bluuebunny/crossref_metadata_2025_split huggingface dataset:
Application of the Wilshire Stress-Rupture and Minimum-Creep-Strain-Rate Prediction Models for Alloy P91 in Tube, Plate and Pipe Form
Authors: Cano Jaime A. , Stewart Calvin M. 
Published: November 2019

Abstract
There exists a challenge in predicting the long-term creep of materials (3 105 hours) where 11+ years of continuous testing is required to physically collect creep data. As an alternative to physical testing, constitutive models are calibrated to short-term data (< 104 hours) and employed to extrapolate the long-term creep behavior. The Wilshire model was introduced to predict the stress-rupture and minimum-creep-strain-rate behavior of materials and the model is well-accepted due to the explicit description of stress- and temperature-dependence allowing predictions across isotherms and stress levels. There is an ongoing effort to determine how alloy form affects the long-term creep predictions of the Wilshire model. In this study, stress-rupture and minimum-creep-strain-rate predictions are generated for alloy P91 in tube, plate, and pipe form. Data is gathered from the National Institute of Materials Science (NIMS) material database for alloy P91 at multiple isotherms. Following the establish calibration method for the Wilshire model, post-audit validation is performed using short-term data from NIMS to vet the extrapolations accuracy of each form at different isotherms. The Wilshire model demonstrates successful extrapolative techniques for the stress-rupture and minimum-creep-strain-rate of tube, plate, and pipe forms across multiple isotherms. Overall the form with the highest extrapolative accuracy for both stress-rupture and minimum-creep-strain-rate is the plate and the lowest one is the pipe. Stress-rupture design maps are provided where stress and temperature are axes and rupture-time is in contour. The design maps can be applied to: (a) given the boundary conditions, determine the design life (b) given the design life, determine the acceptable range of a boundary conditions. The latter is more useful in turbomachinery design.
Analysis of Statistical Characteristics and Global Sensitivity for Forced Response of Bladed Disks Mistuned by Material Anisotropy
Authors: Rajasekharan Rahul , Petrov E. P. 
Published: November 2019

Abstract
High-pressure turbines of modern gas-turbine engines use single crystal blades that exhibit material anisotropy. Due to manufacturing tolerances, each blade in the bladed disk will have different crystal anisotropy axis orientation, thereby creating mistuning in the structure. In this paper, the blade anisotropy angles are considered as uncertain design parameters to study the variation in forced response of a mistuned bladed disk. For realistic, high fidelity model of a bladed disk, linear bonded contact conditions at blade roots and shrouds are considered. The following two kinds of analysis are performed: (a) statistical analysis using polynomial chaos expansion and (b) global sensitivity analysis using Sobol indices. An effective strategy based on gradient information is used to minimize the computational cost involved in statistical and sensitivity analysis. For the first time, the possibility of introducing intentional blade material anisotropy mistuning to reduce the amplification of forced response is investigated.
Numerical Simulation and Design Optimization of an Electrical Submersible Power Recovery Turbine
Authors: Rutter Risa , Hepp Tony , McManus David 
Published: November 2019

