bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transfer Function Modeling and Experimental Variation of Rotor System Considering Morton Effect Caused in Journal Bearing
Authors: Yabui Shota , Chiba Jotaro , Suzuki Takafumi , Tomimatsu Shigeyuki , Inoue Tsuyoshi 
Published: November 2019

Abstract
In recent years, a rotating machinery are required to operate at high rotational speed for high efficiency. However, the rotating machinery may become unstable due to the increase of rotational speed. One cause of unstable vibration is the Morton Effect generated in a journal bearing. To avoid unstable vibration due to the Morton Effect, construction of a mathematical model for predicting it becomes an important subject. Many researches on the Morton Effect have been conducted previously. Conventional researches are mostly divided into two types. The first one is a study based on detailed numerical simulation using computational fluid dynamics (CFD), thermoshydrodynamics (THD) and so on. It tries to find solution of a differential equation which indicates the Morton Effect induced vibration for a specific machine or a test rig. Therefore, this approach has led not comprehensive model. The other one is a study expressed by a simple mathematical formula. However, modeling in the time domain has been mainly focused and modeling in the frequency domain has not been investigated in detail. In this research, a model based on the frequency response that can quantitatively evaluate the Morton Effect induced vibration in the rotating machinery supported by the journal bearing is developed. First, experimental data was collected for modeling by using an experimental rig. Using these experimental data of journal position in the journal bearing and temperature of journal, a model of the Morton Effect was constructed based on frequency responses. In the proposed method, the characteristic of the journal bearing was considered as a proportional differential controller from control engineering point of view. In addition, the proposed model considers the Morton Effect induced vibration as a new bending mode of a rotating shaft caused by thermal difference. Then, the developed model of the Morton Effect was evaluated in the frequency domain. The characteristics of vibration calculated by the proposed model indicated good correlation with that of the experimental data. Finally, the behavior of the rotating shaft at another rotational speed was predicted by using the proposed model. It was confirmed that the experimental data well agreed with the predicted results. These results show the usefulness of the proposed method of this research for predicting the Morton Effect.
Model-Based Analysis of the Start-Up Improvement of a CCPP due to Steam Turbine Warm-Keeping With Air
Authors: Toebben Dennis , Burgard Tobias , Berg Sebastian , Wirsum Manfred , Pei Liu , Zheng Li , Mohr Wolfgang F. D. , Helbig Klaus 
Published: November 2019

Abstract
Combined cycle power plants (CCPP) have many advantages compared to other fossil power plants: high efficiency, flexible operation, compact design, high potential for combined heat and power (CHP) applications and fewer emissions. However, fuel costs are relatively high compared to coal. Nevertheless, major qualities such as high operation flexibility and low emissions distinctly increase in relevance in the future, due to rising power generation from renewable energy sources.
An accelerated start-up procedure of CCPPs increases the flexibility and reduces the NOx-emissions, which are relatively high in gas turbine low load operation. Such low load operation is required during a cold start of a CCPP in order to heat up the steam turbine. Thus, a warm-keeping of the thermal-limiting steam turbine results in an accelerated start-up times as well as reduced NOx-emissions and lifetime consumption.
This paper presents a theoretical analysis of the potential of steam turbine warm-keeping by means of hot air for a typical CCPP, located in China. In this method, the hot air passes through the steam turbine while the power plant is shut off which enables hot start conditions at any time. In order to investigate an improved start-up procedure, a physical based simplified model of the water-steam cycle is developed on the basis of an operation data set. This model is used to simulate an improved power plant start-up, in which the steam turbine remains hot after at least 120 hours outage. The results show a start-up time reduction of approximately two-thirds in comparison to a conventional cold start. Furthermore, the potential of steam turbine warm-keeping is discussed with regards to the power output, NOx-emissions, start-up costs and lifetime consumption.
Effect of Turbulence Model on the Prediction of Performance and Span-Wise Mixing in High-Speed Highly-Loaded Multi-Stage Axial-Flow Compressor
Authors: Goto Takashi , Oshio Tetsuya , Tani Naoki , Aotsuka Mizuho , Pallot Guillaume , Kato Dai 
Published: November 2019

