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DOE OSTI2024

A decade of insights: Delving into calendar aging trends and implications

Lithium-ion batteries remain at rest for extended periods and experience calendar aging. Although lithium-ion batteries are expected to perform for over 10 years at room temperature, long-term calendar aging data are seldom reported over such timescales. We present a dataset from 232 commercial cells across eight cell types and five manufacturers that underwent calendar aging across various temperatures and states of charge (SOCs) for up to 13 years. We analyze calendar aging across these conditions by tracking capacity loss and resistance growth as the cells degrade. This dataset is used to validate simple models, primarily the Arrhenius law and the power law, which explain the temperature and storage time on calendar aging. Certain applications of Arrhenius and power law fail to describe the dependence of capacity loss on temperature and resistance growth on storage time. Through this dataset, we demonstrate the complexity of calendar aging and the challenges in reducing trends into phenomenological models.

25 ENERGY STORAGE↗
DOE OSTI2022

Phase transitions in Zr at sub-nanosecond time scales

Here solid-solid phase transitions are investigated in Zr thin films using shock compression induced by a short laser pulse (<1 ns). Shock wave profiles are measured at free surfaces for films of different thicknesses (a few micrometers) using chirped-pulse line velocimetry with 10 ps time resolution. Experiments are performed at pressures up to ~50 GPa, which is sufficient to reach the ω and β phases under equilibrium conditions. The shock wave structures are analyzed using a general Lagrangian analysis method, which allows for the calculation of stress–strain paths and assessments of phase transition behavior. In agreement with recent short laser pulse experiments using ultra-fast x-ray diffraction, we do not find any clear evidence of the α–ω transition, though this would be expected from the phase diagram. Instead, we infer a direct transformation to a metastable β-phase at lower shock pressures (<20 GPa) and equilibrium β at higher pressures. Through the velocimetry analysis, we find α–β transformation onset times of less than ~100 ps and completion times of less than ~200 ps.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Large-momentum effective theory’s asymptotic extrapolation vs the inverse problem

Large-momentum effective theory is a physics-guided systematic expansion to calculate light-cone parton distributions, including collinear (PDFs) and transverse-momentum-dependent ones, at any fixed momentum fraction 𝑥 within a range of [𝑥 min , 𝑥 max ]. It theoretically solves the ill-posed inverse problem that afflicts other theoretical approaches to collinear PDFs, such as short-distance factorizations. Recently, Dutrieux et al. raised practical concerns about whether current or even future lattice data will have sufficient precision in the subasymptotic correlation region to support an error-controlled extrapolation—and if not, whether it becomes an inverse problem where the relevant uncertainties cannot be properly quantified. While we agree that not all current lattice data have the desired precision to qualify for an asymptotic extrapolation, some calculations do, and more are expected in the future. We comment on the analysis and results in Dutrieux et al. and argue that a physics-based systematic extrapolation still provides the most reliable error estimates, even when the data quality is not ideal. In contrast, reframing the long-distance asymptotic extrapolation as a data-driven-only inverse problem with ad hoc mathematical conditioning could lead to unnecessarily conservative errors.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Design and Challenges of Edge Computing ASICs on Front-End Electronics

In situ or hardware-embedded data processing of raw signals, close to their source, in radiation detectors is expected to provide dramatic improvements in data quality and volumes. However, the implementation of artificial neural networks (ANNs) in the front-end electronics, and the design of custom integrated circuits (ASICs), comes with challenges. In addition, detectors have to operate with limited power budget and implement complex functionalities in a very dense space. They often are exposed to extreme conditions as they work in high-radiation environments and/or cryogenic temperatures. This paper presents examples of applications and design methodologies for in-situ ANNs, along with the challenges of retaining the fidelity of the trained networks. For illustration, we use the problem of estimating the energy deposited by the radiation from digitized waveforms. The proposed implementation starts with an ML algorithm trained in Qkeras and eventually leads to an equivalent ASIC implementation. The associated design challenges in realizing energy and area efficient implementations in CMOS processes are reviewed. Novel approaches that employ hybrid technologies (combination of CMOS with memristors), in-memory computing models, and bio-inspired spiking neural networks are also highlighted

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

FY2020 performance assessment annual review for the E-area low-level waste facility

