bluuebunny/crossref_metadata_2025 huggingface dataset:
Does the Use of Gastric‐Acid Suppressants Increase the Risk of Peritonitis in Patients Undergoing Peritoneal Dialysis? A Meta‐Analysis
Authors: Yao Lili , Ni Linfeng , Wu Xu
Published: August 2024

Gastric‐acid suppressants (GASs) are commonly prescribed to patients undergoing peritoneal dialysis for various gastrointestinal disorders. However, long‐term GAS use has been linked with the risk of enteric peritonitis in this patient population. To assess the association between the enteric peritonitis risk and GAS use in patients undergoing peritoneal dialysis for end‐stage renal disease, we conducted a systematic search for relevant articles published until December 2023 in PubMed, Embase, and the Cochrane Library databases. We included 11 articles on the association between GAS use and enteric peritonitis risk in patients undergoing peritoneal dialysis. We calculated pooled odds ratios (ORs) with 95% confidence intervals (CIs) using fixed and random‐effects models to obtain overall effect estimates. We also explored potential sources of heterogeneity through subgroup analyses. We qualitatively analyzed data from 11 studies (n = 1993 participants), out of which, nine studies were included in meta‐analysis. The overall results revealed a significant association between the enteric peritonitis risk and the use of GASs (OR, 1.61; 95% CI, 1.26–2.05; p < 0.00001). The analysis of study design subgroups showed a significant association in retrospective cohort studies (OR, 1.70; 95% CI, 1.42–2.03; p < 0.00001) but not in case–control studies. Histamine‐2 receptor antagonist (H2RA) use was significantly associated with enteric peritonitis (OR, 1.49; 95% CI, 1.05–2.11, p = 0.03), whereas proton pump inhibitor use was not (OR, 1.13; 95% CI, 0.72–1.77, p = 0.28). Our findings suggest a significant association between the development of enteric peritonitis and GAS use in patients undergoing peritoneal dialysis. However, the observed heterogeneity in study characteristics warrants caution in interpreting the results.
Design and Implementation of an Experimental Test Bench for the Study of Active Flow Control in Scale Wind Turbines
Authors: Franco Jesus Alejandro , Salinas-Anaya Gael
Published: August 2024

Advances in wind turbine technology are critical in the global renewable energy landscape. The continuous growth of wind turbine capacities has presented various challenges for flow and power control strategies. Developing novel smart systems capable of monitoring and controlling loads and power is required for optimal operation in modern wind generation systems. Several methods have been proposed, but the experimental validation contains complications like operation costs, size, and time required to fabricate a fully scaled wind turbine prototype. Concerning this, the implementation of reduced-scaled wind turbine test benches offers an alternative to validate new flow control strategies for optimizing the efficiency of wind turbines.

This paper presents designing and implementing a wind turbine test bench for active flow control systems in small-scale wind turbines. The system includes a multi-degree mounting system, a dynamic torque sensor, a PMG (Permanent Magnet Generator), and a configurable hub for different wind rotor designs. The process design includes a FEM (Finite Element Method) analysis to evaluate the different configurations of the proposal system. As a result, the design and implementation of the overall functional structure, dynamic sensors, and complementary elements are presented. Finally, an approach of the scaling methodology is revealed based on the mathematical criteria of similarity conditions between a lab-scale wind turbine model and a reference prototype, providing helpful information to optimize wind turbine performance. It contributes to developing more efficient and reliable wind energy control solutions.
Configuration of a Heat Transfer Design Verification Test System Using Airfoil Additive Manufacturing
Authors: Kim Keekeun , Suh Junwon , Kim Dongwha , Kwon Youngmin , Moon Kwanho , Ryu Gyongwon
Published: August 2024

In the process of designing novel high-pressure turbine components, temperature emerges as a pivotal factor, given its profound impact on material stress thresholds and operational life. Hence, it is imperative not only to derive efficient cooling designs but also to establish methods for their effective and reliable validation. In this study, we employed an additive manufacturing (AM) method to fabricate turbine blades and vane specimens that closely resemble the shape of actual components, intended for surface temperature measurements. Additionally, we established a high-temperature test rig equipped with three types of pyrometers for simultaneous acquisition of cooling airfoils surface temperature data. For the AM test specimens, we built channels in both the pressure and suction sides, allowing for the insertion of thermocouples with a 0.8mm diameter from the cooling air supply to the airfoil surface. For the test rig, we configured an annular flow path to accommodate multiple cooling airfoil specimens and established a bypass system capable of supplying high-temperature gas at a flow rate of 3kg/s by combusting liquid fuel. Through these experiments, we were able to compare errors based on measurement methods and obtain data for selecting sensors suitable for observations under different test conditions.
Performance Improvement of a Heat Sink for Battery Thermal Management System
Authors: Rasimarzabadi Faezeh , Azarkish Hassan , Crain Alexander , Recoskie Steven , Bordatchev Evgueni , Shirazy Mahmood
Published: August 2024

Dissipating heat generated by onboard battery systems is a key thermal management challenge for hybrid/electric aircraft. The National Research Council Canada is collaborating with Calogy Solutions, Ltd. (Sherbrooke, Quebec, Canada) to support their development of a novel aviation battery module. The goal of the project is to optimize the heat sink design for battery thermal management system by minimizing thermal resistance as well as reducing overall weight, considering fabrication cost to be used by the industry.

