bluuebunny/crossref_metadata_2025_split huggingface dataset:
Focus Variation Measurement and Prediction of Surface Texture Parameters Using Machine Learning in Laser Powder Bed Fusion
Authors: Özel Tuğrul , Altay Ayça , Kaftanoğlu Bilgin , Leach Richard , Senin Nicola , Donmez Alkan 
Published: November 2019

Abstract
The powder bed fusion-based additive manufacturing process uses a laser to melt and fuse powder metal material together and creates parts with intricate surface topography that are often influenced by laser path, layer-to-layer scanning strategies, and energy density. Surface topography investigations of as-built, nickel alloy (625) surfaces were performed by obtaining areal height maps using focus variation microscopy for samples produced at various energy density settings and two different scan strategies. Surface areal height maps and measured surface texture parameters revealed the highly irregular nature of surface topography created by laser powder bed fusion (LPBF). Effects of process parameters and energy density on the areal surface texture have been identified. Machine learning methods were applied to measured data to establish input and output relationships between process parameters and measured surface texture parameters with predictive capabilities. The advantages of utilizing such predictive models for process planning purposes are highlighted.
Reliability-Based Design Optimization of Complex Problems With Multiple Design Points via Narrowed Search Region
Authors: Wang Yutian , Hao Peng , Guo Zhendong , Liu Dachuan , Gao Qiang 
Published: November 2019

Abstract
The expensive computational cost is always a major concern for reliability-based design optimization (RBDO) of complex problems. The performance of RBDO can be lowered by the inaccuracy of reliability analysis (RA) which is caused by multiple local optimums and multiple design points in highly non-linear space. In order to reduce the computational burden and guarantee the accuracy of RA (and thus to improve the RBDO performance), a global RBDO algorithm by adopting an improved constraint boundary sampling (GRBDO-ICBS) method is proposed. Specifically, the GRBDO-ICBS method first narrows the concerned search region by using a Kriging-based global search. The accuracies of the design points are verified by the expected risk function (ERF), and the corresponding inaccurate design points are added into training samples to update Kriging. Then a multi-start gradient-based sequential RBDO is carried out, which tries to find out all multiple design points in the concerned search region. The performance of GRBDO-ICBS is demonstrated by four examples. All results have shown that the proposed method can achieve similar accuracy as Monte Carlo simulation (MCS)-based RBDO but with a much lower computational cost.
Calculating the Fold Angles of Any Vertex Roof Using a Spherical Image Technique
Authors: Eatough Daniel T. , Seffen Keith A. 
Published: November 2019

Abstract
The shape of a vertex roof is defined by the geometry of its constituent flat facets and the relative angle of folding across them. The spherical image of the roof, originally from Gauss, expresses these properties simultaneously. We present a method for calculating the image properties and thence the shape of any vertex roof based on subdividing the image into an array of suitable spherical triangles. In particular, we introduce a truss representation of the vertex for choosing viable subdivisions of the image, which allow full calculations to be made. Additionally, this allows us to construct generalized closed-form expressions for the fold angles of vertex roofs, presented here for roofs with up to six facets.
Wrench-Feasible Workspace of Mobile Cable-Driven Parallel Robots
Authors: Rasheed Tahir , Long Philip , Caro Stéphane 
Published: November 2019

Abstract
Cable-driven parallel robots (CDPRs) hold numerous advantages over conventional parallel robots in terms of high speed and large workspace. Cable-driven parallel robots whose workspace can be further increased by the modification of their geometric architecture are known as reconfigurable cable-driven parallel robots. A novel concept of reconfigurable cable-driven parallel robots that consists of a classical cable-driven parallel robot mounted on multiple mobile bases is known as mobile CDPR. This paper proposes a methodology to trace the wrench-feasible workspace of mobile cable-driven parallel robots by determining its available wrench set. Contrary to classical cable-driven parallel robots, we show that the available wrench set of a mobile cable-driven parallel robot depends, not only on the cable tension limits but also on the static equilibrium conditions of the mobile bases. The available wrench set is constructed by two different approaches known as convex hull approach and hyperplane shifting method. Three case studies are carried out for the validation of the proposed methodology. The proposed approach is experimentally validated on a mobile cable-driven parallel robot with a point-mass end-effector and two mobile bases.
Compressor Speed Decay During Emergency Shutdowns
Authors: Kurz Rainer , Garceau Sean , Ji Min , Brun Klaus 
Published: November 2019