Abstract
In oilfield applications, an Electrical Submersible Pump (ESP) comprised of centrifugal pump, seal, and motor is placed inside a well to provide energy to lift reservoir fluids from the formation to the surface when the reservoir’s natural lift energy is insufficient. The use of an ESP as an Electrical Submersible Power Recovery Turbine (ESPRT) is the focus of this paper. As fluid is injected from the well surface to the pump discharge, through the pump stages, and out the pump intake, the ESPRT shaft rotates in reverse (counterclockwise from an uphole vantage point), compared to an ESP shaft. The moving fluid in the stages transmits energy to the impellers, which turns the motor shaft; the induction motor thereby becomes a generator. We simulated and optimized the performance of a conventional ESP stage using Computational Fluid Dynamics (CFD) and single-phase water.
Before any laboratory or field testing, we simulated ESPRT performance at various speeds and flow rates to predict the performance of the turbine. The CFD prediction of the turbine follows the performance in the third quadrant of a typical four-quadrant pump curve. During the pre-field test CFD study, we did not attempt to predict the stage thrust. Later field trial results, however, showed the impellers operated in up thrust due to fluid flow through the turbine stages producing an upward reaction force on the impellers. We used the field test results to improve the CFD model and, afterwards, the stage design in order to reduce up thrust. The turbine, and pump upon which it is based, are designed to operate in down thrust.
We investigated the effects of changing the diameter of the impeller balance holes and impeller-to-diffuser clearance at the impeller’s skirt and balance ring. Through several CFD iterations, we identified the optimum balance hole and clearance sizes; decreasing the size of the former feature and increasing the latter feature moved the impeller into the down thrust regime. Neither change reduced the stage head and corresponding power output.
Effect of Blade Secular Change on Unsteady Flows in Middle Pressure First-Stage Steam Turbines
Authors: Uemura Akihiro , Miyazawa Hironori , Furusawa Takashi , Yamamoto Satoru , Yonezawa Koichi , Umezawa Shuichi 
Published: November 2019

Abstract
This paper presents the effect of blade secular changes in stator and rotor blade passages on unsteady flows through the first-stage in a middle pressure steam turbine. The scales from the boilers may collide with the stator and rotor blade surfaces, and the blades could become gradually thinned or adhered over time because of the collision. The secular-changed blades influence the performance of steam turbines and may further induce unexpected accidents. Therefore, the maintenance, repair, and overhaul (MRO) of steam turbines is essential. The optimization of MRO scheduling is quite crucial for electric power companies. We simulated unsteady steam flows through an actual middle pressure steam turbine working at a coal-fired power plant while setting manufactured and secular-changed blades. The shape of the secular-changed blades was measured from actual blades during overhaul. The numerical method developed at Tohoku University was employed for the simulation. The difference in the results between the manufactured and secular-changed blades is shown, and the effect of secular changes on unsteady flows is investigated. In addition, the possibility of utilizing the results in the MRO of real turbines is highlighted.
Experimental Study on Analogy Principle of Overall Cooling Effectiveness for Composite Cooling Structures With Both Internal Cooling and Film Cooling
Authors: Xie Gang , Liu Cun-liang , Wang Rui , Ye Lin , Niu Jiajia 
Published: November 2019

Abstract
The previous theoretical work showed the matching principles of analogy parameters for effusion-impingement cooling model. The mismatch of temperature ratios Tg/Tc may result in different matching performance in laboratory condition. Thus, the analogy principles of overall cooling effectiveness were evaluated by experiments in different laboratory conditions for effusion-impingement cooling model. The film plate had 8 rows of cylinder film holes with staggered arrangement and the impingement holes was also employed staggered pattern. Four kinds of cases with different temperature ratios, varied from 1.1 to 2, were tested under three momentum flux ratios and corresponding blowing ratios. The 2D contours of overall cooling effectiveness were measured by using IR thermography. The results for cases with the same mainstream side Biot number and momentum flux ratio show similar contours and values of overall cooling effectiveness, although temperature ratios of these cases are different. And the maximum deviation of overall cooling effectiveness is within 0.02 for these cases. However, there were 0.04∼0.08 difference in the overall cooling effectiveness when the blowing ratios were matched. The overall cooling effectiveness significantly decreases under each blowing ratios with the increase of temperature ratios.
Predictions of Impingement Heat Transfer With Dimples, Pin-Fins and Zig-Zag Rib Obstacles: Conjugate Heat Transfer Computational Fluid Dynamics Predictions
Authors: El-Jummah Abubakar M. , Andrews Gordon E. , Staggs John E. J. 
Published: November 2019

