bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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.
A Robust Implementation of a Reynolds Stress Model for Turbomachinery Applications in a Coupled Solver Environment
Authors: Roos Launchbury David , Mangani Luca , Casartelli Ernesto , Del Citto Francesco 
Published: January 2021

Abstract
In the industrial simulation of flow phenomena, turbulence modeling is of prime importance. Due to their low computational cost, Reynolds-averaged methods (RANS) are predominantly used for this purpose. However, eddy viscosity RANS models are often unable to adequately capture important flow physics, specifically when strongly anisotropic turbulence and vortex structures are present. In such cases the more costly 7-equation Reynolds stress models often lead to significantly better results. Unfortunately, these models are not widely used in the industry. The reason for this is not mainly the increased computational cost, but the stability and convergence issues such models usually exhibit.
In this paper we present a robust implementation of a Reynolds stress model that is solved in a coupled manner, increasing stability and convergence speed significantly compared to segregated implementations. In addition, the decoupling of the velocity and Reynolds stress fields is addressed for the coupled equation formulation. A special wall function is presented that conserves the anisotropic properties of the model near the walls on coarser meshes.
The presented Reynolds stress model is validated on a series of semi-academic test cases and then applied to two industrially relevant situations, namely the tip vortex of a NACA0012 profile and the Aachen Radiver radial compressor case.
Design, Flow Field and Heat Transfer Characterization of the Conjugate Aero-Thermal Test Facility at NETL
Authors: Ramesh S. , Robey E. , Lawson S. A. , Straub D. , Black J. 
Published: January 2021

Abstract
A new aerothermal test facility was constructed for the purpose of studying film cooling performance in an environment that accurately simulates conjugate heat transfer characteristics that exist in engine operation. This paper details the design of the facility and the plan for conducting steady-state film cooling experiments to improve the understanding of conjugate heat transfer scaling from laboratory to engine conditions. The test facility consists of two separate flow channels (hot gas/coolant) and each gas path has a flow conditioning section, a convergent nozzle and a test section/channel with viewports. Numerical simulations were conducted to predict flow field characteristics supporting the design of the flow loop facility. Preliminary experiments were conducted to characterize the flow field using velocity and temperature profile measurements. In addition, infrared (IR) thermography methods were developed to measure surface temperatures on the hot side of the test plate. The IR measurement methods including calibration of the IR camera is explained in detail. It was concluded that appropriate hot gas path flow conditioning could be achieved using a strainer-like tube, a perforated plate, and a honeycomb-mesh screen system upstream of the test section. Flow field measurements from preliminary experiments showed that the boundary layer profile follows the law of the wall.
Profile Loss Investigations With a S-CO2 Axial Turbine Aerofoil
Authors: Kumaran R. Senthil , Alone Dilipkumar B. , Kumar Pramod 
Published: January 2021

Abstract
Axial turbines are being extensively designed for supercritical carbon-di-oxide (S-CO2) Brayton cycle power blocks. But very little information is available in the open literature on the aerodynamics of S-CO2 axial turbines, their aerofoils and loss mechanisms. The understanding of real gas behavior of S-CO2 inside a turbine is still very far from complete. Profile losses contribute to more than 50% of overall losses in a turbine. Hence, estimation of profile losses at the outset of the design process is very important. In the present study, the mean section aerofoil of the first stage of a 5 MWe Brayton cycle high temperature turbine is investigated for profile loss characteristics. The basic aerodynamic characteristics of the aerofoil in a linear cascade were initially studied using CFD simulations and cascade test experiments with air as the fluid medium. The aerofoil cascade is then subjected to numerical simulations with S-CO2 as the fluid medium. CFD simulations were carried out using a commercial RANS solver with SST k-ω turbulence model for closure. Air was modelled as ideal gas and S-CO2 was modelled as real gas with Refrigerant Gas Property tables generated over the appropriate pressure and temperature ranges using NIST Refprop database. Losses are also calculated using Craig and Cox loss model. Experiments were carried out by testing a linear cascade model comprising 12 two dimensional blades, in a high-speed cascade wind tunnel. Cascade tests were carried out over a range of exit Mach numbers and incidence angles with air as the working medium. Losses, flow deflection and blade loading were measured during the experiments. Scaling of the profile losses between air and S-CO2 fluid mediums were examined over a range of Mach numbers, Reynolds numbers and incidence angles. Detailed analysis of data generated from numerical simulations, experiments and loss model (mainly in the transonic regime) are discussed in this paper. Losses with S-CO2 was 1.5% lower than that of air while the flow deflection roughly remained the same.
Trade-Off Assessments for Part Load Controlled Cooling Air in Stationary Gas Turbines
Authors: Woelki Dominik , Peitsch Dieter 
Published: January 2021

