Validating Numerical CFD Simulations With Experimental Data for Turbulence Phenomena in Axial Flow Gas Turbine Diffusers

2009 ◽  
Author(s):  
Farrokh Zarifi-Rad ◽  
Hamid Vajihollahi ◽  
James O’Brien
Keyword(s):  
Experimental Data ◽  
Gas Turbine ◽  
Turbine Blades ◽  
Axial Flow ◽  
Experimental Results ◽  
Scale Model ◽  
Data Set ◽  
Pressure Profiles ◽  
Scale Models ◽  
Inlet Conditions

Scale models give engineers an excellent understanding of the aerodynamic behavior behind their design; nevertheless, scale models are time consuming and expensive. Therefore computer simulations such as Computational Fluid Dynamics (CFD) are an excellent alternative to scale models. One must ask the question, how close are the CFD results to the actual fluid behavior of the scale model? In order to answer this question the engineering team investigated the performance of a large industrial Gas Turbine (GT) exhaust diffuser scale model with performance predicted by commercially available CFD software. The experimental results were obtained from a 1:12 scale model of a GT exhaust diffuser with a fixed row of blades to simulate the swirl generated by the last row of turbine blades five blade configurations. This work is to validate the effect of the turbulent inlet conditions on an axial diffuser, both on the experimental front and on the numerical analysis approach. The object of this work is to bring forward a better understanding of velocity and static pressure profiles along the gas turbine diffusers and to provide an accurate experimental data set to validate the CFD prediction. For the CFD aspect, ANSYS CFX software was chosen as the solver. Two different types of mesh (hexagonal and tetrahedral) will be compared to the experimental results. It is understood that hexagonal (HEX) meshes are more time consuming and more computationally demanding, they are less prone to mesh sensitivity and have the tendancy to converge at a faster rate than the tetrahedral (TET) mesh. It was found that the HEX mesh was able to generate more consistent results and had less error than TET mesh.

Performance Study of a 1 MW Gas Turbine Using Variable Geometry Compressor and Turbine Blade Cooling

2010 ◽  
Author(s):  
Cleverson Bringhenti ◽  
Jesuino Takachi Tomita ◽  
Joa˜o Roberto Barbosa
Keyword(s):  
Gas Turbine ◽  
Guide Vane ◽  
Turbine Blades ◽  
Axial Flow ◽  
Operating Conditions ◽  
Inlet Guide Vane ◽  
Variable Geometry ◽  
Performance Study ◽  
Turbine Blade Cooling ◽  
Blade Cooling

This work presents the performance study of a 1 MW gas turbine including the effects of blade cooling and compressor variable geometry. The axial flow compressor, with Variable Inlet Guide Vane (VIGV), was designed for this application and its performance maps synthesized using own high technological contents computer programs. The performance study was performed using a specially developed computer program, which is able to numerically simulate gas turbine engines performance with high confidence, in all possible operating conditions. The effects of turbine blades cooling were calculated for different turbine inlet temperatures (TIT) and the influence of the amount of compressor-bled cooling air was studied, aiming at efficiency maximization, for a specified blade life and cooling technology. Details of compressor maps generation, cycle analysis and blade cooling are discussed.

Comparison of Large Eddy Simulation Methods for Flows Over Gas Turbine Blades

2007 ◽  
Author(s):  
M. Karimi ◽  
M. Paraschivoiu
Keyword(s):  
Experimental Data ◽  
Large Eddy Simulation ◽  
Gas Turbine ◽  
Compressible Flows ◽  
Turbine Blades ◽  
Classical Problem ◽  
Numerical Dissipation ◽  
Simulation Methods ◽  
Eddy Simulation ◽  
Large Eddy

In recent years there has been a considerable effort toward applying large eddy simulation methods (LES) to real industrial problems. However, there are still several challenges to be addressed to achieve a reliable LES solution, especially in the context of compressible flows. Furthermore, complex geometries require the unstructured meshes which then interdict the use of very high order schemes. Therefore, LES models are mainly derived and tested on classical problem of simple geometry for incompressible flow and based on higher order schemes. Here, the flow over a gas turbine blade at high Reynolds and Mach numbers is investigated using a mixed finite-volume-finite-element method. Implicit LES method (ILES) as well as Smagorinsky and its dynamic version have been studied. Different variations of the Smagorinsky method have been examined too. The interaction of the numerical dissipation of the scheme with LES models has been explored. The results show the capability of the ILES to take into account the effective viscosity of the flow and the negligible difference of the different LES models in this flow condition. Fairly good agreement with experimental data is found which is superior to RANS results. It is found that there are still some challenges in industrial LES applications which have to be addressed to lead to a better agreement with experimental data.

