bluuebunny/crossref_metadata_2025 huggingface dataset:
Aero-Thermal Aspects of Film Cooled Nozzle Guide Vane Endwalls: Part 2 — Thermal Measurements
Authors: Alqefl Mahmood H. , Nawathe Kedar P. , Chen Pingting , Zhu Rui , Kim Yong W. , Simon Terrence W.
Published: January 2021

Flow over gas turbine endwalls is complex and highly three-dimensional. As boundaries for modern engine designs are pushed, this already-complex flow is affected by aggressive application of film cooling flows that actively interact. This two-part study describes, experimentally, the aero-thermal interaction of cooling flows near the endwall of a first stage nozzle guide vane passage. The approach flow conditions represent flow exiting a low-NOx combustor. The test section includes geometric and cooling details of a combustor-turbine interface in addition to endwall film cooling flows injected upstream of the passage. The first part of this study describes in detail, the passage aerodynamics as affected by injection of cooling flows. It reveals a system of secondary flows, including the newly-discovered Impingement Vortex, which redefines our understanding of the aerodynamics of flow in a modern, film-cooled, first-stage vane row. The second part investigates, through thermal measurements, the distribution, mixing and disruption of cooling flows over the endwall. Measurements are made with and without active endwall film cooling. Descriptions are made through adiabatic surface effectiveness measurements and correlations with in-passage velocity (presented in part one) and thermal fields. Results show that the newly-discovered impingement vortex has a positive effect on coolant distribution through passage vortex suppression and by carrying the coolant to hard-to-cool regions in the passage, including the pressure surface near the endwall.
Background-Grid Based Mapping Approach to Film Cooling Meshing: Part III — Applications in a Full-Cooled Turbine Vane
Authors: Wang Ruiqin , Yan Xin
Published: January 2021

To cool a high-pressure gas turbine blade, many rows of cooling holes with different arrangements and configurations are manufactured to achieve higher cooling effect and lower aerodynamic loss. To evaluate the heat transfer and film cooling effect in the full-cooled turbine blade, efficient numerical simulations are required in the design and performance optimization processes. From the view of numerical accuracy, the structured grids have to be employed because of higher resolution in flow and heat transfer than the unstructured grids. Because many splitting, attaching and merging manipulations are involved in meshing the cooling features and curved boundaries, it is very complex and time-consuming for a researcher to generate multi-block structured grids for a full-cooled gas turbine blade. As a result, in the industrial applications, almost all researchers preferred to generate unstructured grids instead of structured grids for the full-cooled blade.

Unlike the previous research, the aim of this study is to apply the Background-Grid Based Mapping (BGBM) method proposed in Part I to generate multi-block structured grids for a full-cooled gas turbine vane. With the strategy of BGBM method, meshes were conveniently generated in the computational space with simple geometrical features and plain interfaces, and then were mapped back into physical space to obtain the multi-block structured grids which can be used for numerical simulations. With the experimental data, the present numerical methods and BGBM strategy were carefully validated. Then, the flow and film cooling performance in the full-cooled NASA GE-E3 nozzle guided vane were numerically investigated. The effects of coolant mass flow rate and land extensions on film cooling effectiveness were discussed. The results show that film cooling effectiveness near the stagnation point is the lowest and film cooling effectiveness on the pressure side is slightly higher than that on the suction side. When the coolant mass flow rate increases up to the value of 1.5 design flow, the relative outflow mass flow rates of cooling hole arrays and slots are no longer affected by the increase of the coolant flow rate. At half design flow, the outflow mass flow rates of No.5 hole-array to No.10 hole-array are almost zero, and the area-averaged film cooling effectiveness on vane surface is as low as 0.268. Compared with the cases of half design flow and double design flow, better film cooling performance is obtained in the cases of design flow and 1.5 design flow. Compared with the vane without lands, the area-average cooling effectiveness on vane surface is slightly higher for the vane with lands. Land extensions have a considerable influence on film cooling performance in the cutback region.
A Methodology to Calibrate Gas-Dynamic Models of Turbocharged Petrol Engines With Variable Geometry Turbines and With Focus on Dynamics Prediction During Tip-in Load Transient Tests
Authors: Serrano José Ramón , Arnau Francisco José , De la Morena Joaquín , Gómez-Vilanova Alejandro , Guilain Stephane , Batard Samuel
Published: January 2021

The variable geometry turbines (VGT) technology has been proved as beneficious for diesel engines turbocharging, becoming the standard for passenger car diesel engines when high boosting pressure and short transient response are pursued.

It has not been until recent times that OEMs and turbocharger manufacturers are able to explore the advantages of VGTs in petrol engines. The high exhaust gases temperature and the low boost pressure prevented the introduction of petrol VGTs up to now. In modern direct injection petrol engines relevant fuel consumption benefits have been obtained from significant to moderate boosting pressure (thanks to downsizing strategies). This benefit joint with the advances in materials and turbocharger cooling technologies have fostered exploring the limits of VGT technology in petrol engines.

