SEARCH · Search NASA

Results for “MIXING RATIO”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 253 records · Page 14

All sources NASA NTRS DOE OSTI

DOE OSTI2020

Co-Pyrolysis of Chicken and Cow Manure

Conventional pyrolysis is a relatively simple way for biochar production; however, a single biomass feedstock approach is not promising for the development of multiple properties of biochar used in various applications. Here, this study provides a detailed comparison in terms of pyrolysis kinetics between the cow manure and chicken manure, in addition to the co-pyrolysis by mixing the two livestock at different ratios. Eight different heating rates were tested, 5–40 °C/min with 5 °C/min step, on both livestock using the nitrogen as a gas agent with a flowrate of 50 ml/min. The initial results show that for the slow heating rates, 5 °C/min, the thermal degradation of the cow manure is different compared to that obtained from chicken manure. For the cow manure, the first peak, associated with hemicellulose decomposition, is higher than the second peak, associated with cellulose decomposition, which is the other way around for chicken manure. At 5 °C /min, the hemicellulose decomposition took place at 250 °C and 300 °C for the chicken manure and cow manure, respectively. The cellulose decomposition was started at 300 °C for chicken manure and 470 °C for cow manure. The lowest heat rate was selected for the co-pyrolysis case study to allow a quasi-equilibrium state to avoid measurement errors and heat transfer limitation in terms of thermal lag. Co-pyrolysis is studied with different blend ratios between the chicken and cow manure, where the 40% cow manure shows a positive result in terms of keeping an exothermic reaction over the co-pyrolysis process.

09 BIOMASS FUELS↗

DOE OSTI2024

Micro-Quantification of Helium-3 and Helium-4 in TPBAR Components

This report documents the method development for measuring helium isotopes in micrometer-sized samples of tritium producing burnable absorption rod (TPBAR) components. Helium isotopes were measured as a tracer for tritium, which decays to 3 He with a half-life of 12.33 years. Getter and cladding materials from the TPBARs were analyzed, as they are designed to trap tritium. Therefore, constraining the diffusivity of tritium through these materials is of key importance. To first establish the reliability of the noble gas mass spectrometer, a reference gas with a relative 4 He/ 3 He ratio of 1000 was pre-mixed. This standard was measured several times to ensure measurements were reproducible. Unirradiated and irradiated getter and cladding samples of TPBARs were cut into 1-100 µm 3 cubes and analyzed for 3 He and 4 He content. The unirradiated materials had helium content equal to or less than that of the measured instrument background. Irradiated cladding also had instrument background levels of helium while irradiated getters had elevated levels of 3 He, interpreted to be the decay product of tritium. No diffusion of 4 He was observed in any of these materials, however, indicating that the 3 He detected in the irradiated getter was produced in situ after tritium diffusion and decay. These findings validate this method as a way to trace tritium diffusion in reactor materials.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2024

The Mu2e Experiment and Progress in the Year 2024

The Mu2e Experiment is a search for Charged Lepton Flavor Violation (CLFV) in the process of a coherent neutrinoless mu- N -> e- N transition. This process is allowed under the Standard Model in the presence of neutrino mixing; albeit, at unobservable rates (branching ratio below 10-50). The sensitivity of the Mu2e experiment is a factor of 104 improvement over the current limit. This search both compliments and extends current searches for muon to electron+gamma at MEG and new physics searches at the LHC. Another interesting process that Mu2e will search for is the neutrionless conversion of stopped negative muons into positrons: mu- N -> e+ N'. This process violates both lepton flavor and lepton number (LNV) and would provide proof that neutrinos are Majorana particles. Progress has been made in many areas in preparation for beam. A description of the Mu2e Experiment and a synopsis of this experiment s progress in the year 2024 towards data collection will be presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2023

