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At least 181 records · Page 10

Combustor exhaust-emissions and blowout-limits with diesel number 2 and Jet A fuels utilizing air-atomizing and pressure-atomizing nozzles

The effect of fuel properties on exhaust emissions and blowout limits of a high-pressure combustor segment is evaluated using a splash-groove air-atomizing fuel injector and a pressure-atomizing simplex fuel nozzle to burn both diesel number 2 and Jet A fuels. Exhaust emissions and blowout data are obtained and compared on the basis of the aromatic content and volatility of the two fuels. Exhaust smoke number and emission indices for oxides of nitrogen, carbon monoxide, and unburned hydrocarbons are determined for comparison. As compared to the pressure-atomizing nozzle, the air-atomizing nozzle is found to reduce nitrogen oxides by 20%, smoke number by 30%, carbon monoxide by 70%, and unburned hydrocarbons by 50% when used with diesel number 2 fuel. The higher concentration of aromatics and lower volatility of diesel number 2 fuel as compared to Jet A fuel appears to have the most detrimental effect on exhaust emissions. Smoke number and unburned hydrocarbons are twice as high with diesel number 2 as with Jet A fuel.

Ingebo, R. D.↗

Understanding Isomeric Effects on Properties of Aviation Fuels via a Group Contribution Method: Preprint

The molecular composition of aviation fuels, including conventional and sustainable aviation fuels (SAFs), significantly influences their performance, safety, and environmental impact. This study examines the effect of isomeric variation for compounds with the same carbon number and chemical family on key fuel properties, focusing on compounds commonly found in conventional jet fuels and SAFs. A group contribution method (GCM) is employed to predict thermophysical and combustion properties, providing an efficient analytical approach to evaluate the contributions of individual compounds to overall fuel mixture behavior. As part of this work, we introduce FuelLib, an open-source Python tool built around the GCM, to calculate individual compound and fuel mixture properties using various mixing rules. Our work evaluates whether the GCM can capture isomeric effects, that are often overlooked in traditional fuel property estimation. This is particularly important for SAFs, which often are composed of a more limited set of compound classes than conventional fuels, making isomeric differences more critical. Two-dimensional gas chromatography (GCxGC) data, which can be obtained from small fuel samples, provides weight percentages of compounds grouped by chemical family and carbon number rather than detailed information about individual compounds. As a result, assumptions must be made when decomposing GCxGC data into functional groups for GCM applications. Using GCxGC data, we show that the FuelLib tool can be used to predict the fuel properties of conventional jet fuels, with validation against experimental data. The provided tool enables researchers to predict fuel properties of candidate fuels and supports the design of new SAFs at both the component and mixture levels. This capability provides a foundation for studying fuel and combustion properties during SAF development, reducing reliance on costly experimental methods and advancing progress toward certification of new SAFs.The molecular composition of aviation fuels, including conventional and sustainable aviation fuels (SAFs), significantly influences their performance, safety, and environmental impact. This study examines the effect of isomeric variation for compounds with the same carbon number and chemical family on key fuel properties, focusing on compounds commonly found in conventional jet fuels and SAFs. A group contribution method (GCM) is employed to predict thermophysical and combustion properties, providing an efficient analytical approach to evaluate the contributions of individual compounds to overall fuel mixture behavior. As part of this work, we introduce FuelLib, an open-source Python tool built around the GCM, to calculate individual compound and fuel mixture properties using various mixing rules. Our work evaluates whether the GCM can capture isomeric effects, that are often overlooked in traditional fuel property estimation. This is particularly important for SAFs, which often are composed of a more limited set of compound classes than conventional fuels, making isomeric differences more critical. Two-dimensional gas chromatography (GCxGC) data, which can be obtained from small fuel samples, provides weight percentages of compounds grouped by chemical family and carbon number rather than detailed information about individual compounds. As a result, assumptions must be made when decomposing GCxGC data into functional groups for GCM applications. Using GCxGC data, we show that the FuelLib tool can be used to predict the fuel properties of conventional jet fuels, with validation against experimental data. The provided tool enables researchers to predict fuel properties of candidate fuels and supports the design of new SAFs at both the component and mixture levels. This capability provides a foundation for studying fuel and combustion properties during SAF development, reducing reliance on costly experimental methods and advancing progress toward certification of new SAFs.

