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At least 397 records · Page 22

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DOE OSTI2022

Thermal barrier coatings for internal combustion engines

A thermal barrier coating for an internal combustion engine includes an insulating thermal spray coating, where a chosen material of the insulating thermal spray coating has a thermal conductivity lower than 2 W/mK in fully dense form and the chosen material includes a coefficient of thermal expansion within 5 ppm/K of a coefficient of thermal expansion of a material of a component of the internal combustion engine upon which the coating is placed.

Jordan, Eric↗

DOE OSTI2022

System and method for combustion of non-gaseous fuels and derivatives thereof

The present disclosure relates to apparatuses and methods that are useful for one or more aspects of a power production plant. More particularly, the disclosure relates to combustor apparatuses and methods for a combustor adapted to utilize different fuel mixtures derived from gasification of a solid fuel. Combustion of the different fuel mixtures within the combustor can be facilitated by arranging elements of the combustor controlled so that a defined set of combustion characteristics remains substantially constant across a range of different fuel mixtures.

Fetvedt, Jeremy Eron↗

DOE OSTI2022

Passive selective catalytic reduction (SCR) system and method for low-temperature combustion (LTC) engine

A combustion mode module is configured to switch operation of a low-temperature combustion (LTC) engine between a spark ignition (SI) mode, a positive valve overlap (PVO) mode, and a negative valve overlap (NVO) mode. A spark control module is configured to control a spark plug to generate a spark in a cylinder of the LTC engine when the LTC engine is operating in the SI mode. A valve control module is configured to control intake and exhaust valves of the cylinder to yield a PVO and a NVO when the LTC engine is operating in the PVO mode and the NVO mode, respectively. An air/fuel (A/F) control module is configured to adjust a desired A/F ratio of the LTC engine to a rich A/F ratio when operation of the LTC engine is switched to the PVO mode from either one of the SI mode and the NVO mode.

Yun, Hanho↗

DOE OSTI2022

Thermal barrier coatings for internal combustion engines

Jordan, Eric↗

DOE OSTI2022

Combustion Characteristics of a Tier II Gasoline Certification Fuel and its Surrogate with Iso-butanol: experiments and detailed numerical modeling

This presentation will describe results of an experimental and numerical study of combustion of a Tier II gasoline certification fuel and its surrogate blended with iso-butanol as a potential biofuel additive. The experiments were carried out under conditions where gas transport originated entirely by fuel evaporation with external convection (both forced and natural) were minimized. The resulting near spherically symmetric droplet flames were amenable to detailed numerical modeling. The droplet initial diameters were in the narrow range of 0.55 mm to 0.62 mm while and burning is performed under standard atmosphere. The combustion characteristics such as evolution of droplet, flame and soot shell diameters for indolene/iso-butanol and surrogate/iso-butanol mixtures are compared. The presence of iso-butanol is experimentally found to reduce the formation of soot as the iso-butanol concentration was increased. Simulations are also reported using a detailed kinetic chemistry comprised of 324 species and 17608 reactions using the CRECK POLIMI mechanism. The detailed numerical model included unsteady gas and liquid transport, soot chemistry and radiative transport. Droplet burn rates were well predicted while flame diameters showed more variability depending on how the flame was defined in the numerical simulation (peak gas temperature and OH concentration). Simulations also show the influence of iso-butanol concentration on flame temperature, greenhouse gas emissions and particulate emissions.

Guo, Songtao↗

DOE OSTI2022

Experiments and numerical modeling of surrogate droplet combustion for a 93 octane gasoline calibration fuel

