The nonaxismmetric endwall aerodynamic optimization design for a large turbine cascade with a midgap

2017 ◽  
Vol 233 (3) ◽  
pp. 1000-1010
Author(s):  
Lei He ◽  
Hao Liu ◽  
Xiaocheng Zhu ◽  
Ouyang Hua ◽  
Zhaohui Du
Keyword(s):  
Secondary Flow ◽  
Optimization Design ◽  
Transport Model ◽  
Design Procedure ◽  
Turbine Cascade ◽  
Evaluation Tool ◽  
Aerodynamic Optimization ◽  
Pressure Loss Coefficient ◽  
Shear Stress Transport Model ◽  
Assembly Features

The nonaxisymmetric endwall has been verified to be an effective method in reducing the endwall secondary flow loss. Some assembly features, such as the midgap in the hub of real aircraft engines, may have an influence on the endwall secondary flow. In the present work, a nonaxisymmetric endwall with midgap structure is designed for a large linear turbine cascade. A nonaxisymmetric endwall optimization design procedure is developed to minimize the total pressure loss coefficient at the passage exit. The profile of the endwall is designed using automatic numerical optimization with the Kriging surrogate method. The numerical simulation based on a transition shear stress transport model is used as the aerodynamic evaluation tool for the optimization system. When the midgap is considered in the design, mixing loss between midgap flows and main flow is significantly reduced. However, the loss relative to the passage vortex is increased to some extent.

The aerodynamic optimization design of turbine cascade nonaxisymmetric endwall and the midgap influence assessment

2017 ◽  
Vol 232 (15) ◽  
pp. 2760-2774 ◽  
Author(s):  
Hao Liu ◽  
Chenxing Hu ◽  
Xin Shen ◽  
Xiaocheng Zhu ◽  
Hong Yang ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Secondary Flow ◽  
Optimization Design ◽  
Large Scale ◽  
Three Dimensional ◽  
Design Procedure ◽  
Efficient Global Optimization ◽  
Aerodynamic Optimization ◽  
Flow Losses ◽  
Flow Loss

The nonaxisymmetric endwall profiling has been proven to be an effective tool to reduce the secondary flow loss in turbomachinery. In the present work, first, without considering the endwall midgap in the real machine, an endwall optimization design procedure for reducing secondary flow losses has been developed, which allowed complete three-dimensional parameterization turbine endwall design. The profile of the endwall has been designed using automatic numerical optimization by means of an improved efficient global optimization algorithm based on kriging surrogate model. Next, a large-scale linear cascade with a low-speed wind tunnel has been chosen for the experimental validation of the optimization results. The experimental measurements and numerical simulations both demonstrated that the total pressure loss and secondary flow intensity were reduced with the nonaxisymmetric endwall used in the cascade passage. Then, in order to evaluate the ability of the optimized nonaxisymmetric endwall with the midgap, the midgap was added in for both the baseline flat endwall and the optimized nonaxisymmetric endwall in the numerical simulations analysis. The entropy generation rates analysis were used for the investigation of loss distribution in the passage. For the cascade in the present work, with the midgap added in, the optimized nonaxisymmetric endwall did not perform as well as the situation without the midgap in the loss reduction. In addition, comparing to the baseline flat endwall, the optimized nonaxisymmetric endwall needed more net leakage flow to avoid the ingress of passage flow into the midgap.

Non-Axisymmetric Turbine Endwall Aerodynamic Optimization Design: Part I — Turbine Cascade Design and Experimental Validations

2014 ◽  
Author(s):  
Hao Sun ◽  
Jun Li ◽  
Liming Song ◽  
Zhenping Feng
Keyword(s):  
Secondary Flow ◽  
Evaluation Method ◽  
Pressure Coefficient ◽  
Optimization Method ◽  
Experimental Measurements ◽  
Turbine Cascade ◽  
Aerodynamic Optimization ◽  
Flow Losses ◽  
Flow Intensity ◽  
Performance Evaluation Method

