bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation into the Characteristics of Fuel-Borne Nitrogen Pollutants in Ammonia-Diesel Dual Fuel Engines through Implementing Atmospheric Nitrogen Unreactivity
Authors: Yang Ruomiao , Liu Junheng , Liu Zhentao , Liu Jinlong 
Published: December 2024

Abstract
Amidst the global trend towards decarbonization, ammonia-diesel dual-fuel engines, which utilize ammonia port fuel injection and diesel direct injection to ignite ammonia-air premixed combustion, emerge as a viable option for heavy-duty applications. However, the characteristics of nitrogen-based pollutants in such engines are not well understood, largely due to the introduction of nitrogen-based fuels that enhance nitrogen reactivity during combustion. Since nitrogen-based pollutant emission features are governed by the fuel-borne nitrogen mechanism, this study investigates fuel-borne nitrogen pollutants in ammonia-diesel dual-fuel engines by rendering atmospheric nitrogen unreactive in the chemical mechanism of a three-dimensional (3D) computational fluid dynamics (CFD) model. Simulation results indicate that unburned ammonia is the primary nitrogen-based pollutant, with ammonia slip resulting from larger regions unreachable by the diesel diffusion flame and higher concentrations of ammonia in these areas. Additionally, concentrations of nitrous oxide (N2O) are found to be comparable to those of nitrogen oxides (NOx), primarily because the formed NOx is reduced by amino groups, while N2O continues to be produced during the late oxidation stage. Consequently, ammonia-diesel dual-fuel operation yields lower NOx concentrations compared to pure diesel operation, and an increased ammonia energy ratio further reduces NOx emissions. Among NOx species, nitric oxide (NO) concentrations remain predominant; however, nitrogen dioxide (NO2) plays a crucial role in the diesel auto-ignition process. The concentration of NO2 in the exhaust gases exhibits limited sensitivity to changes in the ammonia energy ratio. Despite these findings being derived from CFD simulations that deactivate nitrogen kinetics in the air, they help in understanding the nitrogen-based emission features of ammonia-diesel dual-fuel engines. Moreover, these findings underscore the complexity of nitrogen-based pollutant emissions in ammonia-diesel dual-fuel engines compared to traditional petroleum-fueled engines, highlighting the need for further fundamental research to develop effective control strategies for nitrogen-based pollutants and facilitate the market introduction of ammonia-diesel dual-fuel engines.
Experimental Investigation Into the Combustion Characteristics of Biodiesel Fuel in a 4-Stroke Locomotive Engine
Authors: Ewphun Pop-Paul , Biruduganti Munidhar , El-Hannouny Essam , Longman Douglas , Vojtech Ryan , Svoboda Kathryn , Blase James 
Published: December 2024

Abstract
The leaders of the Departments of Energy, Transportation, Housing and Urban Development, and the Environmental Protection Agency released the U.S. National Blueprint for Transportation Decarbonization, the landmark interagency framework of strategies and actions to remove all emissions from the transportation sector by 2050. As a result, the transportation industry is encouraged to reduce its carbon footprint by using low-carbon-intense fuel. The rail transportation sector has expressed interest in electrification as a solution for locomotive engines running on short line rails. However, the long-haul locomotive is still difficult to electrify and locomotive engines are expected to operate for a long lifetime. Because of these challenges, the rail industry must look for a short-term solution to reduce its carbon footprint. One promising solution is using net-zero and/or low-carbon fuels, such as biodiesel. Previous research on other internal combustion engines has shown that biodiesel has the potential to reduce emissions, especially particulate matter emissions. This paper investigates the combustion characteristics of plant-based biodiesel. The experiment was carried out on a 4-stroke single-cylinder locomotive engine under various speed load conditions. The combustion characteristics were investigated by using heat release rate analysis and exhaust emissions measurement. The higher cetane number of biodiesel fuel is effective in shortening the ignition delay. Moreover, using biodiesel significantly reduced soot emissions and decreased CO and CO2 emissions.
Multi-Dimensional Modeling of Mixture Formation in a Hydrogen-Fueled Heavy-Duty Optical Engine With Direct Injection
Authors: Wang Yiqing , Scarcelli Riccardo , Bestel Diego , Demir Sinan , Srna Aleš 
Published: December 2024

