CREATE: Advanced CFD for HPC Performance Improvement

2012 ◽  
Author(s):  
A. Pesteil ◽  
D. Cellier ◽  
O. Domercq ◽  
V. Perrot ◽  
J. C. Boniface
Keyword(s):  
High Pressure ◽  
Performance Improvement ◽  
Optimization Methods ◽  
Computational Effort ◽  
Flow Path ◽  
Main Flow ◽  
Secondary Flows ◽  
Vortex Generators ◽  
Flow Vortex ◽  
Selection Of

The present paper provides an overview of technological evolutions aimed at improving the aerodynamic performance of Snecma’s High Pressure Compressors. Several concepts were investigated under its CREATE compressor research program, involving an extensive simulation effort. An overview of the computational approaches involved in the evaluation and selection of innovative and most promising concepts will be given in the paper. The main topics dealt with are: 1) Aeromechanical optimization of airfoils and flow path: In recent years, great efforts have been made to improve the aerodynamic design of airfoils. Among them, optimization methods have been progressively implemented in the design process with an increased complexity logic. The latest methods used at Snecma involve multi-objective, multi-parameters aeromechanical optimization including mean camber line, stacking axis, flow path contouring and more. This work is illustrated by two practical examples. 2) Vortex generators: In order to control the flow, vortex generators can be forecasted as a promising step forward. The goal is to create exogenous vorticity that will counter-balance the endogenous vorticity. Thus they appear as a tool to reduce losses and improve stability in highly loaded turbomachinery devices such as modern high pressure compressors. This section of the paper will give an overview of the dedicated numerical simulations completed. 3) Clocking: Numerous studies are related to the benefit drawn from turbine clocking on turbomachinery performance. However, fewer examples of successful compressor clocking exist. The recent capability of computational fluid dynamics tools to reduce the computational effort necessary to investigate such an issue (by the use of harmonic balance methodology) gives the opportunity for a renewed evaluation. 4) Optimization of shroud leakage flow with main flow: A strong interaction exists with the secondary flows originated in the inner flow path cavities. Coupled main flow path and cavities aerodynamic simulations were conducted to improve the relevance of the computations and understand the mechanisms involved. 5) Tandem bladings and splitters in axial rotors: The last aspect of the study was focused on dual blading concepts. After a brief review of the literature, some simulations were carried out to explore the relevance of such concepts from the viewpoint of modern high pressure compressors performance improvement.

FLOvane: A New Approach for High-Pressure Vane Design

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Dingxi Wang ◽  
Francesco Ornano ◽  
Yan Sheng Li ◽  
Roger Wells ◽  
Christer Hjalmarsson ◽  
...  
Keyword(s):  
High Pressure ◽  
Gas Turbines ◽  
Fluid Dynamic ◽  
Flow Path ◽  
Secondary Flows ◽  
Cooling Flow ◽  
Starting Point ◽  
Industrial Gas Turbines ◽  
Improved Performance ◽  
Cfd Analyses

This paper presents a new unconventional philosophy for high-pressure (HP) vane design. It is proposed that the most natural design starting point for admitting and accelerating flow with minimum loss and secondary flow is a trumpet-shaped flow-path which gradually turns to the desired angle. Multiple trumpet-shaped inlets are seamlessly blended into the (annular or partitioned) combustor walls resulting in a highly lofted flow-path, rather than a traditional flow-path defined by distinct airfoil and endwall surfaces. We call this trumped-shaped inlet the fully lofted oval vane (FLOvane). The purpose of this paper is to describe the FLOvane concept and to present back-to-back CFD analyses of two current industrial gas turbines with conventional and FLOvane-modified designs. The resulting designs diverge significantly from conventional designs in terms of both process and final geometric form. Computational fluid dynamic predictions for the FLOvane-modified designs show improved aerodynamic performance characteristics, reduced heat load, improved cooling performance, improved thermal–mechanical life, and improved stage/engine efficiency. The mechanisms for improved performance include reduction of secondary flows, reduced mixing of coolant flow with the mainstream flow, reduced skin friction, and improved coolant distribution. In the two current industrial gas turbine engines, the absolute (percentage point) improvement in stage isentropic efficiency when the FLOvane design was included was estimated at 0.33% points and 0.40% points without cooling flow reduction, and 1.5% points in one case and much more is expected for the other case when cooling flow reductions were accounted for.

