bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluating the Use of Leaned Stator Vanes to Produce a Non-Uniform Flow Distribution Across the Inlet Span of a Mixed Flow Turbine Rotor
Authors: Morrison Richard , Spence Stephen , Kim Sung In , Leonard Thomas , Starke Andre 
Published: November 2019

Abstract
Current trends in the automotive industry have placed an increased emphasis on downsized turbocharged engines for passenger vehicles. The turbocharger is increasingly relied upon to improve power output across a wide range of engine operating conditions, placing a greater emphasis on turbocharger offdesign performance. An off-design condition of significant importance is performance at low turbine velocity ratios, since it is relevant to engine transient response and also to efficient energy extraction from pressure pulses in the unsteady exhaust flow. An increased focus has been placed on equipping turbochargers with mixed flow turbine rotors instead of conventional radial flow turbine rotors to improve off-design performance and to reduce rotor inertia.
A recognized feature of a mixed flow turbine is the spanwise variation of flow conditions across the blade leading edge. This is a consequence of the reduction in leading edge radius from shroud to hub, coupled with the increasing tangential velocity of the flow due to conserved angular momentum as the radius decreases. The result is increasingly positive incidence towards the hub side of the leading edge. The resulting region of highly positive incidence at the hub produces separation from the suction surface and generates significant loss within the rotor passage.
The aim of this study was to determine if the losses in a MFT could be reduced by the use of leaned stator vanes, which deliberately created a significant spanwise variation of flow angle between hub and shroud at rotor inlet, to reduce the positive incidence at the hub. The turbine performance with a series of leaned vanes was compared against that of a straight vane using a validated CFD model. It was found that increasing vane lean improved turbine performance at all operating points considered. An increase of 3.2 percentage points in stage total-to-static efficiency was achieved at a key off-design operating point.
Experimental testing of a set of leaned vanes and the baseline vanes confirmed the advantage of the leaned vanes at all operating points, with an increase in measured efficiency of 2.6 percentage points at the key off-design condition. Unsteady CFD models confirmed the same level of improvement at this operating point.
The CFD and experimental results confirmed that the losses in a MFT can be reduced by the use of leaned stator vanes to shape the flow at rotor inlet.
Comparison of the Predicted Creep Life and Hot Spin Tests for the Turbine Wheel in Automotive Turbocharger
Authors: Sakamoto K. , Ozaki M. , Furuta Y. , Yoshida T. 
Published: November 2019

Abstract
In this study, it is confirmed the accuracy of a technique to predict creep damage using Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) analysis. First of all, the metal temperature of the turbine wheel was measured by a thermo-camera. Next, heat transfer analysis was carried out to confirm the accuracy of the thermal boundary condition. After that, hot spin tests for turbine wheels were carried out. The results confirmed that the predicted creep life was in good agreement with the rupture time from the hot spin test. With this technique, it was possible to develop a high durability turbine wheel under severe high temperature and high turbo speed conditions.
Numerical and Experimental Studies of Labyrinth Seal Aeroelastic Instability
Authors: Miura Toshimasa , Sakai Naoto 
Published: November 2019