Consequently, the 1-D and gas-dynamic modelling of turbocharged petrol engines for matching, benchmarking or analysis purposes has become a significantly more complex task. The reason is the energy loop interaction between VGT, petrol engine and compressor; which makes that all relevant system variables (boosting pressure, back-pressure, VGT inlet gas temperature, residuals, volumetric efficiency, etc) are coupled among them. In this case, a proper simulation strategy of the whole system with existing 1-D gas-dynamic codes, i.e.: avoiding excessive use of spurious-non-physical fitting coefficients, has not been enough explored either described in the literature yet.

In addition, proper models of the turbocharger (both compressor and VGT) are more relevant now, since the VGT mechanism is a new variable with a first order influence. It can be destabilizing or tricking the whole system, depending on the engine operative conditions and turbo-model quality.

In this paper, a systematic methodology, with physical perspective, for calibrating 1D codes of petrol engines with VGTs is clearly described. The methodology can be easily followed by other engineers or researchers in their modelling activities. In addition, the importance of the turbocharger sub-model for achieving successfully previous objectives is depicted. Standard characteristic maps used as look-up tables are shown to be a poor source of information when compared with pre-processed adiabatic and extrapolated maps. The focus is kept in low end torque at full load steady state and transient tip-in, for being the most challenging situations. Being, low-end torque simulation in steady state the baseline point for the transient simulation.
Comparative Life Cycle Assessment of Different Gas Turbine Axial Compressor Water Washing Systems
Authors: Dominizi Ilaria , Gabriele Serena , Serra Angela , Borello Domenico
Published: January 2021

Nowadays the climate change is widely recognized as a global threat by both public opinion and industries. Actions to mitigate its causes are gaining momentum within all industries. In the energy field, there is the necessity to reduce emissions and to improve technologies to preserve the environment. LCA analyses of products are fundamental in this context.

In the present work, a life cycle assessment has been carried out to calculate the carbon footprint of different water washing processes, as well as their effectiveness in recovering Gas Turbine efficiency losses. Field data have been collected and analyzed to make a comparison of the GT operating conditions before and after the introduction of an innovative high flow online water washing technique. The assessments have been performed using SimaPro software and cover the entire Gas Turbine and Water Washing skids operations, including the airborne emissions, skid pump, the water treatment and the heaters.
Sensitivity Analysis and Uncertainty Quantification for Rim Seal Ingestion With 1-D Network Models
Authors: Pozo Dominguez Alejandro , Hills Nicholas , Marques Simao
Published: January 2021

Accurate prediction of turbine rim seal ingestion remains a challenge, even sophisticated unsteady computational models have had limited success due to the complexity and uncertainties present in this type of problems. For this reason, it is of interest to perform stochastic analysis taking into account the variability in the input parameters as well as uncertainties and assumptions associated with a given model of choice. This study focuses on a Secondary Air System (SAS) of a gas turbine, considering a generic cavity in a high pressure turbine (HPT) in which hot gas ingestion occurs and uncertainty in geometrical, operational and modelling parameters is present. Several statistical methods are applied to a 1D gas network model in order to evaluate the impact of the tolerances of the main geometrical parameters in the output, followed by a broader analysis including other operational and modelling variables. Results indicate that most influential parameters are the sealant mass flow rate, a modelling constant and the minimum gap of the wheelspace cavity.
Blade Root Joint Modelling and Analysis of Effects of Their Geometry Variability on the Nonlinear Forced Response of Tuned and Mistuned Bladed Disks
Authors: Koscso Adam , Petrov E. P.
Published: January 2021

One of the major sources of the damping of the forced vibration for bladed disk structures is the micro-slip motion at the contact interfaces of blade-disk joints. In this paper, the modeling strategies of nonlinear contact interactions at blade roots are examined using high-fidelity modelling of bladed disk assemblies and the nonlinear contact interactions at blade-disk contact patches. The analysis is performed in the frequency domain using multiharmonic harmonic balance method and analytically formulated node-to-node contact elements modelling frictional and gap nonlinear interactions.

The effect of the number, location and distribution of nonlinear contact elements are analyzed using cyclically symmetric bladed disks. The possibility of using the number of the contact elements noticeably smaller than the total number of nodes in the finite element mesh created at the contact interface for the high-fidelity bladed disk model is demonstrated. The parameters for the modeling of the root damping are analysed for tuned and mistuned bladed disks.

