bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Different Turbulence Models Applied in Turbopump’s Hydraulic Turbine
Authors: Barbosa Daniel Ferreira Corrêa , Tonon Daniel da Silva , Whitacker Luiz Henrique Lindquist , Tomita Jesuino Takachi , Bringhenti Cleverson 
Published: September 2021

Abstract
The aim of this work is an evaluation of different turbulence models applied in Computational Fluid Dynamics (CFD) techniques in the turbomachinery area, in this case, in an axial turbine stage used in turbopump (TP) application. The tip clearance region was considered in this study because it has a high influence in turbomachinery performance. In this region, due to its geometry and the relative movement between the rotor row and casing, there are losses associated with vortices and secondary flow making the flowfield even more turbulent and complex. Moreover, the flow that leaks in the tip region does not participate in the energy transfer between the fluid and rotor blades, degradating the machine efficiency and performance. In this work, the usual flat tip rotor blade geometry was considered.
The modeling of turbulent flow based on Reynolds Averaged Navier-Stokes (RANS) equations predicts the variation of turbine operational characteristics that is sufficient for the present turbomachine and flow analysis. Therefore, the appropriate choice of the turbulence model for the study of a given flow is essential to obtain adequate results using numerical approximations. This comparison become important due to the fact that there is no general turbulence model for all engineering applications that has fluid and flow.
The turbomachine considered in the present work, is the first stage of the hydraulic axial turbine used in the Low Pressure Oxidizer Turbopump (LPOTP) of the Space Shuttle Main Engine (SSME), considering the 3.0% tip clearance configuration relative to rotor blade height. The turbulence models evaluated in this work were the SST (Shear Stress Transport), the k-ε Standard and the k-ε RNG. The computational domain was discretized in several control volumes based on unstructured mesh. All the simulations were performed using the commercial software developed by ANSYS, CFX v15.0 (ANSYS). All numerical settings and how the boundary conditions were imposed at different surfaces are explained in the work. The boundary conditions settings follow the same rule used in the test facility and needs some attention during the simulations to vary the Blade-Jet-Speed ratio parameter adequately.
The results from numerical simulations, were synthesized and compared with the experimental data published by National Aeronautics and Space Administration (NASA), in which the turbine efficiency and its jet velocity parameter are analyzed for each turbulence model result. The work fluid considered in this work was water, the same fluid used in the NASA test facility.
Influence of Alternative Fuels on the Liner Metal Temperatures in a V2500 Combustor
Authors: Schäflein Lukas , de Guillebon Ludovic , Konle Marco 
Published: September 2021

Abstract
To reach ambitious emission goals, the use of sustainable aviation fuels (SAFs) is a short-term option in current aero engines. The combustion of such fuels can, due to their low soot formation, have an impact on the thermal radiation inside the combustor. This in turn can affect the combustor liner temperatures, which are directly linked to the lifetime of the combustor. To study the impact of SAFs, the authors numerically simulated the flow inside a V2500 aero engine combustor using an OpenFOAM-based solver capable of capturing multi-physics phenomena such as combustion, conjugate heat transfer, thermal radiation and soot formation.
The complex cooling system of the V2500 combustor makes the evaluation of the wall temperatures extremely challenging. To achieve results with the resources available, the authors replaced the densely packed pins inside the cooling channel with a boundary condition. This boundary condition was derived from a highly detailed simulation of a section of the cooling system. With this model reduction, the wall temperatures could be evaluated at four operating points. Back-to-back comparisons of the predicted wall temperatures with pictures of deteriorated combustor hardware out of the field operation reveals the plausibility of the numerical results.
Finally, this numerical model was extended to include the effects of thermal radiation and soot formation. To predict the combustion of Jet-A, both models were used with settings derived from former validation simulations. The SAF combustion with extremely low sooting level was mimicked by deactivating the soot formation completely. The comparison of the radiation source term reveals — as expected — locally a higher radiation emission in areas where soot is formed in the combustor. As consequence, this leads to higher net radiative heat flux into the combustor liners. However, due to its minor importance in the overall energy balance, this change did not lead to significantly different liner temperatures.
A Reduced-Order Model for the Preliminary Design of Small-Scale Radial Inflow Turbines
Authors: Manfredi Marco , Alberio Marco , Astolfi Marco , Spinelli Andrea 
Published: September 2021

