bluuebunny/crossref_metadata_2025_split huggingface dataset:
Off-Design of a Small-Scale Liquefaction Plant Operating With Biomethane
Authors: Baccioli Andrea , Pasini Gianluca , Barbieri Gregorio , Ferrari Lorenzo 
Published: October 2022

Abstract
Liquefied natural gas is recently playing an important role in the heavy-duty vehicle and marine fuel market due to the low ambient impact, easy onboard storage, and low commercial prices. Biomethane from biogas upgrading can integrate the LNG market by providing the added value of an almost zero carbon footprint fuel.
The production rate of biomethane is distributed in various anaerobic digestion plants, and daily amounts are limited to a few tons per day, with a substantial variability depending on digester feed. For this reason, small-scale liquefaction systems are requested to convert biomethane into bio-LNG. The Joule-Brayton reverse cycle is a promising solution for small-scale plants due to its simplicity and ease of regulation.
The control strategy of this plant is important since small-scale installations are characterized by relatively high specific consumption that might increase when the system is operated in part-load or off-design conditions. For this reason, the comparison between two control strategies is proposed in this study: variable rotating speed control strategy and inventory control are compared and assessed. A steady-state off-design model of the plant was implemented in Aspen Hysys by considering the behavior of all the main system components, including compressors, turbine, intercoolers and aftercoolers, turbine, and cold-box. Typical analytical relations for heat exchanger off-design were considered as well as typical characteristic maps for the fluidmachinery. The two control systems were introduced in the model by implementing the control equations at the steady-state. Results showed that inventory control allows the system to achieve better performance and results to be more flexible. Variable rotating speed control strategy led to surge issues at low small biomethane production and low ambient temperature. By considering a plausible biomethane production profile, inventory control allows the specific consumption to be reduced by 4.3 %, and liquefied biomethane production increases by about 131 t with respect to variable speed control.
Use of Multiple Tracer Gases to Quantify Vane Trailing Edge Flow Into Turbine Rim Seals
Authors: Monge-Concepción Iván , Barringer Michael D. , Berdanier Reid A. , Thole Karen A. , Robak Christopher 
Published: October 2022

Abstract
Overlapping features are commonly used as rim seals between stationary and rotating components in a turbine stage. These rim seals are used to prevent main gas path ingestion to the wheelspace cavity, which reduces the lifespan of critical engine components such as the turbine disk. In addition to the overlapping features, purge flow, diverted from the compressor, is injected into the rim cavity to act as an airflow sealing mechanism. Previous research identified that in addition to the purge flow in the rim cavity, cooling flow from the vane trailing edge (VTE) is ingested into the rim seal cavity carrying the potential to cool components in the wheelspace. These previous findings, however, were not able to distinctly separate purge from VTE cooling flows, which is the contribution of this paper based on uniquely using two different tracer gases. A one-stage test turbine operating at engine-relevant conditions and consisting of real engine hardware was used to validate and quantify the ingestion of the VTE flow by independently seeding the purge and VTE flows with two different tracer gases. Experimental results show the presence of VTE flow in the rim seal throughout all purge flowrates evaluated. Circumferential variation of VTE flow was also studied both experimentally and computationally using a computational fluid dynamics model. Results showed that ingested VTE flow can reduce the detrimental effect of hot gas ingestion particularly at higher purge flowrates.
Thermodynamic Assessment of Exhaust Gas Recirculation in High-Volume Hydrogen Gas Turbines in Combined Cycle Mode
Authors: Ravelli Silvia 
Published: October 2022