Abstract
A labyrinth seal is commonly used to decrease the flow leakage loss between rotating and static components in aero engines. It is susceptible to aeroelastic instability because of its low stiffness. The aim of this study is to clarify the physical mechanism of labyrinth seal flutter and to establish a method to predict and suppress it effectively. To achieve this, both numerical and experimental investigations are conducted using ANSYS CFX and ANSYS Mechanical. These solvers are coupled to simulate the flutter precisely. Also, to assess the accuracy of the simulation qualitatively and quantitatively, a test rig is built.
In the first part of this study, the accuracy of the numerical method is confirmed for several test cases with different seal clearance variations. Both one-way and two-way fluid structure interaction (FSI) analyses are performed. Flutter inception is evaluated in detail for various pressure ratios and rotation speeds. The numerical results show reasonably good agreement with the experimental results. It is also confirmed that the aeroelastic instability is very sensitive to the seal clearance variations. These results show the same tendency as those in previous works [1–5].
In the second part of this study, this paper tries to develop a flutter suppression method without deteriorating the flow leakage performance. This is achieved by changing the seal geometry without changing the seal clearance variation. To detect the important geometric parameters, the contribution of each geometric component to aeroelastic instability is carefully analyzed. On the basis of this, the seal geometry is modified and its performance is also evaluated. The optimized labyrinth seal shows good performance in terms of flow leakage and aeroelastic stability. Through this study, a new method to suppress the flutter with low flow leakage is established.
Design of Control Laws Based on Inverted Decoupling and LMI for a Turboprop Engine
Authors: Chen Huairong , Wang Xi , Zhu Meiyin , Gu Nannan , Yang Shubo 
Published: November 2019

Abstract
A systematic approach of designing control laws for a turboprop engine is proposed. Firstly, the interactions between the control loops of a class of two-input two-output (TITO) plant are qualitatively analyzed. Since inverted decoupling well retains the dynamic characteristics of the original system, it is chosen to decouple the interactions so that the control loops can be divided into two single-input single-output (SISO) control loops. Then, the designed PI controller parameters for each control loop are obtained by solving linear matrix inequalities (LMIs) derived from Static Output Feedback (SOF) and regional pole placement. Considering that the main objective of turboprop engine control system is to ensure the demanded power at a constant propeller speed and component power is difficult to measure, this paper chooses fuel flow rate to control high pressure shaft speed and blade angle to control power turbine speed. Finally, this systematic approach is implemented and tested on integrated model of two-spool turboprop engine (TSTPE) on MATLAB. The simulation analysis and results of each step are presented in this paper. The simulation results show that applying inverted decoupling to decouple the interactions between the control loops of TSTPE is effective, and the designed control laws are capable of controlling fuel flow rate and blade angle of turboprop engine for high pressure shaft speed and power turbine shaft speed commands with appropriate tracking performance.
Design of Contoured Turbine Endwalls in the Presence of Purge Flow: A Feature-Based Approach
Authors: Schreiner B. D. J. , Wilson M. , Li Y. S. , Sangan C. M. 
Published: November 2019

Abstract
Endwall contouring is used to increase the aerodynamic efficiency of both compressor and turbine stages in industrial gas turbines and aeroengines. The complex interaction between the secondary air-leakage, used to cool the turbine disc, and the mainstream gas path, leads to an unsteady flow field that is challenging to compute. Current endwall designs have shown sensitivity to the introduction of secondary air, with stage efficiency improvements being reduced, or in the limit, eliminated altogether.
A computational study of an engine-representative turbine stage was conducted using an unsteady RANS solver. Previously published computations of the baseline axisymmetric endwall were validated with experimental data from a geometrically similar test rig. Understanding from this prior study was used to inform the design process for contoured endwalls, namely through the identification of three key geometric features: the leading-edge feature; the suction-side trough; the pressure-side trough.
The baseline axisymmetric endwall showed periodic unsteadiness, large secondary flow features and an egress plume which dominated the aerodynamics of the stage. The implementation of a suction-side trough (i.e. making the endwall non-axisymmetric) reduced the magnitude of the unsteadiness by controlling the path of the egress plume. The trough also reduced the span-wise migration of the egress plume through the passage and provided modest control over pitchwise position. In corroboration with the findings of other authors, the introduction of a leading-edge feature was also used to reduce the leading edge horseshoe vortex,. The pressure-side trough enabled the prominence of the leading-edge feature to be enhanced, however it increased the span-wise migration of the egress plume. Insight generated from computations of the three distinct geometric features resulted in an improved endwall concept; the improved endwall demonstrated a 0.4% net efficiency gain for the stage relative to the cylindrical baseline.
Study on Analytical Method for Thermal and Flow Field of a Turbocharger With the Catalyst Unit
Authors: Kitamura Tsuyoshi , Ibaraki Seiichi , Kihara Yuichi , Hoshi Toru , Ebisu Motoki 
Published: November 2019

