A Comprehensive CFD Study of Transitional Flows in Low-Pressure Turbines Under a Wide Range of Operating Conditions

2003 ◽  
Author(s):  
Yildirim Suzen ◽  
George Huang ◽  
Ralph Volino ◽  
Thomas Corke ◽  
Flint Thomas ◽  
...  
Keyword(s):  
Low Pressure ◽  
Operating Conditions ◽  
Transitional Flows ◽  
Wide Range

scholarly journals A Computational Fluid Dynamics Study of Transitional Flows in Low-Pressure Turbines Under a Wide Range of Operating Conditions

2006 ◽  
Vol 129 (3) ◽  
pp. 527-541 ◽  
Author(s):  
Y. B. Suzen ◽  
P. G. Huang ◽  
D. E. Ashpis ◽  
R. J. Volino ◽  
T. C. Corke ◽  
...  
Keyword(s):  
Experimental Data ◽  
Transport Equation ◽  
Low Pressure ◽  
Equation Model ◽  
Operating Conditions ◽  
Computational Results ◽  
Transitional Flows ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Intermittency Factor

A transport equation for the intermittency factor is employed to predict the transitional flows in low-pressure turbines. The intermittent behavior of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, μt, with the intermittency factor, γ. Turbulent quantities are predicted by using Menter’s two-equation turbulence model (SST). The intermittency factor is obtained from a transport equation model which can produce both the experimentally observed streamwise variation of intermittency and a realistic profile in the cross stream direction. The model had been previously validated against low-pressure turbine experiments with success. In this paper, the model is applied to predictions of three sets of recent low-pressure turbine experiments on the Pack B blade to further validate its predicting capabilities under various flow conditions. Comparisons of computational results with experimental data are provided. Overall, good agreement between the experimental data and computational results is obtained. The new model has been shown to have the capability of accurately predicting transitional flows under a wide range of low-pressure turbine conditions.

The Off-Design Performance of a Low-Pressure Turbine Cascade

1987 ◽  
Vol 109 (2) ◽  
pp. 201-209 ◽  
Author(s):  
H. P. Hodson ◽  
R. G. Dominy
Keyword(s):  
Reynolds Numbers ◽  
Low Pressure ◽  
Turbine Rotor ◽  
Surface Flow ◽  
Operating Conditions ◽  
Turbine Cascade ◽  
Linear Cascade ◽  
Design Performance ◽  
Low Pressure Turbine ◽  
Wide Range

The ability of a given blade profile to operate over a wide range of conditions is often of the utmost importance. This paper reports the off-design performance of a low-pressure turbine rotor root section in a linear cascade. Data were obtained using pneumatic probes and surface flow visualization. The effects of incidence (+9, 0, −20 deg), Reynolds (1.5, 2.9, 6.0 × 105), pitch-chord ratio (0.46, 0.56, 0.69), and inlet boundary layer thickness (0.011, 0.022 δ*/C) are discussed. Particular attention is paid to the three dimensionality of the flow field. Significant differences in the detail of the flow occur over the range of operating conditions investigated. It is found that the production of new secondary loss is greatest at lower Reynolds numbers, positive incidence, and the higher pitch-chord ratios.

Comprehensive validation of an intermittency transport model for transitional low-pressure turbine flows

2005 ◽  
Vol 109 (1093) ◽  
pp. 101-118 ◽  
Author(s):  
Y. B. Suzen ◽  
P. G. Huang
Keyword(s):  
Transport Model ◽  
Low Pressure ◽  
Operating Conditions ◽  
Transitional Flow ◽  
Pressure Gradients ◽  
Transport Modelling ◽  
Transitional Flows ◽  
Low Pressure Turbine ◽  
Unsteady Wake ◽  
Intermittency Factor

Abstract A transport equation for the intermittency factor is employed to predict transitional flows under the effects of pressure gradients, freestream turbulence intensities, Reynolds number variations, flow separation and reattachment, and unsteady wake-blade interactions representing diverse operating conditions encountered in low-pressure turbines. The intermittent behaviour of the transitional flows is taken into account and incorporated into computations by modifying the eddy viscosity, μτ with the intermittency factor, γ. Turbulent quantities are predicted by using Menter’s two-equation turbulence model (SST). The onset location of transition is obtained from correlations based on boundary-layer momentum thickness, accelaration parameter, and turbulence intensity. The intermittency factor is obtained from a transport model which can produce both the experimentally observed streamwise variation of intermittency and a realistic profile in the cross stream direction. The intermittency transport model is tested and validated against several well documented low pressure turbine experiments ranging from flat plate cases to unsteady wake-blade interaction experiments. Overall, good agreement between the experimental data and computational results is obtained illustrating the predicting capabilities of the model and the current intermittency transport modelling approach for transitional flow simulations.