Abstract
Despite significant advancements in computational power and various numerical modeling in past decades, flow simulation of a multi-stage axial-flow compressor is still one of the most active areas of research, for it is the critical component in engine performance and operability, and there are so many elements that need to be looked into to predicting correct matching of the stages and accurate flow distribution inside the machine. Modeling unsteadiness, both deterministic and random types, and real geometries are among the most important features to be considered in such prediction.
The authors have conducted in their previous studies a series of unsteady RANS (URANS) simulations of a 6.5-stage high-speed highly-loaded axial-flow compressor, and explored many unsteady effects as well as effects of real geometries such as Variable Stator Vane (VSV) clearance and inter-stage seal leakage flow on the compressor performance. However, all the analyses failed to predict correct stage matching, total pressure and temperature radial profiles, or mass-flow with adequate accuracies.
In the present study, an Improved Delayed Detached Eddy Simulation (IDDES) with SST k-omega model is applied to the simulation of the same compressor configuration at aerodynamic design point. Fifth-order WENO scheme is employed for improved spatial accuracy to suppress significant increase in mesh size. Total number of mesh points are over 400 million for 1/10th sector model. Computations are ensemble averaged for 20 sector passage. Computed overall performance and flow field are compared with the compressor rig test data. The predictions of inter-stage total temperature radial profiles are noticeably improved over the URANS with the same mesh, discretization scheme and eddy turbulence model. Good comparison with the rig data indicates the current simulation is properly capturing the span-wise mixing phenomena. Unsteady flow field are compared between IDDES and URANS to locate the cause for the enhanced mixing. It is shown that components of Reynolds stress responsible for radial diffusion and anisotropic features are intensified in the tip leakage vortex at the rotor exit for the IDDES.
Effect of Wet Gas Behavior on Centrifugal Compressor Shaft Power
Authors: Kawaguchi Daisuke , Kobayashi Katsutoshi 
Published: November 2019

Abstract
The focus of this work is the influence of atomizing flow on a centrifugal compressor. First, the authors clarify that the performance of the centrifugal compressor under wet gas conditions decreases with the increase of LMF as a result of an increase to the impeller shaft power, as suggested in their previous report. A new method for predicting the compressor shaft power based on the liquid behavior in the impeller is then proposed. The authors hypothesize that the increment of the impeller shaft power under wet gas conditions is different when liquid film is dominant in the impeller than when liquid droplets are. In the previous report, the predicted shaft power under the condition that the liquid film was assumed to be dominant in the impeller was experimentally verified. This paper experimentally verifies the predicted shaft power under the condition that the liquid droplets are assumed to be dominant.
Scale-Resolving Simulations of a Fundamental Trailing-Edge Cooling Slot Using a Discontinuous-Galerkin Spectral-Element Method
Authors: Garai Anirban , Murman Scott M. , Madavan Nateri K. 
Published: November 2019

Abstract
The accurate prediction of turbulent mixing in high-pressure turbines that incorporate various airfoil surface-cooling strategies is becoming increasing critical to the design of modern gas turbine engines where the quest for improved efficiency is driving compressor overall pressure ratios and turbine inlet temperatures to much higher levels than ever before. In the present paper, a recently developed computational capability for accurate and efficient scale–resolving simulations of turbomachinery is extended to study the turbulent mixing mechanism of a simplified abstraction of an airfoil trailing-edge cooling slot — a plane wall jet with finite lip thickness discharging into an ambient flow. The computational capability is based on an entropy–stable, discontinuous–Galerkin approach that extends to arbitrarily high orders of spatial and temporal accuracy. The numerical results show that the present simulations capture the trends observed in the experiments. Discrepancies between the simulations and experiments are believed to be due to differences in the inflow profiles and tunnel side–wall effects. The thick lip configuration leads to a thicker wake and higher unsteadiness in the wall jet compared to the thin lip. A detailed comparison of the turbulent flowfields is presented to highlight differences arising due to lip thickness variations.
Effect of Curvilinear Element Blade for Open-Type Centrifugal Impeller on Stator Performance
Authors: Tsukamoto Kazuhiro , Sakamoto Kiyohide , Hiradate Kiyotaka , Shinkawa Yasushi 
Published: November 2019

Abstract
The effect of a curvilinear element blade for an open-type centrifugal impeller on stator performance was investigated by experiment using an actual single stage compressor. This investigation focused on the stator part performance located at the downstream of the impeller for both a vane-less diffuser and a vaned diffuser.
Centrifugal compressors are widely used in various industrial plants, and some customers require higher stage performance. The curvilinear element blade technique, which is one of the key techniques for increasing the efficiency of closed-type centrifugal impellers, was investigated, and it effected an increase in stator efficiency. For this reason, the effect of the curvilinear element blade for the open-type centrifugal impeller was investigated. Our previous study reported that the curvilinear element blade with the open-type impeller increased the impeller efficiency by decreasing the loss derived from the impeller tip leakage flow with the parameter study of the curvilinear element blade geometries using numerical simulations. This paper reports the results of the experimental verifications using the geometries from the previous report.
Experimental results indicated that the compressor stage efficiency increased by 0.7% compared with that of the conventional impeller, which has a linear element blade by using the vane-less diffuser. However, a rotating stall occurred at a higher flow rate than that of the conventional case in the vane-less diffuser. This is due to the decrease of the impeller outlet flow angle derived from the effect of the curvilinear element blade, which makes the velocity distribution equal and reduces the blockage regions near the shroud side.
On the other hand, the curvilinear element blade impeller could increase the stage efficiency by 1.2% over the conventional impeller by using the vaned diffuser. This is due to not only the impeller performance increase but also the diffuser performance increase derived from the equality of the flow distributions by the curvilinear element blade. In addition, there was no diffuser rotating stall.
Probabilistic Response of a Bladed Disk With Uncertain Geometry
Authors: Carassale Luigi , Cavicchi Andrea , Bruzzone Silvia , Brunenghi Michela Marrè 
Published: November 2019

