PERFORMANCE AND CONTROL OF THE PRIMARY HEAT EXCHANGER IN A CLOSED-LOOP SCO2 BRAYTON CYCLE WITH SOLID FUEL COMBUSTION
Performance of a solid fuel primary heat exchanger in a closed loop sCO2 cycle
20 FOSSIL-FUELED POWER PLANTS↗
SEARCH · Engineering Papers
Results for “fuel combustion”
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.
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Exploring the potential benefits of high-efficiency dual-fuel combustion on a heavy-duty multi-cylinder engine for SuperTruck I
In support of the Daimler SuperTruck I team’s 55% brake thermal efficiency (BTE) pathway goal, researchers at Oak Ridge National Laboratory performed an experimental investigation of the potential efficiency and emissions benefits of dual-fuel advanced combustion approaches on a modified heavy-duty 15-L Detroit™ DD15 engine. For this work, a natural gas port fuel injection system with an independent injection control for each cylinder was added to the DD15 engine. For the dual-fuel strategies investigated, 65%–90% of the total fuel energy was supplied through the added port fuel injection natural gas (NG) fueling system. The remaining fuel energy was supplied by one or more direct injections of diesel fuel using the production high pressure diesel fueling system. The production DD15 air handling system and combustion geometry were unmodified for this study. Efficiency and emissions with dual-fuel strategies including both low temperature combustion (LTC) and non-LTC approaches such as dual fuel direct-injection were investigated along with control authority over combustion phasing. Parametric studies of dual-fuel NG/diesel advanced combustion were conducted in order to experimentally investigate the potential of high-efficiency, dual-fuel combustion strategies to improve BTE in a multi-cylinder engine, understand the potential reductions in engine-out emissions, and characterize the range of combustion phasing controllability. Characterization of mode transitions from mixing-controlled diesel pilot ignition to kinetically controlled ignition is presented. Key findings from this study included a reproducible demonstration of BTE approaching 48% at up to a 13-bar brake mean effective pressure with significant reductions in engine-out NOx and soot emissions. Additional results from investigating load transients in dual-fuel mode and initial characterization of particle size distribution during dual-fuel operation are presented.
33 ADVANCED PROPULSION SYSTEMS↗
Hybrid rocket fuel combustion and regression rate study
The objectives of this study are to develop hybrid fuels (1) with higher regression rates and reduced dependence on fuel grain geometry and (2) that maximize potential specific impulse using low-cost materials. A hybrid slab window motor system was developed to screen candidate fuels - their combustion behavior and regression rate. Combustion behavior diagnostics consisted of video and high speed motion pictures coverage. The mean fuel regression rates were determined by before and after measurements of the fuel slabs. The fuel for this initial investigation consisted of hydroxyl-terminated polybutadiene binder with coal and aluminum fillers. At low oxidizer flux levels (and corresponding fuel regression rates) the filled-binder fuels burn in a layered fashion, forming an aluminum containing binder/coal surface melt that, in turn, forms into filigrees or flakes that are stripped off by the crossflow. This melt process appears to diminish with increasing oxidizer flux level. Heat transfer by radiation is a significant contributor, producing the desired increase in magnitude and reduction in flow dependency (power law exponent) of the fuel regression rate.
Strand, L. D.↗
A Comparative Experimental Analysis of Natural Gas Dual Fuel Combustion Ignited by Diesel and Poly OxyMethylene Dimethyl Ether
Dual-fuel low-temperature combustion is a possible solution for alleviating the tradeoff between oxides of nitrogen and soot emissions in conventional diesel combustion, albeit with poor combustion stability, high carbon monoxide, and unburned hydrocarbon emissions at low engine loads. The present work compares emissions and combustion (heat release and other metrics) of both diesel and poly-oxy methylene dimethyl ether as high-reactivity fuels to ignite natural gas while leveraging spray-targeted reactivity stratification, which involved multiple injections of the high-reactivity fuels. The experiments included six parametric sweeps of: (1) start of first injection, (2) start of second injection, (3) percentage of energy substitution of natural gas, (4) commanded injection duration ratio, (5) rail pressure, and (6) intake pressure. The experiments were performed on a 1.8 L heavy-duty single-cylinder research engine operating at a medium speed of 1339 rev/min. Not-to-exceed limits for the indicated oxides of nitrogen emissions, maximum pressure rise rate, and the coefficient of variation of the indicated mean effective pressure were set to 1 g/kWh, 10 bar/CAD, and 10%, respectively. The indicated emissions decreased and combustion improved significantly for both fueling combinations when the experimental procedure was applied.
Partridge, Kendyl Ryan↗
Fuel Vapor Pressures and the Relation of Vapor Pressure to the Preparation of Fuel for Combustion in Fuel Injection Engines
This investigation on the vapor pressure of fuels was conducted in connection with the general research on combustion in fuel injection engines. The purpose of the investigation was to study the effects of high temperatures such as exist during the first stages of injection on the vapor pressures of several fuels and certain fuel mixtures, and the relation of these vapor pressures to the preparation of the fuel for combustion in high-speed fuel injection engines.