Abstract
Power production from waste heat recovery represents an attractive and viable solution to contribute to the reduction of pollutant emissions generated by industrial plants and automotive sector. For transport applications, a promising technology can be identified in bottoming mini-organic Rankine cycles (ORCs), devoted to heat recovery from internal combustion engines (ICE). While commercial ORCs exploiting turbo-expanders in the power range of hundreds kW to several MW are a mature technology, well-established design guidelines are not yet available for turbines targeting small power outputs (below 50 kW). The present work develops a reduced-order model for the preliminary design of mini-ORC radial inflow turbines (RITs) for high-pressure ratio applications, suitable to be integrated in a comprehensive cycle optimization. An exhaustive review of existing loss models, whose development pattern is retraced up to the original approaches, is proposed. This investigation is finalized in a loss models effectiveness analysis performed by testing several correlations over six existing geometries. These test case turbines, operating with different fluids and covering a wide range of target expansion ratio, size, and gross power output, are then employed to carry out the validation procedure, whose results prove the robustness and prediction capability of the proposed reduced-order model.
Start-Up Process of 50kW-Class Gas Turbine Firing Ammonia Gas
Authors: Kurata Osamu , Iki Norihiko , Fan Yong , Matsunuma Takayuki , Inoue Takahiro , Tsujimura Taku , Furutani Hirohide , Kawano Masato , Arai Keisuke , Okafor Ekenechukwu C. , Hayakawa Akihiro , Kobayashi Hideaki 
Published: September 2021

Abstract
Ammonia combustion gas turbines have drawn much attention for their potential to power hydrogen-carrier applications. In 2014, 21-kW of power generation was achieved with kerosene-ammonia co-combustion using a 50-kW-class micro gas turbine. In 2015, methane-ammonia co-combustion and 100% ammonia gas combustion were separately employed to generate 42-kW of power in both cases. However, this microgas turbine still requires kerosene to start. In gas turbines, the suitability of the air flow for ignition depends on the fuel. Low-NOx combustors were developed using the staged combustion concept to achieve rich-lean combustion. These combustors can burn kerosene at start-up but not at full load. We have also developed a micro gas turbine system that utilizes 100% ammonia gas in combustion during full-load operation. However, start-up with ammonia gas is difficult without hot air. The ignition of ammonia gas is so difficult that during the startup process, a more easily ignitable fuel is also used. In this study, we developed a new 50-kW-class micro gas turbine that can be started with gaseous fuel. Start-up with methane gas was achieved using a newly designed low-NOx combustor. In addition, because hydrogen can be easily obtained from ammonia decomposition, the addition of hydrogen gas to ammonia gas has garnered attention for ammonia gas turbine applications. The application of hydrogen to initiate combustion in a micro gas turbine was also investigated.
Unsteady Effects of Blade Row Interaction on Flow Field and Aerodynamic Performance of a Transonic Centrifugal Compressor Impeller
Authors: Yamada Kazutoyo , Kubo Kosuke , Iwakiri Kenichiro , Ishikawa Yoshihiro , Higashimori Hirotaka 
Published: September 2021