The geometric shapes of blade roots and corresponding slots in disks cannot be manufactured perfectly and there is inevitable root joint geometry variability within the manufacturing tolerances. Based on these tolerances, the extreme cases of the geometry variation are defined and the assessment of the possible effects of the root geometry variation on the nonlinear forced response are performed based on a set of these extreme cases.
Feasibility Study of a Radical Vane-Integrated Heat Exchanger for Turbofan Engine Applications
Authors: Jonsson Isak , Xisto Carlos , Abedi Hamidreza , Grönstedt Tomas , Lejon Marcus
Published: January 2021

In the present study, a compact heat exchanger for cryogenically fueled gas turbine engine applications is introduced. The proposed concept can be integrated into one or various vanes that comprise the compression system and uses the existing vane surface to reject core heat to the cryogenic fuel. The requirements for the heat exchanger are defined for a large geared-turbofan engine operating on liquid hydrogen. The resulting preliminary conceptual design is integrated into a modified interconnecting duct and connected to the last stage of a publicly available low-pressure compressor geometry. The feasibility of different designs is investigated numerically, providing a first insight on the parameters that govern the design of such a component.
Redesign of the TG20 Heavy-Duty Gas Turbine to Increase Turbine Inlet Temperature and Global Efficiency
Authors: Baratta Mirko , Cardile Francesco , Misul Daniela Anna , Rosafio Nicola , Salvadori Simone , Forno Luca , Toppino Marco
Published: January 2021

The even more stringent limitations set by the European Commission on pollutant emissions are forcing gas turbine manufacturers towards the redesign of the most important components to increase efficiency and specific power. Current trends in gas turbine design include an increased attention to the design of cooling systems and enhanced best practices for the study of components interaction. At the same time, the recent crisis suffered by the oil and gas industry reduced the interest in brand new gas turbines, thus increasing the service market. Therefore, original equipment manufacturers would rather propose the replacement of specific components within the gas turbine plant during its maintenance with compatible elements that are likely to guarantee increased performance and longer residual lifetime at a more desirable nominal working point.

In the present activity the cooling system of the TG20 heavy-duty gas turbine has been redesigned to increase the turbine inlet temperature while contemporaneously reducing the total amount of coolant mass-flow. Specifically, the cooling scheme of the rotating blade of the first turbine row has been reviewed at the Department of Energy (DENERG) of Politecnico di Torino in cooperation with EthosEnergy Italia S.p.a.. The paper presents a new design, which, starting from the original solution featuring fifteen smooth pipes, adopts an improved geometry characterized by the presence of turbulators.

The activity has been carried out using Computational Fluid Dynamics (CFD) for the coolant/blade interaction and one-dimensional models developed at EthosEnergy for the redistribution of the cooling flows in the cavities. The mutual effects between the coolant fluid and the blade are analyzed using a Conjugate Heat Transfer (CHT) approach with Star-CCM+. The validation of the computational approach has been performed exploiting the experimental data available for the NASA C3X test case. The TG20 rotating blade of the first turbine row has been analyzed considering the two different coolant configurations. The impact of the main flow on the thermal field has initially been included by imposing a temperature field on the blade surface. The latter field has in turn been obtained by means of a separate computation for the solid only. Full CHT simulations has hence been performed, thus quantifying the accuracy of the proposed approach. The obtained results are discussed in terms of thermo-fluid-dynamic effects.
An Investigation of Reversing Axial Turbomachinery for Thermal Energy Storage Application
Authors: Harris Paul , Wolf Tom , Kesseli Jim , Laughlin Robert B.
Published: January 2021

This paper investigates the feasibility of reversing axial turbomachinery for a thermal energy storage application. Under the proposed concept, the direction of flow and spool rotation is reversed when changing from electrical generation to heat pump mode, and the axial turbomachinery components function as either a compressor or turbine depending on the energy storage system’s mode of operation. Such reversing pump-turbines are widely used in pumped hydro installations but have not been employed for compressible flow applications to our knowledge to date. The preliminary aerodynamic design approach for the reversing blade geometry is described, followed by a CFD-based evaluation of turbomachinery performance for the case of a 50MW thermal storage plant. The demand for high efficiency in both modes leads to an unconventional design with a large number of stages for a given pressure ratio. A statorless counter-rotating architecture is utilized for efficiency considerations, and to reduce the overall number of turbomachinery components. Initial CFD results indicate that the reversing axial turbomachinery is capable of achieving high efficiency in both modes of operation, and of satisfying the performance goals of the thermal energy storage application.
Numerical and Experimental Research of the Highly Loaded Compressor 1st Stage: Part 1 — Aerodynamics
Authors: Druzhinin Iaroslav , Mileshin Victor , Petrovichev Alexander , Stepanov Alexander
Published: January 2021

Investigation object is a 1.5-stage with wide-cord rotor blades modeling a full-scale first stage of advanced highly loaded high pressure compressor. Overall total pressure ratio of the stage in the design point is 2.28.

Numerical part of the investigation includes a series of the simulations in 3D RANS statement to assess the integral performances of the stage. The simulation is carried out using the blade geometries defined with taking into account pressure distribution at the blade sides. The second part of the simulation is devoted to the analysis of unsteady row interaction in URANS statements at the design rotational speed. Finite volume grid covering full-annulus blade rows was generated. Total numbers of meshed passages are: 3 blades of inlet struts, 29 inlet guide vanes, 29 rotor blades, 58 stator vanes. Through flow simulation is carried out using dual time-stepping scheme with physical time step corresponding the movement by approximately 1 cell at the rotor-stator interface at 1 time step. The calculation continues until the flow parameters become periodic in time. The analysis of instantaneous and time averaged flow distributions is carried out. Viscous wakes propagation from struts, vanes and rotor blades through the flowpath is studied. The comparison between time averaged flow fields and the distribution from steady RANS shows some features in different problem statement. Unsteady pressure distribution at blade sides is extracted at each time step for mechanical analysis.