Abstract
The emergency shutdown of a compressor train is a necessary safety feature. In this event, the power supply (either from a gas turbine or an electric motor) is cut off. The compressor train will continue to spin due to its inertia, but the speed will reduce fast. To avoid damage of the equipment during a shutdown event, compressor surge must to be avoided. In many instances, the dynamic behavior of the compression system is simulated to ensure that the necessary recycle valves are sized, and arranged properly. One of the key problems of dynamic simulation, and a major source of uncertainty in the results, is the correct treatment of the speed decay of the compressor train. The present study provides the background to evaluate the speed decay, and includes data from actual rundown situations. The evaluation shows general trends, that can be used to reduce the simulation uncertainties in dynamic simulations.
Aerodynamic Shape Optimization of a Turbine Blade Considering Geometric Uncertainty Using an Adjoint Method
Authors: Luo Jiaqi , Zheng Yao 
Published: November 2019

Abstract
Aerodynamic shape optimization of turbomachinery blades taking the performance impact of geometric uncertainty into account is presented in the paper. A continuous adjoint method for the steady-state Euler equations is used to calculate the first order (FO) sensitivities of performance functions to the design parameters. For each performance function, all the sensitivities can be obtained by about two equivalent flow computations, regardless of the number of design parameters. The performance changes due to the geometric variations are evaluated on use of the second order (SO) sensitivities. A direct-ad joint method is used to calculate the FO and SO sensitivities of performance functions to the basis modes of geometric variations, which are extracted from a covariance function using principal component analysis method. Firstly, the sensitivities of the mass-averaged adiabatic efficiency and mass flow rate to the basis modes of geometric variations for a three-dimensional turbine blade are calculated. The validations of sensitivity-based performance impact are then illustrated. For the optimization maximizing the adiabatic efficiency with mass flow rate constrained, a series of shape functions are imposed on the turbine blade to perturb the aerodynamic shape. For each deformed blade with respect to each design parameter, the statistic mean values of performance changes are evaluated by using the method of moment and then contribute to the calculation of the corresponding FO sensitivity of performance functions. The design optimization without and with geometric uncertainty are finally presented. The results are compared in detail to demonstrate the effects of geometric variations to the optimization, especially to the statistical performance of the optimized blades. Through design optimization, the shock loss can be significantly reduced, compared with the original blade. The optimized blade is more robust in respect of geometric uncertainty.
Gas Turbine Health State Prognostics by Means of Bayesian Hierarchical Models
Authors: Losi Enzo , Venturini Mauro , Manservigi Lucrezia 
Published: November 2019

Abstract
The prediction of the time evolution of gas turbine performance is an emerging requirement of modern prognostics and health management (PHM), aimed at improving system reliability and availability, while reducing life cycle costs.
In this work, a data-driven Bayesian Hierarchical Model (BHM) is employed to perform a probabilistic prediction of gas turbine future health state thanks to its capability to deal with fleet data from multiple units.
First, the theoretical background of the predictive methodology is outlined to highlight the inference mechanism and data processing for estimating BHM predicted outputs. Then, BHM is applied to both simulated and field data representative of gas turbine degradation to assess its prediction reliability and grasp some rules of thumb for minimizing BHM prediction error.
For the considered field data, the average values of the prediction errors were found to be lower than 1.0 % or 1.7 % for single- or multi-step prediction, respectively.
Property Risk Assessment for Liquefied Natural Gas Liquefaction Plants
Authors: Orme George J. , Venturini Mauro 
Published: November 2019

Abstract
Liquefied Natural Gas (LNG) liquefaction plants have become increasingly important as natural gas is exported from the United States of America to markets world-wide. Downtime of any part of the process train (gas turbine, compressors, controls, etc.) due to failure of one or more of its components can result in high costs. The total cost of loss is of great concern to the LNG industry as it moves towards increased LNG exports with required operational efficiency, and downtime reduced to a minimum.
This paper reports the application of a methodology of property risk assessment, providing insight into the use of PML (Probable Maximum Loss) and MFL (Maximum Foreseeable Loss) risk measures. Major sources of risk are analyzed, drawing from both technical literature and operational information on typical large LNG liquefaction plants.
The outcome of this paper is an estimation of the economic loss associated with property risk for two hypothetical LNG liquefaction plants, based upon sample plants located in North America and characterized by different capacity. These plants represent recently built and commissioned plants and are chosen to take advantage of current technology and plant capacities.
Wheel Box Test Aeromechanical Verification of New First Stage Bucket With Integrated Cover Plates for MS5002 GT
Authors: Mariottini Marco , Pieroni Nicola , Bertini Pietro , Pacifici Beniamino , Giorgetti Alessandro 
Published: November 2019