Eastern Interconnection Wide-Area Oscillation Assessment and Study Report

To meet the government mandates such as Renewable Portfolio Standards (RPS), conventional synchronous generators with rotating mass are being displaced by inverter-based resources (IBRs), leading to high penetration of renewable energy sources (RES). As a result, the inherent properties and characteristics of the transformed generation mix may significantly impact the grid behaviour, and it is of paramount significance that the impact and the consequences of the resource mix change is thoroughly understood to adopt measures to maintain reliable grid operations. Of great concern is the inter-area low-frequency oscillation, which usually propagates through a large region and has a system-wide impact. Such oscillations may lead to unnecessary or inadvertent tripping of generators, that may be simply reacting to the oscillation originating from geographically remote sites. Such tripping of generators can lead to cascading outages, system split and load loss events. Over the years, several system-wide oscillation events have been observed across all three North American interconnections. This project titled Wide-area Oscillation Assessment and Trending Study, sponsored by the Office of Electricity (OE) of the Department of Energy (DOE), aims to conduct the required research to capture and investigate the potential changes in wide-area oscillatory performance of the system as a result of resource mix transition. The Pacific Northwest National Laboratory (PNNL) conducted this research and technical staff of Federal Energy Regulatory Commission (FERC) served as advisors to the project. The primary objective of this study is to assess whether there are significant trends in the power system wide-area oscillatory behaviours, as a result of the generation-mix changes due to the increased penetration of RES in the U.S. Eastern Interconnection (EI). The analysis presented in this report can serve as reference for future grid planning and operation of the EI system. This research conducted in this project evaluates the wide-area oscillatory behaviour of the EI, using a model-based approach for potential future resource mixes, and the measurement-based analysis with 21-month phasor measurement unit (PMU) time series. The oscillation modes in EI system along with the impact of the changes of the generation mix on the frequency and damping ratio (DR) of the oscillations have been studied.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2025

Light, High Performance and Scalable Coal-Derived Composites for Construction: Precast and Cast-in-Place Applications

The overall objective of this project was to produce a coal-based construction material that has up to ~95 weight percent (wt. %) coal with physical, chemical, and thermal properties exceeding those of ordinary Portland cement (OPC)-based construction materials. Additionally, the project aimed to minimize external binders by implementing novel mixing techniques, while exceeding the performance/cost ratio of OPC. Finally, the project was to demonstrate production of precast products via the design and fabrication of products via a bench scale process. Consistent with some of these objectives, the project successfully fabricated samples of coal-based composite materials with >80 wt% coal with physical, chemical and thermal properties on par with cement-based concrete. Select samples demonstrated compressive strengths with >7,000 psi and flexural strength of >420 psi. The composite materials minimized external binders and also demonstrated durability, as evidenced by resistance to acidic and basic solutions. Finally, larger slab and beam type samples were produced using a process developed by the Recipient, although, the process was not semicontinuous in nature. Taken together, the results of this project suggest that domestic coal has potential to serve as a replacement for cementitious materials utilized in incumbent construction technologies, which could significantly reduce the energy and emissions of the construction industry

01 COAL, LIGNITE, AND PEAT↗

DOE OSTI2023

Twin-screw granulation: Mechanistic understanding of the effect of material properties on key granule quality attributes through the analysis of mixing dynamics and granulation rate mechanisms

This study focuses on understanding the effect of material properties on granule quality attributes through the analysis of mixing dynamics and granulation rate mechanisms. Powder wettability, binder viscosity, and liquid-to-solid (L/S) ratio were the factors that were investigated in this study. Further, the mixing occurring inside the twin-screw granulator (TSG) was quantitatively assessed by obtaining the axial dispersion coefficient from the experimentally measured residence time distribution (RTD) curves. It was observed that the quality of the nuclei fed to the kneading zone significantly affected the mixing dynamics. The quality of nuclei was governed by nucleation kinetics, which in turn was principally affected by the liquid saturation of the nuclei and the ratio of drop penetration time and encounter time, which in turn were affected by the L/S ratio and binder viscosity respectively. The hydrophobicity of the blend mainly affected the extent of nucleation. The type of nuclei entering the kneading zone and mixing dynamics in the TSG also determined whether the granulation growth mechanism was “layering-dominant” or “viscous-dominant”. It was also shown that the resultant granule quality attributes were a reflection of the growth mechanisms. Ultimately, a mechanistic link between material properties, mixing dynamics, granulation rate mechanisms, and granule quality attributes was established.