Gasoline is the world’s most prolific liquid transportation fuel for ground transportation vehicles. Yet, a fundamental understanding of its burning characteristics is still lacking. Complicating this matter is the highly multicomponent nature of gasoline (comprised of hundreds of chemical species) and the seasonable variability of its composition due to variations in the crude oil feedstocks used in refining. The need to bring order to this complex problem has led to development of calibration fuels (Tier II in presented study) which on average will provide repeatable metrics that replicate performance of refined gasoline for various engine designs. This study presents results of experiments using the configuration of an isolated droplet to study the combustion dynamics of calibration fuel and three different surrogates (S4, S5, S6) for the calibration fuel. Droplet burning is under microgravity conditions, where gas transport is determined entirely by fuel evaporation in order to promote spherical symmetry in the burning process. The initial droplet diameters ranged between 0.55 mm and 0.60 mm. The droplets were spark-ignited and their burning histories were recorded by digital video cameras to obtain quantitative data. For each fuel, the evolutions of droplet, flame, and soot-shell diameters were measured to calculate the burn rates, flame-droplet diameter ratios (FSR) and soot-droplet diameter ratios. Additionally, a detailed numerical modeling is presented. This simulation includes multicomponent phase equilibrium, unsteady gas and liquid transport, radiative heat transfer, internal liquid diffusion and detailed combustion chemistry of different fuels during their burning process. Experiment results show that the calibration fuel and surrogates have a close burn rates and FSR, and S5 presents a relatively similar results with calibration fuel. Predictions from the numerical simulation using the surrogate are compared with experiment measurements, which showed a good agreement with the experiment results, including the droplet burning rate and FSR.

Guo, Songtao↗

DOE OSTI2023

Combustion control using spiking neural networks

A system that controls a combustion engine stores network vectors in a memory that represent diverse and distinct spiking neural networks. The system decodes the network vectors and trains and evaluates the spiking neural networks. The system duplicates selected network vectors and crosses-over the duplicated network vectors that represent modified spiking neural networks. The system mutates the crossed-over duplicated network vectors by randomly modifying one or more portions of the crossing-over duplicated network vectors. The system meter exhaust gas into an intake manifold when an engine temperature exceeds a threshold, an engine load exceeds a threshold, an engine's rotation-per-minute rate exceeds a threshold, and a fuel flow exceeds a threshold. The system modifies fuel flow into an engine's combustion chamber on a cycle-to-cycle basis by the trained spiking neural network.

Puente, Brian P. Maldonado↗

DOE OSTI2023

Fuel and fuel blend for internal combustion engine

A fuel or fuel blending agent for an internal combustion engine includes a ketone compound that is a C 4 to C 10 branched acyclic ketone, cyclopentanone, or a derivative of cyclopentanone. The ketone compound may be blended with a majority portion of a fuel selected from the group consisting of: gasoline, diesel, alcohol fuel, biofuel, renewable fuel, Fischer-Tropsch fuel, or combinations thereof. The ketone compound may be derived from biological sources. A method for powering an internal combustion engine with a fuel comprising the ketone compound is also provided.

Dec, John E.↗

DOE OSTI2023

Method of transient control for robust enrichment operation in low temperature combustion engine

A method of transient control for enrichment operation in a low-temperature combustion engine. The method includes determining if a current mode of the low-temperature combustion (LTC) engine is a positive valve overlap (PVO) mode. Determining if a previous mode of the LTC engine was also the PVO mode when the current mode is the PVO mode, wherein the previous mode is immediately prior to the current mode. Determining if the previous mode of the LTC engine was a negative valve overlap (NVO) mode when the previous mode was not the PVO mode. Initiating a predetermined enrichment PVO mode for the LTC engine based on the previous mode of the LTC engine. The predetermined enrichment PVO mode includes initiating a deep enrichment PVO mode, when the previous mode of the LTC engine was the NVO mode, and initiating a shallow enrichment PVO mode, when the previous mode of the LTC engine was not the NVO mode.

Yun, Hanho↗

DOE OSTI2023

Energy Arbitrage with Hydrogen: HTSE + Combustion Turbine

The Light Water Reactor Sustainability (LWRS) program seeks to keep Nuclear Power Plants (NPPs) competitive in the changing energy market. The Flexible Plant Operation and Generation (FPOG) pathway investigates Energy Storage Systems (ESS) to give operators an alternative to curtailment or paying to put power on the grid. This work investigates the concept of diverting heat and electricity to High Temperature Steam Electrolysis (HTSE) to produce hydrogen when grid demand is low, storing that hydrogen, then burning it in a combustion turbine to produce zero-emission electricity when grid demand is high. A process model of the combustion turbine was developed in Aspen HYSYS, which was used to complete a parametric analysis and techno-economic analysis.

