bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigating the Origins of Cyclic Variability in Internal Combustion Engines Using Wall-Resolved Large Eddy Simulations
Authors: Wu Sicong , Patel Saumil S. , Ameen Muhsin M. 
Published: October 2022

Abstract
Modern internal combustion engines (ICE) operate at the ragged edge of stable operation characterized by high cycle-to-cycle variations (CCV). A key scientific challenge for ICE is the understanding, modeling, and control of CCV in engine performance, which can contribute to partial burns, misfire, and knock. The objective of this study is to use high-fidelity numerical simulations to improve the understanding of the causes of CCV. Nek5000, a leading high-order spectral element, open source code, is used to simulate the turbulent flow in the engine combustion chamber. Multicycle, wall-resolved large-eddy simulations (LESs) are performed for the General Motors (GM), Transparent Combustion Chamber (TCC-III) optical engine under motored operating conditions. The mean and root-mean-square (rms) of the in-cylinder flow fields at various piston positions are validated using particle image velocimetry (PIV) measurements during the intake and compression strokes. The large-scale flow structures, including the swirl and tumble flow patterns, are analyzed in detail and the causes for cyclic variabilities in these flow features are explained. The energy distribution across the different scales of the flow are quantified using one-dimensional (1D) energy spectra, and the effect of the tumble breakdown process on the energy distribution is examined. The insights from this study can help us develop improved engine designs with reduced cyclic variabilities in the in-cylinder flow leading to enhanced engine performance.
High-Fidelity Energy Deposition Ignition Model Coupled With Flame Propagation Models at Engine-Like Flow Conditions
Authors: Kazmouz Samuel J. , Scarcelli Riccardo , Kim Joohan , Cheng Zhen , Liu Shuaishuai , Dai Meizhong , Pomraning Eric , Senecal Peter K. , Lee Seong-Young 
Published: October 2022

Abstract
With the heightened pressure on car manufacturers to increase the efficiency and reduce the carbon emissions of their fleets, more challenging engine operation has become a viable option. Highly dilute, boosted, and stratified charge, among others, promise engine efficiency gains and emissions reductions. At such demanding engine conditions, the spark-ignition process is a key factor for the flame initiation propagation and the combustion event. From a computational standpoint, there exist multiple spark-ignition models that perform well under conventional conditions but are not truly predictive under strenuous engine operation modes, where the underlying physics needs to be expanded. In this paper, a hybrid Lagrangian–Eulerian spark-ignition (LESI) model is coupled with different turbulence models, grid sizes, and combustion models. The ignition model, previously developed, relies on coupling Eulerian energy deposition with a Lagrangian particle evolution of the spark channel, at every time-step. The spark channel is attached to the electrodes and allowed to elongate at a speed derived from the flow velocity. The LESI model is used to simulate spark ignition in a nonquiescent crossflow environment at engine-like conditions, using converge commercial computational fluid dynamics (CFD) solver. The results highlight the consistency, robustness, and versatility of the model in a range of engine-like setups, from typical with Reynolds-averaged Navier–Stokes (RANS) and a larger grid size to high fidelity with large-eddy simulation (LES) and a finer grid size. The flame kernel growth is then evaluated against Schlieren images from an optical constant volume ignition chamber with a focus on the performance of flame propagation models, such as G-equation and thickened flame model, versus the baseline well-stirred reactor model. Finally, future development details are discussed.
Experimental Investigation of Friction Damping in Blade Root Joints
Authors: Botto Daniele , Cuccovillo Federica , Iannotti Veronica 
Published: October 2022