scholarly journals Study on the Phase Selection and Debye Temperature of Hyper-Peritectic Al-Ni Alloy under High Pressure

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 84
Author(s):  
Xiaohong Wang ◽  
Zhipeng Chen ◽  
Duo Dong ◽  
Dongdong Zhu ◽  
Hongwei Wang ◽  
...  
Keyword(s):  
High Pressure ◽  
Ambient Pressure ◽  
Competitive Growth ◽  
Phase Selection ◽  
Debye Temperatures ◽  
Ni Alloy ◽  
Temperature Heat ◽  
Low Temperature Heat Capacity ◽  
New Phase ◽  
Selection Of

The phase selection of hyper-peritectic Al-47wt.%Ni alloy solidified under different pressures was investigated. The results show that Al3Ni2 and Al3Ni phases coexist at ambient pressure, while another new phase α-Al exists simultaneously when solidified at high pressure. Based on the competitive growth theory of dendrite, a kinetic stabilization of metastable peritectic phases with respect to stable ones is predicted for different solidification pressures. It demonstrates that Al3Ni2 phase nucleates and grows directly from the undercooled liquid. Meanwhile, the Debye temperatures of Al-47wt.%Ni alloy that fabricated at different pressures were also calculated using the low temperature heat capacity curve.

scholarly journals A Review of Numerical Simulations of Secondary Flows in River Bends

Water ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 884
Author(s):  
Rawaa Shaheed ◽  
Abdolmajid Mohammadian ◽  
Xiaohui Yan
Keyword(s):  
Numerical Modeling ◽  
Numerical Simulations ◽  
Secondary Flow ◽  
Cross Section ◽  
Turbulence Models ◽  
Main Flow ◽  
Secondary Flows ◽  
River Bends ◽  
River Cross Section ◽  
River Bend

River bends are one of the common elements in most natural rivers, and secondary flow is one of the most important flow features in the bends. The secondary flow is perpendicular to the main flow and has a helical path moving towards the outer bank at the upper part of the river cross-section, and towards the inner bank at the lower part of the river cross-section. The secondary flow causes a redistribution in the main flow. Accordingly, this redistribution and sediment transport by the secondary flow may lead to the formation of a typical pattern of river bend profile. It is important to study and understand the flow pattern in order to predict the profile and the position of the bend in the river. However, there are a lack of comprehensive reviews on the advances in numerical modeling of bend secondary flow in the literature. Therefore, this study comprehensively reviews the fundamentals of secondary flow, the governing equations and boundary conditions for numerical simulations, and previous numerical studies on river bend flows. Most importantly, it reviews various numerical simulation strategies and performance of various turbulence models in simulating the flow in river bends and concludes that the main problem is finding the appropriate model for each case of turbulent flow. The present review summarizes the recent advances in numerical modeling of secondary flow and points out the key challenges, which can provide useful information for future studies.

scholarly journals Computational Modeling of Vortex Generators for Turbomachinery

2002 ◽  
Author(s):  
R. V. Chima
Keyword(s):  
Computational Models ◽  
Body Force ◽  
Secondary Flows ◽  
The Body ◽  
Vortex Generators ◽  
Force Model ◽  
Suction Surface ◽  
Near Surface ◽  
Compressor Rotor ◽  
Surface Particle

In this work computational models were developed and used to investigate applications of vortex generators (VGs) to turbomachinery. The work was aimed at increasing the efficiency of compressor components designed for the NASA Ultra Efficient Engine Technology (UEET) program. Initial calculations were used to investigate the physical behavior of VGs. A parametric study of the effects of VG height was done using 3-D calculations of isolated VGs. A body force model was developed to simulate the effects of VGs without requiring complicated grids. The model was calibrated using 2-D calculations of the VG vanes and was validated using the 3-D results. Then three applications of VGs to a compressor rotor and stator were investigated: 1. The results of the 3-D calculations were used to simulate the use of small casing VGs used to generate rotor preswirl or counterswirl. Computed performance maps were used to evaluate the effects of VGs. 2. The body force model was used to simulate large partspan splitters on the casing ahead of the stator. Computed loss buckets showed the effects of the VGs. 3. The body force model was also used to investigate the use of tiny VGs on the stator suction surface for controlling secondary flows. Near-surface particle traces and exit loss profiles were used to evaluate the effects of the VGs.

