bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of the Thermodynamic Potential of Supercritical Carbon Dioxide Cycles: A Systematic Approach
Authors: Crespi Francesco , Gavagnin Giacomo , Sánchez David , Martínez Gonzalo S. 
Published: August 2017

Since the renewed interest in supercritical carbon dioxide cycles, a large number of cycle layouts have been proposed in literature. These analyses, which are essentially theoretical, consider different operating conditions and modelling assumptions and thus the results are not comparable.
There are also works that aim to provide a fair comparison between different cycles in order to assess which one is most efficient. These analyses are very interesting but, usually, combine thermodynamic and technical restrictions thus making it difficult to draw solid and general conclusions with regards to which the cycle of choice in the future should be .
With this background, the present work provides a systematic thermodynamic analysis of twelve supercritical carbon dioxide cycles under similar working conditions, with and without technical restriction in terms of pressure and/or temperature. This yields very interesting conclusions regarding which the most interesting cycles are amongst those proposed in literature. Also, useful recommendations are extracted from the parametric analysis with respect to the directions that must be followed when searching for more efficient cycles.
The analysis is based on efficiency and specific work diagrams with respect to pressure ratio and turbine inlet temperature in order to enhance their applicability to plant designs driven by fuel economy and/or footprint.
Parametric Investigation of Gurney Flaps for the Use on Wind Turbine Blades
Authors: Alber Joerg , Pechlivanoglou Georgios , Paschereit Christian Oliver , Twele Jochen , Weinzierl Guido 
Published: August 2017

This paper presents a strategy to model the aerodynamic Gurney flap effect on two-dimensional airfoils and subsequently on the rotor blade performance of horizontal axis wind turbines.
The first part consists of the parametric investigation of 26 airfoil polar data-sets, derived from different, but comparable, wind tunnel experiments. They are evaluated and processed in terms of the lift and drag increase caused by Gurney flaps in comparison to each Baseline configuration. Consequently, a model is developed, transforming Baseline- into Gurney flap polar data for varying flap-heights. The results of the emerging Gurney Flap Polar Calculator are validated against the experimental lift and drag curves.
In the second part, the blade design of the NREL 5 MW Reference Turbine is modified by implementing polar data-sets of varying Gurney flap-heights, which are imported into the rotor simulation software QBlade. Thereupon, blade optimization strategies are examined regarding the two main Gurney flap applications on rotor blades: the retrofit and the design solution. The optimized retrofit solution on existing blades indicates power performance improvements, albeit at the expense of increasing structural loads. The optimized design solution on to-be-constructed blades, on the other hand, suggests chord-length reductions, while keeping the performance characteristics on a similar or even enhanced level.
It is concluded that aerodynamic improvements are achieved by relatively small Gurney flap-heights, which are applied at specific blade positions.
Numerical Study on the Reduction of NOx Emissions From Pulse Detonation Combustion
Authors: Djordjevic Neda , Hanraths Niclas , Gray Joshua , Berndt Phillip , Moeck Jonas 
Published: August 2017

A change in the combustion concept of gas turbines from conventional isobaric to constant volume combustion (CVC), such as in pulse detonation combustion (PDC), promises a significant increase in gas turbine efficiency. Current research focuses on the realization of reliable PDC operation and its challenging integration into a gas turbine. The topic of pollutant emissions from such systems has so far received very little attention. Few rare studies indicate that the extreme combustion conditions in PDC systems can lead to high emissions of nitrogen oxides (NOx). Therefore, it is essential already at this stage of development to begin working on primary measures for NOx emissions reduction, if commercialization is to be feasible.
The present study evaluates the potential of different primary methods for reducing NOx emissions produced during pulsed detonation combustion of hydrogen. The considered primary methods involve utilization of lean combustion mixtures or its dilution by steam injection or exhaust gas recirculation. The influence of such measures on the detonability of the combustion mixture has been evaluated based on detonation cell sizes modelled with detailed chemistry. For the mixtures and operating conditions featuring promising detonability, NOx formation in the detonation wave has been simulated by solving the one-dimensional reacting Euler equations. The study enables an insight into the potential and limitations of considered measures for NOx emissions reduction and lays the groundwork for optimized operation of pulse detonation combustion systems.
Transient Thermal Modelling of Whole GT Engine With a Partly Coupled FEM-Fluid Network Approach
Authors: Giuntini Sabrina , Andreini Antonio , Facchini Bruno , Mantero Marco , Pirotta Marco , Olmes Sven , Zierer Thomas 
Published: August 2017