In this research, the original heat sink used by Calogy (plate-fin type) was numerically simulated using commercial software and the results were compared with the experiment. This was done to validate the numerical simulation was accurate enough to be used for future simulations. The heat transfer of the heat sink was enhanced by optimizing fin dimensions and spacing, and fin design modification (a first in this application), based on system analysis of a kW scale hybrid/electric aircraft.

The selected model as the optimized heat sink resulted in about 34% improvement in heat transfer coefficient, and about 24% reduction in weight comparing with the original plate-fin type heat sink.
Impact of Lean on Aerodynamic Performance of a Turbine Rear Structure
Authors: Deshpande Srikanth , Ricchi Mattia , Larsson Jonas , Vikhorev Valentin , Chernoray Valery
Published: August 2024

Jet engine components typically have constraints from multiple disciplines that impact their design. One such component is the Turbine Rear Structure (TRS), situated aft of the Low-Pressure Turbine (LPT) in a jet engine. Due to constraints, some TRSs have vanes with large lean angles up to 30 degrees, with the pressure side leaning towards the hub. Both experimental and numerical studies are conducted to evaluate the impact of large lean angles on the aerodynamics of a TRS. The test facility provides engine-realistic Reynolds numbers and inlet swirl profiles for a TRS. The instrumentation and experimental methods employed in the rig are presented. The experimental results provide valuable data for validating numerical methods used in industry. The validation efforts revealed that today’s numerical methods can effectively predict most of the physical phenomena observed in the measurements with leaned vanes. Following a comprehensive validation of the numerical methods, a study was initiated to understand the aerodynamic distinctions between a radial vane design and a leaned vane design operating under the same flow conditions. A radial vane design was created by eliminating the lean angle from a leaned vane design without applying any further changes to other parameters. This modification resulted in a static pressure decrease on the pressure side at the hub. Additionally, comparing leaned vanes and radial vanes, the results show that the vortices tend to migrate locally and hence loss redistribution occurs near the hub.
Data-Driven Aerodynamic Optimization of a 15-Stage Compressor With Tandem Outlet Guide Vanes
Authors: Liu Yijie , Chen Jiang , Liu Yi , Xiang Hang
Published: August 2024

The aerodynamic design and performance improvement of compressors in gas turbine development, especially in multistage axial flow compressors with numerous design parameters, pose challenges relying on manual design experience. To address computational inefficiency in aerodynamic optimization of multistage turbomachinery, an aerodynamic optimization platform is developed based on the Direct Free-Form Deformation (DFFD) method. This method, offering full-geometry three-dimensional parameterization with arbitrary degrees of freedom, conducts direct manipulation of control vertex displacement, generating smooth shapes, reducing control variables, and achieving dimensionality reduction. The optimization framework combines the DFFD method with a Pre-screen data-driven single-objective optimization algorithm using differential evolution and a hybrid surrogate model. Introducing machine learning techniques significantly reduces Computational Fluid Dynamics (CFD) simulations, enhancing iteration efficiency. Applied to a 15-stage gas turbine compressor, the platform resulted in a 0.37 percentage points efficiency improvement, reducing parameterized variables to 32. Utilizing isentropic efficiency as the pre-screening criterion with a population size of 200 and 560 true evaluations, the entire optimization process took 79.2 hours. This data-driven aerodynamic optimization platform demonstrates efficiency and stability in three-dimensional rapid parameterized optimization for highly loaded multi-stage compressors, presenting a novel approach for such optimization challenges.
Real-Time Jet Engine Performance Analysis System With Compressor Surge and Turbine Choked Flow Detection Functions
Authors: Nguyen Huy Hoang , Vu Xuan Hung , Pham Tuan Anh , Bui Van Son , Trinh Thanh Nam , Ngo Ngoc Vinh , Nguyen Viet Linh , Nguyen Thanh Duong
Published: August 2024

This paper introduces an analysis system for the performance and thermodynamics characteristics of a jet engine in real-time. Parameters such as air mass flowrate, fuel to air ratio, temperature before turbine are calculated continuosly in real-time. Basis functions of the program are calculations of isentropic exponent and specific heat coefficients according to air temperature and fuel to air ratio. Energy conservation calculation process and shaft power balance calculation process are the keys to determine all thermodynamics parameters. These processes ensure that analysis results are consistent, precise and reliable. Engine performance charts such as Combustion efficiency, Compressor efficiency, Turbine efficiency, Thermal cycle, Compressor map, Turbine map, Brayton cycle are presented instantaneously while the engine runs. Based on these real-time parameters and charts, compressor surge detection and turbine choked flow detection functions are developed. Compressor surge is detected by the oscilation of air mass flowrate. Turbine choked flow is detected by a sideways or downward movement of turbine mass flowrate reduced when turbine pressure ratio increases. The system has been applied to analyse data from several axial compressor turbojet engine prototypes and it is capable of running online while the engine operates and offline to analyze test data from a text file. A summary report on thermodynamics and performance of the engine can be created after the end of the test. This report can help analyze the performance of each component in the engine at different operating points to detect abnormalities, or help improve engine efficiency.
Dynamic Response of a Pivot-Mounted Squeeze Film Damper: Measurements and Predictions
Authors: Kasprzyk Marie , Delgado Adolfo
Published: August 2024

Squeeze film dampers (SFDs) are widely used to reduce vibration levels in rotating equipment. These devices are installed in series with bearings and are subjected to precessional motions with the inner and outer damper surfaces remaining parallel. Alternatively, this paper evaluates the dynamic performance of a damper describing angular motions.