Abstract
This paper discusses the unsteady effects associated with the impeller/diffuser interaction on the internal flow field and aerodynamic performance of a centrifugal compressor. In centrifugal compressors with a vaned diffuser, the flow field is inherently unsteady due to the influence of interaction between the impeller and the diffuser, and the unsteadiness of the flow field can often have a great influence on the aerodynamic performance of the compressor. Especially in high-load compressors, it is considered that large unsteady effects are produced on the compressor performance with a strong flow unsteadiness. The unsteady effect on aerodynamic performance of the compressor has not been fully revealed yet, and sometimes the steady-state RANS simulation finds it difficult to predict the compressor performance.
In this study, numerical simulations have been conducted for a transonic centrifugal compressor with a vaned diffuser. The unsteady effects were clarified by comparing the numerical results between a single-passage steady-state RANS analysis and a full-annulus unsteady RANS analysis. The comparison of simulation results showed the difference in entropy generation in the impeller. The impingement of diffuser shock wave with the impeller pressure surface brought about a cyclic increase in the blade loading near the impeller trailing edge. Accordingly, with increasing tip leakage flow rate, a second tip leakage vortex was newly generated in the aft part of the impeller, which resulted in additional unsteady loss generation inside the impeller.
Optimization of a Tip Appendage for the Control of Tip Leakage Vortices in Axial Flow Fans
Authors: Meyer Thomas O. , van der Spuy Sybrand J. , Meyer Christiaan J. , Corsini Alessandro 
Published: September 2021

Abstract
This paper presents the numerical optimization of a tip appendage design for the passive control of tip leakage vortices in subsonic axial flow cooling fans. The studied class of fan was designed in the conventional manner without the consideration of tip clearance effects. As such, the objective of this investigation is the improvement of the aerodynamic performance characteristics of the datum fan through consideration of the blade tip geometry. Based on previous studies involving fan performance enhancement using various tip end-plate configurations, the most promising end-plate geometry which is found to best improve the fan’s performance characteristics is selected for further development through optimization. Before the optimization process can begin, initialization of the chosen end-plate’s design space using the Design of Experiments (DoE) technique is performed. Formulation of the response surface is based on a multi-objective multi-point objective function which considers the fan’s various performance metrics. Considering the optimization process, the Design and Analysis of Computer aided Experiments (DACE) method is used in the development of the Kriging based surrogate model’s (SM) database. The resulting database is coupled with an Efficient Global Optimization (EGO) algorithm which completes the workflow of the optimization routine. The Pareto-front of non-dominated solutions is used to guide the optimal design selection, on which the experimental evaluations are based. The experimental results of the optimized design indicate improved fan performance characteristics at greater than peak efficiency flow rates. This design is found to increase the datum fan’s design point performance characteristics by a value of 32.90 percent in total-to-static pressure rise and a 7.66 percentage point increase in total-to-static efficiency at the fan’s design speed of 722 rpm.
A Cradle to Gate Approach for Life-Cycle-Assessment of Blisk Manufacturing
Authors: Fricke Kilian , Gierlings Sascha , Ganser Philipp , Seimann Martin , Bergs Thomas 
Published: September 2021

Abstract
The aviation industry has been growing continuously over the past decades. Despite the current Covid-19 crisis, this trend is likely to resume in the near future. On an international level, initiatives like the Green Recovery Plan promoted by the European Union set the basis towards a more environmentally friendly future approach for the aero-industry. The increasing air traffic and the focus on a more sustainable industry as a whole lead to an extensive need for a more balanced assessment of a products life cycle especially on an ecological level.
Blisks (or IBRs) remain a central component of every current and very possible every future aero engine configuration. Their advantages during operation compared to conventional compressor rotors are met with a considerably complex manufacturing and production process. In the high-pressure compressor segment of an engine, the material selection is limited to Titanium alloys such as Ti6Al4V and heat-resistant Nickel-alloys such as Inconel718. The corresponding process chains consist of numerous different process steps starting with the initial raw material extraction and ending with the quality assurance (cradle to gate). Especially the central milling process requires a highly qualified process design to ensure a part of sufficient quality.
Life-Cycle-Assessments enable an investigation of a products overall environmental impact and ecological footprint throughout its distinct life-cycle. Formal LCAs are generally divided by international standards into four separate steps of analysis: the goal and scope definition, the acquisition of Life Cycle-Inventory, the Life-Cycle-Impact-Assessment and the interpretation. This content of this paper focuses on a general approach for Life-Cycle-Assessment for Blisk manufacturing.
• Firstly, the goal and scope is set by presenting three separate process chain scenarios for Blisk manufacturing, which mainly differ in terms of raw material selection and individual process selections for blade manufacturing.
• Secondly, the LCI data (Life-Cycle Inventory) acquisition is illustrated by defining all significant in- and outputs of each individual process step.
• Thirdly, the approach of a Life-Cycle-Impact-Assessment is presented by introducing the modelling approach in an LCA-software environment.
• Fourthly, an outlook and discussion on relevant impact-indicators for a subsequent interpretation of future results are conducted.
Establishing an Acceptance Criteria for Assessing Fatigue of Additive Repair Processes
Authors: Scott-Emuakpor Onome , Sheridan Luke , Beck Joseph , Runyon Brian , George Tommy 
Published: September 2021