Abstract
The design of disk assemblies requires the capability to predict their dynamic behavior. To achieve this objective, knowledge of friction damping on the contact between blade and disk is of paramount importance. This paper proposes an experimental technique to measure the loss factor and the dynamics, in terms of natural frequencies, of blade-disk attachment. The free decay is used to infer the dynamic parameters from dummy blades. The identification method is based on the Hilbert transform that allows extracting the dynamic parameters from nonlinear system. This paper shows the test rig utilized in the experimental analysis and details the excitation system used to displace the dummy blade. This system must be a real or a “virtual” noncontact system to avoid injecting external damping into the blade under test. Tests were performed on both a dovetail and a fir-tree type attachment. On the dovetail, tests were performed both with dry contact surfaces and with contact surfaces covered by a film of lubricant to achieve a low coefficient of friction. This low coefficient of friction better simulates dry surfaces at high temperatures, as friction coefficients decrease with temperatures. This paper presents the results obtained on the first and second bending mode. The experimental results show the loss factor and the natural frequency for different axial loads. The measured loss factor depends on the amplitude of vibrations. As predicted with theoretical analyses the loss factor shows a maximum then approaching zero for large amplitude of vibrations. As a rule, it decreases with increasing centrifugal loads.
A Photoconductance Mechanism for Oil Shale Pyrolysis Process Detection
Authors: Miao Xinyang , Wu Haoqiang , Liu Zhi , Li Yudong , Yu Yawen , Zhan Honglei , Zhao Kun 
Published: October 2022

Abstract
Kerogen in oil shale plays a crucial part in the shale oil and gas generation. Here, photoconductive measurement was used to evaluate the decomposition process of Huadian oil shale. The photoconductivity of the semi-coke is a clear indicator of different pyrolysis stages, including moisture evaporation, primary pyrolysis of kerogen, decomposition of asphalt monomer, and mineral decomposition. Furthermore, the distribution model of electrical resistance (R) and photoconductance (ΔI) for Huadian oil shale is plotted, indicating an inverse proportion between R and ΔI. We believe that the photoconductive measurement will be a valuable means for the nondestructive characterization of oil shale pyrolysis, which is helpful to optimize the comprehensive utilization of this unconventional resource.
Efficient Test Method for Determining the Thermomechanical Fatigue Lifetime of Additively Manufactured Combustion Chamber Tiles Under Component-Related Conditions
Authors: Schlesinger Michael , Schackert Sophie , Sikorski Igor , Mathiak Georg 
Published: October 2022

Abstract
Combustion chamber tiles of aircraft engines are subject to locally high thermomechanical fatigue (TMF) loading during flight operations. The TMF loading in these components results in a cyclic bending load over the wall thickness. Additional stress concentrations occur at geometric features such as fillets or effusion cooling holes. Thus complex loading conditions arise that cannot be reliably assessed using conventional material database and computational design methods. In the context of this article, a new test method is presented that consists of a bending test rig for applying component-related loading conditions to corresponding specimens, here called subelements, that represent significant geometric, lifetime-limiting features of the component. In various test series on additively manufactured subelements, geometric, manufacturing, thermal, mechanical and time-dependent parameters are investigated concerning their influence on fatigue crack growth and lifetime. The results from these tests are compiled in a database, which is used to validate an advanced computational assessment approach for crack growth and lifetime accounting for stress gradients in the depth direction due to the bending and along the surface due to possible geometric features. The method can be applied to component geometries such as combustion chamber tiles using a mechanical finite element analysis (FEA) followed by postprocessing steps to increase reliability of lifetime predictions.
Numerical Investigation of an Automotive Axial Fan: A Comparison Among Different CFD Software Packages and Experimental Validation
Authors: Aldi Nicola , Casari Nicola , Oliani Stefano , Pinelli Michele , Mollica Enrico , Menichini Filippo 
Published: October 2022