This paper includes the design and development of a test rig, and the experimental dynamic response of the pivot-mounted journal benchmarked with a predictive finite element code. The experimental setup uses a housing with two different radial clearances — 3 mils (76.2 μm) for the lower land and 12 mils (304.8 μm) for the upper land — which is open to atmosphere. This work also includes developing a pivot-mounted SFD computer code, capable of predicting the dynamic performance of unpressurized 2π and segmented dampers. The numerical tool can predict the dynamic performance of a damper that has multiple land diameters with different clearances. The experimental results identify stiffness, damping, and added mass for both the SFD and its structure, showing a close correlation with the numerical calculations using three different fluid viscosities.
Heat Transfer Enhancement in Pulsating Flows: A Bayesian Approach to Experimental Correlations
Authors: Ignuta-Ciuncanu Matei Cristian , Noon Chris , Martinez-Botas Ricardo F.
Published: August 2024

This research focuses on improving the modelling of heat transfer effects in pulsating exhaust flows. We address the challenges of understanding oscillating flow by employing the Metropolis-Hastings Markov Chain Monte Carlo sampling method for parameter estimation, accounting for measurement uncertainties.

The knowledge can be applied to waste heat from reciprocating devices, pulsating turbocharger performance, and flow fields with significant cyclic variations. We demonstrate the feasibility of characterising heat transfer capacity in pulsating flows using Bayesian inference and polynomial regression for experimental data correlation. This methodology is furthermore applied to identify heat transfer patterns in cold gas flow through a heated pipe across a range of mass flow rates and pulsating frequencies. To achieve this, the thermal performance variations across the length of the pipe through temperature and pressure changes are quantified. The model developed exhibits robust performance and high data efficiency (R2 ∈ [0.83, 0.89]) and notable extrapolation capacity in predicting mean heat transfer beahviour based on boundary measurements. The results address the lack of experimental insights on pulsating flows encountered in heavy-duty transport applications and can be extended for heat recovery in systems such as exhaust manifolds and Organic Rankine Cycle gas turbines.
A Parametric Study on NOx Emissions From Ammonia Containing Product Gas in Rich Quench Lean Combustion
Authors: Raslan Ahmed , Yang Silin , Durocher Antoine , Güthe Felix , Bergthorson Jeff
Published: August 2024

Due to climate change, there has been an increasing demand for fuels that can accelerate the transition away from fossil fuels to clean energy. Humidified product gas obtained from gasifying biomass is emerging as a promising candidate to replace natural gas, as it is composed of a gaseous mixture of hydrogen, steam, carbon monoxide and methane. However, the gasification process releases ammonia and other nitrogen bearing compounds into the product gas, resulting in substantial increases in nitric oxides, NOx, in the exhaust. As such, there has been a recent push to understand the underlying chemical kinetics that drive NOx formation in order to optimize gas turbines to mitigate emissions at the source. In this study, a simplified CRN model for a gas turbine Rich-Quench-Lean (RQL) type combustor was developed in Cantera. The following parameters were investigated in this study: equivalence ratio of the primary section (1.1 to 1.6), overall equivalence ratio (0.6 to 1.1), steam dilution (25% and 50% molar dilution), post flame residence time (0 to 75 ms) and recirculation from the post quench region to the primary section (0 and 40% by mass). Additionally, a benchmark CRN representing a Lean Burner (LB) as also developed. Results of the CRN model suggest that, when comparing to LB, a RQL type combustor delivers up to a 75% reduction in emissions. Additionally, it was found that, for both the LB and RQL combustors, an overall lean to stoichiometric equivalence ratio is well suited to reduce emissions in highly humidified fuels, while for moderately humidified fuels it is preferable to operate in an overall slightly rich equivalence ratio. The difference observed is mainly due to the fact that, at high humidification and lean conditions, the temperature is favourable for the conversion of ammonia to nitrogen. While, at moderate humidification and rich conditions, NO reacts with ammonia in the reburn process. Finally, it is suggested that the incorporation of recirculation from the secondary section to the primary section of the RQL burner results in a broader low emission region, due to more favourable conditions for ammonia conversion to nitrogen in the primary section.
The Unsteady Shock-Boundary Layer Interaction in a Compressor Cascade – Part 2: High-Fidelity Simulation
Authors: Klose Bjoern F. , Morsbach Christian , Bergmann Michael , Munoz Lopez Edwin J. , Hergt Alexander , Kügeler Edmund
Published: August 2024

