoud (c) The i
Page 103 and 104: 6 S. Mendez and F. Nicoud CALCULATI
Page 105 and 106: 8 S. Mendez and F. Nicoud Name Numb
Page 107 and 108: 10 S. Mendez and F. Nicoud x/d z/d
Page 109 and 110: 12 S. Mendez and F. Nicoud main, it
Page 111 and 112: 14 S. Mendez and F. Nicoud 1.0 a 1.
Page 113 and 114: 16 S. Mendez and F. Nicoud ROWS 1 3
Page 115 and 116: 18 S. Mendez and F. Nicoud Figure 1
Page 117 and 118: 20 S. Mendez and F. Nicoud 30 ◦ 3
Page 119 and 120: 22 S. Mendez and F. Nicoud & Mahesh
Page 125 and 126: 28 S. Mendez and F. Nicoud film, th
Page 127 and 128: 30 S. Mendez and F. Nicoud Region t
Page 129 and 130: 32 S. Mendez and F. Nicoud Expressi
Page 131 and 132: 34 S. Mendez and F. Nicoud geometri
Page 133 and 134: 36 S. Mendez and F. Nicoud (f) Two
Page 135 and 136: 38 S. Mendez and F. Nicoud Mendez,
Page 137 and 138: Chapitre 6 Un modèle adiabatique p
Page 139 and 140: ρ Mass density, kg/m 3 P T V i τ
Page 141: cence of the jets. This is particul
Page 145 and 146: chosen to compare with numerical re
Page 147 and 148: pressure drop of 41 Pa is effective
Page 149 and 150: Region total plate hole solid wall
Page 151 and 152: This equality is almost verified at
Page 153 and 154: V U σ V inj jet cotan(α′ ) V U
Page 155 and 156: PERIODIC Z INFLOW 1 WALL 24 OUTFLOW
Page 157 and 158: part of the plate. Downstream of th
Page 159 and 160: streamwise momentum flux. As a cons
Page 161 and 162: 8 Fric, T. and Roshko, A., “Vorti
Page 163 and 164: Discussion sur la modélisation de
Page 165 and 166: 20 15 10 y/d 5 0 -5 -10 0.0 0.2 0.4
Page 167 and 168: Chapitre 7 Simulations numériques
Page 169 and 170: Primary flow (burnt gases) Secondar
Page 171 and 172: Figure 7: Nusselt number over the s
Page 173 and 174: the perforated plate. A Large-Eddy
Page 175 and 176: Les tableaux de flux permettent de
Page 177 and 178: Conclusion générale Dans cette é
Page 179 and 180: Conclusion générale En ce qui con
Page 181 and 182: Bibliographie AKSELVOLL, K. & MOIN,
Page 183 and 184: BIBLIOGRAPHIE CORON, X. 2001 Étude
Page 185 and 186: BIBLIOGRAPHIE HALE, C. A., PLESNIAK
Page 187 and 188: BIBLIOGRAPHIE LIEUWEN, T. & YANG, V
Page 189 and 190: BIBLIOGRAPHIE MOST, A. & BRUEL, P.
Page 191 and 192: BIBLIOGRAPHIE SCHILDKNECHT, M., MIL
Page 193:
Annexes
Page 196 and 197:
ARTIFICIAL VISCOSITY MODELS A.2.1 T
Page 198 and 199:
ARTIFICIAL VISCOSITY MODELS - 4 th
Page 200 and 201:
ARTIFICIAL VISCOSITY MODELS As a co
Page 202:
ARTIFICIAL VISCOSITY MODELS 202
show all

these simulation numerique et modelisation de l'ecoulement autour ...

Create successful ePaper yourself

Delete template?

Save as template?