Joachim, William F↗
Editorial: Particulate Matter Emissions From Conventional and Reformulated Fuel Combustion: Advances in Experiments and Simulations
Particulate matter (PM or soot) emissions generated by combustion of conventional and reformulated fuels adversely impact the environment and human health (Bond et al., 2013; Landrigan et al., 2018; World Health Organization (WHO), 2016), generating public awareness and motivating efforts towards the mitigation of their harmful effects. Soot formation is one of the most complex phenomena in combustion, involving interactions between combustion chemistry, fluid mechanics, mass/heat transport, and particle dynamics, spanning different spatial and temporal scales. A fundamental understanding of soot formation process is thus necessary to achieve a strong reduction of PM emissions and design cleaner and more efficient combustion systems. This has motivated a longstanding and ongoing research activity aimed at improving our understanding of the physical and chemical processes involved in soot formation, well reviewed in these recent works (Wang and Chung, 2019; Michelsen et al., 2020; Martin et al., 2022). Despite the wide interest, the transition from gas-phase molecules to incipient soot particles is still elusive and the successive particle growth and oxidation processes are far from being fully understood, especially in conditions relevant to real-world applications. Recent advances in combustion PM emission diagnostic and computational capabilities helped in improving the predictability of fundamental chemical and aerosol models for practical applications, thus tackling some of the above-mentioned challenges. The aim of this research topic is to display the ongoing research efforts in addressing the existing gaps on particulate formation from various fuel sources and in conditions typical of practical combustion applications (e.g. flames, engines, pool fires), through both experimental and numerical approaches.
42 ENGINEERING↗
NASA/General Electric broad-specification fuels combustion technology program, phase 1
The use of broad specification fuels in aircraft turbine engine combustion systems was examined. Three different combustor design concepts were evaluated for their ability to use broad specification fuels while meeting several specific emissions, performance, and durability goals. These combustor concepts covered a range from those having limited complexity and relatively low technical risk to those having high potential for achieving all of the program goals at the expense of increased technical risk.
Dodds, W. J.↗
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)↗
Fire on the Moon: Solid Fuel Combustion Experiments
As NASA plans to return people to the Moon for extended durations, we present an experiment concept to understand fire and material flammability there. A small combustion chamber would be used to conduct the first-ever combustion tests on another world. Multiple fuel samples are to be individually burned in Lunar gravity, with cameras and other sensors recording flame characteristics. The main hypothesis is that some materials burning in Lunar-g are more flammable than on Earth. The reason is that buoyant flow has two counteracting effects on material flammability. Increasing gravity level permits more fresh oxygen to be supplied to the flame, but if the buoyant speed is too high, combustion chemistry and increased cooling hinder combustion. This has important implications for the current 1-g material screening method used by NASA. Oxygen limits for upward and downward spread on the Moon will be compared to 1-g values. Earth-based partial gravity facilities (drop towers, aircraft, and sounding rockets) will be used to refine the experiment and provide some limited-duration data. Measured flame characteristics in 1-g and Lunar-g will be compared to a detailed model. These will refine pressure-gravity scaling relations that will then be applied to other g-levels. The work directly addresses knowledge gaps in flammability and crew safety as defined in several NASA strategic documents.
Fire↗
Reduced Gravity Studies of Soret Transport Effects in Liquid Fuel Combustion
Soret transport, which is mass transport driven by thermal gradients, can be important in practical flames as well as laboratory flames by influencing transport of low molecular weight species (e.g., monatomic and diatomic hydrogen). In addition, gas-phase Soret transport of high molecular weight fuel species that are present in practical liquid fuels (e.g., octane or methanol) can be significant in practical flames (Rosner et al., 2000; Dakhlia et al., 2002) and in high pressure droplet evaporation (Curtis and Farrell, 1992), and it has also been shown that Soret transport effects can be important in determining oxygen diffusion rates in certain classes of microgravity droplet combustion experiments (Aharon and Shaw, 1998). It is thus useful to obtain information on flames under conditions where Soret effects can be clearly observed. This research is concerned with investigating effects of Soret transport on combustion of liquid fuels, in particular liquid fuel droplets. Reduced-gravity is employed to provide an ideal (spherically-symmetrical) experimental model with which to investigate effects of Soret transport on combustion. The research will involve performing reduced-gravity experiments on combustion of liquid fuel droplets in environments where Soret effects significantly influence transport of fuel and oxygen to flame zones. Experiments will also be performed where Soret effects are not expected to be important. Droplets initially in the 0.5 to 1 mm size range will be burned. Data will be obtained on influences of Soret transport on combustion characteristics (e.g., droplet burning rates, droplet lifetimes, gas-phase extinction, and transient flame behaviors) under simplified geometrical conditions that are most amenable to theoretical modeling (i.e., spherical symmetry). The experiments will be compared with existing theoretical models as well as new models that will be developed. Normal gravity experiments will also be performed.