Experimental part of the investigation consists of series of tests at CIAM compressor test rig at wide range of rotational speed. The instrumentation of the stage allows to measure steady and unsteady flow parameters and to control mechanical behavior of rotor blades by strain gages and tip timing method.

Finally, the comparison between measured data is performed in integral performances and flow distributions.
Defining Key Environmental Performance Factors (KEPF) for Gas Turbines Eco-Design and Production Through Life Cycle Assessment
Authors: Musacchio Alessandro , Corona Andrea , Cencioni Luca , Serra Angela , Bartocci Pietro , Fantozzi Francesco
Published: January 2021

Nowadays environmental impact assessment of a new product is necessary to meet rising sustainability requirements also in the Oil & Gas and Power Generation markets, especially for industrial gas turbines. From the conceptual phase to the detailed design, engineer’s work is supported by a wide range of tools aimed to define and evaluate typical parameters such as performances, life and costs, etc. However, considering environmental impact aspects from the early stages of product development may not be easy if the involved engineers are not provided by a specific Life Cycle Assessment (LCA) knowledge.

Scope of this paper is to introduce and explain the development of a methodology aimed to define and evaluate the Key Environmental Performance Factors (KEPF) during the whole design process. The proposed methodology enables easy and fast eco-design evaluations and supports sustainable design assessments. Preliminary analysis of the entire processes involved in gas turbine (GT) design and production as well as testing and commissioning phases were performed to evaluate which factors affect mostly the Carbon Footprint of each process, referred to their specific functional unit. Extrapolating the KEPF from Cradle-to-Gate LCA they can be combined with case-specific qualitative and quantitative information such as material selection, manufacturing processes, mass quantity, presence of coatings etc. to provide environmental assessments.

A case study of LCA applied to a heavy-duty GT is presented to outline the relative weight of each KEPF.
The Influence of Parameterisation Setup on the Constrained Adjoint Optimisation of Transonic Fan Blades
Authors: John Alistair , Qin Ning , Shahpar Shahrokh
Published: January 2021

The power of adjoint optimisation is that the computational cost of the optimisation is almost independent of the number of design parameters. Thus, hundreds or even thousands of parameters can be used with relatively little increase in cost. But how much benefit does this provide, and is it always beneficial to increase the number of parameters? This work investigates the benefit achieved during the optimisation of transonic fan and compressor blades using various resolutions and layouts of Free Form Deformation grid. A method to constrain thickness throughout the blade span (to maintain mechanical integrity) during the optimisation is implemented and the effect of constraining thickness on the resulting blade designs demonstrated. It is shown that increasing the number of parameters generally leads to improved optimised designs, but that increasing the number of free-form parameters in the axial and circumferential directions is more beneficial than increasing the number of radial control parameters.
Prediction of the Acoustic Reflection in a Realistic Aeroengine Intake With Three Numerical Methods to Analyze Fan Flutter
Authors: Bontemps Thomas , Aubert Stéphane , de Pret Maxime
Published: January 2021

For a particular range of frequencies, an acoustic coupling between the fan and the air intake can modify fan stability regarding flutter. Previous works have shown that characterizing the reflection on the intake opening might be a crucial element to target operating points for which the risk of acoustic driven flutter is high. To do so, three methodologies are compared in this paper: an aeroelastic CFD simulation, an acoustic potential simulation and an analytical model. Each of them has a different fidelity level and computational cost, what makes their usage more beneficial at some step in the design process. It is shown that results of aeroelastic CFD and acoustic potential simulations are in excellent agreement. Fast acoustic simulations are then a good option in the early design process. The analytical model presents an important error mainly on the phase, and should be adapted before usage.
Aero Engine Concepts Beyond 2030: Part 1 — The Steam Injecting and Recovering Aero Engine
Authors: Schmitz Oliver , Klingels Hermann , Kufner Petra
Published: January 2021

Recognizing the attention currently devoted to the environmental impact of aviation, this three-part publication series introduces two new aircraft propulsion concepts for the timeframe beyond 2030. This first part focuses on the steam injecting and recovering aero engine concept. In the second part, the free-piston Composite cycle engine concept is presented. A third publication, building upon those two concepts, presents the project which aims for demonstrating the proof of concept with numerical simulation and test-bench experiments up to a technology readiness level of three.

In the steam injecting and recovering aero engine concept, exhaust heat generated steam is injected into the combustion chamber. The humidified mass flow contains significantly more extractable energy than air. Furthermore, the pumping of liquid water up to the necessary pressure requires a magnitude less power than the compression of air, which reduces the internal power demand. Both lead to a noticeable increase in specific power compared to a conventional gas turbine and, foremost, to a significant increase in thermodynamic efficiency. By use of a condenser, installed behind the steam generator, the water is recovered from the exhaust gas-steam mixture.

