bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaporation of Volatile Liquid Pools Under Forced Convection: Part 2—Integration of a Vaporization Model in a CFD Software
Authors: Doué Nicolas , Loueslati Karim , Alonso Dominique , Genin Ghislain , Molière Michel 
Published: August 2013

The transfer under dynamic conditions of volatile species from a liquid pool to the surrounding air is gaining interest in the engineering community.
In particular, increasingly stringent regulations and standards apply to all types of flammable substances. This is especially the case in stationary gas turbine applications, where the vaporization of accidentally occurring pools of liquid fuels attracts increasing attention.
Since the flame-to-explosion transition cases are insufficiently controlled, the current, only practicable approach to assess the explosion risks arising from a fuel pool in an enclosure consists in quantifying the amount of vapor that leaves the pool and minimizing, by means of a proper dilution strategy, the potential damages entailed by the ignition of the resulting cloud. This approach requires two steps:
(1) The accurate assessment of vaporization rates under given ventilation conditions, a task that calls for skills in thermal and mass transfers.
(2) The reliable prediction of the transport of the vapors in the ventilation stream, a task specifically focused on fluid dynamics.
The three teams involved in this paper have joined their efforts to achieve this multidisciplinary objective. As a first task, the LRGP team (Laboratoire des Reactions et Génie des Procédés) and GE Energy have experimentally validated a vaporization model initially devised for water pools. This work has been reported in a recent paper. Concurrently, EURO/CFD and GE Energy have developed a CFD approach devoted to the mixing/dilution processes in defined enclosure geometries and under specified ventilation conditions. Finally both approaches havebeen coupled by EURO/CFD to produce predictive isopleth pictures of the vapor clouds generated under given temperature and velocity conditions.
The present paper covers the integration of the liquid pool vaporization model in thecommercial CFD software ANSYS Fluent and sets out the results obtained.
This dual, concerted approach is a first of the kind to the authors’ knowledge and proves fruitful for the prediction of the spatial distributions of the volatile species developed when a volatile pool vaporizes in a ventilated enclosure. It fills a gap in the analysis of safety scenarios arising from spillages of liquid fuels and provides a rational tool in zone classification studies.
Measurement of Thermal Contact Conductance of a Heat Shield for Gas Turbine Combustors in a Realistic Test Rig Set-Up
Authors: Facchini B. , Simonetti F. , Tarchi L. , Abram R. , Maritano M. 
Published: August 2013

This paper presents the results of the experimental campaign on the measurement of thermal contact conductance (TCC) in a realistic test rig replicating the contact between the ceramic heat shield and the liner for an ANSALDO Energia s.p.a. heavy-duty gas turbine. The designed test rig is made up of a single sector consisting of a combustor ceramic brick and a liner sector with a non-rigid ceramic fiber textile insulating layer in between, to better replicate the operating conditions of the combustor components.
The experimental campaign was carried out with a steady-state technique applying an uniform thermal load on the heat shield surface. The effect of brick-holders, that in the actual combustor anchor the bricks on the liner walls, was replicated with static loads.
The liner sector was tested without the brick-holder grooves first and afterwards their effect was assessed in the same test conditions; the test campaign also aimed at measuring the load cycling effect on TCC. Validation of the measured TCC was then performed with a finite element code to compare the predicted temperature profiles with the measured ones.
Leading Edge Shielding Concept in Gas Turbines With Can Combustors
Authors: Aslanidou Ioanna , Rosic Budimir , Kanjirakkad Vasudevan , Uchida Sumiu 
Published: August 2013