The present work aims at investigating a new methodology developed at Ansaldo Energia, for the transient finite element modelling of the whole engine with an axisymmetric approach.
The strong coupling and non linearity in the heat transfer process during transient thermal analyses are handled by a partly coupled scheme. The 2D axisymmetric finite element model includes a dedicated thermal fluid network where fluid-metal temperatures are computed. In the overall procedure the selected finite element solver is a customized version of CalculiX®, while mass flow rates and pressure distributions in each thermal fluid network element are provided by external fluid network solvers in terms of customized time series.
This paper represents a first insight about a fully integrated WEM (Whole Engine Modelling) procedure currently under development. Geometrical changes during operation, lead to different fluid properties affecting heat transfer coefficients too. These modified conditions in their turn impact the material temperature and displacements. The future implementation steps will be oriented on the adoption of a customized version of the native CalculiX® fluid network solver with the aim of developing a fully integrated procedure able to take into account the interaction between the secondary air system and the modifications in the clearances and gaps due to the thermal and mechanical loads.
In this paper, a detailed description of the procedure will be reported with comprehensive discussions about some fundamental modelling aspects. Preliminary results, related to the first application of the new methodology to the transient thermal modelling of a simplified test case representative of real engine geometries, will be presented.
The Response to Incident Acoustic Waves of the Flow Field Produced by a Multi-Passage Lean-Burn Aero-Engine Fuel Injector
Authors: Treleaven Nicholas C. W. , Su Jialin , Garmory Andrew , Page Gary J. 
Published: August 2017

Previous work has shown that compressible unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations, with suitable acoustic boundary conditions, are capable of correctly predicting the acoustic impedance of simplified fuel injectors. In this work the method developed is applied to simulating the acoustically forced flow in and downstream of a realistic multipassage fuel injector. The simulations are validated by comparing the impedance of the injector with data obtained experimentally by a multi-microphone technique. Such results can then be used in conjunction with a suitable low-order thermo-acoustic network model to predict the stability of combustors. However the validated simulations can also be used to reveal further details about the effect of acoustic forcing on the flow field.
The velocity flow field produced by the injector with and without acoustic forcing is analysed using snapshot POD to determine the large scale energy containing structures within the flow. In the non-acoustically forced simulations it was found that the first four POD modes correspond to two rotating spiral modes, designated as the m = 1 and m = 2 modes with a peak frequency content of 450 Hz for the first mode and 1000 Hz for the second mode corresponding to experimental Hot-Wire measurements made in a separate study. It is hypothesised that these spiral modes will affect the atomisation, evaporation and mixing of the fuel in subsequent planned two-phase simulations. POD analysis of the flow subjected to 300 Hz, 300 Pa acoustic excitation shows that the first four POD modes correspond to similarly shaped spiral modes. The acoustic excitation is responsible for the appearance of 4 POD modes within the injector body that correspond to two push-pull velocity modes with axes of symmetry perpendicular to each other. The acoustic forcing also produces two additional POD modes that most likely represent the non-linear interaction between the push-pull and spiral modes.
Further analysis of the fluctuations in pressure, mass flow rate, angular velocity and swirl number, within the passages and at the injector exit plane, show that the fluctuations in pressure and mass flow rate average across the passages while variations in angular velocity and swirl number sum across the passages. The relationship between mass flow rate, angular velocity and swirl number is discussed with reference to general observations of the sensitivity of flames to fluctuations in these quantities.
Continuous Closed-Loop Transonic Linear Cascade for Aero-Thermal Performance Studies in Micro-Turbomachinery
Authors: Yakirevich E. , Miezner R. , Leizeronok B. , Cukurel B. 
Published: August 2017

The present work summarizes the design process of a new continuous closed-loop hot transonic linear cascade. The facility features fully modular design which is intended to serve as a test bench for axial micro-turbomachinery components in independently varying Mach and Reynolds numbers ranges of 0 – 1.3 and 2·104 – 6·105 respectively. Moreover, for preserving heat transfer characteristics of the hot gas section, the gas to solid temperature ratio (up to 2) is retained. This operational environment has not been sufficiently addressed in prior art, although it is critical for the future development of ultra-efficient high power or thrust devices.
In order to alleviate the dimension specific challenges associated with micro-turbomachinery, the facility is designed in a highly versatile manner, and can easily accommodate different geometric configurations (pitch, ±20° stagger angle, ±20° incidence angle), absent of any alterations to the test section. Owing to the quick swap design, the vane geometry can be easily replaced without manufacturing or re-assembly of other components. Flow periodicity is achieved by the inlet boundary layer suction and independently adjustable tailboard mechanisms. Enabling test-aided design capability for micro gas turbine manufacturers, aero-thermal performance of various advanced geometries can be assessed in engine relevant environments.
Effect of Uneven Wall Heating Conditions Under Different Buoyancy Numbers for a One Side Rib-Roughened Rotating Channel
Authors: Wang Zhi , Corral Roque 
Published: August 2017