36 MATERIALS SCIENCE↗

DOE OSTI2025

The interaction of edge dislocations with hydrogen-helium bubbles in tungsten

In fusion reactors, plasmas-facing components undergo degradation due to displacement damage and injection of gas impurities. Significant amounts of hydrogen (H) and helium (He) impurities can be introduced into materials through plasma exposure and nuclear transmutation, and their synergistic effects lead to the formation of mixed He/H bubbles under irradiation, changing their hardening mechanisms. In this study, molecular dynamics (MD) models were developed to study the interaction between ½<111> edge dislocations with mixed He/H-bubbles in W. The critical resolved shear stress (CRSS) that is required for dislocation breakaway increases with He/H-to-vacancy ratio at 600 K, indicating strong pinning effects of mixed He/H bubbles. However, as the temperature increases up to 1400 K, the mixed He/H bubbles become unstable as the H atoms are increasingly emitted from the mixed He/H bubbles and migrate into W matrix, which lowers bubble pressure and CRSS. Overall, these results highlight the synergistic effects of He and H on dislocation behavior in irradiated W during deformation.

36 - MATERIALS SCIENCE↗

DOE OSTI2021

Seasonal Variability in Local Carbon Dioxide Biomass Burning Sources Over Central and Eastern US Using Airborne In Situ Enhancement Ratios

We present observations of local enhancements in carbon dioxide (CO 2 ) from local emissions sources over three eastern US regions during four deployments of the Atmospheric Carbon Transport-America (ACT-America) campaign between summer 2016 and spring 2018. Local CO 2 emissions were characterized by carbon monoxide (CO) to CO 2 enhancement ratios (i.e., ΔCO/ΔCO 2 ) in air mass mixing observed during aircraft transects within the planetary boundary layer. By analyzing regional-scale variability of CO 2 enhancements as a function of ΔCO/ΔCO 2 enhancement ratios, observed relative contributions to CO 2 emissions were separated into fossil fuel and biomass burning (BB) regimes across regions and seasons. CO 2 emission contributions attributed to biomass burning (ΔCO/ΔCO 2 > 4%) were negligible during summer and fall in all regions but climbed to ∼9%–11% of observed combustion contributions in the South during winter and spring. Relative CO 2 fire emission trends matched observed winter and spring BB contributions, but conflictingly predicted similar levels of BB during the fall. Satellite fire data from MODIS and VIIRS suggested the use of higher spatial resolution fire data that might improve modeled BB emissions but were not able to explain the bulk of the discrepancy.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2020

Influence of Borate on Sorption of Strontium and Barium to Calcium Silicate Hydrate - 20148

Radioactive waste with the decommissioning process at the Fukushima Daiichi Nuclear Power Plant (FDNPP), contains borate with relatively high concentration. As with general low-level wastes, such waste is also assumed the solidification with cementitious materials which calcium silicate hydrate (C-S-H) is one of the main components. In this study, the sorption behavior of strontium (Sr) ions and barium (Ba) ions to C-S-H in the presence of borate was examined by the sorption experiments without drying process. In the sorption experiments, C-S-H was synthesized by the mixture of calcium oxide, fumed silica and a solution with setting the Ca/Si molar ratios to 0.4, 0.8, 1.2 and 1.6. The total amount of a solid phase was 1.5 g, and the total volume of the solution containing borate and adsorbed ions (Sr or Ba) was 30 mL. The concentration of borate was set to 0 M or 0.6 M and the sodium/boron (Na/B) ratios was set to 0.2 or 1.0 by mixing boric acid and sodium hydroxide. The concentration of Sr ions or Ba ions was adjusted to 1 mM. The sorption period was set to 7 days. In the results, the sorption ratios of Sr ions and Ba ions for C-S-H exceeded 80% under all experimental conditions, although the sorption competition of cations with Na ions and the inhibition of the C-S-H formation with generating borate compounds observed by Raman spectroscopy might slightly reduce the sorption of them. These suggest that cationic radionuclides will be immobilized by C-S-H contained in the cements even in the presence of borate. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2024

New insights into the flow dynamics of a deep freshwater aquifer in the semi-arid and saline Cuvelai-Etosha Basin, Northern Namibia: Results of a multi-environmental tracer study