The Savannah River Site (SRS) E-Area Low-Level Waste Facility (ELLWF) consists of six types of disposal units described in the Performance Assessment (PA) (WSRC, 2008): Low Activity Waste Vault (LAWV), Intermediate Level Vault (ILV), Trenches [Slit Trenches (STs), Engineered Trenches (ETs), and Component-in-Grout (CIG) Trenches], and Naval Reactor Component Disposal Areas (NRCDAs). The ELLWF is a part of the Solid Waste Management Facility (SWMF). SWMF is managed and operated by the SRS Management and Operations prime contractor, Savannah River Nuclear Solutions (SRNS). Within SRNS, the Solid Waste Management (SWM) organization is responsible for operating the SWMF, and the Savannah River National Laboratory (SRNL) is the technical agency responsible for preparing and maintaining the PA. SWMF operations have been performed at SRS since 1952. The mission of the SWMF is to provide storage, processing, disposal, and shipment of radioactive, hazardous, and mixed waste. The SWMF is committed to treat, store, and dispose of these waste products in a manner that protects the environment and the health and safety of the facility worker, the co-located worker, and the offsite general public. Wastes handled in the SWMF include low level waste, transuranic waste, hazardous waste, Toxic Substances Control Act waste, and mixed waste (containing both hazardous and radioactive constituents). The FY2020 PA Annual Review for the ELLWF affirms that the disposal facility continued to operate within the bounds of the current PA and Composite Analysis (CA) baseline and the subsequent SA’s and satisfied all the requirements, conditions, and limitations identified in the 2008 DAS (DOE 2008a), RWMB SRNL_STI-2020-00588 Revision 0 vi (McGill, 2020), and ELLWF Low-Level Waste Acceptance Criteria (SRS-1S, 2014). This annual review affirms that the supporting studies performed in FY2020 do not alter the conclusions of the ELLWF PA (WSRC, 2008) and that there is a reasonable expectation that the ELLWF will meet the performance objectives delineated in DOE Manual 435.1-1 (DOE 2011)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Demonstrate new plasticity models for doped UO 2 that capture dislocation mechanisms

In light water reactors, fuel vendors are investigating the use of dopants to modify the properties of UO 2 pellets, with the goal of improving pellet-cladding mechanical interactions during operation. Dopants are expected to ‘soften’ the pellets; that is, the doped pellets have higher plastic deformation than conventional UO 2 . This leads to a reduction in the severity of mechanical pellet-cladding interactions, helping to reduce the hoop strain on the cladding. By minimizing the strain exerted by the pellet on the cladding, it is anticipated that cladding performance under accident conditions can be enhanced (i.e., lowering the risk of burst during a LOCA). Dopants such as chromium (Cr) promote grain growth during pellet fabrication, leading to larger grains; therefore, understanding the link between chemistry, microstructure and mechanical deformation (enhanced creep rates) behavior of UO 2 is critical to helping operators further substantiate the benefits of doping UO 2 . Historically, the nuclear energy industry has relied on empirical models to make assessments of performance. Compared to empirical models, mechanistic physics-based models provide benefits, such as, fewer data points for validation and better extrapolation where experimental data is scarce or non-existent. In this report, Bayesian inference techniques have been applied to a previously developed lower length-scale-informed diffusional creep model. The objective is to i) infer lower-length-scale parameter distributions from available experiment and then ii) determine the uncertainties in the measurable quantity (in this case creep rates) after propagating the inferred lower length scale parameter uncertainties. The approach requires many evaluations of the model, which becomes computationally insurmountable; therefore, a neural-network model is trained to data obtained by sampling the full model over the most important parameters. This neural-network is then used in the Bayesian inference approach to determine probability distributions in the parameter values that represent the uncertainty in the model given what is known from the experiments (posterior). A significant reduction compared to conservative initial (prior) uncertainties is achieved through inference against the experimental data, demonstrating the efficacy of this approach. Furthermore, by accounting for uncertainties in the experimental conditions and sample non-stoichiometry, it is possible to resolve apparent discrepancies in experimental measurements within a self-consistent grain boundary (Coble) creep model that is sensitive to chemistry. This work has been written up and submitted to Nuclear Technology for a special issue on accelerated fuel qualification (AFQ). This uncertainty quantification (UQ) work not only improves the diffusional model, while accounting for uncertainty, but also establishes a framework which can readily be applied to the mechanistic models of dislocation deformation developed in this study. The most likely values from the Bayesian analysis are incorporated into our UO 2 diffusional creep model and a lower length scale-informed irradiation UO 2 creep mechanistic model to generate a dataset. This dataset has been provided to our INL collaborators for training an artificial neural network surrogate model, which will be implemented in the BISON fuel performance code to assess how the results differ from those currently obtained using a fully empirical model and that of using the nominal (uncalibrated) atomic scale parameters in our mechanistic model. Plastic deformation (creep and glide) in UO 2 is a complex phenomenon, governed by multiple underlying processes such as local defect concentrations, applied stresses, and microstructural characteristics. Consequently, there is a need for a meso-scale model with polycrystalline resolution capable of extrapolating to large grain sizes applicable to doped UO 2 , where data is limited and the model can help bridge the knowledge gap. By integrating atomistic data into the polycrystal LApx code, it becomes possible to predict dislocation climb and glide plasticity that simple analytical models cannot accurately represent. The application of atomic-scale data within LApx demonstrated the importance of climb and glide mechanisms in reproducing high-stress UO 2 behavior. Behaviors such as this are crucial to capture and implement in BISON, as parts of the fuel pellet can reach temperatures where glide can occur before pellet cracking. This model which captures dislocation based mechanisms for UO 2 is then used to stand up the doped model accounting for larger grain sizes. It was found that larger grain sizes can lead to enhanced deformation rates in the glide regime, and therefore can help with the pellet cladding mechanical interaction. Therefore if the fuel pellet reaches conditions (stress/temperature) where glide is active, the enhanced creep rates for larger grains in the glide regime (doped UO 2 ) can help with pellet cladding mechanical interactions. Plastic deformation in UO 2 involves multiple mechanisms, including diffusional creep, dislocation climb, and glide. This milestone contains two parts: (1) UQ of a pre-existing lower length scale informed mechanistic diffusional creep model, and (2) development of a new LApx based model for dislocation-mediated creep mechanisms in UO 2 , with application to large-grain doped UO 2 .