Computational Modelling of Tip Heat Transfer to a Super-Scale Model of an Unshrouded Gas Turbine Blade

2008 ◽  
Author(s):  
Brian M. T. Tang ◽  
Pepe Palafox ◽  
David R. H. Gillespie ◽  
Martin L. G. Oldfield ◽  
Brian C. Y. Cheong
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Computational Study ◽  
Turbulence Models ◽  
Scale Model ◽  
Tip Leakage Flow ◽  
Blade Tip

Control of over-tip leakage flow between turbine blade tips and the stationary shroud is one of the major challenges facing gas turbine designers today. The flow imposes large thermal loads on unshrouded high pressure turbine blades and is significantly detrimental to turbine blade life. This paper presents results from a computational study performed to investigate the detailed blade tip heat transfer on a sharp-edged, flat tip HP turbine blade. The tip gap is engine representative at 1.5% of the blade chord. Nusselt number distributions on the blade tip surface have been obtained from steady flow simulations and are compared to experimental data carried out in a super-scale cascade, which allows detailed flow and heat transfer measurements in stationary and engine representative conditions. Fully structured, multiblock hexahedral meshes were used in the simulations, performed in the commercial solver Fluent. Seven industry-standard turbulence models, and a number of different tip gridding strategies are compared, varying in complexity from the one-equation Spalart-Allmaras model to a seven-equation Reynolds Stress model. Of the turbulence models examined, the standard k-ω model gave the closest agreement to the experimental data. The discrepancy in Nusselt number observed was just 5%. However, the size of the separation on the pressure side rim was underpredicted, causing the position of reattachment to occur too close to the edge. Other turbulence models tested typically underpredicted Nusselt numbers by around 35%, although locating the position of peak heat flux correctly. The effect of the blade to casing motion was also simulated successfully, qualitatively producing the same changes in secondary flow features as were previously observed experimentally, with associated changes in heat transfer to the blade tip.

Computational Modeling of Tip Heat Transfer to a Superscale Model of an Unshrouded Gas Turbine Blade

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Brian M. T. Tang ◽  
Pepe Palafox ◽  
Brian C. Y. Cheong ◽  
Martin L. G. Oldfield ◽  
David R. H. Gillespie
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nusselt Number ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Computational Study ◽  
Turbine Blades ◽  
Turbulence Models ◽  
Tip Leakage Flow ◽  
Blade Tip

Control of over-tip leakage flow between turbine blade tips and the stationary shroud is one of the major challenges facing gas turbine designers today. The flow imposes large thermal loads on unshrouded high pressure (HP) turbine blades and is significantly detrimental to turbine blade life. This paper presents results from a computational study performed to investigate the detailed blade tip heat transfer on a sharp-edged, flat tip HP turbine blade. The tip gap is engine representative at 1.5% of the blade chord. Nusselt number distributions on the blade tip surface have been obtained from steady flow simulations and are compared with experimental data carried out in a superscale cascade, which allows detailed flow and heat transfer measurements in stationary and engine representative conditions. Fully structured, multiblock hexahedral meshes were used in the simulations performed in the commercial solver FLUENT. Seven industry-standard turbulence models and a number of different tip gridding strategies are compared, varying in complexity from the one-equation Spalart–Allmaras model to a seven-equation Reynolds stress model. Of the turbulence models examined, the standard k-ω model gave the closest agreement to the experimental data. The discrepancy in Nusselt number observed was just 5%. However, the size of the separation on the pressure side rim was underpredicted, causing the position of reattachment to occur too close to the edge. Other turbulence models tested typically underpredicted Nusselt numbers by around 35%, although locating the position of peak heat flux correctly. The effect of the blade to casing motion was also simulated successfully, qualitatively producing the same changes in secondary flow features as were previously observed experimentally, with associated changes in heat transfer with the blade tip.