In the second part of this three-paper series, high-fidelity simulations of the Transonic Cascade TEAMAero at the aerodynamic design point with Rein = 1.35 × 106 and Main = 1.21 are presented. A high-order discontinuous Galerkin spectral element method with finite-volume subcell shock capturing is employed to simulate the flow based on an implicit LES scheme and advanced over several buffeting cycles to reliably capture the shock unsteadiness. A study on the spanwise domain size shows that the shock oscillation amplitude decreases with increasing span, although its frequency and mean location remains fixed through the simulations. By comparing high- and low-resolution LES results, it is further presented that deviations from under-resolution are mostly limited to the separated region past the shock, where the high-fidelity results match experimental results more closely. In addition to the LES, low-fidelity URANS is shown to capture the shock unsteadiness correctly, but at a reduced amplitude and fails to match the force distributions on the blade surface. Through examination of instantaneous flow features, space-time relations and spectral proper orthogonal decomposition, a basic analysis of the shock-boundary layer interaction is presented and indicates that velocity perturbations travel upstream through the subsonic boundary layer and periodically cause oblique shock waves, transporting the information from the boundary layer into the passage.
Impact of High Freestream Turbulence on LPT Endwall Flow – Part II: Endwall Flow Dynamics
Authors: Donovan Molly H. , Marks Christopher R. , Fletcher Nathan , Rumpfkeil Markus P.
Published: August 2024

The flow field surrounding low-pressure turbine blades is associated with significant losses in the endwall region. The exact location and behavior of the endwall structures is tied to the incoming boundary layer state; therefore, the incoming freestream turbulence is expected to impact dynamic characteristics of these structures and the associated losses. As discussed in Part I, the incoming turbulence intensity was varied between < 1% and 7% at three different Reynolds numbers within a linear cascade of high-lift high-work low-pressure turbine blades. The focus of this paper will be on the effect elevated freestream turbulence has on the unsteady dynamics of the endwall flow structures. Three planes of high-speed stereoscopic particle image velocimetry were collected within the passage of the turbine blades capturing cross-sectional slices of key endwall vortices. From a detailed flow analysis completed with SPIV measurements, it was established that elevating the turbulence levels had a direct impact on the locations and time-dependent characteristics of the endwall topology. Differences in temporal characteristics were observed in all planes with the introduction of elevated turbulence; however, the bimodal behavior documented by other researchers near the leading edge was still observed. The horseshoe vortex was found to intermittently lose coherence at the leading edge and in the passage. The frequency of the loss of coherence events as well as the vortex position was altered as the freestream turbulence was elevated.
A Practical Evaluation of Equations of State and the New PTC-10 Polytropic Calculations for Centrifugal Compressors
Authors: Srinivasan Anand , Kurz Rainer , David Timothy
Published: August 2024

The ASME Performance Test Code (PTC-10) stipulates the need for a unified polytropic calculation procedure on reporting out performance characteristics for centrifugal compressors. The accurate determination of enthalpy and entropy, in addition to the thermodynamic gas constants, plays a crucial role in predicting the performance of a compressor. The measured temperatures and pressures at the inlet and exit of the compressor are used to obtain the thermodynamic properties, which are in turn used to evaluate the compressor performance. These thermodynamic properties depend on the equation of state used for the calculations. In this paper, the influence of equation of state on the performance of centrifugal compressors on carbon dioxide and natural gas is investigated. Several commonly used equations of state including REFPROP, Redlich-Kwong, Lee-Kesler-Ploecker and Peng-Robinson are used for the comparison. The recently-released 2022 revision to the ASME PTC-10 code proposes the use of the Sandberg-Colby & Huntington’s methods to evaluate the polytropic performance of a centrifugal compressor. The use of these methods is investigated in this paper to evaluate the performance of gas compressors. A discussion on the use of these methods on natural gas as a function of discharge pressure is also presented in this paper.
Numerical Study on Separation Flows of a Compressor Transition Duct
Authors: Liu Zhenliang , Wu Yadong , Zhang Xinze , Ouyang Hua
Published: August 2024

The transition duct is a core part of aeroengines, connecting low and high-pressure compressors (LPC & HPC). Nowadays, the balance between the stability of airflow and the compactness of transition ducts has been the major concern of designers. Unstable flows growth at low mass flow rate operating point and may cause accidents. A detailed understanding of the flow field of the transition ducts is crucial for achieving an optimal and safe design. A URANS simulation is conducted based on a combined model of a strutted transition duct and the outlet guide vane (OGV) of LPC. Focusing on the dynamics of vortices inside OGV and strut passages, the development and evolution of vortices are carefully discussed. The separations within OGV passages are categorized into closed and open separation, with the latter significantly blocking the passage and migrating circumferentially. Trailing vortex pair and corner separation vortex around the struts are stable, showing no interaction between passages. Further, the Proper Orthogonal Decomposition (POD) method is utilized. The corresponding relationship between instantaneous features of the pressure field at OGV passages and POD modes is revealed. Equally spaced peaks in the frequency domain are presented by different modes. In lower span, more energy is preserved in low-frequency modes. In higher span, more energy is preserved in high-frequency modes.
Design, Analysis, and Testing of an Additively Manufactured Catalytic Combustor for a Micro-Wave Rotor Turbine
Authors: Tüchler Stefan , Adamou Adamos , Akbari Pejman , Copeland Colin D.
Published: August 2024