Abstract
Criteria for assessing high cycle fatigue (HCF) capability is important for transitioning additive repair technologies to turbine engine applications. By studying the fatigue results of two laser directed energy deposition additive manufacturing repairs on airfoil representative Titanium 6Al-4V coupons, acceptable HCF results for repairs can be determined by observing the confidence in predicted values and the reliability of the empirical data compared to baseline results. The following document details the steps and philosophies behind fabricating coupons that capture the repair capability. Furthermore, regression analysis as well as investigations of dataset distribution, fractography, and microscopy are necessary for instilling confidence in the understanding of repair fatigue behavior. The findings in this work provide a decision gate with quantifiable metrics for advancing novel repair techniques.
Self-Excited High-Frequency Transverse Limit-Cycle Oscillations and Associated Flame Dynamics in a Gas Turbine Reheat Combustor Experiment
Authors: McClure Jonathan , Berger Frederik M. , Bertsch Michael , Schuermans Bruno , Sattelmayer Thomas 
Published: September 2021

Abstract
This paper presents the investigation of high-frequency thermoacoustic limit-cycle oscillations in a novel experimental gas turbine reheat combustor featuring both auto-ignition and propagation stabilised flame zones at atmospheric pressure. Dynamic pressure measurements at the faceplate of the reheat combustion chamber reveal high-amplitude periodic pressure pulsations at 3 kHz in the transverse direction of the rectangular cross-section combustion chamber. Further analysis of the acoustic signal shows that this is a thermoacoustically unstable condition undergoing limit-cycle oscillations. A sensitivity study is presented which indicates that these high-amplitude limit-cycle oscillations only occur under certain conditions: namely high power settings with propane addition to increase auto-ignition propensity. The spatially-resolved flame dynamics are then investigated using CH* chemiluminescence, phase-locked to the dynamic pressure, captured from all lateral sides of the reheat combustion chamber. This reveals strong heat release oscillations close to the chamber walls at the instability frequency, as well as axial movement of the flame tips in these regions and an overall transverse displacement of the flame. Both the heat release oscillations and the flame motion occur in phase with the acoustic mode. From these observations, likely thermoacoustic driving mechanisms which lead to the limit-cycle oscillations are inferred. In this case, the overall flame-acoustics interaction is assumed to be a superposition of several effects, with the observations suggesting strong influences from autoignition-pressure coupling as well as flame displacement and deformation due to the acoustic velocity field. These findings provide a foundation for the overall objective of developing predictive approaches to mitigate the impact of high-frequency thermoacoustic instabilities in future generations of gas turbines with sequential combustion systems.
On the Correlation Between Span-Wise Inducer Incidence and Impeller Diffusion for Ruled Surface and Barreled Sweep-Bow Impeller Design at IGV-Off-Design
Authors: Hildebrandt A. , Ceyrowsky T. , Klausmann J. , Metz K. A. 
Published: September 2021