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2020

Using Residential and Office Building Archetypes for Energy Efficiency Building Solutions in an Urban Scale: A China Case Study

Building energy consumption accounts for 36% of the overall energy end use worldwide and is growing rapidly as developing countries continue to urbanize. Understanding the energy use at urban scale will lay the foundation for identification of energy efficiency opportunities to be deployed at speed. China has almost half of global new constructions and plays an important role in building suitability. However, an open source national building energy consumption database is not available in China. To provide data support for building energy consumptions, this paper used a simulation method to develop an urban building energy consumption database for a pilot city in Wuhan, China. First, residential, small, and large office building archetype energy models were created in EnergyPlus to represent typical building energy consumption in Wuhan. The baseline reference model simulation results were further validated using survey data from the literature. Second, stochastic simulations were conducted to consider different design parameters and occupants’ energy usage intensity scenarios, such as thermal properties of the building envelope, lighting power density, equipment power density, HVAC (heating, ventilation and air conditioning) schedule, etc. A building energy consumption database was generated for typical building archetypes. Third, data-driven regression analysis was conducted to support quick building energy consumption prediction using key high- level building information inputs. Finally, a web-based urban energy platform and an interface were developed to support further third-party application development. The research is expected to provide fast energy efficiency building design solutions for urban planning, new constructions as well as building retrofits.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Smaller than Expected Bright-spot Offsets in Spitzer Phase Curves of the Hot Jupiter Qatar-1b

We present Spitzer full-orbit thermal phase curves of the hot Jupiter Qatar-1b, a planet with the same equilibrium temperature—and intermediate surface gravity and orbital period—as the well-studied planets HD 209458b and WASP-43b. We measure secondary eclipse depths of 0.21 ± 0.02% at 3.6 μm and 0.30 ± 0.02% at 4.5 μm, corresponding to dayside brightness temperatures of 1542{sub −31}{sup +32} K and 1557{sub −36}{sup +35} K, respectively, consistent with a vertically isothermal dayside. The respective nightside brightness temperatures are 1117{sub −71}{sup +76} and 1167{sub −74}{sup +69} K, in line with a trend that hot Jupiters all have similar nightside temperatures. We infer a Bond albedo of 0.12{sub −0.16}{sup +0.14} and a moderate day–night heat recirculation efficiency, similar to HD 209458b. General circulation models for HD 209458b and WASP-43b predict that their bright spots should be shifted east of the substellar point by tens of degrees, and these predictions were previously confirmed with Spitzer full-orbit phase curve observations. The phase curves of Qatar-1b are likewise expected to exhibit eastward offsets. Instead, the observed phase curves are consistent with no offset: 11° ± 7° at 3.6 μm and −4° ± 7° at 4.5 μm. The discrepancy in circulation patterns between these three otherwise similar planets points to the importance of secondary parameters like rotation rate and surface gravity, and the presence or absence of clouds, in determining atmospheric conditions on hot Jupiters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Structure factors of the unitary gas under supernova conditions