Abstract
Electrical and fossil fuel powered vehicles require to reject some form of heat produced as a byproduct of their operating principle. This task is performed by radiators, typically equipped with axial flow fans to maximize the specific processed flow rate. These fans, as well as all the other fans that typically equip the vehicles (e.g., for HVAC purposes), are required to be very efficient and to produce a minimum level of noise.
In this framework it is of crucial importance to adopt all the tools that can help in understanding the source of inefficiency and noise. This work presents the adoption of Computational Fluid Dynamics (CFD) as a possible tool for the investigation of the fluid dynamics of an axial flow fan.
In order to let CFD become routinely employed, a sequence of validation steps is required by industries. In this work, two different CFD tools (ANSYS-CFX and OpenFOAM-v2006) are employed and the results of the investigation are compared to experimental data for assessing the reliability and the accuracy of each of these tools. Experimental data are obtained with two test benches: one build in compliance with ANSI/AMCA standards for airflow performance evaluation and one ad hoc developed for PIV measurements (i.e. flow field visualization). The capability of the CFD softwares of correctly replicating the fan performance and flow field even in this complex set-up (due to the loose constraints of the fluid flow) is shown both with steady and transient simulations.
Topological Optimisation and 3d Printing of a Bladed Disc
Authors: Barreau Vincent , Denimal Enora , Salles Loic 
Published: October 2022

Abstract
In turbomachinery, components are pushed to their limits to meet more stringent specifications in order to increase their performances. In this context, structural topology optimisation is a promising technology as it improves substantially the mechanical properties while drastically reducing the mass. With the coming of additive manufacturing, optimised geometry can be manufactured making this technology even more attractive. The aim of this work is to investigate the potential of topology optimisation to optimise a full bladed disc to improve its dynamic performances in terms of mass, stress and modal coincidences.
The topology of a 3D-Finite Element Model of an academic bladed disc is optimised in this work and experimental validation is expected. So first, the disc is designed to fit in the test-rig and the mechanical integrity of the 3D-printed disc is experimentally verified. Second, the topology of the blades is optimised. Based on a trial-and-error process, the appropriate topology optimisation problem properties for vibration optimisation are identified. Thus, adding a static force at the blade tip forces a better material distribution over the domain and increases the blade stiffness. To minimise the number of coincidences, a numerical strategy based on iterative topology optimisation simulations is proposed to identify the correct set of frequential constraints. Final results show that the mass of the blade is reduced up to 32% and the number of frequential coincidences is reduced from 11 to 4. Final geometries are 3D-printed and mounted on the disc.
Film Cooling Hole Shape Effects on Turbine Blade Heat Transfer – Part II: Effects of Mass Flow Rate and Unsteadiness
Authors: Sperling Spencer , Christensen Louis , Mathison Randall , Aksoy Hakan , Liu Jong , Nickol Jeremy 
Published: October 2022

Abstract
To provide a detailed analysis of film cooling in a turbine environment, this study incorporates experimental and computational research performed on a rotating high pressure turbine stage. The turbine blades include rows of three different film cooling hole shapes investigated at several different cooling mass flow rates supplied to the rotor. Film cooling hole shapes include round, fan, and advanced anti-vortex shapes, and the performance of these cooling systems installed on the rotating blades are evaluated on time-averaged and unsteady bases.
Film cooling hole shape and coolant mass flow provide different cooling benefits in different areas of the blade. Across the pressure surface, leading edge, and suction surface, advanced film cooling holes show the most response to changing coolant mass flow, and typically have the highest film effectiveness at the highest film cooling flow rate.
Film cooling jets experience similar motions regardless of hole shape. Unsteady pressure gradients across the film cooling hole outlets on the pressure surface cause cooling jet motion. Fan and Advanced shaped holes cause lateral spread of cooling gas on a steady basis, and due to the increased lateral spread, a larger region on the pressure surface receives consistent film coverage. On a time-average basis, this results in much more lateral spread and increased film coverage for shaped film cooling holes.
The results of this study help identify the performance of shaped film cooling holes in turbine environments. The response of different hole shapes to unsteadiness has a significant impact on the time average film cooling coverage. Additionally, the hole shapes respond differently to increased levels of coolant mass flow rate and provide different degrees of film cooling coverage on different parts of the blade. An increased understanding and appreciation of the unsteady performance of various film cooling geometries is a foundational piece of continued technology development.
Effects on Sustainability by Redesign of a 1° Stage Gas Turbine Nozzle Ring From Investment Casting to Additive Manufacturing: A Life Cycle Environmental Impact Comparison
Authors: Fantaccione Luca , Serra Angela , Buia Giulio , Bartocci Pietro , Gandini Sergio , Fantozzi Francesco 
Published: October 2022