Abstract
Geometric uncertainties in the blade manufacturing process have important consequences in terms of dynamical properties of bladed disks. In this paper we address the problem of modeling a full bladed disk composed by blades having uncertain geometry. The geometric imperfection of the blades is represented and analyzed according to a procedure previously presented by the authors, based on the principal component analysis and the mesh morphing. The dynamical model of the full disk is constructed following the component mode synthesis approach. The blade geometry is represented using a probabilistic model constructed from an experimental dataset. The effect of the geometric uncertainties is assessed using a linear propagation approach, leading to a procedure that is fast enough to be embedded into a Monte Carlo simulation loop.
Implementing Environmental Impact Assessment on the Life Cycle for Industrial Gas Turbines Development
Authors: Musacchio Alessandro , Vicarelli Mattia , Colantoni Simone , Bartocci Pietro , Fantozzi Francesco 
Published: November 2019

Abstract
Nowadays a preliminary evaluation of environmental impact of a new product becomes more and more important, especially when the case study refers to an industrial gas turbine both for power generation and mechanical drive applications. The environmental impact evaluation, as well as the preliminary lifecycle cost analysis, will represent a critical driver to develop a competitive product during the conceptual design phase where the engine architecture is an outcome of different alternatives trade-offs.
Scope of the following paper is the presentation of a set of Design-for-Environment considerations obtained through gas turbine functional decomposition in modules, identification of the most critical, assessment of their contribution compared to the whole engine in terms of environmental impact as well as the effect on the engine use depending on ambient and operating conditions.
The outcome of this study is an approach to preliminarily evaluate the engine life-cycle impact as well as a set of indications to drive machine architecture, material selection and production processes towards the sustainability during manufacturing and operational phases.
Large Eddy Simulation of Combustor and Complete Single-Stage High-Pressure Turbine of the FACTOR Test Rig
Authors: Thomas Martin , Dombard Jerome , Duchaine Florent , Gicquel Laurent , Koupper Charlie 
Published: November 2019

Abstract
Development goals for next generation aircraft engines are mainly determined by the need to reduce fuel consumption and environmental impact. To reduce NOx emissions lean combustion technologies will be applied in future development projects. The more compact design and the absence of dilution holes in this type of engines shortens residence times in the combustion chamber and reduces mixing which results in higher levels of swirl, turbulence and temperature distortions at the exit of the combustion chamber. For these engines interactions between components are more important, so that the traditional engine design approach of component-wise optimization will have to be adapted. To study new lean burn architectures the European FACTOR project investigates the transport of hot streaks produced by a non-reactive combustor simulator through a single stage high-pressure turbine. In this work high-fidelity Large Eddy Simulation (LES) of combustor and complete high-pressure turbine are discussed and validated against experimental data. Measurement data is available on P40 (exit of the combustion chamber), P41 (exit of the stator) and P42 (exit of the rotor) and generally shows a good agreement to LES data.
Assessment of a Machine-Learnt Adaptive Wall-Function in a Compressor Cascade With Sinusoidal Leading Edge
Authors: Tieghi Lorenzo , Corsini Alessandro , Delibra Giovanni , Angelini Gino 
Published: November 2019

Abstract
Near-wall modelling is one of the most challenging aspects of CFD computations. In fact, integration-to-the-wall with low-Reynolds approach strongly affects accuracy of results, but strongly increases the computational resources required by the simulation. A compromise between accuracy and speed to solution is usually obtained through the use of wall functions, especially in RANS computations, which normally require that the first cell of the grid to fall inside the log-layer (50 < y+ < 200) [1]. This approach can be generally considered as robust, however the derivation of wall functions from attached flow boundary layers can mislead to non-physical results in presence of specific flow topologies, e.g. recirculation, or whenever a detailed boundary layer representation is required (e.g. aeroacoustics studies) [2].
In this work, a preliminary attempt to create an alternative data-driven wall function is performed, exploiting artificial neural networks (ANNs). Whenever enough training examples are provided, ANNs have proven to be extremely powerful in solving complex non-linear problems [3]. The learner that is derived from the multi-layer perceptron ANN, is here used to obtain two-dimensional, turbulent production and dissipation values near the walls. Training examples of the dataset have been initially collected either from LES simulations of significant 2D test cases or have been found in open databases. Assessments on the morphology and the ANN training can be found in the paper. The ANN has been implemented in a Python environment, using scikit-learn and tensorflow libraries [4][5]. The derived wall function is implemented in OpenFOAM v-17.12 [6], embedding the forwarding algorithm in run-time computations exploiting Python3.6m C_Api library. The data-driven wall function is here applied to k-epsilon simulations of a 2D periodic hill with different computational grids and to a modified compressor cascade NACA aerofoil with sinusoidal leading edge. A comparison between ANN enhanced simulations, available data and standard modelization is here performed and reported.
Parametric Study on Ported Shroud Locations and Geometries for a Turbocharger Compressor
Authors: Thamizullah Suheab , Nassar Abdul , Davis Antonio , Giri Gaurav , Moroz Leonid 
Published: November 2019