Abstract
The demand for flexible operation of stationary gas turbines, especially at part load, requires the simultaneous design for sufficient efficiency and life time. Both can be addressed by the secondary air system. The here applied concept modulates cooling air supply in off-design. Typically, a reduction of cooling air leads to higher efficiency but shorter turbine life time.
This paper presents investigations on such concepts, aiming for trade-offs between fuel burn and turbine blade life. The considered life time mechanisms are creep, which is dominant in rotor blades, and oxidation. In addition, the effects on emissions from the combustion are outlined. The reference gas turbine is a literature-based, generic gas turbine in the 300 MWpower output segment. Regarding cooling air control, the focus is on the first two stages of the four-stage turbine.
All simulations are performed by application of component zooming with an appropriate in-house tool: a previously introduced coupled model of the reference gas turbine that essentially connects gas turbine performance with a secondary air system network model. This coupled model is now extended with blade life evaluation and emission models.
The results contain trade-offs for different operating points at base and part load. For example, the combined cooling air control of stage 1 rotor blade and stage 2 vane offers several benefits regarding fuel consumption: saving up to Δwfuel,rel = 0.5% in the heat recovery’s kink point operation at 60 % of base load of a combined cycle application. This saving is at the expense of creep life. However, some operating points could even operate at higher blade temperatures in order to improve life regarding hot corrosion. Furthermore, generic sensitivities of controlled secondary air supply to cooling layers and hot gas ingestion at rim seals are discussed. Overall, the presented trades mark promising potentials of modulated secondary air system concepts from a technical point of view.
The Effects of Cooling Holes on SiC/SiC CMC Tensile Strength
Authors: Smith Craig , Presby Michael , Bhatt Ramakrishna , Kalluri Sreeramesh 
Published: January 2021

Abstract
Silicon Carbide fiber-reinforced Silicon Carbide (SiC/SiC) Ceramic Matrix Composites (CMCs) are currently operating in select high temperature components of turbine engines. Primary benefits of CMCs compared to metals are improved temperature capability, reduced cooling requirements and reduced component weight. High temperature materials require less cooling air to be diverted from the compressor, resulting in improved engine performance. However, some amount of film cooling may be necessary when CMCs are implemented in higher temperature applications. Film cooling requires holes to be fabricated at appropriate locations and orientations within these components. It is important to understand how such holes will affect the material properties. While previous studies have shown that CMCs are notch insensitive, the effect of multiple holes and different hole orientations on SiC/SiC CMCs is not well documented. This study examines the effect of cooling holes on SiC/SiC tensile properties. Several hole geometries fabricated in SiC/SiC samples are explored. Mechanical test data on specimens with multiple holes is reported for tensile loading at room temperature. Tools such as Digital Image Correlation (DIC) and Acoustic Emission (AE) are used to monitor strain and cracking in the CMC upon loading.
Comparison of Sodium Sulphate Deposition Rate Models Based on Operational Factors Influencing Hot Corrosion Damage in Aero-Engines
Authors: Pontika Evangelia , Laskaridis Panagiotis , Nikolaidis Theoklis , Koster Max 
Published: January 2021

Abstract
Hot corrosion is defined as the accelerated oxidation/sulphidation in the presence of alkali metal molten salts. It is a form of chemical attack that causes good metal loss. Current lifing models in aircraft engines focus on creep, fatigue and oxidation while hot corrosion damage has been overlooked as being of secondary importance. However, the absence of hot corrosion lifing models for aircraft engines often leads to unexpected and unexplained hot corrosion findings by aircraft engine operators and Maintenance, Repair and Overhaul (MRO) providers during inspections. Although hot corrosion does not cause failure on its own, the interaction with other damage mechanisms can reduce component life significantly, consequently, there is a requirement for including hot corrosion in the damage prediction process of aircraft engines.
In both theoretical and experimental studies in literature, deposition of molten salts is identified as one of the primary conditions for hot corrosion to occur and an increased amount of deposited liquid salts accelerates the attack. Currently, most hot corrosion studies are limited to experimental testing of superalloys which are pre-coated with a controlled layer of salts. Such experimental studies are disconnected from gas turbine operating conditions during service.
The present paper analyses two deposition rate models applicable to gas turbine operating conditions using Design of Experiments. Design space exploration is presented by taking into account gas turbine operating parameters which vary during a flight as well as temperature ranges where hot corrosion can occur. Analysis of variance is presented for 6 input parameters using Box-Behnken 3-level factorial design. Results from the Analysis of Variance indicate that the deposition rate models are sensitive to pressure and salt concentration in the gas flow. Finally, the saturation point of sodium sulphate has been investigated within the operating range of gas turbine and it was found that it can vary significantly under different conditions.
Introducing Life Cycle Cost Analysis in an Undergraduate Gas Turbine Engine Design Capstone Course
Authors: Byerley Aaron R. , Brandt Steve A. 
Published: January 2021