Abstract
Regenerative cooling of low NOx gas turbine combustors was investigated using impingement heat transfer with all the combustion air used for wall cooling prior to passing to the flame stabiliser. 10 rows of impingement holes were modelled. Three obstacles were compared with smooth wall impingement heat transfer. The CHT/CFD methodology used was that validated against experimental results in previous publications of the authors. The impingement heat transfer enhancement geometries investigated were circular pin-fins, dimples and zig-zag ribs, which were aligned transverse to the direction of the cross-flow on the impingement target surface. The obstacles were equally spaced on the centre-line between each row of impingement jets transverse to the cross-flow. One heat transfer enhancement obstacle was used per impingement jet air hole. The CFD calculations were carried out for an air mass flux G of 1.08, 1.48 and 1.94 kg/sm2bara, which are the high flow rates used for regenerative combustor wall cooling. Comparison of the current CFD predictions and previous CFD work, that have experimental data, were made for the flow pressure loss and the surface and locally X2 average HTC, h. It was concluded that none of the obstacles in the impingement gap a significant increase in the surface averaged heat transfer coefficient (HTC). The impact of the obstacles was to increase the flow maldistribution due to the increased pressure loss. This resulted is less heat transfer from the reduced air mass flow in the first 4 holes and increased heat transfer in the last 4 holes, relative to the smooth wall results. The main effect of the obstacles was to increase the heat transfer to the impingement jet surface. The dimpled surface was predicted to have a very poor performance, with significantly reduced impingement heat transfer. This was due to the impingement jets being deflected away from the target surface by the shape of the dimples and this reduced the surface heat transfer.
High Amplitude Combustion Instabilities in an Annular Combustor Inducing Pressure Field Deformation and Flame Blow-Off
Authors: Vignat Guillaume , Durox Daniel , Renaud Antoine , Candel Sébastien 
Published: November 2019

Abstract
This article reports experiments carried out in the laboratory scale annular combustor MICCA-Spray equipped with multiple swirling spray injectors. The experimental setup consists in an air plenum connected to a combustion chamber formed by two concentric cylindrical quartz tubes, allowing full optical access to the flames. A new injection system is introduced and characterized. For a wide range of operating conditions, strong combustion instabilities are observed, but the focus of this article is placed on very high amplitude combustion instabilities coupled by a standing azimuthal mode. It is found that the frequency decreases as the amplitude of the thermoacoustic oscillation grows. New results are obtained using a higher order reconstruction method for the pressure field: its shape is shown to be modified during high amplitude oscillation, leading to asymmetries of the pressure distribution in the system. Flame blow-off occurs near the pressure nodal line when a critical level of oscillation is reached. A method is proposed to reconstruct the acoustic velocity field just before blow-off occurs. Both the velocity field and the blow-off pattern are skewed. The effect of flame blow-off on the frequency of the oscillation is discussed, and it is shown that it leads to the distortion of the pressure field. A new result is also that the phase of the flame response to acoustic perturbation can vary among flames on the same side of the nodal line.
Steam Injected Gas Turbine (STIG) for Load Flexible CHP: Aspects of Dynamic Behaviour, Control and Water Recovery
Authors: Lutsch Thorsten , Gampe Uwe , Buchheim Guntram 
Published: November 2019

Abstract
Industrial combined heat and power (CHP) plants are often faced with highly variable demand of heat and power. Demand fluctuations up to 50% of nominal load are not uncommonly. The cost and revenue situation in the energy market represents a challenge, also for cogeneration of heat and power (CHP). More frequent and rapid load changes and a wide operating range are required for economic operation of industrial power plants.
Maintaining pressure in steam network is commonly done directly by a condensation steam turbine in a combined cycle or indirectly by load changes of the gas turbine in a gas turbine and heat recovery steam generator arrangement. Both result in a change of the electric output of the plant. However, operating cost of a steam turbine are higher than a single gas turbine.
The steam injected gas turbine (STIG) cycle with water recovery is a beneficial alternative. It provides an equivalent degree of freedom of power and heat generation. High process efficiency is achieved over a wide operating range. Although STIG is a proven technology, it is not yet widespread.
The emphasis of this paper is placed on modeling the system behavior, process control and experiences in water recovery. A dynamic simulation model, based on OpenModelica, has been developed. It provides relevant information on system response for fluctuating steam injection and helps to optimize instrumentation and control. Considerable experience has been gained on water recovery with respect to condensate quality, optimum water treatment architecture and water recovery rate, which is also presented.
Asymptotic Description of Forced Response Vibration Saturation by Friction Forces
Authors: Martel Carlos , Martín Juan A. 
Published: November 2019

