Topic Editors

Department of Industrial and Information Engineering and Economics, University of L’Aquila, v. G. Gronchi, 18, 67100 L’Aquila, Italy
Department of Industrial and Information Engineering and Economics (DIIIE), University of L’Aquila, 67100 L’Aquila, Italy
Dr. Marco Di Bartolomeo
Department of Industrial and Information Engineering and Economics, University of L’Aquila, 67100 L’Aquila, Italy

Advanced Engines Technologies

Abstract submission deadline
31 October 2024
Manuscript submission deadline
31 December 2024
Viewed by
13559

Topic Information

Dear Colleagues,

In recent years, the development of internal combustion engines, particularly for the transportation sector, has been pushed by the need to reduce tailpipe pollutant emissions. National and international regulations have been imposed to limit the most harmful pollutants and to preserve the air quality, in particular for urban areas. Moreover, the recent awareness around climate change and the need to also reduce greenhouse gases has stimulated the release of specific regulations to limit CO2 emissions, which can definitively be obtained by decreasing fuel consumption and increasing overall engine and vehicle efficiency.

These limits are progressively more stringent and call for innovative technologies able to reduce the environmental impact of engines. Hence, a portfolio of several technical solutions is under investigation, with the final purpose to increase engine efficiency and reduce pollutants emissions. Therefore, they can be categorized or compared to each other in terms of amount of fuel saved on a specific operating point or driving mission. The effects on specific emissions should also be assessed. These two contributions (fuel and emissions reduction values) participate in the definition of market readiness of the technology proposed, being related to the operating cost of the engine and the avoidance of fines related to exceeding CO2 emission limits.

In this topic, papers related to technical solutions proposed to reduce fuel consumption and/or tailpipe emissions from engines are welcomed. They can be related to mechanical innovations, thermal management, lubrication, aftertreatment devices, sustainable fuels and fuel handling, turbocharging, combustion improvement, powertrain hybridization, auxiliaries’ and components’ electrifications and efficiency increase, energy recovery and integration of energy subsystems, optimized control strategies, and sustainable design. Both theoretical and experimental works will be considered, in transportation applications and other relevant economic sectors, which could help the transition toward the sustainable engines of the future.

Dr. Davide Di Battista
Dr. Fabio Fatigati
Dr. Marco Di Bartolomeo
Topic Editors

Keywords

  • engine
  • efficiency
  • emissions
  • technologies
  • sustainability

Participating Journals

Journal Name Impact Factor CiteScore Launched Year First Decision (median) APC
Energies
energies
3.2 5.5 2008 16.1 Days CHF 2600 Submit
Materials
materials
3.4 5.2 2008 13.9 Days CHF 2600 Submit
Sensors
sensors
3.9 6.8 2001 17 Days CHF 2600 Submit
Sustainability
sustainability
3.9 5.8 2009 18.8 Days CHF 2400 Submit
Vehicles
vehicles
2.2 2.9 2019 22.2 Days CHF 1600 Submit
World Electric Vehicle Journal
wevj
2.3 3.7 2007 14.1 Days CHF 1400 Submit

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Published Papers (16 papers)