The remarkable developments in gas turbine materials and cooling technologies have allowed a steady increase in combustor outlet temperature and hence in gas turbine efficiency over the last half century. However, the efficiency benefits of higher gas temperature, even at the current levels, are significantly offset by the increased losses associated with the required cooling. Additionally, the advancements in gas turbine cooling technology have introduced considerable complexities into turbine design and manufacture. Therefore, a reduction in coolant requirements for the current gas temperature levels is one possible way for gas turbine designers to achieve even higher efficiency levels.
The leading edges of the first turbine vane row are exposed to high heat loads. The high coolant requirements and geometry constraints limit the possible arrangement of the multiple rows of film cooling holes in the so called showerhead region. In the past, investigators have tested many different showerhead configurations, varying the number of rows, inclination angle and shape of the cooling holes. However the current leading edge cooling strategies using showerheads have not been shown to allow further increase in turbine temperature without excessive use of coolant air. Therefore new cooling strategies for the first vane have to be explored.
In gas turbines with multiple combustor chambers around the annulus, the transition duct walls can be used to shield, i.e. to protect the first vane leading edges from the high heat loads. In this way the stagnation region at the leading edge and the shower-head of film cooling holes can be completely removed, resulting in a significant reduction in the total amount of cooling air that is otherwise required. By eliminating the showerhead the shielding concept significantly simplifies the design and lowers the manufacturing costs.
This paper numerically analyses the potential of the leading edge shielding concept for cooling air reduction. The vane shape was modified to allow for the implementation of the concept and non-restrictive relative movement between the combustor and the vane. It has been demonstrated that the coolant flow that was originally used for cooling the combustor wall trailing edge and a fraction of the coolant air used for the vane showerhead cooling can be used to effectively cool both the suction and the pressure surfaces of the vane.
Prediction of De-Swirled Radial Inflow in Rotating Cavities With Hysteresis
Authors: May David , Chew John W. , Scanlon Timothy J. 
Published: August 2013

De-swirl nozzles are sometimes used in turbomachinery to reduce the pressure drop when air is drawn radially inwards through a rotating cavity. However, this can lead to non-unique steady state solutions with operating conditions achieved depending on how the steady point is approached. In the present study, a transient, 1D model of flow in a rotating cavity has been created. The model allows the vortex profile to change with through flow rate, and links this to estimates of disk windage, tangential velocity and, consequently, the vortex pressure gradient. The model was applied to the simulation of de-swirl nozzle fed, rotating cavities with radial inflow. The steady vortex flow characteristics (non-dimensional flow versus pressure ratio) predicted by the model were validated for 2 distinct cases. For a smooth rectangular cavity the flow characteristic was predicted using the model’s default parameters. For an engine-representative case with non-axisymmetric geometric features, the flow characteristic of the cavity was reproduced with some alignment of the model.
The transient model reproduced experimentally observed hysteresis, discontinuity in operating characteristics, and regions where no steady-state solution could be found. A transient model is required as a steady state model would choose one of the possible solutions without physical justification. In the case of the engine-representative rig, part of the flow characteristic could not be obtained in testing. This is determined to be due to the interaction of the negative resistance region of the vortex and the flow modulating valve characteristic. Measures that allow the full capture of the flow characteristic in rig testing are identified.
Experimental Investigation Into Thermal Behaviour of Steam Turbine Components: Part 1—Temperature Measurements With Optical Probes
Authors: Mohr W. F. , Ruffino P. 
Published: August 2013

The first-in-time application of intensity pyrometry to measure in-situ the hot rotor surface temperature of a standard, combined cycle, intermediate pressure steam turbine is presented. The data cover a cold-start and cooling from base load. The pyrometric temperatures are compared to standard temperature measurements on static turbine parts and an upstream steam temperature measured on a thermo well.
It is reported, how the applicability of pyrometry in steam turbines was assessed. Details are given about a newly developed USC autoclave, which was used to measure steam transmittance, and about the measurement of the emissivity of the rotor metal.
Further the steps taken towards a steam-pyrometer are shown; how it was developed, validated in terms of its precision and lifetime in hot steam environment, and how its integration to a standard turbine was prepared.
Experimental Investigation Into Thermal Behavior of Steam Turbine Components: Part 2—Natural Cooling of Steam Turbines and the Impact on LCF Life
Authors: Marinescu Gabriel , Ehrsam Andreas 
Published: August 2013