Exact analysis of the bending of wide beams by a modified elastica approach

2011 ◽  
Vol 225 (11) ◽  
pp. 2759-2764 ◽  
Author(s):  
L F Campanile ◽  
R Jähne ◽  
A Hasse
Keyword(s):  
Finite Element ◽  
Substantial Reduction ◽  
Short Review ◽  
Computational Effort ◽  
Two Dimensional ◽  
Finite Element Calculations ◽  
Dimensional Finite Element ◽  
Wide Beams ◽  
Insight Into ◽  
Selection Of

Classical beam models do not account for partial restraint of anticlastic bending and are therefore inherently inaccurate. This article proposes a modification of the exact Bernoulli–Euler equation which allows for an exact prediction of the beam's deflection without the need of two-dimensional finite element calculations. This approach offers a substantial reduction in the computational effort, especially when coupled with a fast-solving schema like the circle-arc method. Besides the description of the new method and its validation, this article offers an insight into the somewhat disregarded topic of anticlastic bending by a short review of the published theories and a selection of representative numerical results.

Addressing pose estimation issues for machine vision based UAV autonomous serial refuelling

2007 ◽  
Vol 111 (1120) ◽  
pp. 389-396 ◽  
Author(s):  
G. Campa ◽  
M. R. Napolitano ◽  
M. Perhinschi ◽  
M. L. Fravolini ◽  
L. Pollini ◽  
...  
Keyword(s):  
Machine Vision ◽  
Pose Estimation ◽  
Estimation Algorithm ◽  
Computational Effort ◽  
Unmanned Aircraft ◽  
Light Sources ◽  
Estimation Algorithms ◽  
Trade Offs ◽  
Labeling Algorithms ◽  
Selection Of

Abstract This paper describes the results of an effort on the analysis of the performance of specific ‘pose estimation’ algorithms within a Machine Vision-based approach for the problem of aerial refuelling for unmanned aerial vehicles. The approach assumes the availability of a camera on the unmanned aircraft for acquiring images of the refuelling tanker; also, it assumes that a number of active or passive light sources – the ‘markers’ – are installed at specific known locations on the tanker. A sequence of machine vision algorithms on the on-board computer of the unmanned aircraft is tasked with the processing of the images of the tanker. Specifically, detection and labeling algorithms are used to detect and identify the markers and a ‘pose estimation’ algorithm is used to estimate the relative position and orientation between the two aircraft. Detailed closed-loop simulation studies have been performed to compare the performance of two ‘pose estimation’ algorithms within a simulation environment that was specifically developed for the study of aerial refuelling problems. Special emphasis is placed on the analysis of the required computational effort as well as on the accuracy and the error propagation characteristics of the two methods. The general trade offs involved in the selection of the pose estimation algorithm are discussed. Finally, simulation results are presented and analysed.

Life Augmentation of Turbine Exhaust System Compensators Through Integrated MADM Optimization Approach of Stress Based Fatigue Cycles

2021 ◽  
Author(s):  
Nitin D. Pagar ◽  
Amit R. Patil
Keyword(s):  
Exhaust System ◽  
Optimization Methods ◽  
Fractional Factorial ◽  
Design Parameters ◽  
Optimization Approach ◽  
Auxiliary Equipment ◽  
Maximum Expansion ◽  
Optimal Configurations ◽  
Selection Of ◽  
Turbine Exhaust