In this paper, an additively manufactured (AM) Inconel catalytic combustor was tested in combination with a micro-wave rotor turbine with non-axial channels designed for shaft power extraction. This was done in an open-loop configuration over a range of operating conditions in order to characterise the behaviour of the wave rotor and combustor separately. The catalytic combustor data yielded low pressure losses of approximately 1% and provided stable and continuous operation up to outlet temperatures of 900°C and combustion efficiencies of up to 99%. The data also revealed a high sensitivity to local over-fuelling and hot spots that severely reduced service life. This is attributed to the additive manufacturing process producing uneven fuel injector hole sizes that cause uneven fuel mixing upstream of the catalytic reactor. However, it showed that first, it is possible to manufacture and coat an additively manufactured catalytic core. Secondly, it showed that the design freedom of AM could be used to make catalytic combustors viable in commercial applications.
Experimental Evaluation of an Electric Powertrain Designed for a 180-kW Turboelectric Aircraft Ground Test Rig
Authors: Johnsen Joshua , Melvin Joshua , Drake Joshua , Jdiobe Muwanika , Rouser Kurt
Published: August 2024

This paper presents the experimental results of a representative aircraft turboelectric powertrain. The 180-kW hybrid gas-electric ground test rig was designed, fabricated, and experimentally evaluated. Hybrid turboelectric power systems are an enabler for future medium- to long-range electrified aircraft, offering higher energy density over current battery technologies. Previous studies have focused on analytical models of turboelectric power systems. However, as industry stakeholders continue to advance toward implementing turboelectric parallel hybrid aircraft, there is a lack of practical knowledge regarding their implementation. The objectives of this study are twofold. First, the study aims to evaluate the real-time transient performance of turboelectric aircraft. The second objective aims to characterize the real-world challenges of safely constructing and operating a hybrid turboelectric aircraft. To accomplish both objectives, a turboprop-powered ground test vehicle was designed and fabricated. The ground test vehicle was constructed from a modified Cessna-172 aircraft, a modified 180-kW PBS-TP100 turboprop, two wing-mounted electric motors, and a purpose-built hybrid-turboelectric powertrain. A portion of the turboprop shaft power is extracted to generate electricity for the battery system and wing-mounted electric motors. The test vehicle was successfully brought to full engine power and the wing-mounted electric motors were run through a series of operating points to experimentally evaluate transient electrical and mechanical performance. Observations are made regarding the interdependent time responses of the electro-mechanical systems. Results from the test run include engine performance metrics, current, voltage, and acoustic data. The generator peaked at 4-kW and was augmented by 13-kW of battery power to drive distributed propulsors, while the turboprop generated 142-kW of power for the variable pitch propeller. Practical recommendations for safe integration are identified, such as the need for a pre-charge circuit, crowbar circuit, and future short protection circuit. This study provides critical insight into the design and practical implementation of turboelectric power systems for future electrified aircraft.
Multidisciplinary Optimisation of Additive Manufactured Heat Exchangers for Aeronautical Applications
Authors: Chiodi Alessandro , Alaia Alessandro , Lombardi Edoardo , Cisternino Marco , Gkaragkounis Konstantinos , Shahpar Shahrokh
Published: August 2024

In this work, we investigate a new methodology for the multi-scale simulation and optimisation of Micro Channel Heat Exchangers with lattice-like topology based on homogenization theory. The lattice matrix is modelled as an equivalent porous medium and is simulated only at the macroscale using standard CFD tools. Micro and meso-scale effects are incorporated in terms of variable permeability tensor and heat transfer coefficients, which are assumed to be non-linear functions of the local flow conditions and lattice geometry. Scale bridging is achieved thanks to a Machine Learning (ML) model which is trained to infer the required closure relationships from a database of Direct Numerical Simulations (DNS). DNS are performed at the scale of a single lattice cells for several geometries at varying operating conditions. The proposed approach is used to solve a benchmark problem provided by Rolls-Royce plc. The test case involves the optimization of a heat exchanger employed in the cooling system of power electronic. In order to assess the soundness of the proposed methodology, numerical results for three different configurations are presented. The effect of under (over) fitting is also investigated in terms of quality and performances of the final optimal geometry.
Numerical Study on the Influence of Purge Slot Shapes on the Film Cooling Performance of Endwall With the Mainstream Swirl
Authors: Zhang Jinghan , Xie Gang , Lou Yuzhu , Li Haiwang
Published: August 2024