08 HYDROGEN↗

DOE OSTI2022

Influence of gasoline fuel formulation on lean autoignition in a mixed-mode-combustion (deflagration/autoignition) engine

We report stoichiometric spark-ignition engines suffer efficiency penalties due to throttling losses at low loads, a low specific-heat ratio of the stoichiometric working fluid, and limits on compression ratio due to end-gas autoignition leading to undesirable knocking. Mixed-Mode Combustion (MMC) mitigates these shortcomings by using a lean working fluid where a spark-initiated pilot-stabilized deflagrative flame front is followed by controlled end-gas autoignition. This MMC study investigates the effects of initial conditions (intake air temperature, intake pressure, equivalence ratio, and intake oxygen fraction) on autoignition tendency of four gasoline-range fuels with varying properties and composition. The use of fuels with varying octane sensitivity (S) allowed exploring the importance of low-temperature heat release in triggering autoignition. Fuels with high S were less reactive for conditions that promote low-temperature chemistry (operation at high intake air pressure or without N2 dilution). Conversely, an Alkylate fuel with low S showed a greater autoignition resistance at operating conditions that were unfavorable for low-temperature chemistry. Next, the effect of residual gas composition on autoignition tendency of fuels was examined with a chemical-kinetics model. Among the various molecules in the residual gas, nitric oxide (NO) enhanced the low-temperature chemistry and increased the autoignition tendency most significantly. The fuels’ autoignition response to increasing NO amount corroborates the experimental observations. Next, the sequential autoignition of the end-gas was assessed to be less impacted by thermal stratification because of lean mixtures showing relatively less low-temperature chemistry, when compared to stoichiometric mixtures. Next, the effect of changing equivalence ratio on the autoignition was found to be similar for all fuels, regardless of their S. With changing intake air temperature, the response of fuels’ autoignition tendency depended on the dilution level used. At high dilution (i.e. low intake [O2]), fuels’ reactivity increased with increasing intake air temperature. In contrast, for operation without dilution, the autoignition tendency of the low-S Alkylate fuel decreased with increasing intake air temperature, while that of high-S High Cycloalkane fuel still increased with increasing intake air temperature. In conclusion, conventional octane metrics (RON and MON) have utility in assessing the autoignition tendency under lean MMC operation. Moreover, the fuel requirements for MMC align with that of stoichiometric operation: i.e., high RON and high S fuels are desirable for stable non-knocking operation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2021

Rapid prediction of fuel research octane number and octane sensitivity using the AFIDA constant-volume combustion chamber

Current research octane number (RON) and motor octane number (MON) gasoline performance characterization techniques use dated, complex engine testing methodology and limit researchers’ ability to easily characterize small volumes of experimental fuels. A novel methodology is presented that correlates measured ignition delay (ID) time to RON in an Advanced Fuel Ignition Delay Analyzer (AFIDA) constant-volume combustion chamber device at a single pressure/temperature condition, with an r2 of 0.99 and standard error (SE) of 1.0. The correlation of the slope of the ID time between two additional temperature points to octane sensitivity (S) produces an r2 of 0.97 and SE of 0.69; however, fuels with S>12 are indistinguishable. These results are based on methodology calibration using 31 primary and toluene reference fuels containing 0%-40% ethanol with RON values ranging from 85 to 113. Validation of these methods using a 102-sample fuel matrix spanning an array of base fuels and additive chemistry designed to test the robust applicability of the method, along with pump gasoline and high-octane surrogate blend samples, demonstrates an r2 of 0.94 and SE of 1.3 for the RON correlation over all samples, whereas the equivalent S correlation produces an r2 of 0.78 and SE of 1.2 by excluding two additives, 3-pentanone and diisobutylene, which displayed poor S correlation results. This novel AFIDA analysis method can be performed in 1 h and with 40 mL of fuel, offering significant improvements in time and volume requirements over traditional techniques.