The proposed concept is expected to reduce fuel burn and CO2 emissions by about 15 % and NOx formation can be almost completely avoided compared to state-of-the-art engines of the same technology level. Moreover, the described concept has the potential to drastically reduce or even avoid the formation of condensation trails. Thus, the steam injecting and recovering aero engine concept operated with sustainable aviation fuels offers the potential for climate-neutral aviation.

Based on consistent thermodynamic descriptions, preliminary designs and initial performance studies, the potentials of the concepts are analyzed. Complementarily, a detailed discussion on concrete engineering solutions considers the implementation into aircraft. Finally, the impact on emissions is outlined.
Parallel Harmonic Balance Method for Analysis of Nonlinear Dynamical Systems
Authors: Blahoš J. , Vizzaccaro A. , Salles L. , El Haddad F.
Published: January 2021

Controlling vibration in jet engine remains one of the biggest challenges in aircraft engine design and conception. Methods dealing with vibration modelling usually rely on reduced order modelling techniques. This paper aims to provide a high fidelity method to solve vibration problems. It presents a parallel harmonic balance method applied to a full size problem. In order to be computationally efficient, a parallel harmonic balance method is used for the first time in solid mechanics. First, the parallel implementation of harmonic balance method is described in detail. The algorithm is designed to minimize communication between cores. Then, the software is tested for both beam and blade geometries. Finally, a scalability study shows promising acceleration when increasing the number of cores.
CFD Modelling Strategies for the Simulation of Roughness Effects on Friction and Heat Transfer in Additive Manufactured Components
Authors: Mazzei Lorenzo , Da Soghe Riccardo , Bianchini Cosimo
Published: January 2021

It is well-known from the literature that surface roughness affects significantly friction and heat transfer. This is even more evident for additive manufactured (AM) components, which are taking an increasingly important role in the gas turbine field. However, the exploitation of numerical approaches to improve their design is hindered by the lack of dedicated correlations and CFD model developed for such high roughness conditions.

Usually the additive manufactured components are simulated considering the surfaces as smooth or applying an equivalent sand-grain roughness (ks) that results in a velocity shift in the boundary layer. However, determining a priori the most appropriate value of ks is challenging, as dozens of correlations are available, returning scattered and uncertain results.

The aim of this work is to benchmark some existing modelling strategies (among which the equivalent sand grain roughness) and test a numerical approach capable of narrowing the existing gap between simulated and tested thermal performance of additive manufactured devices. The technology enabler is represented by higher-fidelity CFD simulations accounting for the impact of real surface roughness on pressure drop and heat transfer.

At this purpose, an existing literature model for rough walls has been implemented in ANSYS Fluent and tested on a variety of AM mini-channels so as to determine the best-fitting values of ks and corrected wetted surface ratio Scorr that match the experimental data in terms of friction factor and Nusselt number. Knowing also the measured roughness descriptors of each component, it has been possible to derive valuable guidelines for an effective exploitation of CFD on additive manufactured components, thus allowing a more accurate estimation of the thermal performance in additive manufactured components.
Aeromechanical Characterization of a Last Stage Steam Blade at Low Load Operation: Part 2 — Computational Modelling and Comparison
Authors: Pinelli Lorenzo , Vanti Federico , Peruzzi Lorenzo , Arnone Andrea , Bessone Andrea , Bettini Claudio , Guida Roberto , Marré Brunenghi Michela , Slama Vaclav
Published: January 2021

This paper is part of a two-part publication that aims to experimentally and numerically evaluate the aerodynamic and mechanical damping of a last stage ST blade at low load operation. A three-stage downscaled steam turbine with a snubbered last stage moving blade LSMB has been tested in the T10MW test facility of Doosan Skoda Power R&D Department in the context of the FLEXTURBINE European project (Flexible Fossil Power Plants for the Future Energy Market through new and advanced Turbine Technologies).

Aerodynamic and flutter simulations of different low load conditions have been performed. The acquired data are used to validate the unsteady CFD approach for the prediction of the aerodynamic damping in terms of logarithmic decrement. Numerical results have been achieved through an upgraded version of the URANS CFD solver, selecting appropriate and robust numerical setups for the simulation of very low load conditions, such as increased condenser pressure at the exhaust hood outlet.

The numerical methods for blade aerodamping estimation are based on the computation of the unsteady pressure response caused by the row vibration. They are usually classified in time-linearized, harmonic balance and non-linear approaches both in frequency and time domain. The validation of all these methods historically started in the field of aeronautical low-pressure turbines and has been gradually extended to compressor blades and steam turbine rows.

For the analysis of a steam turbine last rotor blade operating at strong part load conditions, non-linear methods are recommended as these approaches are able to deal with strong nonlinear phenomena such as shock waves and massive flow separations inside the domain.

Experimental data have been used to separate the contributions of mechanical and aerodynamic damping, extrapolating to zero mass flow the total measured damping.

