Vortex Structures Analysis and Loss Mechanisms in Axial Compressor Cascade With and Without Bleeding Slot Using Large Eddy Simulation

2021 ◽  
Author(s):  
Yun Gong ◽  
Shaowen Chen ◽  
Haipeng Zheng ◽  
Songtao Wang
Keyword(s):  
Large Eddy Simulation ◽  
Axial Compressor ◽  
Vortex Structures ◽  
Compressor Cascade ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Loss Mechanisms

Vortex Structures Analysis and Loss Mechanisms in Axial Compressor Cascade With and Without Bleeding Slot Using Large Eddy Simulation

2020 ◽  
Author(s):  
Yun Gong ◽  
Shaowen Chen ◽  
Haipeng Zheng ◽  
Songtao Wang
Keyword(s):  
Large Eddy Simulation ◽  
Axial Compressor ◽  
Vortex Structures ◽  
Leakage Flow ◽  
Compressor Cascade ◽  
Tip Leakage Flow ◽  
Tip Leakage ◽  
Eddy Simulation ◽  
Passage Vortex ◽  
Large Eddy

Abstract Tip leakage flow is one of the main sources of flow losses in an axial compressor, and the understanding of the tip leakage flow helps to explore better flow control methods and design more advanced compressors. Therefore, the vortex structures and loss mechanisms were analyzed in a compressor cascade with tip clearance in the present paper. Large eddy simulation was used to better resolve the vortices with more accurate numerical results. The iso-surface of Q criterion in the compressor cascade is captured for recognizing and analyzing the vortex structures. The horse shoe vortices, tip leakage vortex, induced vortex, tip separation vortex and passage vortex were well captured and their interactions were interpreted. Fast Fourier Transformation was also applied to analyze the frequency signal in the flow field. Afterwards, the case with an upstream bleeding slot was also calculated and compared with the original case without a bleeding slot. The bleeding rate is 2.8% of the mass flow rate at inlet. The removal of the inlet boundary layer resulting from the bleeding leads a 42.4% reduction of the total pressure loss coefficient compared with that of the case without the bleeding slot. In the case with the bleeding slot, the size of the passage vortex is greatly reduced, and the mixing between the tip leakage vortex and passage vortex is postponed. Better performance is achieved with the bleeding slot accordingly.

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.

Application of High-Resolution Large Eddy Simulation to Simplified Turbomachinery Flows

2016 ◽  
Author(s):  
Susumu Teramoto ◽  
Takuya Ouchi ◽  
Hiroki Sanada ◽  
Koji Okamoto
Keyword(s):  
Boundary Layer ◽  
High Resolution ◽  
Turbulent Boundary Layer ◽  
Large Eddy Simulation ◽  
Reynolds Stress ◽  
Sudden Expansion ◽  
Compressor Cascade ◽  
Rans Model ◽  
Eddy Simulation ◽  
Large Eddy

Fully resolved large eddy simulation (LES) is applied to two simple geometry flowfields with well-defined boundary conditions. The LES results are compared with simulations based on a Reynolds-averaged Navier-Stokes (RANS) model with turbulence, and pros and cons of using high-resolution LES for turbomachinery flows are discussed. One flow is a linear compressor cascade flow composed of the tip section of GE rotor B at Rec = 4 × 105 with a clearance, and the other is a Mach 1.76 supersonic turbulent boundary layer at Reδ = 5000 that laminerizes through a 12-degree expansion corner. The grids are prepared fine enough to resolve the turbulent boundary layer through a grid sensitivity study. The liner cascade result shows that all the turbulent shear layers and boundary layers including those in the small tip clearance are well resolved with 800 million grid points. The Reynolds stress derived from the LES results are compared directly with those predicted from the Spalart-Allmaras one-equation RANS turbulence model. The two results agreed qualitatively well except for the shear layer surrounding the tip leakage vortex, demonstrating that the RANS model performs well at least for flowfields near the design condition. From the simulation of the turbulent boundary layer experiencing sudden expansion, noticeable decreases of both Reynolds stress and local friction coefficient were observed, showing that the turbulent boundary layer has relaminarized through the sudden expansion. The boundary layer downstream of the expansion exhibits a nonequilibrium condition and was different from the laminar boundary layer.

scholarly journals Large-eddy simulation of 3-D corner separation in a linear compressor cascade

2015 ◽  
Vol 27 (8) ◽  
pp. 085105 ◽  
Author(s):  
Feng Gao ◽  
Wei Ma ◽  
Gherardo Zambonini ◽  
Jérôme Boudet ◽  
Xavier Ottavy ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Compressor Cascade ◽  
Linear Compressor ◽  
Corner Separation ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Linear Compressor Cascade

Detailed Investigation of RANS and LES Predictions of Loss Generation in an Axial Compressor Cascade at Off Design Incidences

2016 ◽  
Author(s):  
John Leggett ◽  
Stephan Priebe ◽  
Richard Sandberg ◽  
Vittorio Michelassi ◽  
Aamir Shabbir
Keyword(s):  
Best Practice ◽  
Axial Compressor ◽  
Navier Stokes ◽  
Compressor Cascade ◽  
Free Stream Turbulence ◽  
Loss Analysis ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Reynolds Averaged Navier Stokes ◽  
Prediction Techniques

In the design of modern jet engines the need for accurate loss prediction techniques is ever present. The most common tool currently in use is Reynolds Averaged Navier-Stokes model which provides good estimation at design conditions but can struggle with off design conditions. With accuracy being such an important requirement, an alternative method such as Large Eddy Simulation presents an opportunity to improve and assess the off design performance. Although still limited by computational resources, the use of Large Eddy Simulations in conjunction with more detailed loss analysis methods forms a powerful tool for assessing and improving current Reynolds Averaged Navier-Stokes techniques. The simulations performed here are an incidence sweep at off-design conditions with free stream turbulence. The results of the two methodologies are compared with the use of loss breakdown analysis and the best practice of applying the loss breakdown technique to compressors is outlined.

Large Eddy Simulation of Axial and Compound Angle Holes With Varying Hole Length-to-Diameter Ratio

2017 ◽  
Author(s):  
Weihong Li ◽  
Wei Shi ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Large Eddy Simulation ◽  
Film Cooling ◽  
Vortex Structures ◽  
Diameter Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Compound Angle ◽  
Length To Diameter Ratio

The effect of hole length to diameter ratio on flat plate film cooling effectiveness and flow structures of axial and compound angle hole is investigated by large eddy simulation (LES). Film cooling simulations are performed for three blowing ratios (M) ranging from 0.4 to 1.2, three hole length-to-diameter ratios (L/D) from 0.5 to 5 and two compound angle (β: 0°, 45°). The prediction accuracy is validated by the reported hydrodynamic data and present film effectiveness data measured by pressure sensitive paint (PSP). Results indicate that discrete hole with L = 0.5 show highest film cooling effectiveness regardless of compound angle. Round hole generally shows an increasing trend as L increases from 2 to 5, while compound angle hole shows a complex trend concerning with blowing ratios and length to diameter ratios. This is associated with the fact that length-to-diameter ratio influences the in-tube flow behavior, formation of Kelvin-Helmholtz (K-H) structures, and development of single asymmetric main vortex (SAMV). Scalar field transportation features are investigated to clarify how different vortex structures affect the temperature distribution and the film cooling effectiveness. It is also demonstrated that the counter rotating vortex pair (CRVP) which is observed in the time-averaged flow field of axial hole is originated in different vortex structures with varying blowing ratios and length to diameter ratios.

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