Abstract Exhaust expansion joints, also known as compensators, are found in a variety of applications such as gas turbine exhaust pipes, generators, marine propulsion systems, OEM engines, power units, and auxiliary equipment. The motion compensators employed must have accomplished the maximum expansion-contraction cycle life while imposing the least amount of stress. Discrepancies in the selecting of bellows expansion joint design parameters are corrected by evaluating stress-based fatigue life, which is challenging owing to the complicated form of convolutions. Meridional and circumferential convolution stress equations that influencing fatigue cycles are evaluated and verified with FEA. Fractional factorial Taguchi L25 matrix is used for finding the optimal configurations. The discrete design parameters for the selection of the suitable configuration of the compensators are analysed with the help of the MADM decision making techniques. The multi-response optimization methods GRA, AHP, and TOPSIS are used to determine the parametric selection on a priority basis. It is seen that weighing distribution among the responses plays an important role in these methods and GRA method integrated with principal components shows best optimal configurations. Multiple regression technique applied to these methods also shows that PCA-GRA gives better alternate solutions for the designer unlike the AHP and TOPSIS method. However, higher ranked Taguchi run obtained in these methods may enhance the suitable selection of different design configurations. Obtained PCA-GRG values by Taguchi, Regression and DOE are well matched and verified for the all alternate solutions. Further, it also shows that stress based fatigue cycles obtained in this analysis for the L25 run indicates the range varying from 1.13 × 104 cycles to 9.08 × 105 cycles, which is within 106 cycles. This work will assist the design engineer for selecting the discrete parameters of stiff compensators utilized in power plant thermal appliances.

A More Effective Formulation of the Path Generation Mechanism Synthesis Problem

1994 ◽  
Author(s):  
Irfan Ullah ◽  
Sridhar Kota
Keyword(s):  
Objective Function ◽  
Error Function ◽  
Mathematical Optimization ◽  
Optimization Methods ◽  
Complex Nature ◽  
Mechanism Synthesis ◽  
Structural Error ◽  
Crank Angle ◽  
The Common ◽  
Selection Of

Abstract Use of mathematical optimization methods for synthesis of path-generating mechanisms has had only limited success due to the very complex nature of the commonly used Structural Error objective function. The complexity arises, in part, because the objective function represents not only the error in the shape of the coupler curve, but also the error in location, orientation and size of the curve. Furthermore, the common introduction of timing (or crank angle), done generally to facilitate selection of corresponding points on the curve for calculating structural error, has little practical value and unnecessarily limits possible solutions. This paper proposes a new objective function, based on Fourier Descriptors, which allows search for coupler curve of the desired shape without reference to location, orientation, or size. The proposed objective function compares overall shape properties of curves rather than making point-by-point comparison and therefore does not requires prescription of timing. Experimental evidence is provided to show that it is much easier to search the space of the proposed objective function compared to the structural error function.

Interaction of Shroud Leakage Flow and Main Flow in a Three-Stage LP Turbine

2003 ◽  
Vol 127 (4) ◽  
pp. 649-658 ◽  
Author(s):  
Jochen Gier ◽  
Bertram Stubert ◽  
Bernard Brouillet ◽  
Laurent de Vito
Keyword(s):  
Main Flow ◽  
Secondary Flows ◽  
Test Facility ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Jet Engines ◽  
Flow Interactions ◽  
Lp Turbine ◽  
The Impact ◽  
The Ideal

Endwall losses significantly contribute to the overall losses in modern turbomachinery, especially when aerodynamic airfoil load and pressure ratios are increased. In turbines with shrouded airfoils a large portion of these losses are generated by the leakage flow across the shroud clearance. Generally the related losses can be grouped into losses of the leakage flow itself and losses caused by the interaction with the main flow in subsequent airfoil rows. In order to reduce the impact of the leakage flow and shroud design related losses a thorough understanding of the leakage losses and especially of the losses connected to enhancing secondary flows and other main flow interactions has to be understood. Therefore, a three stage LP turbine typical for jet engines is being investigated. For the three-stage test turbine 3D Navier-Stokes computations are performed simulating the turbine including the entire shroud cavity geometry in comparison with computations in the ideal flow path. Numerical results compare favorably against measurements carried out at the high altitude test facility at Stuttgart University. The differences of the simulations with and without shroud cavities are analyzed for several points of operation and a very detailed quantitative loss breakdown is presented.

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