Abstract
To achieve a net-zero approach, while ensuring grid reliability and resiliency, gas turbine (GT) technology has a place for years to come thanks to high efficiency, low turndown, quick starts and fast ramp rates. However, shifting to low-carbon fuels, such as hydrogen, is the key to maintain positive returns in combined cycle (CC) power plants.
By recirculating a fraction of the exhaust gas exiting the heat recovery steam generator (HRSG) back to the inlet of a natural gas (NG) and hydrogen co-fired GT, the gas flow passing through the compressor and entering the combustor has a reduced oxygen concentration thus lowering flame temperature and hence NOx formation. Hydrogen reactivity is then turned into a benefit since the exhaust gas recirculation (EGR) rate can be higher than that with conventional fuels, without facing flame stability issues. In light of this, a thermodynamic assessment of EGR effects on a 2 × 1 large-scale CC is presented considering GT with hydrogen capability up to 65%. The impact of partially replacing NG with hydrogen on GT behavior and overall CC performance was firstly evaluated at both full and part load, with no EGR. Then EGR was simulated for a rate up to 0.5 for different fuel mixtures, under the assumptions of GT inlet flow at low (ISO) and high (up to 47°C) temperature. The analysis was again carried out at full and part load. In the latter case, EGR was exploited to improve CC efficiency at very low loads. For each scenario, CO2 emission intensity was computed thus highlighting the environmental benefits of hydrogen-natural gas blends.
Update of the sCO2-Test Rig at Cranfield University
Authors: Anselmi Eduardo , Belleoud Pierre , Roumeliotis Ioannis , Pachidis Vassilios 
Published: October 2022

Abstract
Since 2018, there is an experimental supercritical carbon dioxide (sCO2) facility operating at Cranfield University. The purpose of this rig is to enable the exploration of supercritical carbon dioxide as a working fluid for future bottoming power cycle applications and, more recently, for thermal management applications. The core of the rig is a transcritical closed loop, which has recently been upgraded. The upgrades include an increase in the number of measurement stations, changes to the types of measurements taken, as well as the addition of a new, dedicated data acquisition system. A summary of some of the lessons learned from different test campaigns conducted from 2018 to 2021 is provided, along with a discussion on the measurement upgrades performed. The experience obtained with this rig, as recounted in this paper, could be relevant to similar test rigs or future power cycles applications.
ICME Modeling of Erosion in Gas-Turbine Grade CMC and HVOF Test
Authors: Abdi Frank , Eftekharian Amirhossein , Huang Dade , Choi Sung , Morscher Gregory N. , Panakarajupally Ragavendra P. 
Published: October 2022

Abstract
Erosion of gas turbine grade ceramic matrix composites (CMC) has recently attracted attention because it limits performance and component life in hot engines. This study developed physics of erosion failure evolution including delamination, cavity formation, and fiber loss using an integrated computational material engineering (ICME) approach. The erosion behavior of two CMC systems at two elevated temperatures (ET) under two high velocities is tested utilizing a high velocity oxygen fuel (HVOF). Two CMC erodent systems were selected, and experiments showed that erodent type and size affect erosion degradation which shows sensitivity to retained strength test after erosion. A computational Multi-Scale Progressive Failure Analysis (MS-PFA) predicted the erosion and post-erosion behavior of CMC’s. Prediction of material degradation, micro-crack formation, interfacial degradation, and retained strength closely matched test observations.
Method: A Multiphysics-based ICME methodology, and virtual design of experiment (DOE) software method includes: 1) Thermo-physics modeling of galvanic ash particles of layered ceramics predicting the mass transfer, 2) Micro-Mechanical Material model including layered CMC interphase and microcrack density, predicting progressive erosion evaluation and delamination, fracture toughness and hardness, and 3) Finite element explicit software predicting: a) Erosion rate as a function of impact angle under ambient temperature conditions; b) Effect of erodent concentration on erosion rate; c) Erosion rate as a function of velocity at 815°C and 1200°C under normal impact conditions; d) Variation of erosion rate with impingement angle and particle size, and velocity range; and e) Erosion rate as a function of erodent concentration, particle size, temperature and velocity under normal impact conditions.
Evolution of Turbine Rear Frame Design for Aero Derivative Engine
Authors: Katti Srinidhi , Reddy Vishnu Vardhan , Chippa Anil Kumar , Babu S. , Casadio Federico 
Published: October 2022