Abstract
Energy companies are committing to protect the environment and reducing their product carbon footprint. To accomplish these objectives, they need to establish their baseline, including the life cycle emissions of key products and services. The life cycle emissions assessment will help to support customers and suppliers, many of which have set their own carbon footprint reduction targets, in finding opportunities to reduce their own environmental impact.
The purpose of this study is to compare the environmental impact of two manufacturing processes, namely Additive Manufacturing (AM) and Investment Casting (IC), for the production of a 1° stage gas turbine nozzle ring in order to determine which method is the most sustainable on the Life Cycle. AM technologies brought to the world new design possibilities which become very useful for those items whose production rate decreases due to a drop in demand or a suspended production. In this case study, which considers a serviced Gas Turbine, the production volume is very low compared to the standard production of a gas turbine. For this reason, AM revealed to be a key strategy for the investigated product for environmental, cost and lead time sustainability.
The LCA is conducted under Cradle-to-Gate boundaries, hence it investigates every energy/material input and output from the raw materials extractions, to the production of the good at the gate of the company ready for shipping.
Raw material extraction, powder atomization, machining, finishing, and coating phases are included into the analysis. The choice of the manufacturing strategy requires different materials and different suppliers are involved into the manufacturing chain, which means also differences in transportation and sources for electricity production.
Development of an Open-Source Autonomous CFD Meta-Modeling Environment for Small-Scale Combustor Optimization – Part II
Authors: Briones Alejandro M. , Rankin Brent A. 
Published: October 2022

Abstract
This work presents an improved open-source autonomous CFD meta-modeling environment (OpenACME) for small-scale combustor design optimization. OpenACME couples several object-oriented programming open-source codes for CFD-assisted engineering design meta-modeling. OpenACME is fully automated and can be used in PC workstations or HPC clusters. OpenACME uses a global metaheuristic optimization algorithm based on multiple-objective evolutionary algorithm (i.e., NSGA-II). An initial design population is first computed with Latin Hypercube Sampling and subsequent iterations generate offspring based on tournament mating, uniform crossover, and polynomial mutation. OpenACME is capable of computing multiple parallel CFD design points concurrently, speeding up the meta-simulations. The CFD are based on steady-state, incompressible, three-dimensional simulations with multi-phase k-ω SST RANS and “frozen” flamelet progress variable (FFPV) combustion model. There are fifteen design variables. There are three meta-simulations. The meta-simulations report Pareto Frontier from which optimum designs can be selected based on thermodynamic cycle requirements. Conjugate heat transfer provides the most realistic liner temperature and combustor performance. Acritical is still recommended as a cost function when liner durability is a concern. OpenACME demonstrated to be a viable tool for combustor design optimization.
Flow Separation Modelling Dowstream of Military Low Pressure Compressors
Authors: Ruiz Domingo Javier , Pieyre Amanda 
Published: October 2022