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18 pages, 3970 KiB  
Article
Experimental Study of a Homogeneous Charge Compression Ignition Engine Using Hydrogen at High-Altitude Conditions
Sustainability 2024, 16(5), 2026; https://doi.org/10.3390/su16052026 (registering DOI) - 29 Feb 2024
Viewed by 82
Abstract
One of the key factors of the current energy transition is the use of hydrogen (H2) as fuel in energy transformation technologies. This fuel has the advantage of being produced from the most primary forms of energy and has the potential [...] Read more.
One of the key factors of the current energy transition is the use of hydrogen (H2) as fuel in energy transformation technologies. This fuel has the advantage of being produced from the most primary forms of energy and has the potential to reduce carbon dioxide (CO2) emissions. In recent years, hydrogen or hydrogen-rich mixtures in internal combustion engines (ICEs) have gained popularity, with numerous reports documenting their use in spark ignition (SI) and compression ignition (CI) engines. Homogeneous charge compression ignition (HCCI) engines have the potential for substantial reductions in nitrogen oxides (NOx) and particulate matter (PM) emissions, and the use of hydrogen along with this kind of combustion could substantially reduce CO2 emissions. However, there have been few reports using hydrogen in HCCI engines, with most studies limited to evaluating technical feasibility, combustion characteristics, engine performance, and emissions in laboratory settings at sea level. This paper presents a study of HCCI combustion using hydrogen in a stationary air-cooled Lombardini 25 LD 425-2 modified diesel engine located at 1495 m above sea level. An experimental phase was conducted to determine the intake temperature requirements and equivalence ratios for stable HCCI combustion. These results were compared with previous research carried out at sea level. To the best knowledge of the authors, this is the first report on the combustion and operational limits for an HCCI engine fueled with hydrogen under the mentioned specific conditions. Equivalence ratios between 0.21 and 0.28 and intake temperatures between 188 °C and 235 °C effectively achieved the HCCI combustion. These temperature values were, on average, 100 °C higher than those reported in previous studies. The maximum value for the indicated mean effective pressure (IMEPn) was 1.75 bar, and the maximum thermal efficiency (ITEn) was 34.5%. The achieved results are important for the design and implementation of HCCI engines running solely on hydrogen in developing countries located at high altitudes above sea level. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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74 pages, 8424 KiB  
Review
Review of Organic Rankine Cycles for Internal Combustion Engine Waste Heat Recovery: Latest Decade in Review
Sustainability 2024, 16(5), 1924; https://doi.org/10.3390/su16051924 - 26 Feb 2024
Viewed by 226
Abstract
The last decade (2013–2023) was the most prolific period of organic Rankine cycle (ORC) research in history in terms of both publications and citations. This article provides a detailed review of the broad and voluminous collection of recent internal combustion engine (ICE) waste [...] Read more.
The last decade (2013–2023) was the most prolific period of organic Rankine cycle (ORC) research in history in terms of both publications and citations. This article provides a detailed review of the broad and voluminous collection of recent internal combustion engine (ICE) waste heat recovery (WHR) studies, serving as a necessary follow-on to the author’s 2013 review. Research efforts have targeted diverse applications (e.g., vehicular, stationary, and building-based), and it spans the full gamut of engine sizes and fuels. Furthermore, cycle configurations extend far beyond basic ORC and regenerative ORC, particularly with supercritical, trilateral, and multi-loop ORCs. Significant attention has been garnered by fourth-generation refrigerants like HFOs (hydrofluoroolefins), HFEs (hydrofluoroethers), natural refrigerants, and zeotropic mixtures, as research has migrated away from the popular HFC-245fa (hydrofluorocarbon). Performance-wise, the period was marked by a growing recognition of the diminished performance of physical systems under dynamic source conditions, especially compared to steady-state simulations. Through advancements in system control, especially using improved model predictive controllers, dynamics-based losses have been significantly reduced. Regarding practically minded investigations, research efforts have ameliorated working fluid flammability risks, limited thermal degradation, and pursued cost savings. State-of-the-art system designs and operational targets have emerged through increasingly sophisticated optimization efforts, with some studies leveraging “big data” and artificial intelligence. Major programs like SuperTruck II have further established the ongoing challenges of simultaneously meeting cost, size, and performance goals; however, off-the-shelf organic Rankine cycle systems are available today for engine waste heat recovery, signaling initial market penetration. Continuing forward, next-generation engines can be designed specifically as topping cycles for an organic Rankine (bottoming) cycle, with both power sources integrated into advanced hybrid drivetrains. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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14 pages, 2811 KiB  