The non-axisymmetric endwall profiling has been proven to be an effective tool to reduce the secondary flow loss in turbomachinery. In this work, the aerodynamic optimization for the non-axisymmetric endwall profile of the turbine cascade and stage was presented and the design results were validated by annular cascade experimental measurements and numerical simulations. The parametric method of the non-axisymmetric endwall profile was proposed based on the relation between the pressure field variation and the secondary flow intensity. The optimization system combines with the non-axisymmetric endwall parameterization method, global optimization method of the adaptive range differential evolution algorithm and the aerodynamic performance evaluation method using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and k–ω SST turbulent with transition model solutions. In the part I, the optimization method is used to design the optimum non-axisymmetric endwall profile of the typical high loaded turbine stator. The design objective was selected for the maximum total pressure coefficient with constrains on the mass flow rate and outlet flow angle. Only five design variables are needed for one endwall to search the optimum non-axisymmetric endwall profile. The optimized non-axisymmetric endwall profile of turbine cascade demonstrated an improvement of total pressure coefficient of 0.21% absolutely, comparing with the referenced axisymmetric endwall design case. The reliability of the numerical calculation used in the aerodynamic performance evaluation method and the optimization result were validated by the annular vane experimental measurements. The static pressure distribution at midspan was measured while the cascade flow field was measured with the five-hole probe for both the referenced axisymmetric and optimized non-axisymmetric endwall profile cascades. Both the experimental measurements and numerical simulations demonstrated that both the secondary flow losses and the profile loss of the optimized non-axisymmetric endwall profile cascade were significantly reduced by comparison of the referenced axisymmetric case. The weakening of the secondary flow of the optimized non-axisymmetric endwall profile design was also proven by the secondary flow vector results in the experiment. The detailed flow mechanism of the secondary flow losses reduction in the non-axisymmetric endwall profile cascade was analyzed by investigating the relation between the change of the pressure gradient and the variation of the secondary flow intensity.

Steady CFD Analysis on Gas Turbine Stage Cascade Based on Mixing Plane Model

2012 ◽  
Vol 184-185 ◽  
pp. 473-476 ◽  
Author(s):  
Gao Su ◽  
Guo Yi Zhou ◽  
Fei Du
Keyword(s):  
Gas Turbine ◽  
Optimization Design ◽  
Flow Model ◽  
Scientific Management ◽  
Turbine Cascade ◽  
Wall Function ◽  
Turbine Stage ◽  
Aerodynamic Optimization ◽  
Plane Model ◽  
Explicit Solver

Based on a standard dual-equation turbulent flow model and coupled explicit solver,a wall function method was employed to closure the Reynolds averaged N-S equation .The mixing plane method was adopted to tranfer parameters between rotor and stator cascades. A approximate linear law is obtained in gas turbine cascade for supercharged marine boiler,which governs the variation of some parameters at the outlet of the turbine stage cascade along the blade height direction,such as pressure,velocity,as well as temperature and Ma.The results can provide guidelines for aerodynamic optimization design of the gas turbine stage cascade and the scientific management of this kind of set.

The Aerodynamic Optimization Design of Turbine Cascade With Nonaxisymmetric Endwall and Experimental Validations

2017 ◽  
Author(s):  
Hao Liu ◽  
Xin Shen ◽  
Xiaocheng Zhu ◽  
Zhaohui Du ◽  
Hong Yang ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Secondary Flow ◽  
Optimization Algorithm ◽  
Optimization Design ◽  
Shape Function ◽  
Design Procedure ◽  
Design System ◽  
Decay Function ◽  
Correlation Vector ◽  
Flow Loss

The nonaxisymmetric endwall profiling has been proven to be an effective tool to reduce the secondary flow loss in turbomachinery. In the present work, an endwall optimization design procedure for reducing secondary flow losses has been developed which allowed complete 3-dimensional parameterization design of the turbine endwall. A so-called shape function and a decay function were used for the definition of the nonaxisymmetric endwall. The shape function was used to control the curvature in the circumferential direction and the decay function was used to control the curvature in the axial direction. The design of the endwall was generated by the product of these two functions. The sinusoidal function was used for the shape function and the B-spline was used for the decay function. This parametrization allowed influencing the contouring of the specific endwall region. The profile of the endwall has been optimized using automatic numerical optimization by means of an improved efficient global optimization algorithm based on kriging surrogate model. The niching micro genetic algorithm was used to get the correlation vector of Kriging model, which eliminated the dependence of correlation vector starting search points. This method reduced the difficulty of finding appropriate penalty parameters and increased the robustness of the optimization method. The 3D-Reynolds-averaged Navier-Stokes flow solver based on CFX, with a k-ω model for turbulence model, was used for all numerical calculations. An in-house optimization design system was developed to close the loop of the geometry definition, flow solving and the optimization algorithm which allowed the solution of non-linear problems. A large-scale linear cascade with a low-speed wind tunnel has been chosen for the experimental validation of the optimization results. The experimental measurements and numerical simulations both demonstrated that the total pressure loss and secondary flow intensity were reduced with the nonaxisymmetric endwall used in the cascade passage. The detailed flow pattern comparisons between the passage with based flat endwall and the optimization nonaxisymmetric endwall were given by the numerical simulations method and entropy generation rates analysis were used for the investigation of the secondary flow loss reduction mechanism in the nonaxisymmetric endwall profile cascade.