Experimental and Numerical Investigation of the Flow in a Low-Pressure Industrial Steam Turbine With Part-Span Connectors

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Markus Häfele ◽  
Christoph Traxinger ◽  
Marius Grübel ◽  
Markus Schatz ◽  
Damian M. Vogt ◽  
...  
Keyword(s):  
Flow Field ◽  
Steam Turbine ◽  
Numerical Study ◽  
Three Dimensional ◽  
Low Pressure ◽  
Operating Conditions ◽  
Engineering Practice ◽  
Cfd Model ◽  
Wide Range ◽  
The Impact

An experimental and numerical study on the flow in a three-stage low-pressure (LP) industrial steam turbine is presented and analyzed. The investigated LP section features conical friction bolts in the last and a lacing wire in the penultimate rotor blade row. These part-span connectors (PSC) allow safe turbine operation over an extremely wide range and even in blade resonance condition. However, additional losses are generated which affect the performance of the turbine. In order to capture the impact of PSCs on the flow field, extensive measurements with pneumatic multihole probes in an industrial steam turbine test rig have been carried out. State-of-the-art three-dimensional computational fluid dynamics (CFD) applying a nonequilibrium steam (NES) model is used to examine the aerothermodynamic effects of PSCs on the wet steam flow. The vortex system in coupled LP steam turbine rotor blading is discussed in this paper. In order to validate the CFD model, a detailed comparison between measurement data and steady-state CFD results is performed for several operating conditions. The investigation shows that the applied one-passage CFD model is able to capture the three-dimensional flow field in LP steam turbine blading with PSC and the total pressure reduction due to the PSC with a generally good agreement to measured values and is therefore sufficient for engineering practice.

Numerical Investigation on the Flow Characteristics of a Supercritical CO2 Centrifugal Compressor

2014 ◽  
Author(s):  
Hang Zhao ◽  
Qinghua Deng ◽  
Kuankuan Zheng ◽  
Hanzhen Zhang ◽  
Zhenping Feng
Keyword(s):  
Numerical Investigation ◽  
Centrifugal Compressor ◽  
Supercritical Co2 ◽  
Flow Characteristics ◽  
Low Pressure ◽  
Operating Conditions ◽  
Vaneless Diffuser ◽  
Vaned Diffuser ◽  
Compact Size ◽  
Wide Range

Supercritical CO2 closed-loop Brayton cycles offer the potential of better economical and practical efficiency due to its compact size and smaller compression work as compared with some traditional working fluids cycles, in which compressor is the key component. In this paper, the aerodynamic design and impeller aerodynamic optimization were conducted for a single stage centrifugal compressor with a combined vaneless and vaned diffuser, operating with CO2 slightly above the vapor-liquid critical point. The NIST REFPROP database was used for the computation of supercritical CO2 properties in design analysis and numerical investigation. The flow characteristics of the supercritical CO2 compressor were investigated by NUMECA FINE/Turbo. In order to weaken the low pressure regions, a vaneless diffuser was applied in this design, which would control and reduce the distribution differences of fluid thermodynamic states and increase fluid static pressure. The results indicate that there are no obvious low pressure regions occurring close to the leading edge of vaned diffuser. So it is observed in the design process that the vaneless diffuser could improve the aerodynamic performance of supercritical CO2 compressor. Compared with the operating conditions of the compressor only under centrifugal force, the pressure load from the aerodynamic analysis and the centrifugal load due to high speed of rotation were considered in the study of the stress and deformation of the structure of impeller by ANSYS/Mechanical. It can be concluded that supercritical CO2 provides unique properties for the compressor working process, which have a significant influence on finite element modeling in structural analysis. For the present design the maximum von Mises stress and total deformation are shown much smaller than the maximum allowable values, and thus the compressor could work in a wide range of operating conditions.