Article
Application of Hydraulic Energy-Saving Technology in the Teaching, Research, and Practice of Mechanical Engineering
Sustainability 2024, 16(3), 1315; https://doi.org/10.3390/su16031315 - 04 Feb 2024
Viewed by 513
Abstract
To cope with the current resource, energy, and environmental problems faced by the manufacturing industry, energy conservation has become a long-term national development strategic policy. Specifically, the problems of high energy consumption and low energy efficiency in hydraulic systems have received considerable attention. [...] Read more.
To cope with the current resource, energy, and environmental problems faced by the manufacturing industry, energy conservation has become a long-term national development strategic policy. Specifically, the problems of high energy consumption and low energy efficiency in hydraulic systems have received considerable attention. Based on previous research on hydraulic energy-saving technology, this paper discusses the problems and challenges faced by such technology in higher education, the methods of integrating this technology into the curricula of mechanical majors, and the implementation of teaching reform. In the selected case study, hydraulic energy-saving technology was incorporated into the hydraulic experiment and practical training course of our school, focusing on the integration of energy-saving and emission-reduction concepts in the field of mechanical engineering teaching and research. Integrating hydraulic energy-saving technology into teaching and research not only enriches the content of mechanical engineering degree courses but also integrates professional knowledge with future work practice, provides methods and technical support for future research by teachers and students, and stimulates new ideas for the teaching reform and talent cultivation of mechanical engineering majors. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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15 pages, 4916 KiB  
Article
Synchronous Fracture Expansion Pattern of Hydraulic Fracturing with Different Perforation Spacing
Energies 2024, 17(1), 255; https://doi.org/10.3390/en17010255 - 03 Jan 2024
Viewed by 458
Abstract
Using the self-developed “TCHFSM-I” large-size true triaxial fracturing seepage simulation device and fluid injection flow dynamic monitoring device, we studied the crack initiation and expansion law of multi-fractures under different perforation spacing conditions and revealed the mechanism of multi-fractures expanding from non-equilibrium to [...] Read more.
Using the self-developed “TCHFSM-I” large-size true triaxial fracturing seepage simulation device and fluid injection flow dynamic monitoring device, we studied the crack initiation and expansion law of multi-fractures under different perforation spacing conditions and revealed the mechanism of multi-fractures expanding from non-equilibrium to equilibrium on the basis of the evolution law of the injection pressure and characteristics of the distribution of the injection flow. The results show that when the perforation spacing is small (<60 mm), the central injection fracturing cracks are affected by the extension of the upper and lower injection cracks, and their extension lengths are shorter; on the contrary, the extension lengths of the upper, central and lower injection cracks are basically the same, and the three hydraulically fractured cracks shift from non-equilibrium to equilibrium extension. When the perforation spacing is small, the fracture initiation pressure of the middle perforation is much larger than that of the upper and lower perforations. However, as the perforation spacing increases, the fracture initiation pressure of the middle perforation gradually decreases. Its fracture initiation pressure is basically the same as that of the upper and lower perforations. The expansion of the three hydraulically fractured cracks is independent of each other. In addition, the evolution law of the injection flow rate can better reflect the multi-fracture fracture initiation and expansion pattern, and the evolution pattern of the injection flow rate can better reflect the synchronous fracture initiation and expansion mechanism of multi-fracture fracture. The results of the study can provide technical guidance for efficient coalbed methane extraction. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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16 pages, 2984 KiB  
Article
Multi-Stream Fusion Network for Skeleton-Based Construction Worker Action Recognition
Sensors 2023, 23(23), 9350; https://doi.org/10.3390/s23239350 - 23 Nov 2023
Viewed by 475
Abstract