Steam turbine cool-down has a significant impact on the cyclic fatigue life. A lower initial metal temperature after standstill results in a higher temperature difference to be overcome during the next start-up. Generally, lower initial metal temperatures result in higher start-up stress. In order to optimize steam turbines for cyclic operation, it is essential to fully understand natural cooling, which is especially challenging for rotors.
A two-dimensional numerical procedure is described for the assessment of the thermal regime during natural cooling including the rotors, casings, valves and main pipes. The concept of the cooling calculation is to replace the steam gross buoyancy during the gland steam ingestion phase by an equivalent fluid conductivity, that gives the same thermal effect on the metal parts. The fluid equivalent conductivity is calculated based on measurements. The approach is calibrated with experimental data. Finally, the highly sensitive nature of the cyclic lifetime to the predicted cooling evolution is demonstrated. This paper is complementary with the paper [1].
Measurement Versus Predictions of Rotordynamic Coefficients of a Hole-Pattern Gas Seal With Negative Preswirl
Authors: Brown Philip D. , Childs Dara W. 
Published: August 2013

Test results are presented for rotordynamic coefficients of a hole-pattern annular gas seals at supply pressures to 84 bar and running speeds to 20,200 RPM. The principal test variable of interest was negative preswirl. Preswirl signifies the circumferential fluid flow entering a seal, and negative preswirl indicates a fluid swirl in a direction opposite to rotor rotation. The influences of pressure ratio and rotor speed were also investigated. Measured results produce direct and cross-coupled stiffness and damping coefficients that are a function of excitation frequency Ω.
Changes in pressure ratio had only small effects on most rotordynamic coefficients. Cross-coupled stiffness showed slightly different profiles through the mid-range of Ω values.
Increasing rotor speed significantly increased cross-coupled stiffness and cross-coupled damping. At 10,200 RPM, high negative inlet preswirl produced negative cross-coupled stiffness over an excitation frequency range of 200–250 Hz. Negative preswirl did not affect direct stiffness and damping coefficients.
Effective damping combines the stabilizing effect of direct damping and the destabilizing effect of cross-coupled stiffness. The cross-over frequency is the precession frequency where effective damping transitions from a negative value to a positive value with increasing frequency. At 20,200 RPM with a pressure ratio of 50%, peak effective damping was increased by 50%, and the cross-over frequency was reduced by 50% for high-negative preswirl versus zero preswirl. Hence, reverse swirl can greatly enhance the stabilizing capacity of hole-pattern balance-piston or division-wall seals for compressors.
A two-control-volume model that uses the ideal gas law at constant temperature was used to predict rotordynamic coefficients. The model predicted direct rotordynamic coefficients well, but substantially under predicted cross-coupled rotordynamic coefficients especially at high negative preswirls.
Numerical Study of Transitional Rough Wall Boundary Layer
Authors: Elsner Witold , Warzecha Piotr 
Published: August 2013

The paper presents the verification of boundary layer modeling approach, which relies on a γ-Reθt model proposed by Menter et al. [1]. This model was extended by laminar-turbulent transition correlations proposed by Piotrowski et al. [2] as well as Stripf et al. [3] correlations, which take into account the effects of surface roughness. To blend between the laminar and fully turbulent boundary layer over rough wall the modified intermittency equation is used.
To verify the model a flat plate with zero and non-zero pressure gradients test cases as well as the high pressure turbine blade case were chosen. Further on, the model was applied for unsteady calculations of turbine blade profile as well as the Lou and Hourmouziadis [4] flat plate test case, with induced pressure profile typical for suction side of highly-loaded turbine airfoil. The combined effect of roughness and wake passing were studied.
The studies proved that the proposed modeling approach (ITMR hereinafter) appeared to be sufficiently precise and enabled for a qualitatively correct prediction of the boundary layer development for the tested simple flow configurations. The results of unsteady calculations indicated that the combined impact of wakes and the surface roughness could be beneficial for the efficiency of the blade rows, but mainly in the case of strong separation occurring on highly-loaded blade profiles. It was also demonstrated that the roughness hardly influences the location of wake induced transition, but has an impact on the flow in between the wakes.
Disk Heat Transfer Analysis in a Heated Rotating Cavity With an Axial Throughflow
Authors: Tian Shuqing , Zhu Yatao 
Published: August 2013