Abstract
Hydrogen (H2), as a carbon-free fuel, is considered as one of the most promising solutions to reduce the carbon footprint of hard-to-decarbonize energy and transportation sectors. As such, hydrogen-fueled internal combustion engines (H2 ICEs) have recently been receiving increasing attention, particularly in applications such as on-road/off-road heavy-duty transport and combined heat and power. The direct injection (DI) of gaseous hydrogen into the combustion chamber offers great potential for achieving high power density and high engine efficiency, while mitigating the risk of backfire and reducing pre-ignition. However, the numerical simulation of H2 DI system remains a formidable challenge associated with the high computational cost of reproducing compressible supersonic flow and shocks in narrow injector passages and in near-nozzle regions. In general, there is a lack of well-established and validated practices for the modeling of high-pressure H2 DI in large-bore engines. To this end, this study focuses on computational fluid dynamics (CFD) modeling of the mixture formation process in a heavy-duty optical engine employing a medium-pressure H2 DI system. Both Large Eddy Simulations (LES) and Reynolds Averaged Navier-Stokes (RANS) simulations are performed and evaluated against optical data. Gaseous hydrogen is injected into the combustion chamber via a centrally located outward opening hollow-cone injector at a pressure of 40 bar. Simulations are carried out for two injection timings, namely, −120 and −60°CA. The numerical predictions for H2 distribution in different horizontal and vertical planes during the compression stroke are systematically compared against optical data obtained through planar laser-induced fluorescence (PLIF) measurements. Overall, the LES approach using the Dynamic Structure model is found to have good predictive capabilities for the early jet penetration in terms of length and shape, as well as the later H2 distributions. However, the unsteady RANS approach with the renormalization group (RNG) k-ϵ model, which is widely used by industry to model heavy-duty ICEs, significantly underpredicts the H2 mixing, even at similar mesh resolution to that used in LES. These results indicate that there is a need for the improvement of mixing sub-models within the RANS approach when applied to H2 DI simulations.
Prediction of Spray Collapse Patterns on Different Fuel Mixture Compositions Based on Deep Learning Framework
Authors: Zhao Fengnian , Meng Yangrui , Zhou Ziming , Hung David L. S. 
Published: December 2024

Abstract
Flash boiling significantly enhances fuel atomization quality but concurrently amplifies the incidence of spray collapse — a phenomenon detrimental to combustion efficiency and emission control. This challenge is particularly pronounced in multi-component fuel sprays, which are integral to optimizing biofuel and alternative fuel applications. Despite advances in data-driven methodologies for categorizing spray collapse conditions into discrete states based on fuel composition and experimental parameters, a critical gap remains in our capability to infer the specific morphology of spray plumes. In order to bridge the gap by quantitatively predicting the cross-pattern spray morphologies, this study utilized the macroscopic spray cross-patterns of multiple-component fuel mixtures under 12 different sets of fuel temperatures captured by a high-speed planar laser Mie-scattering imaging system. A dataset obtained under 12 sets of experimental conditions was employed to train a physics-guided deep learning framework. This framework integrates domain-specific knowledge with deep learning algorithms to accurately model the complex interactions between fuel mixture components and their impact on spray dynamics. The results indicated that the proposed framework could efficiently capture the underlying correlations between varying fuel mixture compositions and their resultant spray patterns given certain environmental parameters. Moreover, it exhibited capacities to extrapolate beyond the discrete experimental dataset, predicting the fuel spray morphology under untested fuel compositions. This predictive capability facilitates the identification of optimal mixture states for achieving superior fuel atomization quality, thereby contributing to the advancement of fuel efficiency and emissions reduction strategies.
Investigating the Combustion Performance of Dual Fuel Combustion With Diesel and Port Injected Hydrogen in a Large Bore Locomotive Engine
Authors: O’Donnell Patrick C. , Wu Sicong , Kazmouz Samuel J. , Klingbeil Adam , Lavertu Thomas , Jayakar Vijayaselvan , Sheth Pushkar , Sapkota Pradeep , Liu Shuaishuai , Wijeyakulasuriya Sameera , Ameen Muhsin 
Published: December 2024