Design, Manufacturing and Testing of a New Family of Steam Turbine Low Pressure Stages

2007 ◽  
Author(s):  
Lorenzo Cosi ◽  
Jonathon Slepski ◽  
Steven DeLessio ◽  
Michele Taviani ◽  
Amir Mujezinovic´
Keyword(s):  
Power Generation ◽  
Steam Turbine ◽  
Low Pressure ◽  
Full Scale ◽  
Operating Conditions ◽  
Test Facility ◽  
Steam Turbines ◽  
Wide Range ◽  
The Family ◽  
Last Stage

New low pressure (LP), stages for variable speed, mechanical drive and geared power generation steam turbines have been developed. The new blade and nozzle designs can be applied to a wide range of turbine rotational speeds and last stage blade annulus areas, thus forming a family of low pressure stages—High Speed (HS) blades and nozzles. Different family members are exact scales of each other and the tip speeds of the corresponding blades within the family are identical. Thus the aeromechanical and aerodynamic characteristics of the individual stages within the family are identical as well. Last stage blades and nozzles have been developed concurrently with the three upstream stages, creating optimised, reusable low pressure turbine sections. These blades represent a step forward in improving speed, mass flow capability, reliability and aerodynamic efficiency of the low pressure stages for the industrial steam turbines. These four stages are designed as a system using the most modern design tools applied on Power Generation and Aircraft Engines turbo-machineries. The aerodynamic performance of the last three stage of the newly designed group will be verified in a full-scale test facility. The last stage blade construction incorporates a three hooks, axial entry dovetail with improved load carrying capability over other blade attachment methods. The next to the last stage blade also uses a three hooks axial entry dovetail, while the two front stage blades employ internal tangential entry dovetails. The last and next to the last stage blades utilize continuous tip coupling via implementation of integral snubber cover while a Z-lock integral cover is employed for the two upstream stages. Low dynamic strains at all operating conditions (off and on resonance speeds) will be validated via steam turbine testing at realistic steam conditions (steam flows, temperatures and pressures). Low load, high condenser pressure operation will also be verified using a three stage test turbine operated in the actual steam conditions as well. In addition, resonance speed margins of the four stages have been verified through full-scale wheel box tests in the vacuum spin cell, thus allowing the application of these stages to Power Generation applications. Stator blades are produced with a manufacturing technology, which combines full milling and electro-discharge machining. This process allows machining of the blades from an integral disc, and thus improving uniformity of the throat distribution. Accuracy of the throat distribution is also improved when compared to the assembled or welded stator blade technology. This paper will discuss the aerodynamic and aeromechanical design, development and testing program completed for this new low pressure stages family.

scholarly journals Natural Circulation Characteristics at Low-Pressure Conditions through PANDA Experiments and ATHLET Simulations

2008 ◽  
Vol 2008 ◽  
pp. 1-14 ◽  
Author(s):  
Domenico Paladino ◽  
Max Huggenberger ◽  
Frank Schäfer
Keyword(s):  
Numerical Simulations ◽  
Large Scale ◽  
Natural Circulation ◽  
Low Pressure ◽  
Operating Conditions ◽  
Quality Data ◽  
Experimental Investigations ◽  
Stability Performance ◽  
Wide Range ◽  
Circulation Characteristics

Natural circulation characteristics at low pressure/low power have been studied by performing experimental investigations and numerical simulations. The PANDA large-scale facility was used to provide valuable, high quality data on natural circulation characteristics as a function of several parameters and for a wide range of operating conditions. The new experimental data allow for testing and improving the capabilities of the thermal-hydraulic computer codes to be used for treating natural circulation loops in a range with increased attention. This paper presents a synthesis of a part of the results obtained within the EU-Project NACUSP “natural circulation and stability performance of boiling water reactors.” It does so by using the experimental results produced in PANDA and by showing some examples of numerical simulations performed with the thermal-hydraulic code ATHLET.

