bluuebunny/crossref_metadata_2025_split huggingface dataset:
Innovative Mechanical Integrity Approaches for Steam Turbines: Industrial Needs
Authors: Almstedt Henning , Yiğit-Rohde Zeynep , Havemann Jürgen , Thiemann Thomas , Stadler Martin 
Published: November 2019

Abstract
The increased installation of renewable energy resources results in a requirement for higher steam turbine cycling capabilities. In addition, there is a strong demand to save our environment by improved efficiency, as well as acceptable life-cycle costs whilst keeping a high level of reliability and availability. Optimization using state of the art deterministic methods for dimensioning of components is the traditional way addressing such challenges. The use of more advanced methods like fracture mechanics, assisted by probabilistic design are innovative alternatives that have been pushed significantly in recent years.
However, to fully exploit the latest developments of advanced engineering methods, acceptance criteria are essential. Due to the lack of specific steam-turbine standards for several calculation tasks, today acceptance criteria are often based on OEM internal standards and are part of the specific OEM know-how.
New methods require the definition or modification of existing acceptance criteria. In case of lack of acceptance criteria one option is to refer to available standards for industries dealing with comparable components, materials and loading conditions. An example is the adaption of acceptance criteria from pressure-vessel codes for high-pressure steam turbine components. The obvious advantage is the ease of use, but the drawback might be an unnecessary conservatism in the design. Another option is the development of acceptance criteria for advanced methods.
The main intent of the paper is to contribute to the discussion of acceptance criteria for the application of advanced design methods for steam turbine components. A selected steam-turbine example is discussed, acceptance criteria are compared with available standards and the need for the development of component specific criteria are highlighted.
Theoretical and Experimental Investigation on Rotor Dynamic Behavior of Bladeless Turbine for Innovative Cycles
Authors: Silvestri Paolo , Traverso Alberto , Reggio Federico , Efstathiadis Theofilos 
Published: November 2019

Abstract
This paper focuses on rotor dynamic investigation of a bladeless turbine, or Tesla turbine, for application to innovative small scale cycles. Tesla rotor consists of a shaft with several co-rotating disks with small gaps between each other. The flow through the disks creates a momentum exchange by viscous effect, motoring the shaft.
Thanks to its simplicity and low cost, the Tesla expander is attractive for energy harvesting and waste heat recovery from low/medium temperature in small and micro scale applications. Rotor assembly and its parts may present dynamic criticalities, due to their structural characteristics: to predict and ensure low vibrations during operations, numerical and experimental studies have been carried out on some prototypes.
The activity started considering a non-rotating single Tesla disk both in free and real constrained configuration: an experimental modal analysis was performed, whose results were used to validate a disk numerical model. In this case, an analytical approach with a simplified geometry assumption was considered. All methods results were correlated each other and discrepancies have been identified and analysed.
Furthermore, the investigation of a single disk rotor vibrational behaviour has been extended from static conditions to rotating conditions. Numerical analysis has been carried on taking into account the effect of gyroscopic couples and centrifugal field generated by disk rotation. In parallel, a corresponding experimental activity has been done using a dedicated test rig which allowed to perform vibrational operational measurement while the disk was in motion. Campbell diagram of the single rotating disk on the shaft has been obtained from numerical and experimental analysis allowing to identify system dynamic behaviour and to deepen aspects related to critical speeds.
Finally, a whole rotor model has been developed, allowing the characterization of the dynamic behaviour of a fully assembled turbine rotor. The developed models, validated with experiments, are powerful tools that can predict the bladeless expander vibrational behaviour at the early phase of design.
A Reliable Pre-Processing for the Simulation of Friction Joints in Turbomachineries and its Validation: A Case Study With Policontact
Authors: Firrone Christian M. , Battiato Giuseppe 
Published: November 2019

Abstract
Industry and University collaborates to develop methods to simulate the nonlinear dynamics of components in rotating assemblies like turbine or compressor modules in the presence of friction joints. This collaboration produced fruitful results providing a family of numerical solvers with the goal of foreseeing the safety margins against High Cycle Fatigue failure. Softwares are therefore intended as design tools to exploit the damping effect of joints by controlling geometrical features, materials and contact loads. Contact models, reduction techniques to handle complex blade geometries modeled by Finite Element softwares, and numerical techniques to solve the nonlinear equations of motion are refined to provide the level of vibration amplitude as fast as possible by keeping the representativeness of the physical phenomena that are involved.
A reliable compromise between speed and accuracy must be confirmed by several ‘gates’ to pass through during all the simulation process, in particular during pre-processing phase.
The objective of this paper is to propose a good practice made of a list of actions to check the goodness of the mathematical basis to obtain reliable results from simulation.
Experience gained thanks to the long-lasting collaboration between Politecnico di Torino and GE Avio for the development of the software Policontact provides a case study of an effective synthesis between two requirements that are often opposed to each other: complex mathematical models to simulate the nonlinear forced response of rotating components on one side and a robust, confident implementation of an easy-to-use tool intended for industrial staff with complementary background on the other side.
Multi-Fidelity Global-Local Optimization of a Transonic Compressor Rotor
Authors: Mondal Sudeepta , Joly Michael M. , Sarkar Soumalya 
Published: November 2019