The global concern regarding the monitoring of construction workers’ activities necessitates an efficient means of continuous monitoring for timely action recognition at construction sites. This paper introduces a novel approach—the multi-scale graph strategy—to enhance feature extraction in complex networks. At the core of [...] Read more.
The global concern regarding the monitoring of construction workers’ activities necessitates an efficient means of continuous monitoring for timely action recognition at construction sites. This paper introduces a novel approach—the multi-scale graph strategy—to enhance feature extraction in complex networks. At the core of this strategy lies the multi-feature fusion network (MF-Net), which employs multiple scale graphs in distinct network streams to capture both local and global features of crucial joints. This approach extends beyond local relationships to encompass broader connections, including those between the head and foot, as well as interactions like those involving the head and neck. By integrating diverse scale graphs into distinct network streams, we effectively incorporate physically unrelated information, aiding in the extraction of vital local joint contour features. Furthermore, we introduce velocity and acceleration as temporal features, fusing them with spatial features to enhance informational efficacy and the model’s performance. Finally, efficiency-enhancing measures, such as a bottleneck structure and a branch-wise attention block, are implemented to optimize computational resources while enhancing feature discriminability. The significance of this paper lies in improving the management model of the construction industry, ultimately aiming to enhance the health and work efficiency of workers. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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19 pages, 14445 KiB  
Article
New Insights into Flow for a Low-Bypass-Ratio Transonic Fan with Optimized Rotor
Energies 2023, 16(21), 7230; https://doi.org/10.3390/en16217230 - 24 Oct 2023
Viewed by 546
Abstract
In this paper, a three-dimensional aerodynamics optimization system is built and applied to optimize a rotor blade to balance the conflicts between stall margin, total pressure ratio, adiabatic efficiency, and mass flow rate for the high-loading and transonic-flow fan. A novel flow diagnostic [...] Read more.
In this paper, a three-dimensional aerodynamics optimization system is built and applied to optimize a rotor blade to balance the conflicts between stall margin, total pressure ratio, adiabatic efficiency, and mass flow rate for the high-loading and transonic-flow fan. A novel flow diagnostic method based on vorticity dynamics theory is utilized to analyze the reasons for the improvement in aerodynamic performance in the optimized transonic fan. In the established aerodynamic optimization method, use the blade profile camber line curvature and its leading edge metal angle as the optimization variables, which are optimized by modifying the coordinates of their control points and introducing a genetic algorithm. Finally, the vorticity dynamics parameters, such as the boundary vorticity flux (BVF), azimuthal vorticity and skin-friction lines are used to diagnose the key flow features in the optimized and baseline fan passage. The results indicate that, by controlling skillfully the blade camber line curvature in the optimization improves the aerodynamic performance of the fan stage, increasing the total pressure ratio by 1.90% while increasing the mass flow rate and adiabatic efficiency by 5.82% and 4.45%, respectively. The formulas from the vorticity dynamics diagnosis method indicate a close link between the aerodynamic performance and vorticity dynamic parameters for the axial fan/compressor passage flow, and that both azimuthal vorticity and boundary vorticity flux have significant influence on fan stage performance. Moreover, the boundary layer separation flow on the rotor blade surface is accompanied by a spike of entropy and static pressure, and their derivative/gradient also suffer drastic changes under the effect of shock waves. Detailed flow information can be obtained about the on-wall with high accuracy based on the vorticity dynamics diagnosis method, which provides researchers with a novel method for the turbomachinery aerodynamic design and analysis in the aero-engine engineering development field. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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16 pages, 4783 KiB  
Article
Experimental Investigation on Gasoline—Water Mixture Fuel Impingement Preparation Method and Spray Characteristics with High Injection Temperatures and Pressures
Energies 2023, 16(16), 6026; https://doi.org/10.3390/en16166026 - 17 Aug 2023
Viewed by 556
Abstract
Gasoline–water mixed injections are of great interest because of their advantages for reduced manufacturing costs and improved atomization, with the potential to alleviate engine detonation and reduce emissions. In this work, based on the principle of impinging flow, a real-time gasoline–water mixture preparation [...] Read more.
