Evaluation jet fuel replacement fluid composition for alternative fuel and method using the same

Abstract

To provide an evaluation jet fuel replacement fluid (JRF) composition and its use in a test method.SOLUTION: An evaluation jet fuel replacement fluid comprises a first hydrocarbon and a second hydrocarbon, wherein the first hydrocarbon and the second hydrocarbon may or may not contain an aromatic compound. An evaluation jet fuel replacement fluid (JRF) composition may contain one or more additives such as glycol monomethyl ether. A method for testing compatibility between the evaluation jet fuel replacement fluid (JRF) and aviation fuel is also disclosed. The method can be used to evaluate one or more components or systems of an aerospace vehicle (100), such as a thermosetting resin, a thermoplastic resin, a sealant, an elastomer, a metal, a finishing material, a coating, wiring or a combination thereof.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates generally to assessing the exposure of aerospace components to fuels, and more particularly to evaluating jet reference fluid formulations for fuel exposure testing of aerospace components. [Background technology]

[0002] Current aircraft systems and materials are designed for conventional jet fuel compositions. The aviation industry has a goal of using more sustainable aviation fuels (SAFs) and fuel sources, with the goal of achieving 100% sustainable aviation fuel. Transitioning to cleaner, more efficient fuels, such as those that do not contain some of the compounds in petroleum-based jet fuels, requires significant testing to ensure that systems and materials are compatible with the proposed SAF compositions. This can include testing primers, sealants, finishes, metals, composites, O-rings, and everything else in the aircraft that the fuel comes into contact with.

[0003] Sustainable aviation fuel (SAF) is an alternative fuel designed to reduce the environmental impact of aviation use by lowering greenhouse gas emissions compared to conventional jet fuel. SAF can be produced or refined from renewable resource feedstocks, such as biomass or waste, or by other carbon capture technologies. SAF can be blended with conventional jet fuel or completely replace it for greater versatility. Jet fuels, including SAF, can have a variety of compositions and, consequently, various properties. However, they are classified into two categories: petroleum-derived jet fuels have a wide range of compositions, including those with 0% aromatics, while SAF or synthetic fuels can be completely free of aromatics and sulfur or nitrogen impurities, or any chemicals that may be present in jet fuel but that may affect materials with which they come into contact. One example of an impurity is mercaptans, which may be present in crude oil and may affect sealants in aerospace vehicles.

[0004] It is therefore desirable to have standards, materials, and methods that can be used to better understand and classify the suitability of available SAFs for existing or proposed aviation components. It is important to be able to evaluate various possible fuel compositions and to evaluate the limiting conditions of the fuel composition with respect to the performance of the material or system. Summary of the Invention

[0005] The following presents a simplified summary in order to provide a basic understanding of some aspects of one or more embodiments of the present disclosure. This summary is not an exhaustive overview, and it does not identify key or essential elements of the disclosure, nor does it delineate the scope of the disclosure. Rather, its primary purpose is merely to present one or more concepts in a simplified form as a prelude to the more detailed description presented later.

[0006] The present disclosure provides an evaluation jet fuel surrogate fluid (JRF) composition. The evaluation jet fuel surrogate fluid includes a first hydrocarbon and a second hydrocarbon, wherein the first hydrocarbon and the second hydrocarbon are free of aromatic compounds. In an embodiment of the evaluation jet fuel surrogate fluid (JRF) composition, the first hydrocarbon includes isooctane, or the second hydrocarbon includes n-heptane. The first hydrocarbon is present in an amount of about 1 wt% to about 20 wt% based on the total weight of the evaluation jet fuel surrogate fluid. The second hydrocarbon is present in an amount of about 50 wt% to about 90 wt% based on the total weight of the evaluation jet fuel surrogate fluid. The evaluation jet fuel surrogate fluid (JRF) composition may include glycol monomethyl ether (DiEGME). The glycol monomethyl ether (DiEGME) is present in an amount of about 0.1 wt% to about 10 wt% based on the total weight of the evaluation jet fuel surrogate fluid.

[0007] The present disclosure also provides another evaluation jet fuel surrogate fluid (JRF) composition. The evaluation jet fuel surrogate fluid includes a first hydrocarbon and a second hydrocarbon, wherein one of the first hydrocarbon and the second hydrocarbon includes one or more aromatic compounds. In an embodiment of the evaluation jet fuel surrogate fluid (JRF) composition, the first hydrocarbon includes toluene and the second hydrocarbon includes isooctane. The evaluation jet fuel surrogate fluid (JRF) composition further includes cyclohexane or n-heptane.