Abstract
In aerodynamic design, accurate and robust surrogate models are important to accelerate computationally expensive CFD-based optimization. Machine learning techniques can also enable affordable exploration of high-dimensional design spaces with targeted selection of sparse high-fidelity data. In this paper, a multi-fidelity global-local approach is presented and applied to the surrogate-based design optimization of a highly-loaded transonic compressor rotor. The key idea is to train multi-fidelity surrogates with fewer high-fidelity RANS predictions and more rapid and inexpensive lower-fidelity RANS evaluations. The framework also introduces a global-local search algorithm that can spin-off multiple local optimization threads over narrow and targeted design spaces, concurrently to a constantly adapting global optimization thread. The approach is demonstrated with an optimization of the transonic NASA rotor 37, yielding significant increase in performance within a dozen of optimization iterations.
Characterization of an Additively Repaired Ti-6Al-4V Alloy
Authors: Gyekenyesi Andrew L. , Shrestha Sulochana , Kannan Manigandan , Morscher Gregory , Scott-Emuakpor Onome E. 
Published: November 2019

Abstract
A major disadvantage regarding integrally bladed rotors (IBRs: also referred to as blisks) is the ability to repair damage. Since it is a single part, anything beyond a minor dent requires full removal and either an expensive replacement or a complicated repair. Repair approaches gaining attention include additive metal build-up techniques such as blown powder directed energy deposition (DED). As a start and to attain confidence in such repairs, the characterization of additively modified specimens is required. The work presented here involved the tensile and fatigue testing of stock, annealed Ti-6Al-4V and DED repaired specimens. Thin, dog-bone standard test coupons, consisting of half stock material and half additively manufactured (AM) material with a bond line in the center of the specimen gauge section, were mechanically characterized via tensile and fatigued tests. The behaviors of these “50/50 AM repaired” Ti-6A1-4V coupons were compared to 100% stock Ti-6A1-4V coupons. In addition, metallography and post-test fractography were performed to study the microscopic characteristics and failure initiation sites with special attention to the grain structures in the vicinity of the bond lines. The AM repaired coupons did show a slight degradation in mechanical properties compared to the stock material of this study (tensile strength and elongation as well as fatigue life), with the microstructural dissimilarities explaining the variances. Even so, the AM repaired specimen properties were acceptable and compared favorably to other published results for stock annealed Ti-6A1-4V.
Combustion and Emission Characteristics of a Lean Axial-Stage Combustor
Authors: Stiehl Bernhard , Worbington Tyler , Miegel Alexander , Martin Scott , Velez Carlos , Ahmed Kareem 
Published: November 2019

Abstract
Gas turbine engines with high operational flexibility represent an important area of research. In support of this, the stage change of NOx emissions at high-temperature, full-load conditions are the main target of this research study. To overcome the challenge of decreasing the residence time of hot exhaust gas in the burner, the approach of axial-staged combustion has been used, which aims to burn at lean conditions. A main combustion stage with a conventional burner is followed by a jet-in-crossflow (JIC) stage downstream. This second combustion stage, the test section, burns well over a third of the total fuel amount, which is added by a jet inlet. The entire combustor is designed to run at a pressure of 5 bar, featuring a challenging point of experimental operation. Hence, a steady Computational Fluid Dynamics (CFD) model was created in Star-CCM+ to analyze the JIC stage. A structured mesh grid with local refinement domains was used along with RANS equations, Realizable k-ε turbulence, Complex Chemistry model with Laminar Flame Concept (LFC) applied. The findings of the computational model include a detailed description of the flow field, focusing on vortex formation and penetration depth. Three vortex types and local pressure losses in the shear domain were identified. Results were compared with similar data from literature and a very good match was proven. Optical laser diagnostics should work well to capture the predicted flow penetration. The highest local reaction rates were observed inside a thin flame front between 4 and 6 diameters downstream of the jet. The jet showed a limited expansion into the available channel domain, resulting in a low total heat release and a methane conversion of 52%. Along with production of just under 1% CO, the potential of axial-staged combustion has been outlined by two boundary cases, using either equilibrium main burner stage NOx, which showed a reduction of high incoming NOx, or setting incoming NOx fractions to zero, which yielded a total production of only 17 ppm NOx in the JIC stage.
Experimental and Numerical Assessment of the Impact of Part-Span Connectors on Turbine Efficiency and Flow Field
Authors: Brüggemann C. , Schatz M. , Vogt D. M. , Popig F. 
Published: November 2019