Abstract
The heavy-duty transportation sector has primarily relied on conventional diesel combustion engines given their reliability and high thermal efficiency relative to spark ignition engines, but increased focus on reducing greenhouse gas emissions has led to investigation into alternative fuels. Gaseous hydrogen fuel has garnered a great deal of recent interest in the engine community given it has zero carbon, but hydrogen is not available at the scale and cost that petroleum fuels are currently available, and this is a barrier to adoption for industries that are looking to decarbonize their operations. Because of the fuel flexibility provided, dual fuel technology offers a pathway for some industries to adopt hydrogen as a fuel source while maintaining sufficient flexibility in times and locations where the new fuel is not yet available.
This computational study investigates dual fuel combustion in a large bore locomotive engine architecture using direct injected diesel and port injected gaseous hydrogen fuel. Previous computational work was done with this engine model to obtain an optimal port fuel injection configuration that maximizes hydrogen mass flow into the combustion chamber and minimizes in-cylinder charge stratification [18]. With an optimal port fuel injection configuration, simulations of varying substitution ratio, compression ratio, intake manifold air temperature, diesel injection timing, and diesel injection pressure were performed to understand the effect of each parameter on combustion performance. Results indicated that both increased substitution ratio and higher intake air temperature accelerates hydrogen flame propagation and can result in high peak cylinder pressures and rapid maximum pressure rise rates. It was also seen that a lower compression ratio has the potential to achieve higher substitution ratios at acceptable peak cylinder pressures. Additionally, diesel injection timing and injection pressure were demonstrated as effective methods for controlling dual fuel combustion heat release rates. These simulation results are then discussed in general to understand how to maximize substitution ratio and how direct injection hydrogen could further improve combustion performance.
Lean Limit Extension in Hydrogen Direct Injection Pre-Chamber Opposed-Piston Engines: A Computational Approach
Authors: Menaca Rafael , Shakeel Mohammad Raghib , Moreno-Cabezas Kevin , Vorraro Giovanni , Turner James W. G. , Im Hong G. 
Published: December 2024

Abstract
Opposed-piston 2-stroke (OP2S) engines hold promise for achieving elevated thermal efficiencies stemming from their low surface-to-volume ratio and reduced heat transfer losses. When powered by hydrogen (H2), OP2S engines offer a compelling pathway towards high-efficiency, carbon-neutral powertrains. However, operating these engines at very lean air-to-fuel ratios, while enhancing efficiency, poses challenges to combustion stability. This study aims to investigate the extension of lean limit of H2 using an active pre-chamber (PC) utilizing a small fraction of total fuel provided, in order to enhance the ignition of the ultra-lean bulk mixture by the hot jet injection. A parametric study was conducted by varying the quantity of fuel injected to identify the stable operation limit without misfire. A comparative analysis of PC ignition against spark ignition modes is conducted to demonstrate the superiority of PCs in facilitating ignition and extending lean limit operation.
Computational Analysis of Peripheral Fuel Injection (PeFI) to Enhance Fuel-Oxidizer Mixing in the Near-Field of Diesel Sprays
Authors: Cellek Mehmet Salih , Bittle Joshua A. , Agrawal Ajay K. 
Published: December 2024