[0008] The present disclosure also provides a method for testing aviation fuel compatibility. The method includes providing a predetermined amount of evaluation jet fuel surrogate fluid (JRF) and evaluating one or more components or systems of an aerospace vehicle. The method also includes exposing the predetermined amount of evaluation jet fuel surrogate fluid (JRF) to the one or more components or systems of the aerospace vehicle for a predetermined period of time. The method also includes evaluating the one or more components or systems of the aerospace vehicle after exposing the one or more components or systems of the aerospace vehicle to the evaluation jet fuel surrogate fluid (JRF). In an embodiment of the method for testing aviation fuel compatibility, evaluating the one or more components or systems of the aerospace vehicle includes weighing or visually inspecting the one or more components or systems of the aerospace vehicle. Evaluating the one or more components or systems of the aerospace vehicle after exposing the one or more components of the aerospace vehicle to the evaluation jet fuel surrogate fluid (JRF) includes weighing or visually inspecting the one or more components or systems of the aerospace vehicle. The predetermined period of time may include, for example, a period of about 1 hour to about 72 hours, or about 1 hour to about 5,000 hours, or about 24 hours to about 10,000 hours in a long-term immersion or exposure test of a sealant or thermoplastic resin. The one or more components or systems of an aerospace vehicle may include a thermoset, a thermoplastic, a sealant, an elastomer, a metal, a finish, a coating, or a combination thereof. The one or more components or systems of an aerospace vehicle may include wiring. The one or more components or systems of an aerospace vehicle may include a fuel system. The evaluation jet fuel surrogate fluid (JRF) may include isooctane, n-heptane, toluene, or cyclohexane.

[0009] The above-described features, functions, and advantages may be realized individually in various embodiments, or may be combined with one another in other embodiments, further details of which will become apparent by reference to the following description. [Brief explanation of the drawings]

[0010] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. Note that some details of the drawings have been simplified and are drawn to facilitate understanding of the disclosure, rather than to maintain strict structural accuracy, detail, or scale.

[0011] [Figure 1] FIG. 1 illustrates an exemplary aerospace vehicle application of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Reference will now be made in detail to exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same, similar or like parts.

[0013] The present disclosure relates to an evaluation jet fuel surrogate fluid (JRF) for sustainable aviation fuel that mimics the chemistry and behavior of actual sustainable aviation fuel. The chemical composition of sustainable aviation fuel can vary depending on the feedstock and refining process. The evaluation jet fuel surrogate fluid of the present disclosure can be used to test and evaluate how sustainable aviation fuel interacts with aircraft component materials or systems compared to conventional petroleum-based jet fuel compositions.

[0014] The disclosed evaluation jet fuel substitute fluids (JRFs) for sustainable aviation fuels (SAFs) mimic the extreme conditions of SAF chemistry that will most significantly impact a given material. The chemical composition of SAFs can vary depending on the feedstock and refining process. Therefore, JRFs were developed to test how various types of fuels interact with aircraft materials, such as how 100% synthetic paraffinic kerosene (SPK) might differ from a typical petroleum-derived Jet A, which contains aromatics. For purposes of this disclosure, extreme conditions of a solvent refer to the worst-case conditions that represent the solvent's behavior when used with, in contact with, or exposed to one or more candidate or test parts for aerospace applications, and that are most likely to degrade or damage the one or more candidate or test parts over a given period of time. In some instances, aromatic molecules may increase swelling of certain materials. In other instances, various materials may be more susceptible to dissolving some of their compositions or components in either aromatic or non-aromatic JRFs. Petroleum jet fuels, including SAF, can contain primarily paraffins, such as n-paraffins, isoparaffins, cycloparaffins, or mixtures thereof, with or without aromatics. Therefore, it is important to evaluate materials and fuel systems, covering variations in the composition of petroleum jet fuels and synthetic jet fuels, including SAF.

[0015] This disclosure further relates to an evaluation jet fuel surrogate fluid (JRF) developed to have chemistries representing the limits or worst-case scenarios of possible fuel chemistries and their effects on the following general range of materials: thermosets, thermoplastics, sealants, elastomers, metals, finishes, coatings, and wiring. Understanding the worst-case exposures for materials and fluids is necessary to correlate this understanding with fuel chemistries. Further evaluation of approaches for various types of materials can alter the composition of the evaluation jet fuel surrogate fluid. In some examples, Jet A / A-1 can have 0-25% aromatics by volume. However, Jet A rarely contains low or no aromatics. Meanwhile, the most commonly produced synthetic blend component today is hydrotreated esters and fatty acids (HEFA), which has a maximum allowable aromatic content of 0.5% by mass. Of the bulk components present in jet fuel, the concentration of aromatics has the greatest impact on solubility, surface tension, density, net heat of combustion, and yield sooting index (YSI). Other properties such as viscosity and freezing point depend not only on the class of hydrocarbons present, but also on the structural isomers within the class.

[0016] Solvent selection is based on a variety of factors, including the ratio of n-paraffins to iso-paraffins typically present in both conventional and sustainable fuels, handling safety (e.g., benzene may be the best molecule to represent aromatics in fuels for material compatibility, but toluene is used because of significant EHS concerns), and the range of aromatics found in fuel compositions or allowed by specifications (e.g., 0–25% aromatics by volume). Thus, the composition can be further tailored to the application. For example, small molecules will be most sensitive to elastomers and sealants and can penetrate materials more effectively than larger molecules. Epoxy materials are more sensitive in the presence of water, so JRF testing for epoxies may include water.