Abstract
As the world’s demand for energy continues to grow, gas turbines are looked at as one of main options for power generation. Among the aero derivative and heavy-duty designs, designers are leaning towards aero derivative architecture due to advantage it offers in terms of performance, footprint, and weight. Gas turbine engineers identify “exhaust casing” as the casing which forms the hot gas path after the last stage of the turbine, to recover back pressure and thereby contributing the increased performance of the turbine. In the same way, in aero derivative engines this casing is called as “Turbine Rear Frame (TRF)”. By virtue of aero derivative design philosophy, TRF is exposed to hot gases on one side and colder ventilation air on other side, posing a challenge to designer in terms of thermo-mechanical design aspects. TRF also functions as a load bearing member by transferring loads from all other casings to foundation, using its support legs. The hollow struts of TRF forms a passage for all bearing piping and few secondary flows. All these piping and colder secondary flows have influence on the design of TRF. This paper presents a comparative study of how various configurations of TRF evolved under Baker Hughes Aero derivative portfolio, which concentrates on secondary flow circuit and thermal design aspects, and its impact on component design. This also covers improved aspects in thermal modeling to match the test data measurements. The impact of different thermal behavior on the component with respect to stress, deformation and stiffness are studied. It also captures the effect of secondary flow circuit modifications on the component interfaces. The aspect of design iterations considering the Ultimate load comparing various versions will also be highlighted.
Numerical Study of Three Gaseous Fuels on the Reactor Length and Pollutant Formation Under Lean Gas Turbine Conditions
Authors: Stiehl Bernhard , Otto Marcel , Newmyer Malcolm , Fortin Max , Genova Tommy , Ahmed Kareem , Kapat Jayanta , Orsino Stefano , Arguinzoni Carlo 
Published: October 2022

Abstract
The present paper numerically studies the impact of three gaseous fuels on the reaction characteristics and pollutant formation in a lean combustion system. The models include an equilibrium calculation with Ansys-Chemkin-Pro, as well as a 3D half-width CFD model using Large Eddy Simulation (LES) and Adaptive Mesh Refinement (AMR) models. The outcomes are targeted to benefit the transition to carbon-free operation of aviation turbines. Three fuels, methane (CH4), hydrogen (H2), and ammonia (NH3) as well as blends thereof were compared at constant equivalence ratios to obtain a firing temperature level of T = 1800°C. The kinetic mechanism in use was suggested and validated by Okafor et al., including 42 species to describe CH4/H2/NH3-air combustion and NOx chemistry. The formation of nitrogen oxide pollutants (NO, NO2 and N2O) were analyzed to determine the sensitivity to the three fuels and their blends. Secondly, a fuel injector scaling study was performed, and a significantly larger jet diameter was selected to compensate for the increased stoichiometric mixture fraction and reduced blend density relative to CH4-fueled architecture. Lastly, the three-dimensional AMR-LES model provided validation of the injector re-sizing, as well as further insight into the expected fuel-air distribution by convective mixing. While the substitution of methane-fueled gas turbines with carbon-free alternatives is generally feasible, blending of H2 and NH3 fuels could be a promising strategy to utilize existing turbine combustors, while retaining reaction timescales close to those of CH4-powered systems.
The Effect of Circumferential Lengthscale on Hot Gas Ingestion
Authors: Dawson Michael G. , Otter John J. , Atkins Nicholas R. 
Published: October 2022

Abstract
This paper demonstrates that long wavelength circumferential pressure variations, an order of magnitude smaller than those created by vanes and blades, are a mechanism of hot gas ingestion. Using experimental, analytical, and numerical methods, it is shown that ingestion depends on both the amplitude and wavelength of a pressure variation, and is driven by the superposition of variations with different wavelengths. A model is presented which demonstrates the sensitivity of hot gas ingestion due to these variations. The model uses the linearised Euler equations to calculate the seal velocity field, and track the movement of mainstream gas into the rotor-stator cavity. Following this understanding, full annulus numerical simulations show that the introduction of long wavelength boundary conditions allow accurate prediction of hot gas ingestion for the double-lip seal tested, using unsteady RANS simulations.
IDAES Platform for Evaluating Thermal Energy Storage for Coal-Fired Indirect sCO2 Power Cycles
Authors: Schmitt Joshua , Karg Bulnes Fernando , Mathur Anoop 
Published: October 2022