33 ADVANCED PROPULSION SYSTEMS↗

DOE OSTI2025

Chemical Reactor Network Modeling of Ammonia Rich-Quench-Lean Combustion Using a Partially Stirred Reactor Approach

Ammonia is a promising alternative fuel, but its use is challenging due to low flammability and high nitrogen oxide (NOx) emissions. Two-stage rich-quench-lean (RQL) combustion strategies have shown promise in reducing NOx emissions. This approach involves two stages: a rich stage that oxidizes part of the fuel and decomposes ammonia into hydrogen, and a lean stage that burns out the hydrogen and residual ammonia. Researchers used a chemical reactor network model to study the effects of heat loss and mixing on emissions performance. They found that heat loss and reduced mixing rates can lead to increased NOx emissions and N2O formation. The results will inform the development of optimized two-stage RQL combustors for ammonia, with a focus on minimizing NOx emissions and improving overall efficiency.

ammonia combustion↗

DOE OSTI2021

Development of CuFeMnAlO 4+δ oxygen carrier with high attrition resistance and 50-kWth methane/air chemical looping combustion tests

A Copper-Ferri-Manganese-Aluminate spinel (CuFeMnAlO 4+δ ) oxygen carrier, developed at the US Department of Energy’s (DOE) National Energy Technology Laboratory (NETL), shows promising results for chemical looping combustion with methane. Attrition resistance of the spinel oxygen carrier (160–600 µm) produced by a wet agglomeration method was significantly higher than that observed previously with a Copper-Ferri-Aluminate (CuFeAlO 4 ) oxygen carrier. Improved attrition resistance of the novel carrier can be attributed to minimal alumina phase segregation and minimal carbon formation. Heats of reaction measured by differential scanning calorimetry indicated exothermicity during reduction with methane. The total oxygen transfer capacity of the material was about 10.5 wt% at 850 °C. The attrition resistance and the oxygen transfer capacity of the carrier prepared at a commercial manufacturing facility (180 kg) were very similar to observed values during the development phase with the lab scale preparations. The material displays satisfactory methane conversion and significantly high particle durability during a 54 h test campaign conducted in NETL’s 50-kWth chemical looping dual fluid bed reactor unit at temperatures ranging from 700 to 900 °C. Low oxygen carrier make-up cost, due to the use of natural ore and pigment grade raw materials during synthesis and very low attrition rates, exceeded the performance goals determined by systems studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Chemical looping combustion oxygen carrier production cost study

The objective of this study was to estimate the cost of commercial production of oxygen carriers (OCs) for large-scale application in a mature, chemical looping combustion (CLC) power generation industry. Estimates of cost were made for two production facility scenarios: 1) build and operate an on-site, OC production facility located at a 550 MW CLC power plant site; and 2) build and operate a central production facility to produce and distribute OCs to the U.S. CLC power generation industry. Two OC production techniques were addressed: mechanical mixing and co-precipitation. Representative OCs that have production raw materials with sufficient commercial availability to support a CLC industry are ilmenite, a natural OC, and four engineered OC types, Fe 2 O 3 -based, CuO-based, NiO-based, and CuFeAlO 4 -based, with candidate OC support materials Al 2 O 3 and TiO 2 . The costs of the OC production raw materials represent the major portion of the OC product cost; the OC production cost, in dollars per kg, has been found to be nearly a linear function of the OC raw materials cost, in dollars per kg. In conclusion, the estimated OC product costs can be used to estimate the maximum OC loss rate yielding a designated CLC power plant cost-of-electricity (COE) target as a development guide, and it has been found that the maximum OC makeup rate, in kg per hour, achieving a designated COE reduction goal relative to a conventional pulverized coal (PC) power plant, will be nearly inversely proportional to the OC production raw materials cost, in dollars per kg.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2022

Irradiation-induced amorphization of UO 2 films prepared by spraying-assisted combustion synthesis