This paper investigates the impacts of uneven wall heating conditions under different Buoyancy numbers on flow field and heat transfer performance of a rotating channel with one side smooth and one side roughened by 45 degree inclined ribs. Parametric RANS simulations were conducted under two different wall heating conditions: only ribbed wall heated, as in experiment setup, and all walls heated, under three different Buoyancy numbers. Results are compared, when available, with experimental results.
Numerical results show that uneven wall heating has only a minor impact on non-rotating cases and very low buoyancy rotating cases. However, it has a significant influence, on both, the heat transfer behaviour and the flow field, when the Buoyancy number is large. In the ribbed trailing rotating tests, the all walls heated cases show significantly higher heat transfer rate than only the ribbed wall heated cases. The discrepancy is enlarged as Buoyancy number increases. The heat transfer in the all walls heated case increases monotonically with the Buoyancy number whereas in the ribbed wall heated case is slight reduced. In the ribbed leading rotating tests, the heat transfer sensitivity to the heating conditions is not conspicuous, and for both cases, the heat transfer level slightly reduced as Buoyancy number increases.
The flow field investigation shows that, there is a significant displacement of main flow in the all walls heated cases than only the ribbed wall heated cases under high Buoyancy numbers. This displacement is due to the buoyancy effect and responsible for the heat transfer differences in uneven heating problems. According to the results obtained in the paper, we conclude that when buoyancy effects are relevant, the heating settings can play a significant role in the heat transfer mechanisms and therefore in the experimental and numerical results.
Measurements of Radial Vortices, Spill Forward and Vortex Breakdown in a Transonic Compressor
Authors: Brandstetter Christoph , Jüngst Maximilian , Schiffer Heinz-Peter 
Published: August 2017

The phenomena prior to rotating stall were investigated in a high-speed compressor test rig using optical and pneumatic measurement techniques. A number of throttling procedures was performed at transonic and subsonic speedlines with the aim to detect the unsteady effects initiating rotating stall or large amplitude blade vibrations. At transonic speed radial vortices traveling around the circumference were detected in the upstream part of the rotor using phase-locked PIV measurements above 92% span and unsteady wall pressure measurements. When these radial vortices impinge on a blade leading edge, they cause a forward spill of fluid around the leading edge. The effects are accompanied by a large-scale vortex breakdown in the blade passage leading to immense blockage in the endwall region. At subsonic speeds, the observed flow phenomena are similar but differ in intensity and structure.
During the throttling procedure, blade vibration amplitudes were monitored using strain gauges and blade tip timing instrumentation. Non-synchronous blade vibrations in the first torsional eigenmode were measured as the rotor approached stall. Using the different types of instrumentation, it was possible to align the aerodynamic flow features with blade vibration levels. The results show a clear correlation between the occurrence of radial vortices and blade vibrations.
Comparison of 3D Unsteady Transient Conjugate Heat Transfer Analysis on a High Pressure Cooled Turbine Stage With Experimental Data
Authors: Liu Jong-Shang , Morris Mark C. , Malak Malak F. , Mathison Randall M. , Dunn Michael G. 
Published: August 2017

In order to have higher power to weight ratio and higher efficiency gas turbine engines, turbine inlet temperatures continue to rise. State-of-the-art turbine inlet temperatures now exceed the turbine rotor material capability. Accordingly, one of the best methods to protect turbine airfoil surfaces is to use film cooling on the airfoil external surfaces. In general, sizable amounts of expensive cooling flow delivered from the core compressor are used to cool the high temperature surfaces. That sizable cooling flow, on the order of 20% of the compressor core flow, adversely impacts the overall engine performance and hence the engine power density. With better understanding of the cooling flow and accurate prediction of the heat transfer distribution on airfoil surfaces, heat transfer designers can have a more efficient design to reduce the cooling flow needed for high temperature components and improve turbine efficiency. This in turn lowers the overall specific fuel consumption (SFC) for the engine. Accurate prediction of rotor metal temperature is also critical for calculations of cyclic thermal stress, oxidation, and component life.
The utilization of three-dimensional computational fluid dynamics (3D CFD) codes for turbomachinery aerodynamic design and analysis is now a routine practice in the gas turbine industry. The accurate heat-transfer and metal-temperature prediction capability of any CFD code, however, remains challenging. This difficulty is primarily due to the complex flow environment of the high-pressure turbine, which features high speed rotating flow, coupling of internal and external unsteady flows, and film-cooled, heat transfer enhancement schemes. In this study, conjugate heat transfer (CHT) simulations are performed on a high-pressure cooled turbine stage, and the heat flux results at mid span are compared to experimental data obtained at The Ohio State University Gas Turbine Laboratory (OSUGTL). Due to the large difference in time scales between fluid and solid, the fluid domain is simulated as steady state while the solid domain is simulated as transient in CHT simulation. This paper compares the unsteady and transient results of the heat flux on a high-pressure cooled turbine rotor with measurements obtained at OSUGTL.
A Low Cycle Fatigue Life Prediction Model of Single Crystal Nickel-Based Superalloys Using Critical Plane Approach Combined With Crystallographic Slip Theory
Authors: Mu Lijuan , Dong Xuezhi , Gao Qing , Tian Yongsheng , Tan Chunqing 
Published: August 2017