Abstract
Conventional diesel combustion (CDC) utilizes a centrally mounted multi-hole fuel injector spraying fuel into the piston bowl and towards the cylinder wall. This configuration is prone to jet/flame wall impingement causing wetting and flame quenching, higher coolant heat loss, and higher emissions of unburned hydrocarbons, soot, carbon monoxides, etc. Recently, we have introduced peripheral fuel injection (PeFI) whereby fuel is injected at an angle from the periphery of the cylinder head using multiple single-hole injectors. PeFI has been developed to obtain free flames away from the surfaces to minimize heat loss and to reduce emissions by increasing access to the oxidizer both in the near-field of the injector and in the downstream diffusion flame. In this study, 3D computational fluid dynamics (CFD) analysis is utilized to investigate fuel-air mixing in the near-field of diesel sprays with the goal to compare CDC and PeFI strategies. The study utilizes experimentally determined rate of injection (ROI) profiles for multi-hole and single-hole injectors to replicate published data for non-evaporating CDC and PeFI sprays acquired in a pressurized test chamber. The CFD model thus validated is extended to investigate fuel-air mixing in an evaporating spray at ECN Spray A reference conditions of ambient pressure and temperature. Results show significant differences in the flow field in and around the fuel jet and within the chamber for CDC and PeFI cases. PeFI case with its faster initial ROI ramp-up increases initial mixing and achieves faster fuel vaporization compared to those for CDC case. Quantitative analysis reveals that PeFI case provides 20 to 40 percent increase in entrainment at quasi-steady conditions compared to that for CDC case. These benefits of PeFI case are partially offset by its slower ROI at steady conditions, indicating that the single-hole injector should be carefully designed to replace the un-optimized prototype built from the off-the-shelf multi-hole injector.
Heat Release Characteristics of a Volatile, Oxygenated, and Reactive Fuel in a Direct Injection Engine
Authors: LeBlanc Simon , Cong Binghao , Sandhu Navjot , Yu Xiao , Reader Graham , Zheng Ming 
Published: December 2024

Abstract
Compression ignition diesel engines offer a power dense solution for heavy-duty on-road vehicles. The purpose of combustion management for diesel engines primarily concerns the balance of high efficiency and low emissions. Conventional diesel combustion, i.e. single-shot fuel scheduling, is subject to an extended overlap of fuel injection and combustion promoting the diffusion mode of combustion, that is one highly efficient yet prone to form excessive amounts of nitrogen oxides (NOx) and soot emissions. The application of exhaust gas dilution to reduce NOx below regulation limits leads to an increase in smoke emissions, further magnifying the emission control dilemma. Dimethyl ether (DME) contains suitable reactivity for compression ignition engines while also possessing distinct characteristics to diesel, notably physical properties such as volatility and oxygen content, which significantly lowers engine-out soot emissions. In turn, DME enables direct NOx control via oxygen dilution. Nonetheless, the influence of charge dilution towards the combustion heat release behavior of DME persists.
In this study, the heat release pattern of high-pressure DME combustion was investigated in a single-cylinder direct injection engine. The conventional combustion mode was employed, i.e. a single-shot fuel scheduling, with the start of fuel injection fixed at top dead center wherein the in-cylinder temperature and pressure are highest, and the combustion proceeds in an expanding volume. Throughout the study, the fuel injection pressure, engine load, and oxygen dilution were adjusted separately to characterize their influence on the subsequent combustion process. Diesel combustion operated at matching conditions was used to provide reference and relevance to the results. Most notably, the period of diffusion burning was extended in DME following a longer period of injection-combustion overlap. To add, the heat release of DME combustion was repeatedly shorter than diesel owing to the lack of end-burning combustion phase inherent to diesel combustion.
Experimental Studies of Nanosecond Pulse Discharge Plasma on SI Engine
Authors: V. Avaneesh Athreya , Singh Saurabh , Chaturvedi Shivansh , Boggavarapu Prasad , M. Himabindu , Ravikrishna R. V. 
Published: December 2024