Abstract
This paper demonstrates the modelling of a novel power cycle for coal-fired indirect supercritical carbon dioxide (sCO2). and thermal energy storage (TES). TES integrated with coal fired power plant can improve the efficiency, making the power generator responsive to ramp rate. The parallel models were developed in IDAES, an open-source code developed by the Department of Energy (DOE), and Aspen Plus V.10 by Aspen Technology, Inc., which is used in many industries to model and optimize a variety of chemical processes. The benefit of using Aspen Plus for coal combustion is its ability to model solids and multiphase fluids that will be present in the various coal and sCO2 power cycles. The property database and equations of state (EOS) available in the Aspen and IDAES software provide accurate results for the process conditions present in the cycles involved in this project.
A baseline model was selected from DOE studies and compared against results from the system modelling. Current results from the model are close to those found using Aspen and those in the baseline model. The system model was also connected to a dual-media thermocline thermal energy storage system (DMTES) that uses a Python script to determine temperatures of molten salt provided by the DMTES. The code uses variables of heat flow, mass flow, and temperature to determine the performance of the sCO2 power block IDAES model. From this, the power block output is determined for steady state and quasi steady state conditions. The DMTES system is modeled for dynamic situations and is shown to have near-constant temperature during charge or discharge, depending on the position of the DMTES system thermal transition zone. The results show how temperature is maintained across a large range of state-of-charge.
Gradient Enhanced Kriging Using Modal Sensitivity Approximations in a Reduced Basis Space for As-Manufactured Airfoil Analysis
Authors: Brown Jeffrey M. , Carper Emily B. , Kaszynski Alex A. , Gillaugh Daniel L. , Beck Joseph A. 
Published: October 2022

Abstract
This work develops a new process to efficiently predict the effect of as-manufactured geometry variations on airfoil modal response. A gradient enhanced kriging approach is formulated that uses two sets of results at the training model sites in order to reduce the total number of models required. The first set of results are the frequency or mode shape values and the second are their respective gradients. Computational efficiency is achieved through analytical calculations of eigenvalue and eigenvector sensitivities. This approach avoids the need to recompute full eigensolutions for finite difference sensitivity approximation. Efficiency in mode shape approximation is further enabled through transformation of displacement variations into a principal component reduced-basis space. This allows prediction of the full mode shape variation without emulating each degree of freedom independently. In order to perform gradient enhanced kriging with this space, a novel approach is developed to calculate reduced basis space gradients. The process projects the modal displacement principal component vectors onto first-order Taylor series expansions of the physical mode shape variation at each training site. The resulting perturbed principal component coordinates are used in finite difference estimates of sensitivity that make gradient enhanced kriging in this space possible. This new process is demonstrated on three cases, and it is shown that the new approach provides significant improvements in accuracy and efficiency compared to traditional kriging methods.
Experimental and Numerical Investigation of Effect of Inclination on sCO2 Heat Transfer in a Circular Pipe
Authors: Gabriel-Ohanu Emmanuel , Shah Alok , Khadse Akshay , Fernandez Erik , Kapat Jayanta S. 
Published: October 2022