Abstract
In the present paper, three centrifugal stages of high volume flow coefficient are compared to each-other regarding their aerodynamic performance in design point and off-design point conditions at different speed and IGV-setting angle: two stages with full-blade design (no splitter blades) have been numerically designed with different design geometry methodology. One geometry is based on a classical ruling surface design with a linear leading edge, the second geometry based on a fully-3d surface including a blade bow at the trailing edge and a barreled sweep at the leading edge. According to impeller test rig measurements and CFD-calculation, the classical ruling surface designed impeller outperforms the more sophisticated centrifugal stage with fully-3D-blade at fully axially guided IGV-flow. In the contrary, at closing IGV-off-design setting angles, towards surge operation, the fully-3D-blade-impeller performs with higher efficiency and steeper negative pressure slope. On the search of the geometrical causes for the different aerodynamic performance (especially at IGV-off-design conditions), focus is set on the analysis of IGV-flow-interaction with the inducer flow, and impeller diffusion. The one-dimensional -analysis of the span-wise flow at the impeller leading edge reveals that, compared with the ruling surface impeller, the fully 3D-blade performs with lower flow incidence losses in favor to IGV-off-design operation than at IGV-neutral position. The stream-wise flow analysis confirms the improved flow incidence characteristics of the 3D-blade impeller due to reduction of aerodynamic blockage and entropy production in the vicinity of the impeller leading edge. Based on CFD-calculations, a new correlation of secondary flow and flow incidence is proposed, to be used for one-dimensional modelling.
Aerodynamic Functional Diagnostics Based on Angular Momentum Transport Lines
Authors: Yang Xiang I. A. , Jariwala Vishal , Xu Haosen H. A. , Larosiliere Louis 
Published: September 2021

Abstract
In analogy with the classical concept of mass-flux-based streamlines, we define Angular Momentum Transport (AMT) lines as an aerodynamic functional diagnostic tool. The AMT lines are the ones whose tangents are given by the average angular momentum flux. The mathematical and physical properties of these AMT lines are exploited to study the generation, removal, and transport of angular momentum in turbomachinery components. We illustrate the concept by visualizing AMT lines in two relatively simple flows, namely, vaneless incompressible diffuser and von Karman flow (a model of centrifugal compressors). Next, we apply the proposed diagnostic tool to flow in a return channel. A return channel is a part of a multistage centrifugal compressor stage. Its principal function is to remove angular momentum. In this work, we apply the diagnostic tool of AMT lines to a Reynolds averaged Navier Stokes simulation (RANS) and a wall-modeled large eddy simulation (LES) of flow in the return channel. We show that AMT lines give us insights into the angular momentum transport process that are otherwise not available with conventional visualization tools.
Towards Reduced Order Models of Small-Scale Acoustically Significant Components in Gas Turbine Combustion Chambers
Authors: Kowshik Suhas A. , Shridhar Sumukha , Treleaven N. C. W. 
Published: September 2021

Abstract
Gas turbine combustion chambers contain numerous small-scale features that help to dampen acoustic waves and alter the acoustic mode shapes. This damping helps to alleviate problems such as thermoacoustic instabilities. During computational fluid dynamics simulations (CFD) of combustion chambers, these small-scale features are often neglected as the corresponding increase in the mesh cell count augments significantly the cost of simulation while the small physical size of these cells can present problems for the stability of the solver. In problems where acoustics are prevalent and critical to the validity of the simulation, the neglected small-scale features and the associated reduction in overall acoustic damping can cause problems with spurious, non-physical noise and prevents accurate simulation of transients and limit cycle oscillations. Low-order dynamical systems (LODS) and artificial neural networks (ANNs) are proposed and tested in their ability to represent a simple two-dimensional acoustically forced simulation of an orifice at multiple frequencies. These models were built using compressible CFD, using OpenFOAM, of an orifice placed between two ducts. The acoustic impedance of the orifice has been computed using the multi-microphone method and compared to a commonly used analytical model. Following this, the flow field downstream of the orifice has been modelled using both a LODS and ANN model. Both methods have shown the ability to closely represent the simulated dynamical flows at much lower computational cost than the original CFD simulation. This work opens the possibility of models that can dynamically predict the flow through, for instance, acoustic liners, dilution ports and fuel injectors in real engines during thermoacoustic instabilities without having to mesh and simulate these small-scale features directly. Such models may also assist in the accurate simulation of flame quenching due to cooling flows or the design of effusion cooled aerodynamic surfaces such as nozzle guide vanes (NGVs) and turbine blades.