Abstract
The purpose of this paper is to introduce the basics of life cycle cost analysis for use in an undergraduate, senior-level capstone, gas turbine engine design course. This paper will support the heightened interest within the military acquisition community that now requires life cycle cost analysis to be included in the proposals submitted by defense contractors. The capstone design course includes both the gas turbine engine cycle selection and engine component design that supports a particular aircraft application. While the students have been taught how to estimate the fuel costs, engine development costs, and the time-varying production costs of engines, they have not yet been provided instruction on how to factor all three types of costs into an engineering economics, time-value-of-money, present value analysis. This paper will fill that gap and serve as a resource for the students who must now consider life cycle cost as an element in their design decision matrix along with engine performance, technical risk, and development time. The typical case compares an engine where the upfront development and production costs associated with a more advanced level of technology are high early on in the life cycle but over time has a lower fuel cost compared to an engine with a lower development and production cost but with a higher fuel cost. This paper illustrates how the aerodynamics, thermodynamics, and engineering economics can be brought together to inform and defend a decision about which of the two (or more) alternatives is best. The engineering economic analysis is spreadsheet based and uses inflation adjusted, total annual costs to calculate the present value for use in a decision matrix.
Simulation of Optimizing the Partial Load Performance of a Gas Turbine Combined Cycle Using Exhaust Heat Recuperation and Inlet Bleed Heating
Authors: Moon Seong Won , Kim Tong Seop 
Published: January 2021

Abstract
Extending the operating range and improving the partial load efficiency of the gas turbine combined cycle (GTCC) is becoming increasingly important. This paper proposes a novel method to achieve the two goals simultaneously. To fulfill the research objective, the combination of exhaust heat recuperation and inlet bleed heating (IBH) was adopted and evaluated. A cycle simulation was conducted to confirm whether the research goal could be achieved. A recuperator was installed between the compressor and combustor of the gas turbine, and the degree of heat recuperation was modulated during partial load operation to enhance the cycle efficiency compared to the conventional GTCC plant. In contrast to the conventional GTCC plant, the recuperation ratio was modulated before control of the variable inlet guide vane (VIGV) began. This means that the recuperation control covers the high partial load regime. The gas turbine power remained almost constant in this regime because the inlet flow rate and turbine inlet temperature were kept constant. In contrast, the power of the bottoming cycle decreased with increasing recuperation ratio due to the decrease in exhaust gas energy. After the recuperation ratio reached a limit, the load control was the same, as in conventional plants: VIGV control followed by fuel only control. The purpose of using IBH was to reduce CO emissions in the low load regime. Some of the compressor discharge air was recirculated to the compressor inlet, and the combustion temperature was maintained at a high level. The simulation showed that both IBH and recuperation are effective in extending the operating range. The predicted reduction in the turndown ratio was approximately 10%p. The partial load efficiency improvement by the recuperation was sensible. The efficiency remained higher than the full load efficiency over a wide partial load range. The efficiency of the recuperated GTCC was 4.1%p higher at 50% power than that of the conventional GTCC.
Background-Grid Based Mapping Approach to Film Cooling Meshing: Part I — Strategies and Test Cases
Authors: Wang Ruiqin , Yan Xin 
Published: January 2021

Abstract
Film cooling technique is commonly adopted in modern gas turbine engines to protect high-temperature components from erosion and damage caused by thermal stress. To improve film cooling effectiveness, many efficient prediction tools have been developed and have shown promising results, which are helpful for turbine aero-thermal design. For film cooling, evidence has shown that it is strongly affected by the momentum and heat transport in the boundary layer when hot gas and coolant are mixed downstream of the ejection. From the view of resolution accuracy in the boundary layer, structured grids will be the primary choice in fluid domain. However, the high-pressure gas turbine blades usually have several hundreds of cooling holes with different configurations and arrangements. Numerical simulations often face a big challenge in multi-block structured-grid generations when a large number of cooling holes are involved on curved hole-to-mainstream interfaces. Conventional block-splitting and mesh-generation for all holes are quite time-consuming and cumbersome, because the copying, translating and rotating manipulations cannot be applied on curved hole-to-mainstream interfaces directly. To solve these difficulties, this paper presents a novel mesh-generation strategy, which is a background-grid based mapping (BGBM) method, to generate multi-block structured grids for film-cooled blade efficiently without modifying the existing meshing tools and solvers, which is convenient for CFD users. It consists of three main steps: At first, the correspondence between physical space and computational space is established by two sets of background grids. Then, the sectional curves of geometry features in physical space are projected to the computational space. With these treatments, the curved hole-to-mainstream interfaces are flattened in computational space, where grids can be quickly generated with block copying, translating, rotating and merging manipulations. Thereafter, meshes in computational space are mapped back to the physical space based on the correspondence between physical and computational spaces, and high-quality structured-meshes can be obtained for numerical simulations. To demonstrate the presented meshing strategy, several typical cases with film cooling are selected for testing, including single cooling hole on curved surface, multiple rows of cooling holes on curved surface and NASA C3X vane with multiple hole arrays. In these cases, different holes, including the cylindrical holes and shaped holes with different ejection angles and arrangements, on curved interfaces are taken into consideration. The quality of generated structured grids for each test case is illustrated, which is able to meet the requirement of CFD solver. With the generated meshes, conjugate heat transfer performance in the turbine vane with different cooling arrangements is investigated and also validated with the existing experimental data.