Towards Large Eddy Simulation of Film-Cooling Flows on a Model Turbine Blade with Free-Stream Turbulence

2005 ◽  
Author(s):  
Ioulia Iourokina ◽  
Sanjiva Lele
Keyword(s):  
Large Eddy Simulation ◽  
Turbine Blade ◽  
Film Cooling ◽  
Free Stream ◽  
Free Stream Turbulence ◽  
Cooling Flows ◽  
Eddy Simulation ◽  
Large Eddy

Numerical Simulations of the Near-Field Region of Film Cooling Jets Under High Free Stream Turbulence: Application of RANS and Hybrid URANS/Large Eddy Simulation Models

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Hosein Foroutan ◽  
Savas Yavuzkurt
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Film Cooling ◽  
Free Stream ◽  
Near Field ◽  
Turbulent Heat ◽  
Field Region ◽  
Free Stream Turbulence ◽  
Eddy Simulation ◽  
Large Eddy

This paper investigates the flow field and thermal characteristics in the near-field region of film cooling jets through numerical simulations using Reynolds-averaged Navier–Stokes (RANS) and hybrid unsteady RANS (URANS)/large eddy simulation (LES) models. Detailed simulations of flow and thermal fields of a single-row of film cooling cylindrical holes with 30 deg inline injection on a flat plate are obtained for low (M = 0.5) and high (M = 1.5) blowing ratios under high free stream turbulence (FST) (10%). The realizable k‐ε model is used within the RANS framework and a realizable k‐ε-based detached eddy simulation (DES) is used as a hybrid URANS/LES model. Both models are used together with the two-layer zonal model for near-wall simulations. Steady and time-averaged unsteady film cooling effectiveness obtained using these models are compared with available experimental data. It is shown that hybrid URANS/LES models (DES in the present paper) predict more mixing both in the wall-normal and spanwise directions compared to RANS models, while unsteady asymmetric vortical structures of the flow can also be captured. The turbulent heat flux components predicted by the DES model are higher than those obtained by the RANS simulations, resulting in enhanced turbulent heat transfer between the jet and mainstream, and consequently better predictions of the effectiveness. Nevertheless, there still exist some discrepancies between numerical results and experimental data. Furthermore, the unsteady physics of jet and crossflow interactions and the jet lift-off under high FST is studied using the present DES results.

Loss Predictions in the High-Pressure Film-Cooled Turbine Blade Cascade T120D by Mean of Wall-Resolved Large Eddy Simulation

2020 ◽  
Author(s):  
Mael Harnieh ◽  
Nicolas Odier ◽  
Jérôme Dombard ◽  
Florent Duchaine ◽  
Laurent Gicquel
Keyword(s):  
High Pressure ◽  
Large Eddy Simulation ◽  
Turbine Blade ◽  
Film Cooling ◽  
Load Prediction ◽  
Loss Assessment ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Blade Cascade ◽  
Large Eddy

Abstract Film cooling is commonly used to protect turbine vanes and blades from the hot gases produced in the combustion chamber. The design and optimization of these systems can however only be achieved if a precise prediction of the fluid mechanics and film efficiency is guaranteed at a level where induced losses are fully mastered. Such a prerequisite induces at the numerical level to be able to identify and assess losses. In this context, the present study addresses loss assessment in a wall-resolved Large Eddy Simulation (LES) of the film-cooled high-pressure turbine blade cascade T120D from the European project AITEB II. The objectives are twofolds: (1) to evaluate the capacity of LES to predict adiabatic film cooling effectiveness in a mastered academic case; and (2) to investigate loss generation mechanisms in a fully anisothermal configuration. When it comes to LES predictions of T120D, the flow structure around the blade and the coolant jet organization are coherent with literature findings. Satisfactory agreements are furthermore retrieved for the pressure load prediction as well as the adiabatic film effectiveness if compared to the experiment. Loss generation is then investigated illustrating the fact that aerodynamics losses dominate mixing losses which are mainly located in the coolant film. This is in line with the temperature difference between the hot and coolant flows that is low for this experimental condition. Distinct contributions can however be made available by studying the local loss generation maps by means of Second Law Analysis if recast in the specific context of anisothermal flows when simulated by LES.

Large Eddy Simulation of Leading Edge Film Cooling: Part I — Computational Domain and Effect of Coolant Pipe Inlet Condition

2007 ◽  
Author(s):  
Ali Rozati ◽  
Danesh K. Tafti
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Free Stream ◽  
Leading Edge ◽  
Driving Mechanism ◽  
Computational Domain ◽  
Stagnation Line ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Pipe Inlet