Here, we compute with lattice field theory the vector and axial static structure factors of the unitary gas for arbitrary temperature above the superfluid transition and for fugacities 0.1 < $\mathcal{z}$ < 1.0 . Using the lattice formulation, we calculate beyond the validity of the virial expansion, a commonly used technique in many-body physics. We find qualitative differences in the behavior of the structure factors at high fugacity compared to the predictions of the virial expansion. Due to the large scattering length of neutrons, we expect the unitary gas structure factors to approximate the structure factors of hot neutron gases, and we therefore expect our calculations to be useful in supernova simulations, where neutron gas structure factors are needed to compute in-medium neutrino-neutron scattering rates.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

The effects of electrically exploding gold bridgewires into inert and explosive powder beds

Abstract The particle velocity created in beds of both low-density inert sugar and explosive PETN as a function of distance from an exploding bridgewire was measured using optical velocimetry and a silvered PMMA window. As expected, more violent bridge-bursts (from a greater-stored-energy capacitive discharge unit) resulted in greater particle velocities and a better supported compaction wave in sugar. In all cases, ramp waves, not shocks, were observed in the inert sugar. Large window velocities were observed for very powerful bursts (up to 270 m/s), but bursts required for stochastic detonator operation conditions resulted in sugar/PMMA window velocities of only 8–10 m/s 0.85 mm from the bridge location. In contrast, after a distance of only 0.65 mm, a building shock wave was observed in PETN under both threshold and reliable firing conditions. Subsequently a hot-spot-driven shock-to-detonation (SDT) process was observed prior to full detonation. The measured buildup process accounts for $$\approx $$ ≈ 66% of the so-called excess transit time (ETT) between the observed and theoretical total function time for the particular exploding-bridge-wire (EBW) detonator studied. The remainder must occur in the powerful output pellet region. In contrast to a common understanding, the ETT is found to be a weak function of the discharge energy. Thus, the operation of the detonator after a bridge-burst energy-to-powder reaction transition process is found to be hot-spot-driven SDT in both the low- and high-density pellets.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2022

Molecular weight growth by the phenyl + cyclopentadienyl reaction: Well-skipping, ring-opening, and dissociation

Radical-radical reactions contribute to molecular weight growth of polycyclic aromatic hydrocarbons (PAHs), but their role is not well understood. The phenyl (Ph, C 6 H 5 ) + cyclopentadienyl (C 5 H 5 ) reaction has not been studied but can serve as a surrogate reaction for many reactions of larger aryl-σ radicals with resonance-stabilized π-radicals. The adducts of these reactions easily lose an H atom to produce a new π-radical. Here, through a combination of dilute flash pyrolysis experiments, theory, and simulation, we find that for the title reaction, substantial Ph—C 5 H 4 + H is formed, dominantly by a well-skipping pathway, at conditions around 30 Torr and 1400 K. This radical is thermally stable at moderate temperatures but decomposes at higher temperatures following ring opening of the 5-member ring. Products corresponding to the loss of H, C 2 H 2 , and C 3 H 3 are observed experimentally. Calculation of the C 11 H 9 potential energy surface affirms that these are expected decomposition products and reveals multiple possible pathways.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