Turbulence Modeling and Computation of Viscous Transitional Flows for Low Pressure Turbines

1999 ◽  
Vol 121 (4) ◽  
pp. 824-833 ◽  
Author(s):  
A. Chernobrovkin ◽  
B. Lakshminarayana
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Turbulence Modeling ◽  
Turbulence Models ◽  
Separated Flow ◽  
Low Pressure ◽  
Reynolds Stress Model ◽  
Suction Surface ◽  
Transitional Flows ◽  
Wide Range

Variation of the flow Reynolds number between the take off and cruise conditions significantly affects the boundary layer development on low-pressure turbine blading. A decreased Reynolds number leads to the flow separation on the suction surface of the blading and increased losses. A numerical simulation has been carried out to assess the ability of a Navier-Stokes solver to predict transitional flows in a wide range of Reynolds numbers and inlet turbulence intensities. A number of turbulence models (including the Algebraic Reynolds Stress Model) and transition models have been employed to analyze the reliability and accuracy of the numerical simulation. A comparison between the prediction and the experimental data reveals good correlation. However, the analysis shows that the artificial dissipation in the numerical solver may have a profound effect on the prediction of the transition in a separated flow.

An Investigation of the Performance and Design of the Air Ejector Employing Low-Pressure Air as the Driving Fluid

1950 ◽  
Vol 162 (1) ◽  
pp. 149-166 ◽  
Author(s):  
L. J. Kastner ◽  
J. R. Spooner
Keyword(s):  
High Pressure ◽  
Pressure Ratio ◽  
Initial Pressure ◽  
Low Pressure ◽  
Operating Conditions ◽  
Major Influence ◽  
Engineering Practice ◽  
High Pressure Ratio ◽  
Wide Range ◽  
Air Ejector

The air ejector, in its various forms, is a device which has many applications in engineering practice, and several attempts have been made to analyse its mode of action, some of these having been supported by experimental work. Most of the experimental results available are related to ejectors in which relatively high-pressure steam is utilized as the driving fluid, but even in these cases the information provided is restricted to a narrow field. The investigation described relates to an air ejector employing as the driving fluid air at a relatively low pressure, not exceeding 40 lb. per sq. in. (abs.), and covering a wide range of operating conditions by means of interchangeable nozzles. Two distinct experimental arrangements were built—one for the set of conditions in which the ejector draws in a relatively small quantity of suction fluid and pumps it through a relatively high pressure-ratio, and the other covering conditions in which the quantity of suction fluid is much larger, but the pressure ratio is quite small. For a given initial pressure and quantity of driving fluid, the rate of mass flow of suction fluid depends chiefly on the diameter of the combining tube, in which the driving and suction fluids mix; in the experiments, the ratio of com-bining-tube area to driving-nozzle area was varied in twelve steps, covering a range of area ratios from 1·44 to 1,110·0, and compression ratios ranging from about 3 to about 1·001. Efforts were made to find the best proportions of those parts of the ejector which exert a major influence on performance, and certain conclusions are drawn from the results of the experiments. Theoretical aspects of the problem are briefly discussed.

scholarly journals Arsenic removal from drinking water using low-pressure nanofiltration under various operating conditions

2018 ◽  
Vol 13 (2) ◽  
pp. 295-302 ◽  
Author(s):  
M. Harfoush ◽  
S. A. Mirbagheri ◽  
M. Ehteshami ◽  
S. Nejati
Keyword(s):  
Drinking Water ◽  
Arsenic Removal ◽  
Arsenic Concentration ◽  
Inorganic Arsenic ◽  
Low Pressure ◽  
Operating Conditions ◽  
Polluted Water ◽  
Initial Concentration ◽  
Wide Range ◽  
Arsenite Removal

Abstract Currently, one of the main environmental concerns is the toxicity caused by arsenic. Arsenic-polluted water can cause many human health problems including various cancerous diseases. In natural water, inorganic arsenic can be found in the forms of arsenite and arsenate, which have been found in several Iranian provinces – e.g., East Azerbaijan, Kurdistan, and the city of Bijar – in high concentrations. Modern nanofiltration (NF) technology enables a wide range of water resource pollutants to be controlled efficiently. In this study, in an attempt to enhance arsenic removal (both arsenite and arsenate) from drinking water using low pressure NF, operating conditions like arsenic concentration, the trans-membrane pressure applied, and a range of different temperatures have all been considered. The highest arsenate removal achieved was 94% with an initial concentration of 500 μg/L, at 7 bar pressure, and 28 °C. The highest arsenite removal was 90%, with an initial concentration of 100 μg/L, at 5 bar pressure, and also at 28 °C. Increasing the pressure had a positive effect on the removal of both species, however, increasing the temperature had negative impacts. It was always found that arsenate removal was better than arsenite removal.

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