In the rotating disk cavities of aero-engine compressors, buoyancy-induced flow and heat transfer can occur due to thermal gradients between cooling air and hot surfaces. The simplified rotating cavity with two plane discs, a shaft and a cylindrical rim has been investigated numerically and compared with the available measurements. Two models have been solved using a commercial CFD code, Fluent, with the RNG k-ε turbulence model. The first one is the conventional model with only fluid region solved, a temperature profile with the linear radial gradient imposed at the disk walls, and an isothermal boundary condition imposed at the shroud wall. The second one is the model with thick-walled disks and shroud, an adiabatic boundary condition imposed at the outer walls of the disks, and an isothermal boundary condition imposed at the outer wall of the shroud. The fluid and solid are coupled solved simultaneously. The disk temperatures are computed.
In the present work, the numerical results are in reasonable agreement with the measurements. The computed disk temperatures in the second model have approximately linear radial gradients over the first three-quarters of the disks, and in the last quarter of the disks the temperature radial gradients are obviously non-linear. The different disk temperature profiles in these two models do not lead to obviously different disk heat transfers.
The heat transfer in the rotating cavity leads to a considerable temperature increase of the cavity core fluid, therefore a corresponding increase of the outlet temperature. These two temperature increases are critical for the cooling design in aero-engines.
Cooling Effectiveness of Impingement/Effusion Cooling With and Without Turbulence Promoter Ribs
Authors: Yang Qian , Lin Yuzhen , Xu Quanhong , Zhang Chi , Sung Chih-Jen 
Published: August 2013

In order to solve the cooling problem of aeroengine, a variety of highly efficient cooling methods came into application, such as effusion wall, impingement/effusion wall, etc. The impingement/effusion cooling methods with and without turbulence promoter ribs are introduced here. In the impingement/promoter ribs/effusion walls, turbulence promoter ribs are on the coolant side of effusion wall so as to enhance the internal cooling.
Numerical and experimental approaches were taken to study cooling effectiveness of impingement/effusion liners cooling with and without turbulence promoter ribs. Cooling effectiveness of the two types cooling configurations were investigated on the same hot and cold air condition of inlet. Infrared camera was used to measure the temperature of effusion cooled surfaces on the side of hot main stream. The results showed double wall cooling with turbulence promoter ribs achieves higher cooling effectiveness than impingement/effusion cooling configurations.
In addition, the two test configurations were investigated numerically to get clearer characterization of flow field in the double walls cooling configurations. High velocity vectors were found in the flow field within the gap of the double walls. A heat transfer enhancement was resulted in complex flows and increased area caused by the inclined holes and turbulence promoter ribs.
Windage Measurements in a Rotor Stator Cavity With Rotor Mounted Protrusions and Bolts
Authors: Long C. A. , Miles A. L. , Coren D. D. 
Published: August 2013