Online investigation of users’ attitudes using automatic question answering

2018 ◽  
Vol 42 (3) ◽  
pp. 419-435 ◽  
Author(s):  
Chengzhi Zhang ◽  
Qingqing Zhou
Keyword(s):  
Experimental Data ◽  
Question Answering ◽  
Online Reviews ◽  
Experimental Results ◽  
Question Generation ◽  
Data Set ◽  
Content Type ◽  
Internet Users ◽  
Tourism Services ◽  
Sentiment Computing

Purpose With the development of the internet, huge numbers of reviews are generated, disseminated, and shared on e-commerce and social media websites by internet users. These reviews usually indicate users’ opinions about products or services directly, and are thus valuable for efficient marketing. The purpose of this paper is to mine online users’ attitudes from a huge pool of reviews via automatic question answering. Design/methodology/approach The authors make use of online reviews to complete an online investigation via automatic question answering (AQA). In the process of AQA, question generation and extraction of corresponding answers are conducted via sentiment computing. In order to verify the performance of AQA for online investigation, online reviews from a well-known travel website, namely Tuniu.com, are used as the experimental data set. Finally, the experimental results from AQA vs a traditional questionnaire are compared. Findings The experimental results show that results between the AQA-based automatic questionnaire and the traditional questionnaire are consistent. Hence, the AQA method is reliable in identifying users’ attitudes. Although this paper takes Chinese tourism reviews as the experimental data, the method is domain and language independent. Originality/value To the best of the authors’ knowledge, this is the first study to use the AQA method to mine users’ attitudes towards tourism services. Using online reviews may overcome problems with using traditional questionnaires, such as high costs and long cycle for questionnaire design and answering.

scholarly journals Development of 300kW-Class Ceramic Gas Turbine (CGT301) Engine System

1995 ◽  
Author(s):  
Masashi Tatsuzawa ◽  
Tomoki Taoka ◽  
Takeshi Sakida ◽  
Shinya Tanaka
Keyword(s):  
Gas Turbine ◽  
Development Process ◽  
Thermal Stresses ◽  
Turbine Blades ◽  
Axial Flow ◽  
Thermal Conditions ◽  
Fatigue Tests ◽  
Test Results ◽  
Gas Temperature ◽  
Engine System

CGT301 is a recuperated, single-shaft ceramic gas turbine for co-generation use. Ceramic parts are used in the hot section of the engine, such as turbine blades, nozzle vanes, combustor liners, heat exchanger elements and gas path parts. These ceramic parts are designed axi-symmetrically to reduce their sizes and thermal stresses and to avoid their unexpected deformations. The turbine is a two-stage axial flow type. As a primary feature of this turbine, the rotors are composed of ceramic blades inserted into metallic disks. The ceramic parts of the engine system have been tested before installing them in the engine to assure their reliability in the following manner. The ceramic blades have been examined by hot-spin test with the gas temperature of 1100°C and up to 110% of the engine rated speed. The ceramic stationary parts such as nozzle vanes, combustor liners and gas path parts, have been assembled and installed in a test rig with almost the same constraint and thermal conditions as the engine, and thermal fatigue tests of 100 cycles between 1200°C and 300°C have been conducted. After the proof tests of ceramic parts, they have been installed in the engine, step by step. Finally, the engine has been operated with a TIT of 1200°C at the engine rated speed of 56000 rpm. The present paper describes the development process and shows test results of the ceramic gas turbine at a TIT of 1200°C.