Abstract
In the oil and gas industry, manufacturers are continuously engaged in providing machines with improved performance, reliability and availability. First Stage Bucket is one of the most critical gas turbine components, bearing the brunt of very severe operating conditions in terms of high temperature and stresses; aeromechanic behavior is a key characteristic to be checked, to assure the absence of resonances that can lead to damage. Aim of this paper is to introduce a method for aeromechanical verification applied to the new First Stage Bucket for heavy duty MS5002 gas turbine with integrated cover plates. This target is achieved through a significantly cheaper and streamlined test (a rotating test bench facility, formally Wheel Box Test) in place of a full engine test. Scope of Wheel Box Test is the aeromechanical characterization for both Baseline and New bucket, in addition to the validation of the analytical models developed. Wheel Box Test is focused on the acquisition and visualization of dynamic data, simulating different forcing frequencies, and the measurement of natural frequencies, compared with the expected results. Moreover, a Finite Elements Model (FEM) tuning for frequency prediction is performed. Finally, the characterization of different types of dampers in terms of impact on frequencies and damping effect is carried out. Therefore, in line with response assessment and damping levels estimation, the most suitable damper is selected. The proposed approach could be extended for other machine models and for mechanical audits.
Multifidelity Based Optimization of Shaped Film Cooling Hole and Experimental Validation
Authors: Zhang Hao , Li Yifei , Chen Ziyu , Su Xinrong , Yuan Xin 
Published: November 2019

Abstract
It has been known that in previous optimization problems, surrogate models are widely used to improve the optimization efficiency. The optimization result depends heavily on the accuracy of surrogate model, while it also costs a lot to construct a high-accurate surrogate model. In order to obtain the optimal design of a shaped film cooling hole which is already well-designed, an optimization framework based on multi-fidelity model is proposed in this article. The characteristic of the multi-fidelity model in this work is that it combines the experimental design information and numerical simulation together. The optimization efficiency can be greatly improved by 64.5% with multi-fidelity model and furthermore the prediction accuracy is maintained with a high level. In this work, three geometry parameters are selected as design variables, which are lateral angle, laidback angle and hole length. A combined optimization method which includes GA (generic algorithm) and SQP (sequential quadratic programming) algorithm is used in the optimization process. A validation experiment is further conducted to validate the optimized hole design using PSP (pressure sensitive paint) and 3D printing technology. The optimization results have shown that the overall film cooling performance is 39% higher compared with baseline design. This work shows the merits of multi-fidelity model in high-efficiency optimization film cooling holes and it may provide further guide for other relative works.
Secondary Flow Measurements in a Compressor Cascade Using 3D LDA/PDA: Part B — Dispersed Phase Effects on Flow Topology
Authors: Harbeck Janneck , Geist Silvio , Joos Franz 
Published: November 2019

Abstract
The rapid regulation of gas turbine power plants is becoming increasingly important. In the field of stationary gas turbine power augmentation droplet-laden flows receive special attention as they cool the compressor’s inlet temperature. High fogging is an effective and economic method that secures power supply by reacting rapidly to fluctuating power generation. However, water droplets effect the aerodynamic performance of the compressor negatively. Therefore, the Laboratory of Turbomachinery investigated the interaction between droplets and blades at midspan by using diverse experimental methods to comprehend aerodynamic performance and water film induced losses. Additionally, the knowledge of the separation’s extent for three-dimensional flows with corner separation is of great importance as it leads to a blockage of the flow cross-section and therefore contributes to the losses. This paper enlarges this knowledge base by studying the interactions of the dispersed phase with the gas flow in three-dimensional flow structures as they are found in the near wall regions of every turbo compressor. By utilizing a three-dimensional Phase-Doppler Anemometer spatially resolved information on velocity mean vector, its higher moments as well as droplet diameters were extracted from the separated region for a compressor blade, in middle cross section design, with spray-injection. Streamlines that derive from the mean velocities visualize key features such as saddle and focal points. Then an integral approach is presented to evaluate the effect of the dispersed phase on the flow structure compared to dry flow and the impact back on different diameter classes. Finally, the velocity in streamwise direction shows the influence of the disperse phase on the aerodynamic blockage.
Using a New Entropy Loss Analysis to Assess the Accuracy of RANS Predictions of an HPT Vane
Authors: Zhao Yaomin , Sandberg Richard D. 
Published: November 2019

Abstract
Entropy loss is widely used to quantify the efficiency of components in turbomachines, and empirical relations have been developed to estimate the contribution of different mechanisms. However, further analysis is still needed to not only get a deeper insight of the physics, but also to more accurately quantify the loss generation caused by different terms. In the present study, the entropy transport equations based on averaged flow quantities are first derived, and the entropy generation process is fully decomposed into several terms representing different physical mechanisms, such as mean viscous dissipation, turbulence production, mean and turbulent heat flux, etc. This decomposition framework is then applied to high-resolution LES and RANS results of a VKI LS-89 HPT vane, and a detailed quantification of different entropy generation terms is obtained. The results show that the entropy generation caused by mean flow features like mean viscous dissipation and mean heat flux are in close agreement between LES and RANS, indicating that RANS provides an overall good prediction for the mean flow. Furthermore, we find that turbulence production plays an important role in entropy generation as it represents the energy extracted from the mean flow to turbulent fluctuations. However, the difference between RANS and LES results for the turbulence production term is not negligible, particularly in the wake region. This implies that the failure of RANS to predict the correct total loss might be largely caused by errors in capturing the correct turbulence production in the near wake region.
Power Augmentation Technologies for Gas Turbines: Alternatives for an Existing Simple Cycle Power Plant in Peru
Authors: Celis Cesar , Peralta Sergio , Galarza Walter 
Published: November 2019