Abstract
The estimation of the final vibration amplitude of a turbomachinery bladed disk is of extreme practical importance; it is an essential information for the prediction of the level of high cycle fatigue of the blades, and for the subsequent estimation of its operative life span. The forced response vibration is saturated by the nonlinear damping introduced by the friction forces at the interfaces between blade and disk (and/or at the included dampers). The computation of the final amplitude of the limit cycle oscillation requires to solve a quite complicated nonlinear problem. In the case of a tuned bladed disk, this problem can be reduced to a single sector calculation with phase lag boundary conditions. The solution of this one-sector problem requires to consider many harmonics in order to capture the details of the nonlinear time periodic oscillation that sets in. If the small unavoidable differences among blades (mistuning) are also taken into account, then the situation becomes even more complicated because the solution of the mistuned vibration problem requires to consider not only a single sector but the complete bladed disk. The possibility of applying multiple scales techniques to drastically simplify this problem is explored in this paper. The idea is to exploit the fact that all relevant effects present (forcing, nonlinear friction, and mistuning) are, in most practical situations, small effects that develop in a time scale that is much longer than that associated with the natural elastic vibration frequency of the tuned system. A mass-spring model with microslip nonlinear friction is used to represent the forced bladed disk. The multiple scales method is used to asymptotically derive simplified models for both tuned and mistuned configurations. The results of the asymptotic model are compared with those from the mass-spring system, and used to analyze the particular characteristics of the nonlinear friction effects on the final vibration states.
Numerical Investigation on the Effect of Rotation and Holes Arrangement in Cold Bridge Type Impingement Cooling Systems
Authors: Paccati S. , Cocchi L. , Mazzei L. , Andreini A. 
Published: November 2019

Abstract
This work presents the results of a numerical analysis performed on a gas turbine leading edge cooling system. The investigation was carried out in order to provide a detailed interpretation of the outcomes of a parallel experimental campaign. The cooling geometry consists of a cold bridge type impingement system: a radial channel feeds an array of holes, which in turn generate impingement jets cooling down the inner side of the leading edge surface. Coolant is extracted by five rows of holes, replicating film cooling and showerhead systems. Two impingement geometries were considered, presenting different holes arrangements and diameters but sharing the same overall passage area, in order to highlight the effect of different coolant distributions inside the leading edge cavity.
For both geometries a single test point was investigated in static and rotating conditions, with an equivalent slot Reynolds number of around 8200 and feeding conditions corresponding to the midspan radial section of the blade. Both steady RANS approach and Scale Adaptive Simulation (SAS) were tested. Due to the strong unsteadiness of the flow field, the latter proved to be superior: as a consequence, SAS approach was adopted to study every case. A fairly good agreement was observed between the measured and computed heat transfer distributions, which allowed to exploit the numerical results to get a detailed description of the phenomena associated with the different cases.
Results reveal that the two holes arrangements lead to strongly different heat transfer patterns, related to the specific flow phenomena occurring inside the leading edge cavity and to the mutual influence of the various system features. Rotational effects also appear to interact with the supply condition, altering the jet lateral spreading and the overall heat transfer performance.
Reduced Order Models for Nonlinear Dynamic Analysis With Application to a Fan Blade
Authors: Balmaseda Mikel , Jacquet-Richardet G. , Placzek A. , Tran D.-M. 
Published: November 2019