Study region A paleo-megafan system of the Cubango River in the northern parts of the semi-arid Cuvelai-Etosha Basin, shared by Angola and Namibia. It hosts a deep freshwater aquifer, the so-called Kalahari-Ohangwena 2 (KOH-2), with the potential to resolve the imminent regional water supply shortages. Study focus Hydrogeochemical and multi-environmental tracer studies incorporating the use of age tracers 14 C, 36 Cl, 81 Kr and 4 He to determine the age of groundwater and provide insights into the flow dynamics of the KOH-2. New hydrological insights for the region Stable water isotopes and noble gas thermometry show that in a period with higher rainfall and recharge, temperatures were at least 3 – 4 °C lower than today. Several arguments led to the conclusion that younger groundwater, possibly of an age of 35,000 years, is mixed with ancient saline pore water. These include: 1) the correlation of measured 36 Cl and 81 Kr ratios, as well as 4 He concentrations, using a binary mixing model, and 2) the substantial variation in 81 Kr ages, ranging from 40,000 to 170,000 years, over relatively short distances—a phenomenon challenging to explain by advective groundwater flow equations. Consequently, the ages derived from 81 Kr measurements serve as indicators of the extent of freshening and therefore describe mixing ages rather than absolute travel times.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2022

Experimental quantification of the impact of heterogeneous mix on thermonuclear burn

In inertial confinement fusion, deuterium–tritium (DT) fuel is brought to densities and temperatures where fusion ignition occurs. However, mixing of the ablator material into the fuel may prevent ignition by diluting and cooling the fuel. MARBLE experiments at the National Ignition Facility provide new insight into how mixing affects thermonuclear burn. These experiments use laser-driven capsules containing deuterated plastic foam and tritium gas. Embedded within the foam are voids of known sizes and locations, which control the degree of heterogeneity of the fuel. Initially, the reactants are separated, with tritium concentrated in the voids and deuterium in the foam. During the implosion, mixing occurs between the foam and gas materials, leading to DT fusion reactions in the mixed region. Here, it is shown that by measuring the ratios of DT and deuterium–deuterium neutron yields for different macropore sizes and gas compositions, the effects of mix heterogeneity on thermonuclear burn may be quantified, supporting an improved understanding of these effects.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2024

Chemical properties and single-particle mixing state of soot aerosol in Houston during the TRACER campaign

Abstract. A high-resolution soot particle aerosol mass spectrometer (SP-AMS) was used to selectively measure refractory black carbon (rBC) and its associated coating material using both the ensemble size-resolved mass spectral mode and the event trigger single particle (ETSP) mode in Houston, Texas, in summer 2022. This study was conducted as part of the Department of Energy Atmospheric Radiation Measurement (ARM) program's TRacking Aerosol Convection interactions ExpeRiment (TRACER) field campaign. The study revealed an average (±1σ) rBC concentration of 103 ± 176 ng m−3. Additionally, the coatings on the BC particles were primarily composed of organics (59 %; 219 ± 260 ng m−3) and sulfate (26 %; 94 ± 55 ng m−3). Positive matrix factorization (PMF) analysis of the ensemble mass spectra of BC-containing particles resolved four distinct types of soot aerosol, including an oxidized organic aerosol (OOABC,PMF) factor associated with processed primary organic aerosol, an inorganic sulfate factor (SO4,BC,PMF), an oxidized rBC factor (O-BCPMF), and a mixed mineral dust–biomass burning aerosol factor with significant contribution from potassium (K-BBBC,PMF). Additionally, K-means clustering analysis of the single-particle mass spectra identified eight different clusters, including soot particles enriched in hydrocarbon-like organic aerosol (HOABC,ETSP), sulfate (SO4,BC,ETSP), two types of rBC, OOA (OOABC,ETSP), chloride (ClBC,ETSP), and nitrate (NO3,BC,ETSP). The single-particle measurements demonstrate substantial variation in BC coating thickness with coating-to-rBC mass ratios ranging from 0.1 to 100. The mixing state index (χ), which denotes the degree of homogeneity of the soot aerosol, varied from 4 % to 94 % with a median of 40 %, indicating that the aerosol population lies in between internal and external mixing but has large temporal and source type variability. In addition, a significant fraction of BC-containing particles, a majority enriched with oxidized organics and sulfate, exhibit sufficiently high κ values and diameters conducive to activation as cloud nuclei under atmospherically relevant supersaturation conditions. This finding bears significance in comprehending the aging processes of rBC-containing particles and their activation into cloud droplets. Our analysis highlights the complex nature of soot aerosol and underscores the need to comprehend its variability across different environments for accurate assessment of climate change.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2022