The proton radius (puzzle?) and its relatives

We review determinations of the electric proton charge radius from a diverse set of low-energy observables. We explore under which conditions it can be related to Wilson coefficients of appropriate effective field theories. This discussion is generalized to other low-energy constants. This provides us with a unified framework to deal with a set of low-energy constants of the proton associated with its electromagnetic interactions. Unambiguous definitions of these objects are given, as well as their relation with expectation values of QCD operators. We show that the proton radius obtained from spectroscopy and lepton–proton scattering (when both the lepton and proton move with nonrelativistic velocities) is related to the same object of the underlying field theory with O ( α ) precision. The model dependence of these analyses is discussed. The prospects of constructing effective field theories valid for the kinematic configuration of present, or near-future, lepton–proton scattering experiments are explored.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Unlocking Dysprosium Constraints for China’s 1.5 °C Climate Target

Some key low-carbon technologies, ranging from wind turbines to electric vehicles, are underpinned by the strong rare-earth-based permanent magnets of the Nd, Pr (Dy)–Fe–Nb type (NdFeB). These NdFeB magnets, which are sensitive to demagnetization with temperature elevation (the Curie point), require the addition of variable amounts of dysprosium (Dy), where an elevation of the Curie point is needed to meet operational conditions. Given that China is the world’s largest REE supplier with abundant REE reserves, the impact of an ambitious 1.5 °C climate target on China’s Dy supply chain has sparked widespread concern. Here, we explore future trends and innovation strategies associated with the linkage between Dy and NdFeBs under various climate scenarios in China. We find China alone is expected to exhaust the global present Dy reserve within the next 2–3 decades to facilitate the 1.5 °C climate target. By implementing global available innovation strategies, such as material substitution, reduction, and recycling, it is possible to avoid 48%–68% of China’s cumulative demand for Dy. Nevertheless, ongoing efforts in REE exploration and production are still required to meet China’s growing Dy demand, which will face competition from the United States, European Union, and other countries with ambitious climate targets. Here our analysis urges China and those nations to form wider cooperation in REE supply chains as well as in NdFeB innovation for the realization of a global climate-safe future.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

The effects of laser polarization and wavelength on injection dynamics of a laser wakefield accelerator

Here, we investigate the effects of laser polarization and wavelength on electron injection dynamics in a laser wakefield accelerator. During the ionization process, electrons gain residual momentum and kinetic energy via above threshold ionization, which has a strong dependence on laser polarization. A circularly polarized laser pulse results in a much higher residual momentum and kinetic energy gain for the ionized electrons compared with the linearly polarized case. This residual momentum results in particle injection because of the sensitivity of particle trapping to the initial conditions and enhanced the total injected beam charge in both experiments and particle-in-cell simulations. Due to the strong correlation of above threshold ionization with laser wavelength, in this work we extended the investigation to long wavelength (up to 20 μm) drive pulses using particle-in-cell simulations. Owing to the gain in kinetic energy, it may be expected that the charge trapped would consistently increase for circular polarization with increasing laser wavelength, but this was not observed. Instead, there are oscillations with wavelength in the relative trapped charge between linear and circular polarization cases, which arise because of ionization and heating effects on the plasma. Our studies highlight the complex interplay between several different physical effects, including injection regimes—above threshold ionization assisted injection, wave-breaking injection by carrier-envelope-phase effects and ionization injection—ionization gradient induced laser pulse evolution, and thermal modifications to the wake structure that need considering when extrapolating laser wakefield acceleration to different wavelength regimes.

Ma, Y. (ORCID:0000000239194856)↗
DOE OSTI2020

Optimal Spatial Separation of High-Order Harmonics from Infrared Driving Lasers with an Annular Beam in the Overdriven Regime

We study high-order harmonic generation (HHG) with an annularly shaped high-power, high-repetition-rate laser. In this work we investigate how the spatial separation (or divergence) of the incident laser and the generated high-order harmonics depends on the gas pressure when the laser intensity is in the overdriven regime. It is shown that, when the cone size of the incident annular beam is relatively large, the resulting harmonics are highly collimated along the propagation axis and are spatially separated from the incident beam. Under the overdriven condition, dynamic phase matching favors HHG emissions from short-trajectory electrons that are efficiently built up in the second half of the gas medium. We verify that using an annular beam is a simple and effective method for separating the intense incident infrared laser from the generated high harmonics. Such high-flux and low-divergence light pulses are expected to be powerful sources in the laboratory for ultrafast probing of electron dynamics.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Optimizers for stabilizing likelihood-free inference