33 ADVANCED PROPULSION SYSTEMS↗

Aircraft Engine Particle Emissions during the 2023 NASA-Boeing ecoDemonstrator Field Measurements

Aerosol aircraft emissions are responsible for the formation of contrail cirrus clouds which can alter Earth’s radiation and water budgets exerting substantial effects on climate. However, at present, the impact of aviation on climate forcing remaining uncertain. Recently, NASA has collaborated with Boeing ecoDemonstrator program to improve the understanding of air traffic emissions and the impact of different jet fuel compositions on contrail microphysics. As part of the program, in October 2023 the NASA DC-8 aircraft was used to sample engine exhausts emitted by a Boeing ecoDemonstrator Explorer 737-10 burning sustainable aviation fuel (SAF) and conventional jet fuel over the north western US. In this study, we present unique observations of aerosols properties relevant for contrail-cirrus cloud formation collected during the 2023 ecoDemonstrator research flights and we will discuss the variations of key microphysical contrail parameters in function of different jet fuel compositions and engine conditions.

Francesca Gallo↗

Effect of Aromatic Concentration of a Fischer-Tropsch Fuel on Thermal Stability

Fischer-Tropsch (F-T) jet fuel composition differs from petroleum-based, conventional commercial jet fuel because of differences in feedstock and production methodology. Fischer­ Tropsch fuel typically has a lower aromatic and sulfur content and consists primarily of iso and normal parafins. The ASTM D3241 specification for Jet Fuel Thermal Oxidation Test (JFTOT) break point testing method was used to test the breakpoint of a baseline commercial grade F-T jet fuel, and various blends of this F-T fuel with an aromatic solution. The goal of this research is to determine the effect of aromatic content on the thermal stability of Fischer-Tropsch fuel. The testing completed in this report was supported by the NASA Fundamental Aeronautics Subsonics Fixed Wing Project.

Klettlinger, Jennifer Lindsey Suder↗

Production and Catalytic Upgrading of 2,3-Butanediol Fermentation Broth into Sustainable Aviation Fuel Blendstock and Fuel Properties Measurement

With the increasing demand for sustainable supplies of aviation fuel and need to address climate change, new conversion technologies are needed to efficiently process biomass, produce high quality jet fuel blendstock, and meet carbon emission targets. This study demonstrates the synthesis, conditioning, and catalytic upgrading of 2,3-butanediol (BDO) fermentation broth into a jet fuel blendstock candidate. A high-titer 2,3-BDO fermentation broth (i.e., ~90 g/L) was produced at a 100-L scale and pretreated via nanofiltration to decrease the impurities level in the broth from 4.6 to 0.6 wt%. A novel process for catalytic upgrading of aqueous 2,3-BDO into a jet fuel blendstock candidate was developed, and each step was efficiently demonstrated. The catalytic steps include 1) 2,3-BDO dehydration into methyl ethyl ketone (MEK) over AlPO4, 2) MEK conversion into olefins over Zn1Zr10Ox, 3) oligomerization of olefins over a zeolite beta, and 4) hydrogenation over platinum/carbon. Both the model feed and real 2,3-BDO fermentation broth were tested for upgrading 2,3-BDO to MEK. With the real feed, a continuous loss of conversion (i.e., >50% loss over ~140 h time-on-stream [TOS]) was partly attributed to reversible deactivation from coking species. However, the conversion remained stable with the model feed, which demonstrates the efficiency of the first step for converting aqueous 2,3-BDO (10 wt% in water). For upgrading MEK to olefins, high selectivity to olefins (i.e., 82.5%) was obtained at high conversion levels (i.e., 93-98%) with stable conditions being achieved for > 70-hours TOS. Oligomerization of light olefins, which was demonstrated for > 270 h TOS, mainly led to the formation of dimers (C8-10) and trimers (C13-14). The oligomerized product was hydrogenated and distilled to recover the jet fraction (35 mass% or 40.9% carbon based yield), which consists mostly of desired isoalkanes (31.7 wt%), n-alkanes (24.5 wt%), and cycloalkanes (29.6 wt%). While some improvement is still needed to meet ASTM D7566 specifications for viscosity and final boiling point temperature, freezing point, density, aromatics content, and sulfur content of the jet blendstock candidate were within acceptable ranges, thus highlighting the potential of this process for production of jet fuel blendstock.