Abstract
In the present work reduced order models (ROM) that are independent from the full order finite element models (FOM) considering geometrical non linearities are developed and applied to the dynamic study of a fan. The structure is considered to present nonlinear vibrations around the pre-stressed equilibrium induced by rotation enhancing the classical linearised approach. The reduced nonlinear forces are represented by a polynomial expansion obtained by the Stiffness Evaluation Procedure (STEP) and then corrected by means of a Proper Orthogonal Decomposition (POD) that filters the full order nonlinear forces (StepC ROM). The Linear Normal Modes (LNM) and Craig-Bampton (C-B) type reduced basis are considered here. The latter are parametrised with respect to the rotating velocity. The periodic solutions obtained with the StepC ROM are in good agreement with the solutions of the FOM and are more accurate than the linearised ROM solutions and the STEP ROM. The proposed StepC ROM provides the best compromise between accuracy and time consumption of the ROM.
Modeling of CO Emissions in Multi-Burner Systems With Fuel Staging
Authors: Klarmann Noah , Zoller Benjamin Timo , Sattelmayer Thomas 
Published: November 2019

Abstract
This work presents a novel strategy to numerically predict CO emissions in gas turbines that operate under part-load conditions employing fuel-staging concepts. In multi-burner systems, fuel can be redistributed to solely run a fraction of the available burners. The situation of active burners interacting with air from adjacent cold burners may lead to quenching effects. Our group recently published a flamelet-based combustion model for low-reactive conditions. Furthermore, a model was proposed for the prediction of CO beyond the assumption of thin reaction zones. These models are adopted in this work and further extended in order to capture quenching. All models are implemented and applied to a simple geometry for the purpose of demonstrating basic mechanisms that are relevant for fuel-staged gas turbines operating at part load conditions. Furthermore, validation is performed in a silo combustor that comprises 37 burners. Here, burner groups are switched off during part load, leading to intense interaction between hot and cold burners. Major improvement in comparison to CO predictions from the flamelet-based combustion model is achieved. It is demonstrated that the model is able to predict the correct values of global CO emissions. Furthermore, the models capacity of handling fuel-staging mechanisms like the CO drop during a burner switch-off event is shown.
Experimental and Computational Methods for the Evaluation of Double-Wall, Effusion Cooling Systems
Authors: Murray Alexander V. , Ireland Peter T. , Romero Eduardo 
Published: November 2019

Abstract
Further improvements in gas turbine efficiency can be sought through more advanced cooling systems — such as the double-wall, effusion system — which provide high cooling effectiveness with low coolant utilisation. The double-wall system, as described here, comprises two walls, one with a regular array of impingement holes, the other with a closely-packed, regular array of film holes (characteristic of effusion systems). These walls are mechanically and thermally connected to one another via a bank of pedestals which increase coolant wetted area and turbulent flow features. However, a lack of data exists in the open literature on these systems.
This study presents a novel experimental heat transfer facility designed with the intent of investigating flat plate versions of such double-wall geometries. Key features of the facility are presented including the use of recirculation to increase mainstream-to-coolant temperature ratio and the use of infrared thermography to obtain thermal measurements. Some rig commissioning characteristics are also provided which demonstrate well-conditioned, uniform flow. Both coolant and mainstream Reynolds numbers are matched to engine conditions, with Biot number within around 15% of engine conditions.
The facility is used to assess the cooling performance of four double-wall effusion geometries which incorporate various geometrical features. Both overall effectiveness and film effectiveness measurements are presented at a range of coolant mass flows with conclusions drawn as to preferable features from a cooling perspective. The results from a fully conjugate CFD model of the facility are presented which utilised boundary conditions obtained during experimental runs. Additionally, a computationally efficient decoupled conjugate method developed previously by the authors was adapted to assess the experimental geometries with the results comparing favourably.