Abstract
The influence of different power augmentation techniques used in gas turbines on the performance of simple cycle type power plants is assessed in this work. A computational model and tool realistically describing the performance of a typical simple cycle type power plant at design and off-design point conditions is initially developed. This tool is complemented with different models of power augmentation technologies. Finally, the whole model including both power plant and power augmentation techniques is used to analyze a case study involving a particular power plant in Peru. The results from the simulations of the specific power plant indicate that power output can be increased through all the evaluated power augmentation technologies. These results show indeed that technologies based on absorption refrigeration systems produce the largest gains in terms of power output (7.1%) and thermal efficiency (0.7%). Such results confirm the suitability of these systems for simple cycle type power plant configurations operating under hot and humid operating conditions as those accounted for here. From an economic perspective, considering the net present value as the key parameter defining the feasibility of a project in this category, power augmentation techniques based on absorption cooling systems result also the most suitable ones for the studied power plant. Power augmentation techniques environmental implications are also quantified in terms of CO2 emissions.
Numerical Study on Heat Transfer and Flow Characteristics in Double Turning Areas Ribbed Serpentine Channel With Lateral Outflow
Authors: Zhang Bo-lun , Zhu Hui-ren , Guo Tao , Yao Chun-yi , Fu Zhong-yi 
Published: November 2019

Abstract
The double turning areas ribbed serpentine channel with lateral outflow is an important structure for designing the internal systems of turbine blade. The current work similarly simplifies the internal channel of the real blade. The Nusselt number and pressure coefficient distribution of the double turning areas ribbed serpentine channel with different outflow ratios are numerically researched under static and rotating conditions. The Realizable k-ε turbulence model with enhanced wall treatment is used in the numerical simulation. The inlet Reynolds number is 11000. The rotation numbers vary from 0 to 0.09. Three outflow ratios are 27%/0%/73%, 27%/49%/24% and 27%/73%/0%, respectively. The rotation radius (R) is 46.4d. The result shows that the Nusselt number distribution of the passage 3 under 27%/49%/24% outflow ratio condition is similar to that under 27%/73%/0% outflow ratio condition. There is a large low Nusselt number area in the passage 3 under Dr = 27%/0%/73% condition. The averaged area Nusselt number ratios on the suction side of the passage 1, passage 2 and passage 3 are higher than that on the pressure side under nonrotating condition. Rotation enhances heat transfer on the suction side of the passage 2, and has a positive effect on pressure side heat transfer of passage 1 and passage 3. The averaged area Nusselt number ratio of passage 3 under 27%/73%/0% outflow ratio condition is higher than that under other outflow ratio conditions. With the rotation number increasing, the pressure coefficient of the complete ribbed serpentine channel gradually increases, and the maximum increase is in the first turning area.
Simulation of an Aero-Engine Bearing Compartment Using Two-Way Transition Between Lagrangian Droplets and a Three-Dimensional Eulerian Liquid Film
Authors: Dick Jean-Sebastien , Kumar Vivek , Nakod Pravin , Montanari Federico 
Published: November 2019

Abstract
This paper presents a new hybrid two-phase flow numerical model. It uses the Discrete Phase Model (DPM) and the Volume of Fluid model (VoF) to study the interaction between air, oil droplets and films in a bearing compartment. It allows transition from a trackable Lagrangian particle, such as a droplet, into a continuous liquid structure in a Eulerian frame of reference. The transition can also be performed in the opposite direction, where a continuous liquid structure can be converted back into a trackable particle if specific requirements are met. The method is designated as DPM-VoF-DPM throughout this paper.
Test cases capturing the impingement of a droplet in a liquid film are performed to assess its effectiveness. The simulation of a simplified bearing compartment is compared with measurements and results obtained using a standard VoF modeling approach. Mechanisms which are usually modeled such as droplet splashing, film separation, and droplet stripping, can now be physically captured with reduced computing resources by allowing transition from continuous liquid structures to discrete parcels. The employed modeling strategy allows for high resolution of the oil film at the walls and tracking of the droplets while minimizing mesh size and computing needs. Current results suggest that the proposed DPM-VoF-DPM method can be an efficient and accurate tool for locating air and oil in aero-engine transmission systems.