ADVANCED PROPULSION SYSTEMS,BIOMASS FUELS↗

A Rapid Survey of the Compatibility of Selected Seal Materials with Conventional and Semi-Synthetic JP-8

Since the synthesis of a liquid hydrocarbon fuel from coal by Franz Fischer and Hans Tropsch in 1923, there has been cyclic interest in developing this fuel for military and commercial applications. In recent years the U.S. Department of Defense has taken interest in producing a unified battlespace fuel using the Fischer Tropsch (FT) process for a variety of reasons including cost, quality, and logistics. In the past year there has been a particular emphasis on moving quickly to demonstrate that an FT fuel can be used in the form of a blend with conventional petroleum-derived jet fuel. The initial objective is to employ this semi-synthetic fuel with blend ratios as high as 50 percent FT with longer range goals to use even high blend ratios and ultimately a fully synthetic jet fuel. A significant concern associated with the use of a semi-synthetic jet fuel with high FT blend ratios is the effect these low aromatic fuels will have on fuel-wetted polymeric materials, most notably seals and sealants. These materials typically swell and soften to some degree when exposed to jet fuel and the aromatic content of these fuels contribute to this effect. Semi-synthetic jet fuels with very low aromatic contents may cause seals and sealants to shrink and harden leading to acute or chronic failure. Unfortunately, most of the material qualification tests are more concerned with excessive swelling than shrinkage and there is little guidance offered as to an acceptable level of shrinkage or other changes in physical properties related to low aromatic content. Given the pressing need for guidance data, a program was developed to rapidly survey the volume swell of selected fuel-wetted materials in a range of conventional and semi-synthetic jet fuels and through a statistical analysis to make a determination as to whether there was a basis to be concerned about using fuels with FT blend ratios as high as 50 percent. Concurrent with this analysis data was obtained as to the composition of the fuel absorbed in fuel-wetted materials through the use of GC-MS analysis of swollen samples as well as other supporting data. In this presentation the authors will present a summary of the results of the volume swell and fuel absorbed by selected O-rings and sealants as well as a description of the measurement protocols developed for this program.

Graham, John L.↗

Sustainable Aviation Fuels from 30,000 feet – Scoping Report

A literature review, first principles analysis, and mapping of the airline-fuel infrastructure were performed to reassess the potential for various means of realizing a sustainable aviation sector. The literature review found a plethora of technical methods to make the airline industry net-zero CO 2 but limited work on the emergent barriers to sustainable aviation implementation such as land use, repurposing of fuel refining assets, and airline cost structures. First principles analyses of the energy, land, and costs of three broad net-zero strategies were performed to determine if sustainable aviation is feasible even in the most optimistic scenarios. Those methods were biomass-derived sustainable aviation fuel (SAF), fuel produced from CO 2 captured from the air and H 2 produced from water electrolysis (air-to-fuel: ATF), and offsetting fossil-derived Jet Fuel with carbon dioxide removal from the atmosphere (direct air capture and storage: DACS). Offsetting CO 2 emissions from using fossil Jet Fuel with DACS was found to consume the least energy, require the smallest quantity of land, and be the cheapest option. Replacing Jet Fuel with SAF was found to be only slightly more expensive than DACS but require substantially more land. ATF was found to be the most expensive and energy intensive option, though it did spare land relative to SAF. We found that calls to utilize waste biomass are well-founded, but wastes alone cannot cover the needs of the global airline industry. This means additional land will need to be allocated for biomass cultivation if SAF becomes the primary pathway to sustainable aviation. While differences were found in the performance of different types of biomass, those differences were small relative to differences with ATF and DACS. An analysis of the pricing structure of the airline industry suggests that some of the cost advantage of DACS may be erased by consumer sentiment which could explain why, to-date, the airline industry is focused primarily on SAF and to a lesser extent ATF. Further work is required to estimate the transportation, capital cost, and financing cost implications of greenfield and brownfield sites for SAF, DACS, and ATF. In the final report, we will analyze the potential to retrofit corn ethanol facilities to operate the ethanol-to-jet fuel process in response to decreasing gasoline demand as the electrification of road transport progresses. We will also construct a prioritization of land use to determine whether each net-zero CO 2 aviation pathway can make claim to the land required by their technology.

09 BIOMASS FUELS↗

Investigation of air solubility in jet A fuel at high pressures

The solubility and density properties of saturated mixtures of fuels and gases were measured. The fuels consisted of Jet A and dodecane, the gases were air and nitrogen. The test range included pressures of 1.03 to 10.34 MPa and temperatures of 298 to 373 K. The results were correlated successfully, using the Soave equation of state. Over this test range, dissolved gas concentrations were roughly proportional to pressure and increased slightly with increasing temperature. Mixture density was relatively independent of dissolved gas concentration.