The Effects of Mixing Multi-Component HLW Glasses on Spinel Crystal Size

The Hanford Waste Treatment and Immobilization Plant will vitrify radioactive waste into borosilicate glass. The high-level waste (HLW) glass formulations are constrained by processing and property requirements, including restrictions aimed at avoiding detrimental impacts of spinel crystallization in the melter. To understand the impact of glass chemistry on crystallization, two HLW glasses precipitating small (?5 µm) spinel crystals were individually mixed with a glass that precipitated large (?45 µm) spinel crystals in ratios of 25, 50, and 75 wt%. The size of spinel crystals in the mixed glasses varied from 5 to 20 µm. Small crystal size was attributed to: (1) high concentrations of nuclei due to the presence of ruthenium oxide and (2) chromium oxide aiding high rates of nucleation. Results indicate that the spinel crystal size can be controlled using chromium oxide and/or noble metal concentrations in the melt, even in complex mixtures like HLW glasses. Small crystals tend to settle slowly, so they are acceptable in the melter without a risk of failure. Allowing higher concentrations of spinel-forming waste components in the waste glass enables glass compositions with higher waste loading, thus increasing plant operational flexibility. An additional benefit to the presence of chromium oxide in the glass composition is the potential for the oxide to protect melter walls against corrosion.

Lonergan, Charmayne E.↗

DOE OSTI2024

Shock-driven three-fluid mixing with various chevron interface configurations

When a shock wave crosses a density interface, the Richtmyer–Meshkov instability causes perturbations to grow. Richtmyer–Meshkov instabilities arise from the deposition of vorticity from the misaligned density and pressure gradients at the shock front. In many engineering applications, microscopic surface roughness will grow into multi-mode perturbations, inducing mixing between the fluid on either side of an initial interface. Applications often have multiple interfaces, some of which are close enough to interact in the later stages of instability growth. In this study, we numerically investigate the mixing of a three-layer system with periodic zigzag (or chevron) interfaces, calculating the dependence of the width and mass of mixed material on properties such as the shock timing, chevron amplitude, multi-mode perturbation spectrum, density ratio, and shock mach number. The multi-mode case is also compared with a single-mode perturbation. The Flash hydrodynamic code is used to solve the Euler equations in three dimensions with adaptive grid refinement. Key results include a significant increase in mixed mass when changing from a single-mode to a multi-mode perturbation on one of the interfaces. The mixed width is mainly sensitive to the density ratio and chevron amplitude, whereas the mixed mass also depends on the multi-mode spectrum. In conclusion, steeper initial perturbation spectra have lower mixed mass at early times but a greater mixed mass after the reflected shock transits back across the layer.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2023

Phase composition of polycrystalline HfNx (0.45 ≤ x ≤ 1.60) and effects of low-energy ion irradiation on microstructure, texture, and physical properties

We have investigated the phase composition of HfNx as a function of x and the effects of low-energy ion irradiation on the microstructure and physical properties of polycrystalline layers grown on SiO2 at 350 °C by ultrahigh vacuum reactive dc magnetron sputtering of Hf in mixed N2/Ar discharges. X-ray diffraction and Rutherford backscattering spectrometry results show that the phases obtained in polycrystalline HfNx layers with increasing x are hcp-structure α-Hf:N (x ≲ 0.6); multiphase mixtures consisting of α-Hf, NaCl-structure δ-HfN, rhombohedral ɛ-Hf3N2, and/or ζ-Hf4N3 (0.6 ≲ x ≲ 0.9); δ-HfN single phase (0.9 ≲ x ≲ 1.3); and mixtures of δ-HfN and higher nitrides (x ≳ 1.3). HfNx layers with 0.9 ≲ x ≲ 1.2 grown under mild ion irradiation (incident ion energy Ei ≃ 7 eV and ion-to-Hf flux ratios Ji/JHf = 1−3) are underdense with mixed orientation, low in-plane stress, and rough surface morphology due to limited adatom mobilities resulting in kinetic roughening and atomic shadowing during film growth. However, the use of intense ion irradiation (Ei = 25 eV and Ji/JHf = 4−20) results in HfNx layers, which are fully dense with strongly 111-oriented texture, compressive in-plane stress, and smooth surfaces due to ion irradiation enhanced adatom surface mobilities. In addition, the latter films have lower resistivity and higher hardness. For stoichiometric δ-HfN layers, ρ decreases from 69.7 to 35.2 μΩ cm and H increases from 22.1 to 27.4 GPa, with increasing ion-irradiation intensity. However, for HfNx layers with 1.2 ≲ x ≲ 1.6, the correspondingly higher steady state atomic N surface coverages during deposition alter growth kinetics in favor of 001 texture with a fully dense structure and compressive in-plane stress.