For modern gas turbine design, a slot exists between the first-stage nozzle guide vane and the combustion chamber flame tube due to assembly requirements. This structure’s cooling performance is often overlooked or oversimplified in design. However, this article will consider the real combustion chamber exit flow field and conduct a detailed study of the cooling effect under aggressive swirl flow in the slot. This study employs a boundary condition generation method to evaluate the influence of swirling flow under various inlet conditions through numerical methods. The fundamental model consists of a single-row 45-degree slot combination with C3X nozzle guide vane. On this basis, a novel laterally expanding slot is designed. To assess the influence of swirling flow, two cases under two swirling flow orientations were studied. The numerical findings indicate that, under the conventional slot structure, the positive inlet condition can diminish the cooling effectiveness of the purge slot, whereas the negative swirl flow enhances it. Under uniform inlet, the newly designed laterally expanding slot demonstrates an average adiabatic cooling effectiveness surpassing that of the conventional slot, reaching as high as 76%. This innovative design exhibits superior cooling performance under both positive and negative swirl flow inlet conditions, while also maintaining a high degree of robustness in the presence of swirl flows.
On the Optimum Distribution of Multiple Helmholtz Resonators for Annular Combustors
Authors: Chen Hongwei , Yin Liming , Liu Xiaopei , Chen Mingmin , Yang Dong
Published: August 2024

The combustors of many modern land-based gas turbines and aero-engines are annular. This kind of combustors often suffer from thermoacoustic oscillations, with the occurrence of mostly the circumferential first-order, second-order and third-order oscillation modes in the annular combustion chamber. This could cause severe pressure oscillations in the combustor, which may increase noise and NOx emissions, affect the safe operation of the engine and even cause irreversible damages to the structure. To solve this problem, passive control methods are widely used — adding passive acoustic dampers such as Helmholtz resonators (HRs). Depending on the type and number of HRs, and the possible positions over the circumference to install them, there could easily have millions, or even billions, of possible arrangement patterns. Finding a good design is the key to solve this problem. In this paper, we perform a theoretical and numerical study of an annular combustor installed with multiple types of HRs over the circumference. Firstly, a simple annular duct with arbitrary distributions of these HRs is studied analytically by solving the nonlinear eigenvalue problem of a 1D network model. Based on the results of the analytical method, the impact of the HRs on the acoustic modes of the combustion chamber is studied and the optimum arrangement of multiple resonators is obtained. This arrangement usually gives a null (or small) mode splitting strength and a good damping effect. Finally, we apply the optimum arrangement to damp the thermoacoustic modes that have been captured by numerical simulation for a real annular combustor. We use numerical simulations based on solving the 3D Helmholtz equation in COMSOL to verify the feasibility of the optimum arrangement.
A Deep Learning Based Model for Identifying Recirculation Zones From Experimental Images of Trapped Vortex Combustors
Authors: Dash Priyabrat , Mallik Tanaya , Verma Nikhil , Roy Choudhury Aritra , Ravikrishna R. V. , Aditya Konduri
Published: August 2024

Particle image velocimetry (PIV) is a standard method for studying primary recirculation zones in trapped vortex combustors (TVCs), which can operate in an RQL configuration. However, its intrusive nature can disrupt the flow, flame, and equipment in compact combustors, leading to inaccuracies. As an alternative, we use deep learning models based on generative adversarial networks (GAN, a widely used approach) and vision transformers (ViT, a recently devised promising architecture) to estimate the position and overall structure of large-scale vortices from a non-invasively measured quantity, such as the planar laser-induced fluorescence (PLIF) of a species. These models are trained using datasets from large-eddy simulations (LES) of TVCs with information regarding all scalars constituting the state variable, with the addition of noise to mimic experimental data. Quantitative metrics such as relative errors and PDFs of velocity components and their orientation have been used to demonstrate that the ViT exhibits better performance than the GAN. Sensitivity to the type of noise added to simulation data during training is studied as well. The trained model is then used to infer velocity vectors from noisy OH-PLIF data. In the absence of ground truth for that case, qualitative observations reinforce our earlier notion of the superiority of ViT. Such models will facilitate intelligent data fusion and the development of digital twins of combustors.
Investigation of Flame Response in a Swirling Micromix Hydrogen-Methane Combustor
Authors: Liu Dewen , Feng Zhenzhen , Tian Xiaojing , Xu Liangliang , Gu Mingming , Lin Yang , Xia Xi , Qi Fei
Published: August 2024

Hydrogen-enriched natural gas combustion is a hot topic in industrial and academic communities due to the need for carbon emission reduction. However, thermoacoustic instability poses a major challenge for lean combustion development, particularly the higher frequency combustion oscillations. This study investigates the flame response in micromix hydrogen/methane flames within a low to medium frequency range of 50 to 1200 Hz, revealing a critical mixing ratio. Above this threshold, the flame response is dominated by hydrogen combustion, whereas below it, methane combustion takes precedence. Overall speaking, the hydrogen addition significantly enlarges the low-pass filter limit of the flame transfer function. Simultaneous OH* chemiluminescence and PIV experiments demonstrate that the gain is associated with the flame size and the number of acoustic-induced vortices on the flame surface. Higher frequency acoustic forcing leads to flame responses out of phase at different longitudinal positions, resulting in a low global flame response. Hydrogen addition reduces the flame length and enhances the FTF gain at specific frequencies.
Thermodynamic Optimization of Load-Following Operation in a Decarbonized Combined Cycle Power Plant Under Net-Zero Scenarios
Authors: Ravelli Silvia
Published: August 2024

Post-combustion capture (PCC) by means of mono-ethanolamine (MEA) and hydrogen co-firing, combined with exhaust gas recirculation (EGR), were applied to a typical 2x1 combined cycle (CC) with the goal of reaching net-zero CO2 emissions. The novelty lies in integrating decarbonization solutions into the daily operation of the CC, when power generation is adjusted according to fluctuations in electricity demand, throughout two representative days in summer and winter.