A growing number of applications in particle physics and beyond use neural networks as unbinned likelihood ratio estimators applied to real or simulated data. Precision requirements on the inference tasks demand a high-level of stability from these networks, which are affected by the stochastic nature of training. We show how physics concepts can be used to stabilize network training through a physics-inspired optimizer. In particular, the energy conserving descent (ECD) optimization framework uses classical Hamiltonian dynamics on the space of network parameters to reduce the dependence on the initial conditions while also stabilizing the result near the minimum of the loss function. We develop a version of this optimizer known as , which has few free hyperparameters with limited ranges guided by physical reasoning. We apply to representative likelihood-ratio estimation tasks in particle physics and find on average that it out-performs the widely used Adam optimizer. We expect that ECD will be a useful tool for wide array of data-limited problems, where it is computationally expensive to exhaustively optimize hyperparameters and mitigate fluctuations with ensembling.

Monte Carlo methods↗
DOE OSTI2023

Methods for Estimating Hydrogen Fuel Tank Characteristics

The pressure vessels needed to store hydrogen for next-generation hydrogen fuel cell vehicles are expected to be a substantial portion of the total system mass, volume, and cost. Gravimetric capacity, volumetric capacity, and cost per kilogram of usable hydrogen are key performance metrics that the U.S. Department of Energy (DOE) uses to determine the viability of hydrogen fuel cell systems. Research and development related to hydrogen storage systems covers a wide range of potential operating conditions, from cryogenic temperatures to high temperatures (above ambient) and low pressure to high pressure. Researchers at PNNL have developed methods for estimating these key pressure vessel characteristics to support on-board hydrogen storage system design and performance evaluation and to support decision-making about DOE hydrogen storage system research investments. This article describes the pressure tank estimation methodology that has been used as a stand-alone calculation and has been incorporated into larger system evaluation tools. The methodology estimates the geometry, mass, and material cost of type I, type III, and type IV pressure vessels based on operating pressure and material strength at the system's operating temperature, using classical thin-wall and thick-wall pressure vessel stress calculations. The geometry, mass, and material cost requirements of the pressure vessel have significant impacts on the total system performance. For example, hydrogen storage materials that can separately achieve a very high hydrogen density can be deemed impractical for use in fuel cell vehicle hydrogen storage systems because the pressure tank containing them is too large, heavy, or expensive. This article describes the design philosophy and analytical process of the tank characteristic estimation methodology, which has been implemented in spreadsheet calculation tools and system-level analysis tools used by DOE researchers. Each of the three tank types (type I, type III, and type IV) uses a different analysis methodology with some common elements. This article also provides examples of implementing the methodology to perform parametric studies of all three pressure vessel types. The goal of this article is to present the methodology in sufficient detail so it can be implemented in other hydrogen fuel cell vehicle design and analysis tools.

42 ENGINEERING↗
DOE OSTI2025

Efficiency and emissions of NH3-diesel/bio-pilot dual-fuel combustion in a high-speed four-stroke engine

While dual-fuel ammonia engines are starting to be commercialized for the large low-speed 2-stroke marine engine market, there are still challenges with utilizing ammonia on 4-stroke engines used as auxiliary engines for ocean going vessels and within inland and coastal marine applications. The shorter timescales for high-speed engines pose a particular challenge for low-cetane, high ignition energy fuels like ammonia. In addition to achieving maximum ammonia substitution levels, N2O emissions are a key factor that needs to be understood. This paper reports the results of experiments using a single-cylinder 107mm bore Cummins B-series diesel engine modified for port-fuel injection of gaseous anhydrous ammonia with a direct injection of diesel fuel near-TDC to ignite the premixed ammonia. Combustion data as well as emissions data from an FTIR including NO, NO2, N2O, and unburned ammonia are presented for selected operating points with a focus on high-load operation at 1200rpm with high ammonia energy substitution (over 95% by fuel energy). Several air/fuel ratio conditions are included, sweeping from diesel-like airflow to stoichiometric conditions. The impact of biofuels (biodiesel and renewable diesel) as pilot fuels is also considered. Comparisons for emissions, greenhouse gas performance, and efficiency are made with a conventional diesel combustion baseline. The impact of fuel injection strategy on NOx, N2O, and NH3 emissions is quantified, and the dual-fuel ammonia results on this high-speed 4-stroke engine are expected to provide fundamental insights into further combustion development opportunities for the larger engines used across marine applications.

Kaul, Brian [ORNL] (ORCID:0000000184813620)↗