The Application of Non-Axisymmetric Profiled End-Walls for Axial Flow Turbines in the Embedded Stage Environment

2013 ◽  
Author(s):  
Andreas Lintz ◽  
Liping Xu ◽  
Marios Karakasis
Keyword(s):  
Axial Flow ◽  
Leading Edge ◽  
Surface Flow ◽  
Secondary Flows ◽  
Experimental Results ◽  
Front Part ◽  
Flow Conditions ◽  
Suction Surface ◽  
Inlet Conditions ◽  
End Wall

In this paper, an assessment of the effectiveness of non-axisymmetric profiled end-walls in the embedded stage environment at varying inlet conditions is presented. Both numerical and experimental results were obtained in a three-stage model turbine which offers flow conditions representative of embedded blade rows in a typical high pressure steam turbine. The end-wall profile design was carried out using automatic optimization in conjunction with 3D RANS CFD. The design target is to reduce the end-wall losses by reducing the loading in the front part of the passage, which resulted in a single trough close to the blade suction surface in the leading edge region. 5-hole probe traverses and surface flow visualization show that the intensity of the secondary flows is reduced by about 10%, but overall loss is only reduced slightly. Experimental results have been obtained for the cylindrical end-wall and three different trough depths. With increasing depth, transitional effects at the end-walls might come into play, increasing the total pressure loss in the boundary layer region. The effects of the end-wall design is similar at positive and negative incidence, despite the reduced loading in the front part of the passage at negative incidence. At very high negative incidence angles, such as those occurring at the stator tip with rotor shroud leakage flows, the mechanism of secondary flow generation changes, so that a design under nominal inlet flow conditions shows no effect on the exit flow field.

scholarly journals Experiments With a Gas Turbine Model Combustor Firing Blast-Furnace Gas

1996 ◽  
Author(s):  
Yansong Liu ◽  
Jürg Schmidli
Keyword(s):  
Blast Furnace ◽  
Gas Turbine ◽  
Chemical Kinetics ◽  
Flame Temperature ◽  
Scale Model ◽  
Diffusion Type ◽  
Stability Range ◽  
Blast Furnace Gas ◽  
Slow Kinetics ◽  
Inlet Conditions

On-site atmospheric experiments using a one-fifth-scale model combustor of the ABB gas turbine type 11N2-LBtu have been recently carried out at the Kawasaki Steel Works in Mizushima, Japan. A diffusion type burner of special design was used to match the extremely low heating value (2360 kJ/kg) and the high stoichiometric fuel/air ratio (1.6 kg/kg) of the Blast-Furnace Gas (BFG). Except for pressure, all burner inlet conditions were simulated as in the actual gas turbine. The burner demonstrated an excellent burning stability behaviour over the entire operation range and stably burned pure BFG down to an equivalence ratio of 0.25, without any supplementary fuel. Due to the low adiabatic flame temperature and slow kinetics, approximately 1 ppm NOx was measured in the exhaust gas. The chemical kinetics of NOx production and CO burnout were also calculated using a chemical kinetics code and reasonable agreement with the experimental results was obtained. In dual-fuel operation (BFG with oil, propane, or coke-oven gas) the burner also demonstrated a wide flame stability range.

In Situ Membrane Parameter Determination Using Simultaneously Locally Resolved Impedance Spectroscopy and Dynamic Water Partial Pressure Measurement in PEFCs

2010 ◽  
Author(s):  
M. H. Bayer ◽  
A. Wokaun ◽  
G. G. Scherer ◽  
I. A. Schneider
Keyword(s):  
Experimental Data ◽  
Partial Pressure ◽  
Calculated Data ◽  
Ac Impedance ◽  
Experimental Results ◽  
Tunable Diode Laser ◽  
Polymer Electrolyte Fuel Cell ◽  
Parameter Determination ◽  
Data Set

Tunable diode laser absorption spectroscopy (TDLAS) is used to measure the local ac response of the water partial pressure to a sinusoidal current excitation during locally resolved impedance measurements in a sub-saturated polymer electrolyte fuel cell (PEFC). The experimental results, along with the locally resolved impedance data are compared to calculated data as obtained from a 1+1 dimensional ac impedance model. The detailed experimental data allows model validation and in situ parameter determination. The model results are in good agreement with the experimental results. This emphasizes the importance to consider the build-up of water partial pressure oscillations along the gas channels in ac impedance models for sub-saturated PEFCs. The results show that minor modifications of literature membrane parameters are needed for a good fit to the experimental data set.

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