More specifically, off-design thermodynamic modelling was adapted to incorporate a multivariable optimization problem to find the maximum power plant efficiency as a function of the following decision variables:

- load of each gas turbine (GT), spanning from minimum turndown to full load;

- EGR rate, in a range that depends on the fuel type: [0; 0.4] for 100% natural gas (NG) vs. [0; 0.55] when hydrogen is fed to the combustor;

with the constraint of net power output equal to electricity demand, for given environmental conditions.

Suggestions were made to mitigate the energy penalty due to decarbonization in the load-following operation mode, taking the integration of MEA CO2 capture into the NG-fired CC as a benchmark. The solution in which EGR combines optimally with hydrogen in the fuel mixture, with the addition of PCC to abate residual CO2 emissions, has proven to be the most efficient way to provide dispatchable clean energy, especially in cold climates.
Laboratory Tests in Cyber-Physical Mode for an Energy Management System Including Renewable Sources and Industrial Symbiosis
Authors: Ferrari Mario Luigi , Gini Lorenzo , Pascenti Matteo
Published: August 2024

The aim of this paper regards the laboratory validation of an energy management system (EMS) for an industrial site on the Eigerøy island (Norway). It will be the demonstration district in the ROBINSON project, for a consequent concept replication. This activity in cyber-physical mode is an innovative approach to finalize the EMS tool with real measurement data with prime movers available at laboratory level, considering the necessary EMS robustness and flexibility for replication on other industrial islands. This EMS was designed and developed to minimize variable costs, producing on/off and set-point signals that, through a Model Predictive Control (MPC) software, establish the system status. This smart grid includes renewable sources (e.g., solar panels, a wind turbine, and syngas) and traditional prime movers, such as a steam boiler for the industry needs. Moreover, an energy storage device is installed composed of an electrolyzer with a hydrogen pressure vessel.

The main results reported in this work regard 26-hour tests performed in cyber-physical mode thanks to the real-time interaction of hardware and software. So, a real microturbine and real photovoltaic panels were managed by the EMS in conjunction with software models for components not physically present in the laboratory. Although the optimization target was cost minimization, significant improvement was also obtained in terms of efficiency increase and CO2 emission decrease.
Experimental and Numerical Study on Turbulent Flow Heat Transfer and Turbulent Flow in Rotating Channel Roughened With Vortex Ribs
Authors: Xu Chao , Rao Yu , Chen Jianian , Luan Yong
Published: August 2024

Heat transfer and pressure loss characteristics of novel vortex rib in a cooling channel have been investigated both experimentally and numerically under the Reynolds number (Re) from 10,000 to 80,000 and Rotation number (Ro) Ro = 0–0.385. The vortex rib cooling structure is proposed by combining W-shaped rib and W-shaped elongated dimple. Compared with the W-shaped rib, the vortex rib strengthens heat transfer by 2.6%–11.4% while reducing the pressure loss by 0.6%–18.7% under non-rotating and rotating conditions. Compared to the W-oblong-dimple, the heat transfer of the vortex rib increases by 2.0%–47.9%. The heat transfer dead zones are significantly improved by near-wall vortex induced by vortex rib. It is also noted that the vortex rib can appreciably reduce the turbulent mixing intensity in the mainstream of the cooling fluid but keep the near-wall high turbulent mixing intensity region, guaranteeing the near-wall turbulent heat transport capacity.
Turbulence Generation Mechanisms in Compressor Boundary Layers
Authors: Dellacasagrande Matteo , Przytarski Pawel J.
Published: August 2024

Turbomachinery flows are highly unsteady and feature complex interactions between stationary and rotating blades coupled with high freestream turbulence effects. This unsteadiness can lead to a variety of transition mechanisms. A detailed investigation of turbulence production under various levels of freestream unsteadiness in attached and separated boundary layers may guide the definition of “laminar” and “turbulent” kinetic energies for the development of highly accurate transition models based on laminar kinetic energy concept. For this purpose, high-fidelity scale-resolving simulations of a compressor blade-row exposed to turbulent inflow conditions were studied. The conditions were chosen such that the suction side boundary layer was either predominantly attached or separated. Using a turbulent event recognition technique a local laminar-turbulent discretization of the flow was obtained providing the reference value of the local boundary layer intermittency. Then, the contribution of turbulence production associated with different flow scales was computed for the attached and the separated boundary layers. Comparing the local levels of turbulence production with the local value of the boundary layer intermittency function allowed classifying the individual flow features as “laminar” and “turbulent” depending on their role in transition. It is shown that the fluctuations originating from vortex shedding in separated boundary layers should be classified and included in the turbulent kinetic energy budget. On the other hand, low frequency shear layer fluctuations and streaky structures are seen to mostly contribute to the laminar kinetic energy budget. Data presented in this work is expected to provide insight into the turbulence generation mechanisms in turbomachinery flows and can be adopted for the future construction of physics-based transition models.
A Comprehensive Literature Review on the Resolution of Turbine Engine Performances’ Inverse Problems
Authors: Vu Dong Quan , Razakarivony Sebastien , Marnissi Yosra , Nocture Michel
Published: August 2024