Gasoline–water mixed injections are of great interest because of their advantages for reduced manufacturing costs and improved atomization, with the potential to alleviate engine detonation and reduce emissions. In this work, based on the principle of impinging flow, a real-time gasoline–water mixture preparation system for internal combustion engines was designed and the preparation system performance was compared with the standard swirl mixing technique. An image processing method was established to quantify the uniformity of the prepared mixture. Based on the flash-boiling spray flash-boiling spray experiment, the spray characteristics of different gasoline–water mixtures were analyzed under different injection temperatures (30–160 °C) and pressures (5–15 MPa). The experiments showed that the impinging pressure was the main factor affecting the emulsification performance of the real-time gasoline–water mixture, and that the proposed real-time mixing system could produce a stable gasoline–water emulsion. For temperatures in the 30–160 °C range, the flash-boiling spray flash-boiling spray experiments showed that the spray penetration distance first decreases and then increases with the injection temperature, while the spray angle shows an opposite trend. The turning point corresponded to the flash-boiling point of each gasoline–water mixture. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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19 pages, 3984 KiB  
Review
Electrification of Offshore Oil and Gas Production: Architectures and Power Conversion
Energies 2023, 16(15), 5812; https://doi.org/10.3390/en16155812 - 04 Aug 2023
Cited by 1 | Viewed by 1387
Abstract
Subsea oil and gas (O&G) exploration demands significantly high power to supply the electrical loads for extraction and pumping of the oil and gas. The energy demand is usually met by fossil fuel combustion-based platform generation, which releases a substantial volume of greenhouse [...] Read more.
Subsea oil and gas (O&G) exploration demands significantly high power to supply the electrical loads for extraction and pumping of the oil and gas. The energy demand is usually met by fossil fuel combustion-based platform generation, which releases a substantial volume of greenhouse gases including carbon dioxide (CO2) and methane into the atmosphere. The severity of the resulting adverse environmental impact has increased the focus on more sustainable and environment-friendly power processing for deepwater O&G production. The most feasible way toward sustainable power processing lies in the complete electrification of subsea systems. This paper aims to dive deep into the technology trends that enable an all-electric subsea grid and the real-world challenges that hinder the proliferation of these technologies. Two main enabling technologies are the transmission of electrical power from the onshore electrical grid to the subsea petroleum installations or the integration of offshore renewable energy sources to form a microgrid to power the platform-based and subsea loads. This paper reviews the feasible power generation sources for interconnection with subsea oil installations. Next, this interconnection’s possible power transmission and distribution architectures are presented, including auxiliary power processing systems like subsea electric heating. As the electrical fault is one of the major challenges for DC systems, the fault protection topologies for the subsea HVDC architectures are also reviewed. A brief discussion and comparison of the reviewed technologies are presented. Finally, the critical findings are summarized in the conclusion section. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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14 pages, 4672 KiB  
Article
Heat Transfer Enhancement in Cooling Jacket of Liquid Cooled Spark Ignition Engine
Energies 2023, 16(13), 5126; https://doi.org/10.3390/en16135126 - 03 Jul 2023
Viewed by 906
Abstract
Thermal stresses due to long running of spark ignition engine often results in wear and tear of cylinder near the top dead center (TDC). These high thermal stresses at TDC arise due to the high temperature gradient during spark ignition. This situation eventually [...] Read more.
Thermal stresses due to long running of spark ignition engine often results in wear and tear of cylinder near the top dead center (TDC). These high thermal stresses at TDC arise due to the high temperature gradient during spark ignition. This situation eventually decreases the life and efficiency of an engine. In this study, the numerical and analytical analysis was carried out on 1298 cc in line four stroke spark ignition (SI) engine having a power output of 63 kW to drop the peak temperature at TDC. to reduce the peak value of temperature, square pin fins were used on the surface of engine cylinder wall near TDC. A parametric study is performed to get an optimal solution for removal of the peak temperature load at TDC. The results showed that the fins with dimension of 4 × 4 × 4 mm3 along with uniform spacing of 2 mm provide the optimum solution. It has been observed that the peak temperature at TDC dropped down considerably from 160 °C to 133 °C (a percentage reduction of 16.87%) for the pin fins case as compared to without the fin case. Furthermore, the heat transfer effectiveness for the optimum case was calculated as 3.32, whereas for numerical and analytical study it was calculated as 3.43. The error recorded between both the values was limited to 3.2%. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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27 pages, 5072 KiB  