Abstract
Non-equilibrium plasma-based ignition systems, such as nano-second plasma (NSP) pulsed discharge and microwave (MW) discharge, have gained significant attention due to their ability to ignite lean fuel-air mixtures. Besides thermal enhancement, NSP produces large amounts of radicals, like O, OH, etc., leading to a lower ignition delay than conventional ignition systems. While the NSP finds its applications in diverse fields, its utilization as an ignition system for spark-ignited engines is explored in this study. The tests were carried out on a natural gas-fuelled 200cc 4-stroke, naturally aspirated spark-ignited engine with a compression ratio of 13. Performance parameters such as engine brake torque, thermal efficiency, brake-specific fuel consumption (BSFC), and exhaust gas emission between conventional and NSP ignition systems have been compared. Based on the in-cylinder pressure data, parameters such as ignition delay, combustion duration, and Coefficient of Variation (CoV) were calculated. The experiment has been carried out at 3000 rpm and 8% manifold throttle opening, corresponding to a low load point. During the experiments, the λ has been varied till the lean operation limit of the engine. With NSP, the lean limit was seen to extend from λ = 1.1 to slightly greater than λ = 1.2. The ignition delay was reduced by 36% at λ = 1.2, with NSP indicating faster combustion. Higher heat release rates were observed with NSP, significantly improving engine performance.
Numerical Study of Buoyancy and Flame Characteristics of Ammonia-Air Flames
Authors: Mathai Joel Reji , Rana Shailendra , Shaalan Amr , Nasim Md Nayer , Trelles Juan Pablo , Mack J. Hunter , Assanis Dimitris , Van Dam Noah 
Published: December 2024

Abstract
There is growing interest in ammonia, NH3, as a zero-carbon fuel for use in transportation as part of broader decarbonization efforts. Ammonia has several advantages as an alternative fuel, including an existing global infrastructure and the ability to be stored as a liquid at room temperature and moderate pressures, thereby increasing its volumetric energy density relative to hydrogen. However, ammonia has a very slow flame speed and can be challenging to ignite. There are growing efforts to develop numerical models of ammonia combustion. However, difficulties still remain to match experimental validation data. The low flame speeds of ammonia flames result in significant buoyancy effects, but buoyancy is neglected in standard modeling and analysis approaches. The buoyancy also affects the flame shape, and therefore can affect the flame speed derived from constant volume combustion chamber (CVCC) experiments. This study examines how well different computational fluid dynamics (CFD) modeling setups are able to capture the effects of buoyancy on ammonia flames, and the sensitivity of flame speeds derived from the CVCC simulations to post-processing and simulation parameters.
Enabling Gaseous Ammonia Use in a Compression Ignition Research Engine
Authors: Ristow Hadlich Rodrigo , Kamal Nabil , Loprete Jason , Sirna Amanda , Trelles Juan Pablo , Van Dam Noah , Mack J. Hunter , Assanis Dimitris 
Published: December 2024

Abstract
With regulations imposing tighter restrictions on carbon emissions, it is crucial to explore the use of carbon-free fuels. Ammonia, NH3, is increasingly being perceived as a dominant hydrogen carrier candidate fuel due to its efficient hydrogen atom arrangement, ease of storage, and for already having an extensive transportation network as the second most traded chemical in the world. There are, however, challenges that still need to be overcome to accommodate the use of gaseous ammonia in a traditional internal combustion engine. To this purpose, a thermodynamic analysis of the heat and mass transfer processes that occur during the withdrawal of the fuel from a compressed gas state is presented to aid in the design of research fueling systems. Moreover, other safety precautions must be taken, including the use of specialized personal protective equipment (PPE) due to the high toxicity of ammonia at relatively low ambient concentrations. The selection of appropriate equipment for the safe handling and use of ammonia in a laboratory setting is detailed, including ammonia-compatible hardware and instrumentation as well as necessary safety considerations inclusive of components such as the pressure regulator, flow meter, thermal generation device to prevent fuel system freezing, and consideration for a HORIBA MEXA 7100 style exhaust gas analyzer. The goal if this work is to provide an overview of the challenges regarding the usage of ammonia as a fuel, as well as guidance on the design process and equipment selection for research engine applications.