The anisotropy is the most remarkable characteristic for single crystal nickel-based superalloys, which makes fatigue behavior and life prediction highly correlate with the crystallographic orientation. Based on critical plane approach and preferred crystallographic slip mechanism, an anisotropic LCF life model is proposed to account for orientation-dependent fatigue life in this paper. In addition, the effects of the mean stress and stress-weakening caused by asymmetric loading are also considered. The critical plane is determined by searching for 30 potential slip systems. Moreover, the slip plane with the maximum resolved shear stress amplitude in the crystallographic microstructure of the single crystal nickel-based superalloy is chosen as the critical plane.
The LCF test data are utilized to obtain the regression equation by multiple linear fitting method. The presented LCF life model is applicable for more complex stress state and has higher prediction accuracy than the CDY model.
Tackling Highly Constrained Design Problems: Efficient Optimisation of a Highly Loaded Transonic Compressor
Authors: Baert Lieven , Beaucaire Paul , Leborgne Michaël , Sainvitu Caroline , Lepot Ingrid 
Published: August 2017

Turbomachinery components are designed to achieve high performances while being exposed to a complex flow environment with varying operating conditions. Whereas the purpose of a new design optimisation is straightforward — obtaining a better design than the already existing one — the actual process itself remains a challenging task, permanently confronted to the dual need to reduce the cycle time and to further integrate complexity and multiple physics. The extensive use of numerical simulations has contributed in a significant way to the design of state-of-the-art blade geometries. To deal with expensive high-fidelity computations, surrogate-based optimisation (SBO) has become an established and recognised approach. In order to be useful within an industrial context, it is crucial that this SBO process is capable of efficiently handling high-dimensional design spaces as well as managing highly constrained design problems.
This work presents innovative auto-adaptive surrogates, exploiting a blend of interpolation/regression and classification, implemented in the integrated optimisation platform Minamo. As a demonstrator based on NASA Rotor 37, an aero-mechanical multi-point optimisation has been performed. For a design space with 60 parameters, significant performance gains have been obtained (+4% after 250 evaluations or less than a fortnight’s runtime) while considering over 30 constraints. The proposed SBO approach offers therefore many opportunities for turbomachinery applications tackling highly constrained design problems. Despite the unavoidable curse of dimensionality, the proposed approach is able to efficiently achieve reliable results at a cost that is in line with industrial needs and it provides a conclusive asset in the frame of design specifications evolving along the design cycle.
High Momentum Jet Flames at Elevated Pressure: A — Experimental and Numerical Investigation for Different Fuels
Authors: Lammel Oliver , Severin Michael , Ax Holger , Lückerath Rainer , Tomasello Andrea , Emmi Yeshawini , Noll Berthold , Aigner Manfred , Panek Lukasz 
Published: August 2017

In this work, results of comprehensive high-pressure tests and numerical simulations of high momentum jet flames in an optically accessible combustion chamber are presented. A generic single nozzle burner was designed as a full-scale representation of one duct of a high temperature FLOX® gas turbine combustor with a model pilot burner supporting the main nozzle. As an advanced step of the FLOX® gas turbine combustor development process, tests and simulations of the entire burner system (consisting of a multi nozzle main stage plus a pilot stage) are complemented with this work on an unscaled single nozzle combustor, thus supporting the development and testing of sub concepts and components like the mixing section and dual-fuel injectors. These injectors incorporate a gaseous fuel stage and a spray atomizer for liquid fuels, both separately exchangeable for testing of different fuel placement concepts.
The combustor was successfully operated at gas turbine relevant conditions with natural gas including a variation of the Wobbe index, and with light heating oil with and without water admixture. The presented work is the first of two contributions and covers the description of the experimental setup, an overview of the numerical methods, high-pressure test results for different fuels and variations of the operating conditions including exhaust gas measurements and basic optical diagnostic methods, together with CFD results for several cases. The other part will present detailed and focused investigations of few conditions by complex and extensive optical and laser combustion diagnostics.