Shaw, Benjamin D.↗
Parametric study of the generation of pressure waves by particle-fueled combustion.
Generation of pressure wave by explosion of condensed phase fuel particles dispersed in gaseous oxidizer
FLOW FIELD↗
The NASA broad specification fuels combustion technology program at Pratt and Whitney
The technology required to accommodate the use of broadened properties fuels in commercial aircraft engine combustors with minimum impact on the emissions, performance, durability and engine operational characteristics is discussed. Emphasis was placed on defining the potential for reducing the fuel sensitivity of the reference combustion system through design refinements and the introduction of more advanced technology combustors. To this end the tests conducted included the evaluation of variations of three different combustor concepts representing progressively more advanced technology levels. It was demonstrated that reduced fuel hydrogen content has adverse impacts on current single stage combustors; the best opportunities for reducing the fuel sensitivity of these combustors are through improved fuel injectors and advanced liner cooling and structural concepts and that the advanced technology staged and variable geometry combustor concepts have inherent operational flexibility that can be exploited to accommodate changes in fuel composition. Also, advanced technology combustor concepts were evaluated. A variable geometry combustor capable of airflow modulation during operation and a new concept which is a further evolution of the Vorbix combustor are discussed.
Lohmann, R. P.↗
The NASA broad-specification fuels combustion technology program: An assessment of phase 1 test results
An assessment is made of the results of Phase 1 screening testing of current and advanced combustion system concepts using several broadened-properties fuels. The severity of each of several fuels-properties effects on combustor performance or liner life is discussed, as well as design techniques with the potential to offset these adverse effects. The selection of concepts to be pursued in Phase 2 refinement testing is described. This selection takes into account the relative costs and complexities of the concepts, the current outlook on pollutant emissions control, and practical operational problems.
Fear, J. S.↗
Pressure wave generation in particle-fueled combustion systems. I - Parametric study.
Generation of pressure wave by explosion of condensed phase fuel particles dispersed in gaseous oxidizer
COMBUSTION WAVE↗
Broad Specification Fuels Combustion Technology Program, Phase 2
An experimental evaluation of two advanced technology combustor concepts was conducted to evolve and assess their capability for operation on broadened properties fuels. The concepts were based on the results of Phase 1 of the Broad Specification Fuel Combustor Technology Program which indicated that combustors with variable geometry or staged combustion zones had a flexibility of operation that could facilitate operation on these fuels. Emphasis in defining these concepts included the use of single pipe as opposed to duplex or staged fuels systems to avoid the risk of coking associated with the reduction in thermal stability expected in broadened properties fuels. The first concept was a variable geometry combustor in which the airflow into the primary zone could be altered through valves on the front while the second was an outgrowth of the staged Vorbix combustor, evolved under the NASA/P&W ECCP and EEE programs incorporating simplified fuel and air introduction. The results of the investigation, which involved the use of Experimental Referee Broad Specification (ERBS) fuel, indicated that in the form initially conceived, both of these combustor concepts were deficient in performance relative to many of the program goals for performance emissions. However, variations of both combustors were evaluated that incorporated features to simulate conceptual enhancement to demonstrate the long range potential of the combustor. In both cases, significant improvements relative to the program goals were observed.
Lohmann, R. P.↗
Generation of flow fields in particle fueled combustion systems Technical note no. 1
Dynamic properties of explosion in medium consisting of condensed phase fuel particles dispersed in gaseous oxidizer
GAS PHASE↗
The broadened-specification fuels combustion technology program at Pratt and Whitney Aircraft
The impact of the use of broadened specification fuels on combustor design was investigated. Particular emphasis was placed on establishing the viability of various combustor modifications to permit the use of broadened specification fuels while meeting exhaust emissions and performance specifications and maintaining acceptable combustor operational and durability characteristics. Three different combustor concepts will be evaluated. Various design modifications on the operating capability of each of the combustor concepts with experimental referee broadened specification Fuel. The modifications that were evaluated included perturbations of the combustor airflow schedules to alter local stoichiometry and residence time histories revisions to the fuel injectors, and variations in liner cooling including the use of thermal barrier coatings and/or advanced cooling concepts.
Lohmann, R. P.↗
Diesel-like Fuels, Combustion, and Emissions
The need to reduce the carbon footprint from medium- and heavy-duty diesel engines is clear; low-carbon biofuels are a powerful means to achieve this. Liquid fuels are rapidly deployed because existing infrastructure can be utilized for their production, transport, and distribution. Their impact is unique as they can decrease the greenhouse gas (GHG) emissions of existing vehicles and in applications resistant to electrification. However, introducing new diesel-like bio-blends into the market is very challenging. At a minimum, it requires a comprehensive understanding of the life-cycle GHG emissions of the fuels, the implications for refinery optimization and economics, the fuel’s impact on the infrastructure, the effect on the combustion performance of current and future vehicle fleets, and finally the implications for exhaust aftertreatment systems and compliance with emissions regulations. Such understanding is sought within the Co-Optima project.
02 PETROLEUM↗