A numerical investigation is conducted to study compound angle leading edge film cooling with Large Eddy Simulation. The leading edge has two rows of coolant holes located at ±15° of the stagnation line. Coolant jets are injected into the flow field at 30° (span-wise) and 90° (stream-wise). Mainstream Reynolds number is 100,000 based on the free stream velocity and cylinder diameter. Jet to mainstream velocity and density ratios are 0.4 and 1.0, respectively. It is found that during startup the stagnation line at the leading edge is not stationary but moves on a timescale much larger than the characteristic turbulent scales generated by the jet-mainstream interaction. To alleviate the long time integration necessitated by this feature, only half the domain is calculated (fixed stagnation) by showing that there is very little correlation in the flow structures generated by the jet-mainstream interaction on either side of stagnation. A comparison is made between a laminar uniform profile at the coolant pipe inlet with a time-dependent turbulent profile extracted from an auxiliary turbulent pipe flow calculation. The former over-predicts the span-wise averaged effectiveness, while the latter promotes better mixing in the outer region of jet-mainstream interaction and lowers the adiabatic effectiveness showing good agreement with measurements. In both cases, a characteristic low frequency interaction between the jet and the mainstream is identified at a non-dimensional frequency between 0.79 and 0.95 based on jet diameter and velocity. Even in the absence of any free-stream and jet turbulence, a turbulent boundary layer is established within a diameter downstream of the jet due to the strong lateral entrainment downstream of injection. The entrainment is primarily driven by an asymmetric counterrotating vortex pair in the immediate wake of the coolant jet. The driving mechanism for the formation of these vortices is a low pressure zone in the wake which entrains mainstream flow laterally into this region.

Large-Eddy Simulation of Shaped Hole Film Cooling With the Influence of Cross Flow

2019 ◽  
Author(s):  
Qingsong Wang ◽  
Yifei Li ◽  
Xiutao Bian ◽  
Xinrong Su ◽  
Xin Yuan
Keyword(s):  
Large Eddy Simulation ◽  
Turbine Blade ◽  
Film Cooling ◽  
Cross Flow ◽  
Hairpin Vortices ◽  
Blade Passage ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Cooling Hole ◽  
The Asymmetry

Abstract In the modern highly-loaded gas turbine, due to the large pressure difference between the suction side and the pressure side of the turbine blade, strong cross flow is formed and it strongly affects the aerodynamic and cooling performances in the end-wall region. The film cooling behavior in the environment of strong cross flow is different from the straight channel environment widely studied in the literature. In this research, the effect of cross flow on film cooling is investigated by Large Eddy Simulation (LES) using subgrid-scale (SGS) model. Numerical simulation is carried out in a curved passage to simulate the turbine blade passage. Shaped cooling hole with blowing ratio 1 is studied. The time-averaged friction line results are compared with existing experimental ink trace results. The vortex structures, both time-averaged and instantaneous, are analyzed to study the effect of cross flow on film cooling. At the exit of the cooling hole, the hanging vortices with negative y-vorticity are more flat in shape and closer to the wall in position in contrast to hanging vortex with positive y-vorticity, which is caused by cross flow and results in the asymmetry of hairpin vortices downstream as well as the asymmetry of the distribution of coolant. It has been shown that the vortices from mainstream have a significant impact on the field near the exit of the cooling hole. Those vortices interact with the hairpin vortices from the cooling hole and directly lead to the asymmetry of the hairpin vortices. Proper Orthogonal Decomposition (POD) analysis is further conducted to extract the dominant flow structures and the physical mechanisms of primary POD modes are given to explain the distribution of film cooling effectiveness affected by cross flow. Based on the specific situation in this work, a fast incremental POD (iPOD) approach is adopted since the rank of the field matrix is far less than the rows, which is caused by the tall and thin character of the matrix, which makes the analysis less costly and more effective. This research helps to understand the cooling performance in the real turbine blade passage and to explain the coolant mixing process based on the instantaneous flow field obtained using high precision LES simulation and powerful iPOD.

scholarly journals Loss Prediction in an Axial Compressor Cascade at Off-Design Incidences With Free Stream Disturbances Using Large Eddy Simulation

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
John Leggett ◽  
Stephan Priebe ◽  
Aamir Shabbir ◽  
Vittorio Michelassi ◽  
Richard Sandberg ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Free Stream ◽  
Axial Compressor ◽  
Operating Conditions ◽  
Boundary Layer Transition ◽  
Compressor Cascade ◽  
Free Stream Turbulence ◽  
Eddy Simulation ◽  
Profile Losses ◽  
Large Eddy

Axial compressors may be operated under off-design incidences due to variable operating conditions. Therefore, a successful design requires accurate performance and stability limits predictions under a wide operating range. Designers generally rely both on correlations and on Reynolds-averaged Navier–Stokes (RANS), the accuracy of the latter often being questioned. The present study investigates profile losses in an axial compressor linear cascade using both RANS and wall-resolved large eddy simulation (LES), and compares with measurements. The analysis concentrates on “loss buckets,” local separation bubbles and boundary layer transition with high levels of free stream turbulence, as encountered in real compressor environment without and with periodic incoming wakes. The work extends the previous research with the intention of furthering our understanding of prediction tools and improving our quantification of the physical processes involved in loss generation. The results show that while RANS predicts overall profile losses with good accuracy, the relative importance of the different loss mechanisms does not match with LES, especially at off-design conditions. This implies that a RANS-based optimization of a compressor profile under a wide incidence range may require a thorough LES verification at off-design incidence.

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