scholarly journals Several Cases for the Validation of Turbulence Models Implementation

2021 ◽  
Vol 11 (8) ◽  
pp. 3377
Author(s):  
Michael D. Polewski ◽  
Paul G. A. Cizmas
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Transport Model ◽  
Turbulence Models ◽  
Numerical Results ◽  
Test Cases ◽  
Turbine Cascade ◽  
Near Wake ◽  
Shear Stress Transport Model ◽  
Standard Configuration

This paper presents several test cases that were used to validate the implementation of two turbulence models in the UNS3D code, an in-house code. The two turbulence models used were the Shear Stress Transport model and the Spalart–Allmaras model. These turbulence models were explored using the numerical results generated by three computational fluid dynamics codes: NASA’s FUN3D and CFL3D, and UNS3D. Four cases were considered: a flat plate case, an airfoil near-wake, a backward-facing step, and a turbine cascade known as the Eleventh Standard Configuration. The numerical results were compared among themselves and against experimental data.

Non-Axisymmetric Turbine Endwall Aerodynamic Optimization Design: Part II — Turbine Stage Design and Unsteady Flow Characteristics Analysis

2014 ◽  
Author(s):  
Hao Sun ◽  
Liming Song ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Unsteady Flow ◽  
Secondary Flow ◽  
Optimization Design ◽  
Flow Characteristics ◽  
Aerodynamic Performance ◽  
Turbine Stage ◽  
Aerodynamic Optimization ◽  
Flow Losses ◽  
Unsteady Interaction ◽  
Isentropic Efficiency

Aerodynamic optimization design and experimental validation for the non-axisymmetric endwall profiles of the turbine cascade have been completed in the part I of this research work. Non-axisymmetric endwall profile optimization design of the turbine stage and corresponding steady and unsteady flow characteristics were presented in the part II. Aerodynamic optimization design for the non-axisymmetric endwall profile of the turbine stage was conducted when the maximization of the total-total isentropic efficiency was set as the design objective with constraint on the mass flow rate. The aerodynamic performance of the designed turbine stage was evaluated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) solutions. The non-axisymmetric endwall profiles of the stator hub and shroud as well as the rotor hub in the turbine stage were optimized using developed endwall profile method in the part I. A total of 15 design variables were employed in the optimization for the stator and rotor endwalls. The global optimization method of the adaptive rang differential evolution algorithm was used to search the optimal non-axisymmetric endwall profile. The total-total isentropic efficiency of the turbine stage with the optimized non-axisymmetric endwall profile increases 0.26% by comparison of the referenced axisymmetric endwall design when the effects of the rotor tip clearance were also considered. The secondary flow losses of the stator and rotor were significantly reduced in the optimized non-axisymmetric endwall stage, as well as the tip leakage flow losses. In addition, the unsteady aerodynamic performance of the turbine stage with the optimized non-axisymmetric endwall profile and referenced axisymmetric endwall were numerically investigated and compared. The numerical results indicate that the fluctuating velocity in the rotor blade passage of the optimized non-axisymmetric endwall stage significantly decreases since the stator wake and secondary flow losses are reduced. Thus, the intensity of the unsteady interaction between the stator upstream flow and the flow in the rotor passage decreases. The time-averaged results indicated that the aerodynamic efficiency and output power of the turbine stage with the optimized non-axisymmetric endwall profile are higher than that of the referenced axisymmetric endwall stage. Meanwhile, the transient results at different time steps show that the periodic fluctuating amplitude of the efficiency and power of the optimized non-axisymmetric endwall stage were smaller than that of the referenced axisymmetric endwall stage due to the weaker stator/rotor unsteady interaction effects.

scholarly journals A Two-Round Optimization Design Method for Aerostatic Spindles Considering the Fluid–Structure Interaction Effect

2021 ◽  
Vol 11 (7) ◽  
pp. 3017
Author(s):  
Qiang Gao ◽  
Siyu Gao ◽  
Lihua Lu ◽  
Min Zhu ◽  
Feihu Zhang
Keyword(s):  
Optimal Design ◽  
Optimization Design ◽  
Design Method ◽  
Fluid Structure Interaction ◽  
Design Procedure ◽  
Design Parameters ◽  
Geometrical Parameters ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerostatic Spindle