Finally, the comparisons between the aerodynamic damping coming from measurements and CFD results have been reported in order to highlight the capability to properly predict the last stage blade flutter stability at low load conditions. Such comparisons confirms the flutter free design of the new snubbered LSMB blade.
Part 1: A Swirl Vane Generation Code for Fuel Spray Nozzles
Authors: Andreou Thomas , White Craig , Kontis Konstantinos , Shahpar Shahrokh , Brown Nicholas
Published: January 2021

Achieving an optimal level of flow swirl is required for efficient mixing of air and fuel in order to realise lean combustion. A novel method is devised to achieve a necessary level of swirl, using NACA airfoil profiles as the baseline for swirl stator blades. Formulas for achieving a required level of swirl have been derived and implemented in a computer program that generates aerodynamic vanes which meet the specified swirl. The usability of the program over a broad range of Reynolds numbers is verified. A curve fitting method has been developed, taking into account the trailing edge angles and blade solidity, in order to speed up the iterative process. A significant computational speed-up is achieved from this approach, and an excellent initial preliminary vane design can be obtained, which can later be introduced inside an automated optimisation process.
Numerical Modelling of NOx Emissions and Flame Stabilization Mechanisms in Gas Turbine Burners Operating With Hydrogen and Hydrogen-Methane Blends
Authors: Meloni Roberto , Cerutti Matteo , Zucca Alessandro , Mazzoni Maurizio
Published: January 2021

Main objective of this paper is to assess the capability of numerical models in predicting NOx emissions and flame stabilization mechanisms of a heavy-duty gas turbine burner when operated with hydrogen and hydrogen-methane blends.

Effort focused on the selection of the proper input to pre-tabulated Flamelet Generation Manifold combustion model. A dedicated sensitivity to laminar flame speed formulation has been performed as well, since it primarily affects flame stabilization through the closure term of the progress variable transport equation.

Available NOx emissions data from full scale annular combustor rig test with hydrogen-air mixtures are presented first in this paper: test results have been used to validate the numerical setup for the reference geometry. Then, the model has been used to predict NOx emissions of alternative geometries in case of pure hydrogen, allowing screening of viable options to reduce the scope of a dedicated test campaign.

Concerning flame stabilization mechanisms, simulations have been carried out for a reference geometry first: data from dedicated tests have been used to specialize the tool. Results of modified geometries are shown, to explore the effect of different fuel injection patterns or internal channel modifications.

Based on the analysis outcomes, a discussion is provided regarding advantages and drawbacks of each proposed solution, as well as the ability of modelling setup in catching varied flame stabilization mechanisms.
Design and Performance of a Boundary Layer Ingesting Fan
Authors: Mårtensson Hans , Laban Martin
Published: January 2021

A Boundary Layer Ingesting fan is designed to function in a tail cone thruster configuration on an existing aircraft. This means that the fan ingests part of the boundary layer developing over the fuselage all around the circumference. While the fuselage drag induced on the ingested flow makes it possible to obtain a higher propulsive efficiency, it also means that the fan will operate in a severely distorted flow. In the configuration studied here the incoming flow will generally have a lower impulse near the hub, but also substantial non-axisymmetric components. The incoming flow profile is evaluated from a CFD model of a complete Fokker 100 aircraft modified with a tail cone thruster installed. Having the aircraft modeled in detail allows the extraction of the flow entering the fan inlet, which makes up the inlet boundary condition to design for. In order to make a rational design of the fan, the incoming flow is circumferentially averaged at each radial location to form the radial profile used in the design. A fan map is created to evaluate critical points in the operating envelope in order to demonstrate that the given design is stable in operation. Operation of the fan in static ground conditions is within the operating envelope of the fan without variable nozzle area.
Influence Mechanisms of Manufacture Variations on Supersonic/Transonic Blade Aerodynamic Performances
Authors: Liu Baojie , Liu Jiaxin , Yu Xianjun , Meng Dejun , Shi Wenbin
Published: January 2021

The results of previous studies have proved that manufacture variations can cause a noticeable influence on compressor aerodynamic performance. The main objective of this paper is to investigate the influence rules and mechanisms of manufacture variations on supersonic/transonic blades aerodynamic performance. The variations used in this study were measured from some newly manufactured high-pressure compressors.

In the present study, several blade sections with different design Mach number conditions are selected for further statistical analysis of measured deviation data. Therefore, some systematic errors in the deviation data have been revealed. Based on these data, the computational fluid dynamics (CFD) method has been used to obtain the aerodynamic performances of a large number of the measured blade elements. And then, the analysis of the influence rules of manufacture variations on blade aerodynamic performance in different Mach number conditions has been carried out. The present results indicate that the effects of manufacture variations on blade aerodynamic performance in the lower Mach number (0.8) condition are much more significant comparing to that in the higher Mach number (0.9∼1.2) conditions. Based on this, influence mechanisms of manufacture variations on positive incidence range and negative incidence range have been analyzed. The differences of influence mechanisms in different Mach number conditions are the focus of research.
Model-Based Thermodynamic Analysis of a Hydrogen-Fired Gas Turbine With External Exhaust Gas Recirculation
Authors: Bexten Thomas , Jörg Sophia , Petersen Nils , Wirsum Manfred , Liu Pei , Li Zheng
Published: January 2021