Article
Chemical Modeling of Constant-Volume Combustion of the Mixture of Methane and Hydrogen Used in Spark Ignition Otto Cycles
Energies 2023, 16(12), 4578; https://doi.org/10.3390/en16124578 - 07 Jun 2023
Viewed by 1064
Abstract
This paper develops a chemical model for a closed constant-volume combustion of a gaseous mixture of methane and hydrogen. Since the combustion is strongly dependent on temperature, pressure and fuel composition, these had chosen the actual corresponding thermodynamic systems in this kind of [...] Read more.
This paper develops a chemical model for a closed constant-volume combustion of a gaseous mixture of methane and hydrogen. Since the combustion is strongly dependent on temperature, pressure and fuel composition, these had chosen the actual corresponding thermodynamic systems in this kind of combustion, i.e., spark ignition (SI) reciprocating engines, to assess combustion parameters and flue gas composition. The actual cycles impose extra restrictive operational conditions through the engine’s-volumetric-compression ratio, the geometry of the combustion volume, the preparation method of the mixture of methane and hydrogen, (e.g., one fueling way of a homogeneous mixture obtained in a specific device or by two separate fueling ways for components), the cooling system and the delivered power. The chemical model avoided the unknown influences in order to accurately explain the influence of hydrogen upon constant-volume combustion and flue gas composition. The model adopted hypotheses allowing to generalize evaluated results, i.e., the isentropic compression and expansion processes, in closed constant-volume combustion caused by two successive steps that obey the energy and mass conservation laws, and the flue gas exhaust, which is also described by two steps, i.e., isentropic expansion through the flow section of exhaust valves followed by a constant pressure stagnation (this process, in fact, corresponds to a direct throttling process). The chemical model assumed the homogeneous mixtures of gases with variable heat capacity functions of temperatures, the Mendeleev—Clapeyron ideal gas state equation, and the variable chemical equilibrium constants for the chosen chemical reactions. It was assumed that the flue gas chemistry prevails during isentropic expansion and during throttling of exhaust flue gas. The chemical model allowed for evaluation of flue gas composition and noxious emissions. The numerical results were compared with those recently reported in other parallel studies. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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21 pages, 7072 KiB  
Article
Numerical Research on the Jet Mixing Mechanism of the De-Swirling Lobed Mixer Integrated with OGV
Energies 2023, 16(11), 4394; https://doi.org/10.3390/en16114394 - 29 May 2023
Viewed by 751
Abstract
The outlet guide vane (OGV) is integrated with the lobed mixer to improve the exhaust system’s performance with a high core inlet swirl. The best location for integrating the OGV is along the central line of the lobe’s trough and near the exit [...] Read more.
The outlet guide vane (OGV) is integrated with the lobed mixer to improve the exhaust system’s performance with a high core inlet swirl. The best location for integrating the OGV is along the central line of the lobe’s trough and near the exit plane of the lobed mixer. Two types of lobed mixers (the scalloped reference lobed mixer and the scalloped de-swirling lobed mixer) integrating with/without OGVs, are numerically researched under eight inlet swirl conditions ranging from 0° to 35°. The simulation used the Reynolds-Averaged Navier-Stokes (RANS) method with Shear Stress Transport (SST) model based on an unstructured mesh of 30 million cells. The reserved outlet flow angle of the de-swirling lobed mixer is beneficial for enhancing the strength of downstream streamwise vortices and accelerating the jet mixing. After integrating with OGV: it can significantly suppress the leakage vortex between the lobe trough and the central body and the backflow downstream of the central body; on the other hand, it can further increase the strength and scale of streamwise vortices by expanding the radial range of inner secondary flow, thereby accelerating mixing and reducing total pressure loss & thrust loss. Under the design condition, the integrated de-swirling lobed mixer can increase thrust by 3.18% and reduce the mixing loss by 31.17% compared with the reference lobed mixer. Even under non-design conditions, the integrated de-swirling lobed mixer can still use upstream inlet swirl to enhance the streamwise vortices and accelerate the jet mixing within the conditions studied in this paper. The outlet jet uniformity of the integrated de-swirling lobed mixer is better than that of the integrated reference lobed mixer for the case with the same core inlet swirl. Compared with the latter, the former also has better tolerance to the attack angle, especially for the negative attack angle conditions. Under the condition with a core inlet swirl of 35°, the thrust loss of the integrated de-swirling lobed mixer is 2.15% lower than that of the integrated reference lobed mixer. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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14 pages, 952 KiB  