Spraying-assisted combustion synthesis with uranyl nitrate – acetylacetone – 2-methoxyethanol solutions was used to prepare UO 2 films on an aluminum alloy substrate. The tuning of the spraying parameters and annealing temperatures allowed the preparation of UO 2 films with thicknesses varying from 10–300 nm and 5–10 nm UO 2 grain size. High-resolution electron microscopy and X-ray photoelectron spectroscopy showed that increasing the annealing temperature promotes Mg diffusion from the substrate into the films. The incorporation of Mg reduced the overall crystallinity of the films. The irradiation with Ar 2+ ions (1.7 MeV energy and a fluence of 2 × 10 16 ions/cm 2 ) did not degrade the quality of the films. However, the Mg content significantly influenced the irradiation-induced restructuring of the UO 2 films. Irradiated films with low or no Mg content exhibit high crystallinity, and the UO 2 /Al interfacial layer becomes highly porous. Films with higher Mg content are mostly amorphized after irradiation. The origin of irradiation-induced amorphization was related to the formation of Mg y U 1-y O 2±x solid solutions. Chemically complex, pore-free, and amorphous Mg-Al-O film/substrate interfacial layers enable continuous Mg diffusion during irradiation. As a result, the gradual increase in Mg amounts triggers irradiation-induced precipitation of a crystalline MgO-rich phase within the amorphous films.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2025

Biphasic solvents for post-combustion CO 2 capture from natural gas flue Gas

Fossil fuel fired power plants are generally expected to remain one of the most significant global sources of electricity for decades to come. Consequently, carbon management technologies are needed to reduce or eliminate ongoing emissions from these sources. Amongst the many techniques for carbon capture, aqueous amine-based absorbents (monoethanolamine, MEA, in particular) are, presently, considered the leading technology for post-combustion CO 2 point-source capture. These technologies are nevertheless limited by their high capital and regeneration energy costs. Biphasic solvents have been identified as an attractive alternative to traditional MEA based absorbents due to their potential energy savings. Thus far, however, the research on biphasic solvents has largely focused on their performance in coal flue gas while more dilute natural gas flue gas applications have received relatively little attention. Here, this work examines the performances of two novel biphasic solvent blends, diethylenetriamine (DETA) and triethylenetetramine (TETA), in CO 2 capture from a natural gas flue gas simulant. Across several regeneration tests, both solvents achieved considerable energy savings over the benchmark MEA solution. Specifically, the energy consumption per mol CO 2 recovered for the DETA-based and TETA-based solvents was 46 % and 35 % less than that of the benchmark MEA solution, respectively. Molecular dynamics simulations were also performed to gain a deeper understanding of the phase separation phenomena that occur as a consequence of CO 2 absorption. These simulations indicated that phase change was driven by the strong interaction between the absorption products and water, while the degree of separation depended on the CO 2 loading.

Biphasic solvents↗

DOE OSTI2024

Dielectric and magnetic properties of microwave-absorbing FeAl x O y catalysts fabricated via solution combustion synthesis

Iron-based alumina (FeAl x O y ) nanocomposites are microwave-absorbers and catalysts, which makes them promising for emerging microwave-assisted thermocatalytic technologies. Solution combustion synthesis (SCS) has been used to synthesize FeAl x O y powders, and prior work has demonstrated that adjusting SCS parameters significantly changes phase composition and specific surface area of the products. However, it is unclear how synthesis parameters affect their microwave-absorbing properties, which are essential for optimizing microwave-assisted technologies. To address this challenge, in the present work, twelve different FeAl x O y products were synthesized at different combinations of the SCS parameters such as two fuels (citric acid and glycine), two heating modes (hotplate and muffle furnace), and three Fe:Al molar ratios (2:1, 1:1, 1:2). Dielectric and magnetic properties of the products were characterized using a network analyzer and a vibrating sample magnetometer. Based on the measured permittivity and permeability, penetration depth and reflection loss were calculated as a function of frequency and bed thickness. The products were heated by microwaves at 2.45 GHz and then examined with X-ray diffraction (XRD) analysis. For all products, the magnetic saturation was lower than for bulk iron oxides because of the small crystallite size and aluminum substitution. The use of glycine induced high dielectric losses and enabled fast microwave-heating rates compared to citric acid. Higher Fe:Al ratio also led to higher dielectric and magnetic losses. With glycine fuel, SCS in a furnace induced larger penetration depth and lower microwave absorption than SCS on a hotplate. The minimization of reflected power was more sensitive to the thickness of the product bed than to the frequency of the electromagnetic field. Post-heating XRD analysis revealed different phase transformations in the FeAl x O y powders depending on the SCS parameters. As a result, an FeAl x O y material, synthesized via incipient wetness impregnation, lacked magnetic losses and did not heat well as compared to the SCS products.

Combustion synthesis↗