Abstract
The analytical and experimental study on thermal and flow field of a turbocharger with the catalyst unit has been conducted for the thermal management at the downstream side of turbochargers, which have crucial effects on activation of catalyst units.
CHT (Conjugate Heat Transfer) calculations, working for simulating heat transfer with mutual dependence between solid structures and fluid, are applied to the turbocharger including the turbine section, the bearing housing and the catalyst unit to acquire the whole of thermal and flow field accurately. The modeling for catalyst element has also been developed.
In addition, the gas stand test demonstrated turbochargers under cold start-up condition to validate CHT calculations. Analytical results are evaluated against experimental data. Eventually, the proposed analytical method has been proved to have the advantage of designing for heating catalyst units.
Compressor Characteristics for Transient and Part-Load Performance Simulation
Authors: Kavvalos Mavroudis D. , Kyprianidis Konstantinos G. 
Published: November 2019

Abstract
Compressor performance tests are mainly focused on the typical range of operation, resulting in limited knowledge of compressor behavior in the low-speed region. The main target of this work comprises the generation of compressor characteristics at low part-load by giving particular insight into the physical aspect of this operating condition. It is necessary for running transient and part-load performance simulation and can be considered as the first crucial step toward an optimal engine starting schedule.
Modelling the low part-load operating regime requires accurate component performance maps extended to the low-speed area, where engine starting and altitude relight occur. In this work, a robust methodology for generating compressor maps in the low part-load operating regime is developed. Compressor geometry and typical operation range compressor map are required as inputs. Two different modelling processes are incorporated within this methodology. Extrapolation based on the principle of similarity laws with modified law exponents constitutes the first modelling process, which seems inaccurate when predicting compressor performance at fixed-rotor conditions. Interpolation based on the fixed-rotor characteristic constitutes the second modelling process, which can be either linear or adaptive. The adaptive interpolation scheme was developed by the authors and generates low-speed characteristics using the same allocation trend as the one obtained from given performance data. It is observed that performance data points of each β-line follow an exponential trend in mass flow differences while increasing rotational speed, with a calculated average relativized Root Mean Square (RMS) error of less than 5%. Adapting the same trend in mass flow to the low-speed region, a compressor performance map with continuous exponential trend in all characteristics (for part- and full-load conditions) can be achieved. Implementing the developed methodology on the High Pressure Compressor (HPC) of the Energy Efficient Engine (E3) project is also presented, showcasing its applicability and the merit of it being incorporated into any conventional performance prediction tool. Furthermore, a sensitivity analysis for input variables, namely compressor exit effective area and pressure loss model coefficients is carried out, demonstrating the significant impact of the former on the shape of the low part-load characteristics.
Generation of compressor characteristics at low-speeds with this methodology can be viewed as an enabler for running credible transient starting simulation and transient diagnostics, thereby defining an optimal starting schedule, applicable to both power generation and aerospace industry.
Aerothermal Simulations Comparisons of a Shaped-Hole Film Cooling Flow
Authors: Simon Matthieu , Gautier Sébastien , Vanoli Emmanuel , Auzillon Pierre 
Published: November 2019