Abstract
Turbochargers are commonly used in automotive engines to increase the internal combustion engine performance during off-design operating conditions. When used, the widest operating range for the turbocharger is desired, which is limited on the compressor side by the choke condition and the surge phenomenon. The ported shroud technology is used to extend the operable working range of the compressor, by permitting flow disturbances that block the blade passage to escape and stream back through the shroud cavity to the compressor inlet. The impact of this technology, on a speed-line, at near optimal operating condition, near choke operating condition and near surge operating condition is investigated.
The ported shroud (PS) self-recirculating casing treatment is widely used to delay the onset of surge by enhancing the aerodynamic stability of the turbocharger compressor. While the ported shroud design delays surge, it usually comes with a small penalty in efficiency.
This research involves designing a single-stage centrifugal compressor for the given specifications, considering the application of an automotive turbocharger. The ported shroud was then introduced in the centrifugal compressor. The performance characteristics were obtained, both at the design and at off-design conditions, both with and without the ported shroud. The performance was compared at various off-design operating speed lines. The entire study, from designing the compressor to optimizing the ported shroud configuration, was performed using the commercial AxSTREAM® software platform. Parametric studies were performed to study the effect of ported shroud axial location along the blade axial length on the operating range and performance. The baseline design, without the ported shroud (P0), and the final geometry with it for all PS inlet axial locations (P1 to P5) were analysed using a commercial CFD package and the results were compared with those from the streamline solver.
Experimental Investigation of Heat Transfer on the Internal Tip Wall in a Rotating Two-Pass Rectangular Channel
Authors: Chia Kai-Chieh , Huang Szu-Chi , Liu Yao-Hsien 
Published: November 2019

Abstract
The current study experimentally studied heat transfer characteristics of the blade tip wall in a rotating internal cooling channel. The aspect ratio of this rectangular channel was 1:4, and the hydraulic diameter was 25.6 mm. Due to the impact of the 180° turn, complex three dimensional flow significantly affected heat transfer on the internal tip surface. The liquid crystal method is used to capture the heat transfer contour on the internal tip surface. In this study, the leading and trailing surfaces of the channel wall were either smooth or roughened with 45° angled ribs. The Reynolds number inside the pressurize two-pass cooling channel ranged from 10,000 to 30,000 at both stationary and rotating conditions. Furthermore, two channel orientations (90° and 135°) were tested. The effect of Coriolis force on heat transfer is studied with the rotation number up to 0.53. The tip heat transfer from the smooth channel wall was more sensitive to rotation and the largest heat transfer enhancement as a result of rotation was 68%.
Loss Analysis of Unsteady Turbomachinery Flows Based on the Mechanical Work Potential
Authors: Leggett John , Richardson Edward , Priebe Stephan , Shabbir Aamir , Michelassi Vittorio , Sandberg Richard 
Published: November 2019

Abstract
Loss analysis is a valuable technique for improving the thermodynamic performance of turbomachines. Analysing loss in terms of the ‘mechanical work potential’ (Miller, R.J., ASME Turbo Expo 2013, GT2013-95488) provides an instantaneous and local account of the thermal and aerodynamic mechanisms contributing to the loss of thermodynamic performance. This study develops the practical application of mechanical work potential loss analysis, providing the mathematical formulations necessary to perform loss analysis using practical Reynolds-Averaged Navier-Stokes (RANS) or Large Eddy Simulations (LES). The analysis approach is demonstrated using RANS and LES of a linear compressor cascade, both with and without incoming wakes. Spatial segmentation is used to attribute loss contributions to specific regions of the flow, and phase-averaging is performed in order to associate the variation of different loss contributions with the periodic passage of wakes through the cascade. For this un-cooled linear cascade, viscous dissipation is the dominant source of loss. The analysis shows that the contribution of the viscous reheat effect depends on the operating pressure of the compressor stage relative to the ambient ‘dead state’ pressure — implying that the optimal blade profile for a low-pressure compressor stage may be different from the optimal profile for a high-pressure compressor stage in the same engine, even if the operating conditions for both stages are dynamically-similar.