Abstract
This study presents the results of measurements in an industrial steam turbine test rig operated at the Institute of Thermal Turbomachinery and Machinery Laboratory (ITSM) in Stuttgart, Germany. In order to ensure safe operation over a wide range of operating conditions the last and penultimate rotor blade rows of this turbine feature Part-Span Connectors (PSC). The PSC provide additional coupling and mechanical damping during operation, however, they present a major obstacle to the flow, thus causing additional aerodynamic loss. The focus of the present work is on the aerodynamic impact of the PSC on the flow field of the last stage. To capture this impact, an extensive measurement campaign over a wide range of operating points was performed using two last blade row configurations that are identical with regard to the blade design, except for the fact that one features free-standing blades while the second is equipped with PSC. A performance assessment of these two configurations based on detailed probe measurements and overall turbine efficiency is presented. Additionally, a detailed comparison of 3D CFD-results employing an equilibrium steam (EQS) model and a non-equilibrium steam (NES) model for both configurations is shown with good agreement to the test data. However, comparing the two models reveals major differences whenever there is condensation occurring close to the evaluation plane, thus the advantage of applying the NES model is presented.
3D Printing in Turbomachinery: Overview of Technologies, Applications and Possibilities for Industry 4.0
Authors: Novotny Vaclav , Spale Jan , Stunova Barbora Bryksi , Kolovratnik Michal , Vitvarova Monika , Zikmund Petr 
Published: November 2019

Abstract
Customization and providing tailored products, while keeping highly automated production with minimum manufacturing personnel, is a general trend, and one of the expectations of manufacturing companies from developed countries to stand in competition against cheap mass production. This trend, often also called “industry 4.0”, is taking advantage of many innovative and quickly developing technologies like AM or 3D printing. Applications of 3D printing are also getting into the field of turbomachinery.
The first part of the paper provides a review of current 3D printing technologies with respect to applications in turbomachinery field. Several technologies, mostly for producing a metal or plastic product, exist and can be considered. Applications for the components range from single Watts to hundreds MW scale and similarly for various other operating conditions.
The second part briefly describes possible practical applications concerning multiple situations as research and development, customization of end-product, operative field-testing, or temporary replacements.
Pipeline Compressors Dry Gas Seal Retrofits
Authors: Sihra Inderpal , Goldswain Ian , Twist Christina , Pacheco Jorge 
Published: November 2019

Abstract
Methane emissions are classed as one of the most important contributors to climate change. This greenhouse gas has a global warming potential 21 times that of Carbon Dioxide. In the Oil and Gas industry, pipeline compressor emissions have been identified as an important source of methane released into the atmosphere. Wet seals (oil seals) technology will not meet new targets being set for methane emissions. John Crane has therefore developed a new dry gas seal design with a significantly narrower cross section to allow historically high value compressor assets to continue to function without the need for extensive redesign or replacement.
This dry gas seal has been specifically engineered to replace wet seals within older centrifugal pipeline compressors. The main reasons associated with conversion from wet seals to dry gas seals include: moving to non-contacting technology which reduces seal wear issues, reduced operating costs from removal of oil seal supporting systems including degassing equipment, lower energy consumption due to the shear losses associated with oil seals, reduced maintenance costs by having a simpler supporting system and less frequent routine maintenance, and reduced emissions.
Wet seals are typically compact in nature and are therefore very flexible in how they can be installed into a compressor. Traditional dry gas seals occupy a larger cross-sectional footprint and therefore it was necessary to develop a brand new gas seal that can retrofit into the same cavity without the need for expensive and prohibitive machining of the compressor shaft or housing. The resulting gas seal design is significantly compact when compared to a standard gas seal, yet provides sealing at maximum pipeline compressor duties of up to 120barg and 100m/s.
In order to create a compact seal, John Crane has significantly reduced the cross section of the rotating (mating) and stationary (primary) sealing faces. This change brings about an increased level of complexity associated with dry gas seal design. In-house FEA and CFD simulations have been used to optimize the seal design and groove patterns. Results documenting the extensive design and simulation activities will be presented to demonstrate effective separation of the sealing faces throughout the entire seal performance envelope. A number of tests were specifically designed to thoroughly validate the seal design by simulating compressor field conditions. The product has undergone a series of testing through its entire performance envelope for pressure, speed and temperature. Specific accelerated tests were also designed to replicate the seal lifetime. The paper will describe the test setup and present the validation results.
Experimental Validation of Friction Models for Rotor-Rubbing
Authors: Jauregui Juan , De Santiago Duran Oscar 
Published: November 2019