Article
FragTracer: Real-Time Fragmentation Monitoring Tool for F2FS File System
Sensors 2023, 23(9), 4488; https://doi.org/10.3390/s23094488 - 05 May 2023
Viewed by 1527
Abstract
Emerging hardware devices (e.g., NVMe SSD, RISC-V, etc.) open new opportunities for improving the overall performance of computer systems. In addition, the applications try to fully utilize hardware resources to keep up with those improvements. However, these trends can cause significant file system [...] Read more.
Emerging hardware devices (e.g., NVMe SSD, RISC-V, etc.) open new opportunities for improving the overall performance of computer systems. In addition, the applications try to fully utilize hardware resources to keep up with those improvements. However, these trends can cause significant file system overheads (i.e., fragmentation issues). In this paper, we first study the reason for the fragmentation issues on an F2FS file system and present a new tool, called FragTracer, which helps to analyze the ratio of fragmentation in real-time. For user-friendly usage, we designed FragTracer with three main modules, monitoring, pre-processing, and visualization, which automatically runs without any user intervention. We also optimized FragTracer in terms of performance to hide its overhead in tracking and analyzing fragmentation issues on-the-fly. We evaluated FragTracer with three real-world databases on the F2FS file system, so as to study the fragmentation characteristics caused by databases, and we compared the overhead of FragTracer. Our evaluation results clearly show that the overhead of FragTracer is negligible when running on commodity computing environments. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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11 pages, 3096 KiB  
Article
Dynamic Finite Element Model Based on Timoshenko Beam Theory for Simulating High-Speed Nonlinear Helical Springs
Sensors 2023, 23(7), 3737; https://doi.org/10.3390/s23073737 - 04 Apr 2023
Cited by 1 | Viewed by 1169
Abstract
Helical springs with nonlinear geometric parameters nowadays have shown great advantages over classical linear springs, especially due to their superior performance in diminishing dynamic responses in high-speed situations. However, existing studies are mostly available for springs with linear properties, and the sole FE [...] Read more.
Helical springs with nonlinear geometric parameters nowadays have shown great advantages over classical linear springs, especially due to their superior performance in diminishing dynamic responses in high-speed situations. However, existing studies are mostly available for springs with linear properties, and the sole FE spring models using solid elements occupy significant computational resources. This study presents an FE spring model based on Timoshenko beam theory, which allows for high-speed dynamic simulations of nonlinear springs using a beehive valve spring sample. The dynamic results are also compared with the results of the FE model using solid elements and the results of the engine head test and indicate that the proposed FE model can accurately predict dynamic spring forces and the phenomenon of coil clash when simulating the beehive spring at engine speeds of both 5600 and 8000 RPM. The results also indicate that rapid coil impact brings significant spike forces. It should also be noted that the FE spring model using beam elements displays sufficient accuracy in predicting the dynamic responses of nonlinear springs while occupying much fewer computational resources than the FE model using solid elements. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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16 pages, 3837 KiB  
Article
Knock-Prediction System for Kerosene Engines Using In-Cylinder Pressure Signal
Energies 2023, 16(6), 2766; https://doi.org/10.3390/en16062766 - 16 Mar 2023
Viewed by 884
Abstract
Piston engines fueled by kerosene have a strong application prospect in special vehicles and small aircrafts, but the low amount of octane in kerosene fuel causes its knock combustion phenomenon to be particularly serious. A knock will deteriorate the power and economy of [...] Read more.