Materials Science↗

DOE OSTI2024

Numerical Mixing Suppresses Submesoscale Baroclinic Instabilities Over Sloping Bathymetry

Abstract The impacts of spurious numerical salinity mixing on the larger‐scale flow and tracer fields are characterized using idealized simulations. The idealized model is motivated by realistic simulations of the Texas‐Louisiana shelf and features oscillatory near‐inertial wind forcing. can exceed the physical mixing from the turbulence closure in frontal zones and within the mixed layer. This suggests that simulated mixing processes in frontal zones are driven largely by . Near‐inertial alongshore wind stress amplitude is varied to identify a base case that maximizes the ratio of to in simulations with no prescribed horizontal mixing. We then test the sensitivity of the base case with three tracer advection schemes (MPDATA, U3HC4, and HSIMT) and conduct ensemble runs with perturbed bathymetry. Instability growth is evaluated using the volume‐integrated eddy kinetic energy and available potential energy . While all schemes have similar total mixing, the HSIMT simulations have over double the volume‐integrated and 20% less relative to other schemes, which suppresses the release of and reduces the by roughly 25%. This results in reduced isohaline variability and steeper isopycnals, evidence that enhanced suppresses instability growth. Differences in and between the MPDATA and U3HC4 simulations are marginal. However, the U3HC4 simulations have 25% more . Experiments with variable horizontal viscosity and diffusivity coefficients show that small amounts of prescribed horizontal mixing improve the representation of the ocean state for all advection schemes by reducing the and increasing the .

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2025

Demonstration of a Novel Radiochemical Mix Diagnostic for Fusion Implosions at the National Ignition Facility

Mixing of the ablator material into the fuel of an inertial confinement fusion implosion reduces compression and enhances radiative losses, preventing ignition. Here, we describe a novel use of charged-particle radiochemistry to measure the ablator mix in contact with the fusion hot spot. The capsule uses a graded Be-Cr layer to increase the confinement of the hot spot. 52 Mn and 51 Cr isotopes are collected from the implosion and counted, and the ratio is related to the amount of Cr mixed into the hot spot. Thus, a new diagnostic to determine the degradation due to mix on fusion implosions has been developed.

MacLaren, S. A. [Lawrence Livermore National Labor↗

DOE OSTI2024

Understanding the ignition process and flame structure of conventional and oxygenated fuels under engine relevant conditions – An optical study

Renewably generated synthetic fuels such as poly-oxymethylene ethers (OME) have a significant potential to effectively break the soot-NOX trade-off in compression ignition engines by using exhaust gas recirculation (EGR) to maintain low nitrogen oxide (NOX) emissions while maintaining good efficiency and simultaneously contributing to circular carbon economy. However, owing to the fundamental differences in properties of OME when compared to fossil-based diesel fuels, it is critical to fully understand its ignition and combustion phenomenology to take advantage of this fuel to its utmost potential. In this context, this work outlines the results of a systematic experimental study performed in a heavy-duty, single-cylinder, optical engine probing the spatial and temporal progression of fuel decomposition and ignition behavior of OME when compared to n-dodecane, a diesel-fuel surrogate. Thermodynamic analysis and optical diagnostics techniques including simultaneous HCHO-PLIF and OH-PLIF complemented by high-speed OH* chemiluminescence were employed along with parametric sweeps of intake temperature and EGR dilution rates. OME does not exhibit any observable low temperature heat release irrespective of the ambient oxygen concentration. Differences in the observed diffusive flame structure such as longer flame lift-off length, less pronounced combustion recession, faster premixed burn at ignition (“volumetric” ignition), non-sooting behavior suggest that the inherent presence of fuel-bound oxygen in OME can skew the air-fuel ratio (AFR) distribution within the jet thereby reducing the reliance of combustion on mixing and air entrainment. This leads to rapid late-cycle oxidation leading to shorter combustion duration and favorable combustion phasing. Results also suggest that OME exhibits relatively weak negative temperature coefficient (NTC) behavior, however, the OME fuel-decomposition kinetic-pathways produce significant concentration of HCHO, which might be erroneously interpreted as a product of cool-flames.

Air-fuel ratio↗