Rupprecht, S. D.↗

Thermal Stability Results of a Fischer-Tropsch Fuel With Various Blends of Aromatic Solution

Fischer-Tropsch (F-T) jet fuel composition differs from petroleum-based, conventional commercial jet fuel because of differences in feedstock and production methodology. F-T fuel typically has a lower aromatic and sulfur content and consists primarily of iso and normal paraffins. The ASTM D3241 specification for Jet Fuel Thermal Oxidation Test (JFTOT) break point testing method was used to test the breakpoint of a baseline commercial grade F-T jet fuel, and various blends of this F-T fuel with an aromatic solution. The goal of this research is to determine the effect of aromatic content on the thermal stability of F-T fuel. The testing completed in this report was supported by the NASA Fundamental Aeronautics Subsonic Fixed Wing Project. Two different aromatic content fuels from Rentech, as well as these fuels with added aromatic blend were analyzed for thermal stability using the JFTOT method. Preliminary results indicate a reduction in thermal stability occurs upon increasing the aromatic content to 10% by adding an aromatic blend to the neat fuel. These results do not specify a failure based on pressure drop, but only on tube color. It is unclear whether tube color correlates to more deposition on the tube surface or not. Further research is necessary in order to determine if these failures are true failures based on tube color. Research using ellipsometry to determine tube deposit thickness rather than color will be continued in follow-up of this study.

Lindsey, Jennifer↗

Sustainable Aviation Fuel Blending and Logistics

Worldwide, aviation accounts for 2% of all manmade carbon dioxide emissions and 12% of all transportation CO2 emissions. In 2023, the U.S. accounted for 27% of the world jet fuel consumption. The aviation industry has set sustainability goals, and mandates. Sustainable aviation fuel (SAF), made from nonpetroleum feedstocks, significantly reduces aviation emissions. SAF must be blended with petroleum-based jet fuel prior to its use in aircraft. Jet fuel quality standards and certification documents are essential to fuel performance, operability, and safety and are the primary driver in determining locations for blending. Several locations were evaluated including terminals, airports, refineries, and greenfield/brownfield sites. While all the locations evaluated are technically capable of blending fuel, there are practical considerations that make terminals the optimal location for blending. The report includes background on jet fuel and SAF use, fuel quality standards, modes of transport for both conventional jet fuel and SAF, and terminal information.

09 BIOMASS FUELS↗

Combustor exhaust-emissions and blowout-limits with diesel number 2 and jet A fuels utilizing air-atomizing and pressure atomizing nozzles

Experimental tests with diesel number 2 and Jet A fuels were conducted in a combustor segment to obtain comparative data on exhaust emissions and blowout limits. An air-atomizing nozzle was used to inject the fuels. Tests were also made with diesel number 2 fuel using a pressure-atomizing nozzle to determine the effectiveness of the air-atomizing nozzle in reducing exhaust emissions. Test conditions included fuel-air ratios of 0.008 to 0.018, inlet-air total pressures and temperatures of 41 to 203 newtons per square centimeter and 477 to 811 K, respectively, and a reference velocity of 21.3 meters per second. Smoke number and unburned hydrocarbons were twice as high with diesel number 2 as with Jet A fuel. This was attributed to diesel number 2 having a higher concentration of aromatics and lower volatility than Jet A fuel. Oxides of nitrogen, carbon monoxide, and blowout limits were approximately the same for the two fuels. The air-atomizing nozzle, as compared with the pressure-atomizing nozzle, reduced oxides-of-nitrogen by 20 percent, smoke number by 30 percent, carbon monoxide by 70 percent, and unburned hydrocarbons by 50 percent when used with diesel number 2 fuel.

Ingebo, R. D.↗

Development of an Impinging-jet Fuel-injection Valve Nozzle

During an investigation to determine the possibilities and limitations of a two-stroke-cycle engine and ignition, it was necessary to develop a fuel injection valve nozzle to produce a disk-shaped, well dispersed spray. Preliminary tests showed that two smooth jets impinging upon each other at an angle of 74 degrees gave a spray with the desired characteristics. Nozzles were built on this basis and, when used in fuel-injection valves, produced a spray that fulfilled the original requirements. The spray is so well dispersed that it can be carried along with an air stream of comparatively low velocity or entrained with the fuel jet from a round-hole orifice. The characteristics of the spray from an impinging-jet nozzle limits its application to situations where wide dispersion is required by the conditions in the engine cylinder and the combustion chamber.

Spanogle, J A↗

Computational Analysis of Dynamic SPK(S8)-JP8 Fueled Combustor-Sector Performance

Civil and military flight tests using blends of synthetic and biomass fueling with jet fuel up to 50:50 are currently considered as "drop-in" fuels. They are fully compatible with aircraft performance, emissions and fueling systems, yet the design and operations of such fueling systems and combustors must be capable of running fuels from a range of feedstock sources. This paper provides Smart Combustor or Fuel Flexible Combustor designers with computational tools, preliminary performance, emissions and particulates combustor sector data. The baseline fuel is kerosene-JP-8+100 (military) or Jet A (civil). Results for synthetic paraffinic kerosene (SPK) fuel blends show little change with respect to baseline performance, yet do show lower emissions. The evolution of a validated combustor design procedure is fundamental to the development of dynamic fueling of combustor systems for gas turbine engines that comply with multiple feedstock sources satisfying both new and legacy systems.