Piston engines fueled by kerosene have a strong application prospect in special vehicles and small aircrafts, but the low amount of octane in kerosene fuel causes its knock combustion phenomenon to be particularly serious. A knock will deteriorate the power and economy of the engine and will damage the engine in serious cases. Therefore, knocking is the key problem with kerosene engines. We propose a knock-prediction system for kerosene engines based on in-cylinder pressure signals. Firstly, the intrinsic mode function (IMF) caused by knock resonance is extracted from the in-cylinder pressure signal via empirical mode decomposition (EMD) and a time–frequency domain analysis. A time-domain statistical analysis (TDSA) combined with a principal component analysis (PCA) is used to extract features from the IMF. Finally, the data collected from the test bench are trained by a support vector machine to obtain the knock-prediction model. Compared with other technical combinations for training, the proposed scheme achieved more accurate results in knock prediction. Considering the working characteristics of kerosene engines, a slight knock can increase the power of a kerosene engine. Therefore, some incorrectly predicted cycles (slight-knock cycles) do not affect the normal operation of the engine. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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16 pages, 7921 KiB  
Article
Numerical Research on the Jet-Mixing Mechanism of Convergent Nozzle Excited by a Fluidic Oscillator and an Air Tab
Energies 2023, 16(3), 1412; https://doi.org/10.3390/en16031412 - 31 Jan 2023
Cited by 1 | Viewed by 1060
Abstract
Unsteady numerical simulations, coupled with the SST (Shear Stress Transport) k-ω turbulence model, were conducted to study the mixing-enhancement characteristics of the excited jet generated by the fluidic oscillator and the air tab in a single channel convergent nozzle with an inlet total [...] Read more.
Unsteady numerical simulations, coupled with the SST (Shear Stress Transport) k-ω turbulence model, were conducted to study the mixing-enhancement characteristics of the excited jet generated by the fluidic oscillator and the air tab in a single channel convergent nozzle with an inlet total pressure of 140–200 kPa. Compared with the steady air-tab jet, the sweeping jet generated by the fluidic oscillator has roughly the same penetration in the main flow, but it can induce streamwise vortices and planar vortices of larger scale and longer duration, which is beneficial to enhance jet mixing efficiency in the range of 1.0 DN (DN represents the diameter of the main nozzle outlet) downstream from the main nozzle. When x > 1.0 DN, the jet mixing is mainly dominated by the shear layer between the main jet and the ambient. As the sweeping jet suppresses the expansion of the main jet, which reduces the contact area between the main jet and the ambient, its mixing efficiency is less than that of the air tab in this region. With the increasing inlet total pressure of the fluidic oscillator, the influence range of the sweeping jet is increased, but its mixing efficiency does not increase significantly. In general, the fluidic oscillator can use a small jet flow (<5%) to achieve a high mixing efficiency (i.e., 60% at x = 2.0 DN) at the expense of low total pressure loss (<2.3%), which indicates that it has good engineering applicability. Full article
(This article belongs to the Topic Advanced Engines Technologies)
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9 pages, 2435 KiB  
Communication
Influences of Flow Channel on Electrochemical Characteristics of Polymer Electrolyte Fuel Cells Humidified with NaCl Contained H2O
Sustainability 2023, 15(3), 2415; https://doi.org/10.3390/su15032415 - 29 Jan 2023
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Abstract
In this study, the effects of flow field types on the electrochemical properties of polymer electrolyte membrane fuel cells (PEMFCs) humidified with NaCl solution are systematically investigated. The parallel flow field and serpentine flow field were used to investigate the PEMFCs. Long-term stability [...] Read more.
In this study, the effects of flow field types on the electrochemical properties of polymer electrolyte membrane fuel cells (PEMFCs) humidified with NaCl solution are systematically investigated. The parallel flow field and serpentine flow field were used to investigate the PEMFCs. Long-term stability was evaluated for 20 h using chronoamperometry. Fuel cells with both parallel and serpentine flow fields showed a decrease in performance because of the NaCl solution. Interestingly, the PEMFC with the serpentine flow field showed significantly more severe degradation during long-term stability evaluation compared to the fuel cell with the parallel flow field. Electrochemical impedance spectroscopy analysis showed that a significant increase in faradaic resistance caused the degradation of the performance. After long-term stability examinations, regenerations of fuel cells were performed with deionized water at a constant voltage (0.4 V). After the regeneration, the performance of the fuel cells with the serpentine flow field was improved more (52.96%) than the PEMFC with the parallel flow field (1.22%). Full article
(This article belongs to the Topic Advanced Engines Technologies)
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