Abstract
In military turbofan architectures, a flow separation is operated downstream the Low Pressure Compressor (LPC), mainly to increase the propulsive efficiency and to cool down and provide oxygen to the reheat channel. The flow is separated into a primary flow that goes through the high-pressure components and combustion chamber and a secondary flow which remains cold and is mixed with the primary flow before the reheat. The Bypass Ratio (BPR) represents the mass flow rate ratio between secondary and primary flow. During engine operation from high to low power, the BPR varies drastically. Moreover, current and future military engines present many variable geometries to improve their maneuverability, and the BPR can strongly depend on the settings of these geometries. BPR variations lead to a shift in the LPC exit separation streamline and therefore to modifications on the thermodynamic conditions in both primary and secondary flows.
Existing methods usually perform the separation on the overall LPC map using corrective coefficients. The aim of this work is to provide an alternative method to model the effects of the shifting of the separation line on the thermodynamic parameters. Instead of using an overall compressor map, this method uses two compressor maps, one for the inner and one for the outer stream, at a reference BPR. When the BPR is different from this reference value, corrections are applied to the reference maps. The main hypothesis of this method is that the aerodynamics of the LPC is uncoupled from the splitter, meaning that the total temperature and total pressure profiles do not depend on the BPR. Analytical profiles are used from hub to tip for work and losses coefficients parameters. The analytical profiles are chosen to better fit the actual profiles in the working BPR range of interest. This method is designed to be included in a performance model. The method presented is validated on LPC Rig test and CFD data.
Vortex Unsteadiness in the Endwall Region of a High-Lift Low-Pressure Turbine Passage
Authors: Marks Christopher R. , Fletcher Nathan , Sondergaard Rolf 
Published: October 2022

Abstract
Three-dimensional vortical structures within the endwall region of turbine passages directly affect the aerodynamic efficiency and heat transfer characteristics of the turbine. Interactions between the vortical endwall structures and the suction surface flow have been shown to be a significant source of loss generation through passages. One dominant vortex extends from the leading edge junction region of the blade across the passage, where it interacts with the flow along the suction surface of the adjacent blade. In high-lift low-pressure turbine cascade passages, the vortical structure intermittently loses coherence and exhibits unsteady variations of strength and position as it extends across the passage. The present paper details the temporal behavior through high-speed measurements in a low speed linear cascade of high-lift low-pressure turbine blades. Stereoscopic particle image velocimetry measurements in the passage are used to evaluate the unsteady behavior of the vortex. Space-time iso-surface plots of Q-criterion clearly show the evolution of the vortex over time. Analysis of the data reveals the various time scales of fluctuations in strength and position. Comparisons of the temporal fluctuations in the high-lift turbine passage are made with similar phenomena found in canonical junction flow papers in the literature. Key findings support the hypothesis that in-passage vortex unsteady characteristics near the endwall are influenced by leading edge junction flow dynamics, and provide additional insight into the unsteady endwall flow physics that are necessary to further the development of endwall loss reduction techniques.
Effect of Temperature and Velocity on Microparticle Erosion/Deposition Into Environmental-Barrier-Coated CMC for Aeroengines
Authors: Okita Yoji , Suzuki Masaya , Yamane Takashi , Hasegawa Jun , Mizokami Yosuke , Nakamura Takeshi 
Published: October 2022

Abstract
Ceramic matrix composites (CMCs), especially SiC/SiC, have garnered significant attention owing to their remarkable mechanical properties at higher temperatures. For protection of the substrate from oxidation, the SiC/SiC CMCs inherently require environmental barrier coating (EBC). Because aeroengines must function under a wide range of conditions and environments, the coated CMC must be sufficiently resistant to various damage modes. Among these, the effect of microparticles is one of the limiting factors for durability and performance of components, particularly when the engine is operated in dusty areas.
The main goal of this experimental research is to investigate and determine the surface damage behaviour of the coated CMC caused by micro sand particles. The data were surveyed across a fairly broad range of exposed temperatures and velocities, and covered conditions relevant to advanced hot section designs. In the experiments, silica or alumina sand entrained in the gas stream was jet-blasted from the nozzle and then impinged on the target CMC+EBC coupon.
Owing to the broad testing range, the damage mode and extent of damage varied considerably by condition. The obtained data were then reorganised and compared with several previously proposed particle impact models. This is to first understand and obtain a complete picture of all the probable consequences in the expected design and off-design conditions, and second, to determine the validity of, and deviations from the conventional modelling with the present CMC+EBC material, which will be useful in the next component design phase.