Abstract
Supercritical carbon dioxide (sCO2) can be utilized as a working fluid in various thermal systems including large scale power cycles; portable power production units, centralized coolant systems and standalone cooling devices. However,the lack of accurate prediction tools such as heat transfer coefficient correlations, and insufficient research studies about the mechanisms controlling heat transfer processes, are hindering its practical realization for key energy and cooling systems. The overall objective of this study is to extend fundamental knowledge about heat transfer and fluid dynamic processes in conduits pertinent to sCO2 with an emphasis on flow inclination and directional effects. This paper present the a study on effects of gravity, buoyancy on sCO2 flow at temperature near and away from the pseudocritical temperature. The experimental setup consists of a high temperature and pressure sCO2 heat transfer loop and flow testing facility. Recently researched sCO2 heat exchangers can have tubes oriented at different angles such as 45° or 90° to horizontal. For optimized design of efficient and cost-effective turbo-machinery components utilizing sCO2 as the heat transfer fluid, an understanding of convective heat transfer inside a tube/pipe is equally as important as external heat transfer. This paper presents an experimental and numerical study on sCO2 heat transfer at various inclinations with angles ranging from 0° (horizontal) to 90° (vertical) along with upward and downward flow direction with different inlet temperature. Thermocouple based temperature measurement is utilized at multiple locations within the test section axially and circumferentially to study the temperature distributions on the tube surface. Computational Fluid dynamics (CFD) simulations have been performed using ANSYS Fluent to complement experimental data. The CFD and experiment have been analysed against known Gnielinski nusselt number correlation.
Accurate Blade Tip Timing Placement on a Centrifugal Impeller Using As-Manufactured Modeling
Authors: Gillaugh Daniel L. , Kaszynksi Alexander A. , Tomlin Trevor C. , Brown Jeffrey M. , Beck Joseph A. , Carper Emily B. 
Published: October 2022

Abstract
Non-intrusive stress measurement systems (NSMS) are commonly used during rig and engine tests to ensure safe operation of the test asset. Blade tip timing (BTT) is one form of NSMS that estimates operational stresses of a bladed rotor using time-of-arrival (TOA) data coupled with finite element analysis (FEA) predictions. Traditional FEA techniques assume nominal airfoils to generate stress-to-deflections ratios used with TOA data to predict blade stresses. Recent research has been conducted showing the significant variability in stress-to-deflection ratios when accounting for geometric variations in the blade geometry. As-manufactured finite element modeling has been shown to be a prudent way to account for these geometric variations when developing instrumentation placements and safety limits for rotors. Literature on this topic tends to focus on integrally bladed rotors where every blade is notionally identical. Centrifugal impellers alternatively have a main and splitter blade with significantly different geometries making blade tip timing placement more challenging on these components. Traditional BTT placement techniques will be tailored in this work to achieve optimal probe placement to detect specific vibratory modes of interest for both the main and splitter blades. BTT safety limits will be generated for each mode of interest, and optical scanning and mesh morphing approaches will be used to generate an as-manufactured model of the centrifugal impeller. The BTT safety limit variability due to geometric variations will be assessed for both the main and splitter blades. It will be shown that due to geometric variations within the impeller that the BTT limits can vary between blades. This research further validates the importance of using as-manufactured modeling during component design, test, and throughout the life-cycle.
Experimental Investigation of Inlet Stagnation Pressure Distortion Effects on a Transonic Axial Compressor Rotor
Authors: Oliva Andrew A. , Morris Scott C. 
Published: October 2022

Abstract
This work shows the results of an experimental investigation of a transonic axial compressor subjected to a 120° circumferential inlet distortion. The goal of the investigation was to determine the rotor performance when exposed to a circum-ferentially non-uniform inlet stagnation pressure. The upstream grid was rotated with respect to the fixed instrumentation to provide high resolution information around the annulus. The resulting rotor performance characteristics are shown for 70% and 100% corrected speeds. The results showed that the distorted and undistorted rotor performance differed significantly from the uniform inlet rotor performance. The undistorted compressor performance saw higher maximum inlet Mach numbers than the corresponding uniform characteristic. The distorted compressor performance had stable operating conditions at lower inlet Mach numbers and higher stagnation pressure ratios than the uniform characteristic. The rotor performance orbits were hypothesized to be related to the pre-swirl and counter-swirl created by the inlet circumferential static pressure gradient.