Turbine engine monitoring is a well-known and well-studied subject that proves to be essential for the aeronautic industry. A popular approach in engine monitoring is constructing indicators that reflect systems’ health states by leveraging operational measurements (i.e., sensors’ data during flights) — this is known as the engine performance’s inverse problem. There exists an extensive literature on this topic, especially revolving around two well-used types of performance indicators of aircraft engines: efficiencies and air mass flow rates of engine’s modules. This review aims to provide a comprehensive survey of this particular literature, which so far has not been properly organized and structured. Our first contribution is to propose a novel taxonomy of the relevant methods. In particular, we consider the role of physics-based models — an element that provides specific advantages and challenges in the context of aircraft engines monitoring — and see if each method exploits such models inside or outside the main algorithmic process (or not exploiting them at all). Our second contribution is to identify the pros and cons of each method, along with additional insights with respect to two commonly encountered challenges: under-determined scenarios and time-series data. Finally, we give some guidelines for selecting appropriate strategies in practical situations and perspectives for future works.
FlameSheet™ Combustion System Operation and Experience With Refinery Offgas in a 7FA Gas Turbine
Authors: Hernandez Fred , Yaquinto Matthew , Kalb Bryan , Paskin Marc
Published: August 2024

The petroleum refining industry is a significant industrial consumer of energy and consequently is a significant source of greenhouse gas emissions. Certain processes such as fluid catalytic cracking units (FCCU) produce significant quantities of by-product gases. Onsite recycling and consumption of by-product gases is critical in reducing sources of GHG in a refinery. This paper describes the operational experience on a 7FA Gas Turbine at a powerplant that is co-located at a petroleum refinery. The 7FA Gas turbine, originally designed for operation with natural gas, was retrofitted with a FlameSheet™ combustion system and additional output and efficiency upgrade. It was then demonstrated to operate with a blend of natural gas (NG) and refinery off-gas (ROG) whose composition was varied throughout the validation. The blend gas into the gas turbine operated up to > 80%mass of ROG and low methane levels < 30%vol of CH4. The blend gas variations tested had significant quantities of ethane/ethylene, propane/propene and hydrogen. Hydrogen levels greater than 20%vol were demonstrated in steady operation. At all times, emissions compliance was held with Gas Turbine output emissions < 9 ppm NOx and CO measured at load levels up to baseload and peak overfire. This paper demonstrates the operation experience and presents the detailed results of combustor tuning and operability with ROG blends relative to the baseline Natural Gas operation, as well as provides potential reasons for the changes in observed combustor performance.
High-Fidelity Numerical Investigation of a High Pressure Turbine Cooled Vane
Authors: Gokenis Furkan , Peneklioglu Kagan , Oksuz Ozhan , Erdem Erinc , Eyi Sinan
Published: August 2024

A significant portion of a turbine blade/vane might experience a transitional boundary layer presumably on the suction surface, which affects the rate of heat transfer. Appropriate choice of the turbulence model on predicting a realistic heat transfer rate in the vicinity of the transition region is therefore imperative. Current study presents the numerical assessment effort of an industry-standard Energy Efficient Engine (E3) high pressure turbine (HPT) second stage cooled vane in terms of flowfield and wall temperatures. In order to assess numerical predictions, wall temperature distributions at the cooling design point at 65% and 95% span locations reported by NASA, deduced from core engine tests accompanied with thermal analyses, are utilised. Conjugate heat transfer (CHT) analyses are carried out to reveal wall temperatures. External flow field is examined through the given normalized velocity distributions provided in the NASA reports.

For these studies various turbulence models; k-ω SST, k-ω SST ɣ-Reϴ transitional, Lag EB k-ε (EBL) and V2F were used. As an alternative, Large Eddy Simulation (LES) is conducted on external flow domain to validate the flow field around the vane by comparing the HTC distributions with the other turbulence models. However, LES analysis did not give promising results. It is found that near the end of leading edge region, metal temperatures are significantly overpredicted when the effect of laminar to turbulent transition is not taken into account. In all of the turbulence models, EBL model has captured the laminar-to-turbulent transition and give the best results. Finally, when the platform solid added to the CFD model, the simulation results get close to the NASA results due to conduction.
Supplemental Material: Transverse faulting in the Paradox Basin, Colorado Plateau, USA: Active, intermittent faulting over a 300 million year history of strain accommodation and fluid flow
Authors: Davis George , Reeher Lauren Jane
Published: August 2024

This material constitutes a detailed fault-by-fault narrative based on our comprehensive examination of published geologic maps and our own field observations. It includes minimaps for each of the transverse faults and fault zones. Descriptive details are presented in a common order for each fault: general location, primary map reference, nature of faulting, structural association(s), evidence for fault-related channeling of fluid flow, and timing constraints.