Climate science shows that the limitation of global warming requires a rapid transition towards net-zero emissions of green house gases (GHG) on a global scale. Expanding renewable power generation in a significant way is seen as an imperative measure within this transition. To compensate for the inherent volatility of wind- and solar-based power generation, flexible and dispatchable power generation technologies such as gas turbines are required. If operated with CO2-neutral fuels such as hydrogen or in combination with carbon capture plants, a GHG-neutral gas turbine operation could be achieved. An effective leverage to enhance carbon capture efficiency and a possible measure to safely burn hydrogen in gas turbines is the partial external recirculation of exhaust gas. By means of a model-based analysis of an industrial gas turbine, the present study initially assesses the thermodynamic impact caused by a fuel switch from natural gas to hydrogen. Although positive trends such as increasing net electrical power output and thermal efficiency can be observed, the overall effect on the gas turbine process is only minor. In a following step, the partial external recirculation of exhaust gas is evaluated and compared both for the combustion of natural gas and hydrogen, regardless of potential combustor design challenges. The influence of altering working fluid properties throughout the whole gas turbine process is thermodynamically evaluated for ambient temperature recirculation and recirculation at an elevated temperature. A reduction in thermal efficiency can be observed as well as non-negligible changes of relevant process variables. These changes are are more distinctive at a higher recirculation temperature.
Squeeze Film Damper Bearing With Double-Ended Beam Springs: Part II — Experimental Validation
Authors: Li Wei , Braman Christopher , Hantz Brian , Thorat Manish , Pettinato Brian
Published: January 2021

To validate a new squeeze film damper (SFD) bearing design introduced in [1], a pair of 3.5 inch SFD bearings were manufactured and tested. Static spring compression test was conducted to prove the spring design stiffness calculated through the geometry parametric spring model. High cycle loading fatigue testing of the spring was conducted to validate the design spring fatigue limit. The entire SFD bearing assembly was inspected and checked through a SFD centering bench test before the rotor dynamic test.

Unbalance response correlation and logarithmic decrement (Log. Dec.) measurement using the operational modal analysis (OMA) method were employed for the rotor-dynamic tests. An agreement was seen between the analysis and the experimental measurement. It was seen that the SFD bearing provided the extra damping as expected to suppress the unbalance vibration when passing through the critical speed and also improve the stability (Log. Dec.) of the rotor. It was found that the measured SFD damping was closer to the full film damping model when the squeeze oil film was sealed with O-rings. The SFD improved the logarithmic decrement of the rotor-bearing system from 0.07 to more than 0.21 as compared to the system without SFD.
Study of Buoyancy Effects on Supercritical CO2 Heat Transfer in Circular Pipes
Authors: Khadse Akshay , Vesely Ladislav , Sherwood James , Curbelo Andres , Goyal Vipul , Raju Nandhini , Kapat Jayanta S. , Kim Wanjae
Published: January 2021

Supercritical CO2 (sCO2) can be utilized as a working fluid in various systems including high scale power cycle, portable power production unit, centralized cooling system and standalone cooling device. Lack of accurate predication tools such as heat transfer coefficient correlations and insufficient knowledge behind fundamental heat transfer processes can hinder its practical realization in key energy and cooling systems. The overall objective of the proposed study is to extend fundamental knowledge about heat transfer and fluid flow processes in conduits pertinent to sCO2 power cycle with an emphasis on buoyancy effects. Operational requirement of high pressures and temperatures for intended applications put a significant amount of constraints on measurement strategy and instrumentation. For this paper, experiments were conducted with uniform volumetric heat generation within pipe wall, for a single Reynolds number of 16,600 at test section inlet. The designed test apparatus and data reduction process are validated with high pressure air experiments, complemented by companion computations. Nusselt number was found to be within 10% of conventional correlations.

For the test parameters and pipe size selected, factors of 2 to 4 variations in circumferential Nusselt number distributions are observed in sCO2 flow. Richardson number and other similar parameters to indicate importance of buoyancy-driven flow phenomena suggest that buoyancy forces caused by large density variation of sCO2 in flow cross-sections may cause the observed circumferential variations in Nusselt number.
Aero-Thermal Optimization of Bladeless Turbines
Authors: Braun James , Paniagua Guillermo , Falempin Francois
Published: January 2021