Abstract
Film Cooling is a crucial technology for engine manufacturer to develop high-efficiency gas turbine engines by raising turbine entry temperature. A lot of cooling holes geometries have been studied in the past few years in tests, as well as numerical simulations. Shaped holes are nowadays a standard geometry for protecting the blades, given the performance improvement compared to cylindrical holes. Numerical correlation with physical tests is challenging due to the high sensitivity to thermal mixing and adequate boundary condition predictions.
This paper is devoted to numerical simulation comparisons of the 777 shaped holes configuration of Pennsylvania State University, for an incompressible flow with a density ratio of 1.5, a blowing ratio of 1.5 and a free stream turbulence intensity of 0.5%. Two different simulations have been chosen: a state-of-the-art RANS simulation with k-e Realizable model computed with ANSYS Fluent and a high fidelity solver Lattice-Boltzmann Method computed with Simulia PowerFLOW.
In order to improve the accuracy of numerical simulations against test results, this article deals with an aerothermal model of the complete test bench. This additional modeling allows to strongly improve thermal prediction and to understand initial discrepancies related to test bench environment.
Results show that k-ε Realizable simulation provides a good prediction of average effectiveness, but local differences appear due to inherent RANS modeling limitations. On the other hand, LBM simulation provides excellent results for both aerodynamic and thermal quantities: tests results are very well reproduced.
A Comparison of Turbulence Levels From PIV and CTA Downstream of a Low-Pressure Turbine Cascade at High-Speed Flow Conditions
Authors: Chemnitz Silvio , Niehuis Reinhard 
Published: November 2019

Abstract
The development and verification of new turbulence models for RANS equations based numerical methods require reliable experimental data with a deep understanding of the underlying turbulence mechanisms. High accurate turbulence measurements are normally limited to simplified test cases under optimal experimental conditions. This work presents comprehensive three-dimensional data of turbulent flow quantities, comparing advanced constant temperature anemometry (CTA) and stereoscopic particle image velocimetry (PIV) methods under realistic test conditions. The experiments are conducted downstream of a linear, low-pressure turbine cascade at engine relevant high speed operating conditions. The special combination of high subsonic Mach and low Reynolds number results in a low density test environment, challenging for all applied measurement techniques. Detailed discussions about influences affecting the measured result for each specific measuring technique is given. The presented time mean fields, as well as total turbulence data demonstrate with an average deviation of ΔTu < 0.4% and ΔC/Cref < 0.9% an extraordinary good agreement between the results from the triple sensor hot-wire probe and the 2D3C-PIV setup. Most differences between PIV and CTA can be explained by the finite probe size and individual geometry.
sCO2 Power Cycle Component Cost Correlations From DOE Data Spanning Multiple Scales and Applications
Authors: Weiland Nathan T. , Lance Blake W. , Pidaparti Sandeep R. 
Published: November 2019

Abstract
Supercritical CO2 (sCO2) power cycles find potential application with a variety of heat sources including nuclear, concentrated solar (CSP), coal, natural gas, and waste heat sources, and consequently cover a wide range of scales. Most studies to date have focused on the performance of sCO2 power cycles, while economic analyses have been less prevalent, due in large part to the relative scarcity of reliable cost estimates for sCO2 power cycle components. Further, the accuracy of existing sCO2 techno-economic analyses suffer from a small sample set of vendor-based component costs for any given study. Improved accuracy of sCO2 component cost estimation is desired to enable a shift in focus from plant efficiency to economics as a driver for commercialization of sCO2 technology.
This study reports on sCO2 component cost scaling relationships that have been developed collaboratively from an aggregate set of vendor quotes, cost estimates, and published literature. As one of the world’s largest supporters of sCO2 research and development, the Department of Energy (DOE) National Laboratories have access to a considerable pool of vendor component costs that span multiple applications specific to each National Laboratory’s mission, including fossil-fueled sCO2 applications at the National Energy Technology Laboratory (NETL), CSP at the National Renewable Energy Laboratory (NREL), and CSP, nuclear, and distributed energy sources at Sandia National Laboratories (SNL). The resulting cost correlations are relevant to sCO2 components in all these applications, and for scales ranging from 5–750 MWe. This work builds upon prior work at SNL, in which sCO2 component cost models were developed for CSP applications ranging from 1–100 MWe in size.
Similar to the earlier SNL efforts, vendor confidentiality has been maintained throughout this collaboration and in the published results. Cost models for each component were correlated from 4–24 individual quotes from multiple vendors, although the individual cost data points are proprietary and not shown. Cost models are reported for radial and axial turbines, integrally-geared and barrel-style centrifugal compressors, high temperature and low temperature recuperators, dry sCO2 coolers, and primary heat exchangers for coal and natural gas fuel sources. These models are applicable to sCO2-specific components used in a variety of sCO2 cycle configurations, and include incremental cost factors for advanced, high temperature materials for relevant components. Non-sCO2-specific costs for motors, gearboxes, and generators have been included to allow cycle designers to explore the cost implications of various turbomachinery configurations. Finally, the uncertainty associated with these component cost models is quantified by using AACE International-style class ratings for vendor estimates, combined with component cost correlation statistics.
Static and Dynamic Analysis of a NACA 0021 Airfoil Section at Low Reynolds Numbers: Drag and Moment Coefficients
Authors: Holst David , Balduzzi Francesco , Bianchini Alessandro , Nayeri Christian Navid , Paschereit Christian Oliver , Ferrara Giovanni 
Published: November 2019