This paper reports an experimental investigation of the windage associated with enclosed rotor-stator systems with superposed throughflow, as commonly found in gas turbine engines. The term windage is often used to describe the viscous heating that arises from the interaction of surfaces and fluids in rotating disc systems. Since the presence of circumferentially discreet geometric features strongly alters the magnitude of Windage measured, the physical mechanisms collectively referred to as windage in this paper are separately described as part of the discussion of results.
Tests have been carried out to measure windage directly in the form of shaft torque and also rotor surface temperature. Non-dimensional flow parameters are used to expand the relevance of the data obtained, which encompasses the ranges 0.17 × 107 ≤ Reφ ≤ 1.68 × 107 and 0.24 × 105 ≤ Cw ≤ 1.06 × 105 which corresponds to 0.058 ≤ λT ≤ 0.631. Data has been obtained for smooth disc geometry and also with rotor mounted protrusions of N = 3, 9 and 18; D = 10 mm, 13 mm and 16 mm diameter; H = 11 mm, high, hexagonal bolt shaped protrusions. Bi-hexagonal (twelve sided) bolts of D = 13 mm effective diameter, and height, H = 11 mm, were also tested with conditions closely matched to the 13 mm hexagonal bolts. Finally, tests with 10 mm diameter, 6 mm deep, pockets were also carried out.
Over the range of conditions and geometries tested, increasing the number of bolts increases the moment coefficient and windage heating. At low values of turbulent flow parameter, λT, which correspond to rotational speeds between 8000 and 10000 rev/min, increasing the diameter of the bolts shows a clear trend for both increased windage torque and average disc temperature rise. For these conditions, there also appears to be a clear reduction in windage and temperature rise with the bi-hexagonal shaped bolts compared to the equivalent diameter hexagonal bolt form. Variation in the moment coefficient with the number and diameter of bolts is attributed to variations in form drag between the different configurations. The introduction of the recesses onto the disc has very little effect on either windage heating or moment coefficient; this is attributed to the component of windage mechanism in operation and also the relatively small size in comparison to the protrusions studied here.
This work contributes to the understanding of windage in gas turbines by introducing new low uncertainty data obtained at engine representative conditions and as such is of benefit to those involved with the design of internal air systems and disc fixtures.
Numerical Investigation on the Influence of the Fillet on Film Cooling Rotor Blades in Heavy Duty Gas Turbines With an Object-Oriented CFD Code
Authors: Mangani Luca , Launchbury David Roos , Casartelli Ernesto , Maritano Massimiliano 
Published: August 2013

The present paper examines the numerical simulation of the effects of film wall cooling on rotor blades in a high-pressure-ratio axial turbine. Special attention is given to the differently shaped geometries of the fillet at the blade endwall and their influence on secondary flows, since the fillet is often neglected in CFD calculations in order to minimize the effort in grid generation.
Simulations were conducted using both sharp and radius edge fillet configurations to investigate the effects on film cooling and secondary flows. For this purpose all simulations were performed using a modified in-house 3D RANS solver based on an object-oriented open-source library. The results were compared against experimental measurements in terms of local quantities such as aerodynamic losses and adiabatic effectiveness.
Conjugate Heat Transfer Calculations on GT Rotor Blade for Industrial Applications: Part I—Equivalent Internal Fluid Network Setup and Procedure Description
Authors: Bonini A. , Andreini A. , Carcasci C. , Facchini B. , Ciani A. , Innocenti L. 
Published: August 2013

Gas turbine design has been characterized over the years by a continuous increase of the maximum cycle temperature, justified by a corresponding increase of cycle efficiency and power output. In such way turbine components heat load management has become a compulsory activity and then, a reliable procedure to evaluate the blades and vanes metal temperatures, is, nowadays, a crucial aspect for a safe components design. This two part work presents a three-dimensional conjugate heat transfer procedure developed in the framework of an internal research project of GE Oil & Gas.
The procedure, applied to the first rotor blade of the MS5002E gas turbine, consists of a conjugate heat transfer analysis in which the internal cooling system was modeled by an in-house one dimensional thermo-fluid network solver, the external heat loads and pressure distribution have been evaluated through 3D CFD and the heat conduction in the solid is carried out through a 3D FEM solution.
The first part of this work is focused on the description of the procedures in terms of set up of the equivalent fluid network model of internal cooling system and its tuning through experimental measurements of blade flow function. A first computation of blade metal temperature was obtained by coupling with CFD computations carried out on a de-featured geometry of the blade. Achieved results are compared with the data of a metallographic analysis performed on a blade operated on an actual engine. Some discrepancies are observed between datasets, suggesting the necessity to improve the models, mainly from the CFD side.