The fluid–structure interaction (FSI) effect has a significant impact on the static and dynamic performance of aerostatic spindles, which should be fully considered when developing a new product. To enhance the overall performance of aerostatic spindles, a two-round optimization design method for aerostatic spindles considering the FSI effect is proposed in this article. An aerostatic spindle is optimized to elaborate the design procedure of the proposed method. In the first-round design, the geometrical parameters of the aerostatic bearing were optimized to improve its stiffness. Then, the key structural dimension of the aerostatic spindle is optimized in the second-round design to improve the natural frequency of the spindle. Finally, optimal design parameters are acquired and experimentally verified. This research guides the optimal design of aerostatic spindles considering the FSI effect.

scholarly journals Incidence Angle and Pitch-Chord Effects on Secondary Flows Downstream of a Turbine Cascade

1992 ◽  
Author(s):  
A. Perdichizzi ◽  
V. Dossena
Keyword(s):  
Flow Field ◽  
Secondary Flow ◽  
Incidence Angle ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Turbine Cascade ◽  
Oil Flow ◽  
Secondary Velocity ◽  
Secondary Flow Field

This paper describes the results of an experimental investigation of the three-dimensional flow downstream of a linear turbine cascade at off-design conditions. The tests have been carried out for five incidence angles from −60 to +35 degrees, and for three pitch-chord ratios: s/c = 0.58,0.73,0.87. Data include blade pressure distributions, oil flow visualizations, and pressure probe measurements. The secondary flow field has been obtained by traversing a miniature five hole probe in a plane located at 50% of an axial chord downstream of the trailing edge. The distributions of local energy loss coefficients, together with vorticity and secondary velocity plots show in detail how much the secondary flow field is modified both by incidence and cascade solidity variations. The level of secondary vorticity and the intensity of the crossflow at the endwall have been found to be strictly related to the blade loading occurring in the blade entrance region. Heavy changes occur in the spanwise distributions of the pitch averaged loss and of the deviation angle, when incidence or pitch-chord ratio is varied.

Aerodynamics of Cooling Jets Introduced in the Secondary Flow of a Low-Speed Turbine Cascade

1990 ◽  
Vol 112 (3) ◽  
pp. 539-546 ◽  
Author(s):  
F. Bario ◽  
F. Leboeuf ◽  
A. Onvani ◽  
A. Seddini
Keyword(s):  
Secondary Flow ◽  
Side Wall ◽  
Velocity Fields ◽  
Measuring Apparatus ◽  
Flow Ratio ◽  
Turbine Cascade ◽  
Hot Wire ◽  
Local Pressure ◽  
Low Speed ◽  
Jet Behavior

The aerodynamic behavior of cold discrete jets in a cold secondary flow is investigated. Configurations including single jets and rows of jets are studied. These jets are introduced through the side wall of a low-speed nozzle turbine cascade. The experimental setup and the jet behavior are fully described. The effects of location with respect to the blades, mass flow ratio, yaw, and incidence angles on the aerodynamics of single jets are investigated. The influence of neighboring jets is detailed in the case of multiple jet configurations. The interaction with the secondary flow is presented. The local pressure and velocity fields, trajectories, and visualizations are discussed. The measuring apparatus includes a five-hole probe and a hot wire for intermittency measurements.

scholarly journals Novel Robust Design Method of Multilayer Optical Coatings

ISRN Optics ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Suyong Wu ◽  
Xingwu Long ◽  
Kaiyong Yang
Keyword(s):  
Robust Design ◽  
Optimization Design ◽  
Design Method ◽  
Analytical Calculation ◽  
Design Procedure ◽  
Deposition Process ◽  
Practical Significance ◽  
Optical Coatings ◽  
Optical Films ◽  
Robust Design Method

We present a novel fast robust design method of multilayer optical coatings. The sensitivity of optical films to production errors is controlled in the whole optimization design procedure. We derive an analytical calculation model for fast robust design of multilayer optical coatings. We demonstrate its effectiveness by successful application of the robust design method to a neutral beam splitter. It is showed that the novel robust design method owns an inherent fast computation characteristic and the designed film is insensitive to the monitoring thickness errors in deposition process. This method is especially of practical significance to improve the mass production yields and repetitive production of high-quality optical coatings.

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