Abstract
Wind industry needs high quality airfoil data for a range of the angle of attack (AoA) much wider than that often provided by the technical literature, which often lacks data i.e. in deep- and post-stall region. Especially in case of vertical axis wind turbines (VAWTs), the blades operate at very large AoAs, which exceed the range of typical aviation application. In a previous study, some of the authors analyzed the trend of the lift coefficient of a NACA 0021 airfoil, using the suggestions provided by detailed CFD analyses to correct experimental data at low Reynolds numbers collected in an open-jet tunnel. In the present study, the correction method is extended in order to analyze even the drag and moment coefficients over a wide range of AoAs for two different Reynolds numbers (Re = 140k and Re = 180k) of particular interest for small wind turbines. The utility of these data is again specifically high in case of VAWTs, in which both the drag and the moment coefficient largely contribute to the torque. The investigation involves tunnel data regarding both static polars and dynamic sinusoidal pitching movements at multiple reduced frequencies. Concerning the numerical simulations, two different computational domains were considered, i.e. the full wind tunnel and the open field. Once experimental data have been purged by the influence of the wind tunnel by means of the proposed correction method, they were compared to existing data for similar Reynolds both for the NACA0021 and for similar airfoils. By doing so, some differences in the static stall angle and the extent of the hysteresis cycle are discussed. Overall, the present paper provides the scientific community with detailed analysis of low-Reynolds NACA 0021 data in multiple variations, which may enable, inter alia, a more effective VAWT design in the near future.
Comparison of Hydrogen Micromix Flame Transfer Functions Determined Using RANS and LES
Authors: McClure Jonathan , Abbott David , Agarwal Parash , Sun Xiaoxiao , Babazzi Giulia , Sethi Vishal , Gauthier Pierre 
Published: November 2019

Abstract
Hydrogen has been proposed as an alternative fuel to meet long term emissions and sustainability targets, however due to the characteristics of hydrogen significant modifications to the combustion system are required. The micromix concept utilises a large number of miniaturised diffusion flames to improve mixing, removing the potential for local stoichiometric pockets, flash-back and autoignition. No publicly available studies have yet investigated the thermoacoustic stability of these combustion systems, however due to similarities with lean-premixed combustors which have suffered significant thermoacoustic issues, this risk should not be neglected.
Two approaches have been investigated for estimating flame response to acoustic excitations of a single hydrogen micromix injector element. The first uses analytical expressions for the flame transfer function with constants obtained from RANS CFD while the second determines the flame transfer function directly using unsteady LES CFD. Results show the typical form of the flame transfer function but suggest micromix combustors may be more susceptible to higher frequency instabilities than conventional combustion systems. Additionally, the flame transfer function estimated using RANS CFD is broadly similar to that of the LES approach, therefore this may be suitable for use as a preliminary design tool due to its relatively low computational expense.