Ryder, R.↗

Evaluation of methods and improvement of predictions for specification properties of petroleum-based and alternative aviation fuels

To support our research and process modeling for liquid fuels, including blends, from petroleum and synthetic sources such as from biomass intermediates, we evaluated composition-based prediction methods and improved predictions for five key specification properties of petroleum-based and alternative aviation fuels, namely distillation temperatures (10 % distilled, t 10 , and final boiling point, t FBP ), density, flash point, net heat of combustion, and freezing point. The types of fuels included were petroleum-based jet fuels, jet-fuel surrogate mixtures, synthetic blending components obtained from different sources, and blends of Jet A with many synthetic blending components. Expanded datasets to update associated parameters allowed significant improvements for one of the prediction methods used in earlier work, namely the Modified Weighted Average method published initially by Shi et al. By considering the importance of lighter compounds for flash points and heavier compounds for freezing points, the revised Modified Weighted Average method was further improved. For liquid density, the revised Modified Weighted Average method gave the best overall results. The revised Modified Weighted Average method, the American Society for Testing and Materials D7215 method, and the D7215 method modified by another group gave comparable results for flash point, while the revised Modified Weighted Average and D3338 methods gave the best results for net heat of combustion. Freezing point was well predicted using the revised Modified Weighted Average method and showed the most significant improvements over current predictions. Distillation temperature t 10 was not well predicted, while t FBP was predicted with a mean absolute error comparable to experimental reproducibility.

09 BIOMASS FUELS↗

Sustainable Aviation Fuel: Review of Technical Pathways

The 106-billion-gallon global (21-billion-gallon domestic) commercial jet fuel market is projected to grow to over 230 billion gallons by 2050. Cost-competitive, environmentally sustainable aviation fuels (SAFs) are recognized as a critical part of decoupling carbon growth from market growth. Renewable and wasted carbon can provide a path to low-cost, clean-burning, and low-soot-producing jet fuel. Research shows an opportunity to produce fuel in which aromatics are initially diluted with the addition of renewable iso-alkanes, aromatics are later fully replaced with cycloalkanes, and finally high-performance molecules that provide mission-based value to jet fuel consumers are introduced. Key to this fuel pathway is sourcing the three SAF blendstocks - iso-alkanes, cycloalkanes, and high-performing molecules - from inexpensive resources. When resourced from waste carbon, there are often additional benefits, such as cleaner water when sourcing carbon from wet sludges or less waste going to landfills when sourcing the carbon from municipal solid waste or plastic waste. Jet fuel properties differ from gasoline and diesel, so research will be most successful if it begins with the end result in mind.

09 BIOMASS FUELS↗

Bench-Scale Monolith Autothermal Reformer Catalyst Screening Evaluations in a Micro-Reactor With Jet-A Fuel

Solid oxide fuel cell systems used in the aerospace or commercial aviation environment require a compact, light-weight and highly durable catalytic fuel processor. The fuel processing method considered here is an autothermal reforming (ATR) step. The ATR converts Jet-A fuel by a reaction with steam and air forming hydrogen (H2) and carbon monoxide (CO) to be used for production of electrical power in the fuel cell. This paper addresses the first phase of an experimental catalyst screening study, looking at the relative effectiveness of several monolith catalyst types when operating with untreated Jet-A fuel. Six monolith catalyst materials were selected for preliminary evaluation and experimental bench-scale screening in a small 0.05 kWe micro-reactor test apparatus. These tests were conducted to assess relative catalyst performance under atmospheric pressure ATR conditions and processing Jet-A fuel at a steam-to-carbon ratio of 3.5, a value higher than anticipated to be run in an optimized system. The average reformer efficiencies for the six catalysts tested ranged from 75 to 83 percent at a constant gas-hourly space velocity of 12,000 hr 1. The corresponding hydrocarbon conversion efficiency varied from 86 to 95 percent during experiments run at reaction temperatures between 750 to 830 C. Based on the results of the short-duration 100 hr tests reported herein, two of the highest performing catalysts were selected for further evaluation in a follow-on 1000 hr life durability study in Phase II.

Tomsik, Thomas M.↗