Abstract
The work presented here is a continuation of a set of experiments that were designed for predicting friction forces during rotor rubbing. The experimental set up consisted of a rotor rubbing a fixed surface. The surface had two force sensors, one aligned with the tangential force, and the other aligned in the radial direction. This set up allowed us to measure the friction component and the normal force. The measurements were complemented with a couple of accelerometers mounted on the bearings, and the accelerations and the friction force were measured simultaneously. All the data were analyzed using the Continuous Wavelet Transform (CWT) and the cross-correlation function. The CWT produces a spectrogram that is useful for identifying the nonlinear behavior of the phenomenon. The cross-correlation is used to measure the similarities between the friction force and the acceleration measurements. At low friction levels, experimental results show a sub-synchronous vibration at half of the rotating speed. This pattern is always present regardless of the friction source, but it is impossible to reproduce this effect using current friction models.
The experimental results were compared to numerical results, these results were computed with the Muszynska’s model that is based on the physics of the phenomenon, but their predictions differ significantly from the experimental results. One of the reasons for these discrepancies lay on the fact that rotor-rubbing models consider the friction as an external force instead of modifying the system parameters.
Optical Coarse Droplet Measurement and Wet Loss Analysis on the Wet Air Flow Through the Subsonic Blade Cascade Channel
Authors: Sasao Yasuhiro , Takata Ryo , Miyake Satoshi , Tabata Soichiro , Yamamoto Satoru 
Published: November 2019

Abstract
In order to understand the details of the mechanism of the occurrence of wetness loss between blade rows, the blades of an HP nuclear turbine were modeled in an atmospheric subsonic wind tunnel, and a flow field with wet loss was analyzed in its totality using a three-hole Pitot tube and Phase Doppler Particle Analyzer (PDPA) system.
In the secondary flow loss region and the end wall loss region, a significant increase in pressure loss was confirmed under wet conditions. Analysis by measurement and the Eulerian-Lagrangian coupled solver showed that these loss increases can occur due to the agitation of water droplets and water films in the passage vortex or corner vortex.
Finally, this report contains a breakdown of profile loss, thermodynamic loss and acceleration loss of the wet air flow through the sub-sonic blade row.
Scaling Methodology of the FAA Burner for Pre-Qualification Fire Tests of Aircraft Engine Panels
Authors: Béland Mathieu , deChamplain Alain , Kalla Smail , Robert Etienne 
Published: November 2019

Abstract
The main objective of this work is to design a small kerosene burner to study the fireproofing capacity of aircraft composite materials exposed to an open flame. The standards AC20-135 and ISO-2685 describe how the fireproofing tests have to be performed and serve as guidelines to set the requirements for the design of a small kerosene burner as a less costly alternative to the larger FAA burner. The burner is fed with liquid jet-A fuel and air, which is flowing around the injector in a cylindrical chamber. The combustion generates an unconfined flame. The fuel injector selected is a Delavan spill-return pressure atomizer. There is a custom 3D printed plastic axial swirler at the inlet of the combustion area to promote better mixing between air and jet-A droplets. A computational fluid dynamic analysis (CFD) is presented to better understand the aerodynamic of the burner and to design adequately the swirler. The design of the burner allows changing easily the swirler to test swirlers with different vane angles. An experimental test bench is designed to test the effect of these swirlers on the heat flux measurements under multiple combinations of burner power and equivalence ratio at four axial locations. The experimental investigation allows selecting the final configuration and parameters for the burner. The chosen swirler has 15 vanes that are oriented at the exit at 25° to the burner axis. The best axial location for the measurements from the burner face to the position of the calorimeter is at 7.6 cm (3 in.). It is possible to generate a flame with a diameter smaller than 6.4 cm (2.5 in.) while reaching the required heat flux of 116 kW/m2. This accommodates smaller coupon sizes for the composite material and reduces cost for pre-certification FAA testing. To achieve this flame configuration, the burner power should be set between 10 kW and 20 kW with an equivalence ratio from 0.7 to 0.9.