The harnessing of mechanical power from supersonic flows is constrained by physical limitations and substantial aerodynamic losses. Bladeless axial turbines are a viable alternative to extract power in such harsh conditions without restricting the operating conditions. In this paper, we present a shape optimization of the wavy surface of bladeless turbines to maximize the power extraction, while minimizing convective heat fluxes and pressure losses. First, a baseline geometry was defined and an experimental campaign was carried out on the baseline wavy surface of the bladeless turbine at supersonic conditions in the Purdue Experimental Aerothermal Lab. Pressure, heat flux and skin friction measurements were compared with the Reynolds Averaged Navier Stokes results. Afterwards, the evaluation routine which consisted of the blade generation, grid generation, solving, and post-processing was implemented within an evolutionary optimizer with a multi-objective function to maximize the pressure force and minimize heat flux and pressure loss. Finally, a three-dimensional assessment in terms of power, heat load and pressure drop was performed for the best performing geometry with the commercial solver CFD++ of Metacomp. Turbulence closure was provided with the k-omega-SST turbulence model. The annular chamber of the bladeless turbine consisted of an unstructured mesh of approx. 8–10 million grid points.
Comparison of Performance of Alternative Post Combustion Carbon Capture Processes for a Biogas Fueled Micro Gas Turbine
Authors: Font-Palma Carolina , Lychnos George , Nikpey Somehsaraei Homam , Willson Paul , Assadi Mohsen
Published: January 2021

The urgent need to decrease greenhouse gases (GHG) has prompted countries such as the UK and Norway to commit to net zero emissions by 2050 and 2030, respectively. One of the sectors contributing to GHG emissions is agriculture, by approximately 10% in the EU in 2017. GHG reductions in the production side should involve avoidance at source, reduction of emissions and/or removal of those emissions, with the potential for negative emissions by carbon capture.

This paper focuses on the utilisation of agricultural waste that can be converted into biogas, such as livestock and crops residues which represent around 37% of GHG emissions by agriculture in the EU. The biogas can be used to produce electricity and heat in a micro gas turbine (MGT). Then, the exhaust gases can be sent to a carbon capture plant. This offers the potential for integration of waste into energy for in-house use in farms and fosters a circular-bioeconomy, where the captured CO2 could be used in greenhouses to grow vegetables. This could even allow the integration of other renewable technologies, since the MGT offers flexible operation for rapid start-up and shut down or intermittency of other technologies such as solar or wind. Current carbon capture processes are very costly at the smaller scales typical of remote communities. The alternative A3C (advanced cryogenic carbon capture) process is much more economical at smaller scales. The A3C separates CO2 from process gas that flows counter-currently with a cold moving bed, where the CO2 desublimes on the surface of bed material as a thin layer of frost. This allows enhanced heat transfer and avoids heavy build-up of frost that reduces severely the heat transfer. The phase change separation process employed by A3C and the large thermal inertia of the separation medium gives good flexibility of capture for load changes and on-off despatch.

This study integrates a combined heat and power MGT, Turbec T100, of 100 kWe output. This include developed models for the MGT using characteristics maps for the compressor and turbine and for the cryogenic carbon capture plant, using two software tools, IPSEpro and Aspen Plus, respectively.
Balancing a High-Renewables Electric Grid With Hydrogen-Fuelled Combined Cycles: A Country Scale Analysis
Authors: Colbertaldo Paolo , Guandalini Giulio , Crespi Elena , Campanari Stefano
Published: January 2021

A key approach to large renewable energy sources (RES) power management is based on implementing storage technologies, including batteries, power-to-hydrogen (P2H), pumped-hydro, and compressed air energy storage. Power-to-hydrogen presents specific advantages in terms of suitability for large-scale and long-term energy storage as well as capability to decarbonize a wide range of end-use sectors, e.g., including both power generation and mobility.

This work applies a multi-nodal model for the hourly simulation of the energy system at a nation scale, integrating the power, transport, and natural gas sectors. Three main infrastructures are considered: (i) the power grid, characterized by instantaneous supply-demand balance and featuring a variety of storage options; (ii) the natural gas network, which can host a variable hydrogen content, supplying NG-H2 blends to the final consumers; (iii) the hydrogen production, storage, and re-electrification facilities. The aim of the work is to assess the role that can be played by gas turbine-based combined cycles in the future high-RES electric grid. Combined cycles (GTCCs) would exploit hydrogen generated by P2H implementation at large scale, transported through the natural gas infrastructure at increasingly admixed fractions, thus closing the power-to-power (P2P) conversion of excess renewables and becoming a strategic asset for future grid balancing applications.

A long-term scenario of the Italian energy system is analyzed, involving a massive increase of intermittent RES power generation capacity and a significant introduction of low-emission vehicles based on electric drivetrains (pure-battery or fuel-cell). The analysis highlights the role of hydrogen as clean energy vector, not only for specific use in new applications like fuel cell vehicles and stationary fuel cells, but also for substitution of fossil fuels in conventional combustion devices. The study also explores the option of repowering the combined cycles at current sites and evaluates the effect of inter-zonal limits on power and hydrogen exchange. Moreover, results include the evaluation of the required hydrogen storage size, distributed at regional scale or in correspondence of the power plant sites. Results show that when extra hydrogen generated by P2H is fed to GTCCs, up to 17–24% H2 use is achieved, reaching up to 70–100% in southern regions, with a parallel reduction in fossil NG input and CO2 emissions of the GTCC plants.