[0017] The aviation industry and its various partners are focused on increasing the utilization of sustainable aviation fuels, including achieving 100% SAF capability by 2030. The disclosed fluids, known as evaluation jet fuel replacement fluids (JRFs), can be used to understand how aircraft interact with 100% sustainable aviation fuels (SAFs). In some cases, the definition of a 100% SAF capability target could include 100% synthetic paraffinic kerosene (SPK), which would contain no aromatic components. Additionally, testing of previously known materials and fuels did not address the full range of potential fuel chemistries. Therefore, there may be gaps in our current understanding of the performance of materials in fuels, including current petroleum-derived jet fuels.

[0018] Unlike the fluids described in this disclosure, current evaluation jet fuel surrogate fluids suffer from one or more of the following problems: they may contain high concentrations of aromatics (thus differing significantly from 100% SPK), they may be difficult to manufacture and therefore expensive to obtain (e.g., AMS2629 Jet Reference Fuel), and / or they may be inconsistent from batch to batch. Furthermore, existing published evaluation jet fuel surrogate fluids do not significantly affect metallic materials, and it has been found by those skilled in the art and from examination of the service history of metal components that corrosion can occur in fuel tanks due to the composition of the fuel and / or water that may be present in the fuel tank.

[0019] FIG. 1 illustrates an exemplary aerospace vehicle application according to the present disclosure. As illustrated, the aerospace vehicle 100 may include, for example, an airplane or aircraft. The airframe 130 of the aircraft or vehicle 100 may include, for example, numerous separate components or systems, each of which may be exposed to fuel and may be required to withstand such exposure while maintaining optimal performance over the life of the component or system. Also, although not illustrated herein, the vehicle 100 may include other types of aircraft or watercraft, such as helicopters, unmanned aerial vehicles (UAVs), spacecraft, etc., in addition to or instead of the airplane. In other embodiments, the vehicle 100 may be an automobile, boat, train, etc. In still other embodiments, the systems and methods described below may not be implemented in a vehicle, but may be used to test components or systems comprising or incorporated into the vehicle 100. Aircraft propulsion is typically powered by aviation fuel or conventional jet fuel. Aviation fuel is distinct from other types of fuel due to its required specific energy, i.e., energy per unit mass. Increasing the energy storage capacity of aviation fuel or kerosene fuel, for example, enables long-distance flights. There are numerous types of aviation gasoline, each with its own unique properties, uses, and requirements. The same is true for candidate or recently developed sustainable aviation fuels (SAFs). In some examples, fuel comes into contact with other components, such as coatings, such as organic paints or inorganic finishes; sealants; elastomers, such as gaskets or O-rings; fuel tank materials, such as wiring; a fuel quantity indicating system (FQIS), which may include one or more of the following: a concentration meter; a fuel pump; various engine components; a heat exchanger; or a combination thereof. While exemplary embodiments are illustrated in the context of an aircraft or aerospace vehicle, other systems, such as, but not limited to, a ground-based refueling system, a hydromechanical unit (HMU), or other refueling infrastructure, are also applicable.

[0020] Some typical JRF formulations include non-aromatic JRF (N-JRF) composed of 90% isooctane and 10% n-heptane. This non-aromatic JRF composition does not contain aromatic compounds. Aromatic compounds can be defined as compounds within a broad class of unsaturated compounds characterized by one or more planar rings of atoms joined by two different types of covalent bonds. The unique stability of these compounds is referred to as aromaticity. Examples of aromatic hydrocarbons or aromatic compounds applicable to the JRF compositions of the present disclosure include, but are not limited to, heteroarenes, i.e., compounds in which at least one methine or vinylene (-C= or -CH=CH-) group is replaced with a heteroatom such as oxygen, nitrogen, or sulfur, or benzene-like or benzene-derived compounds, including exemplary aromatic compounds such as toluene, ethylbenzene, xylene, mesitylene, phenylhexane, biphenyl, phenol, aniline, nitrobenzene, and benzoic acid. Thus, these aromatic compounds may contain substituted or unsubstituted aromatic rings. For example, these aromatic rings can be substituted with functional groups such as hydroxy, alkoxy, halogen, nitro, alkanes (e.g., heptylbenzene), or combinations thereof. One or more of the above heteroarenes, heteroatom-containing aromatics, or other substituted aromatic compounds may be present in a smaller proportion, e.g., 50% or less, in the overall composition, or may even be absent. A typical highly aromatic JRF (HA-JRF) can be composed of 30% toluene, 50% isooctane, 10% cyclohexane, and 10% n-heptane.

[0021] The disclosed evaluation jet fuel surrogate fluid (JRF) serves as a surrogate for a candidate SAF, enabling fluid exposure testing of materials at critical conditions. The uses and methods described herein can be incorporated into testing the suitability of one or more components of an aircraft or aerospace vehicle, providing a reproducible view of system suitability. Testing with the disclosed JRF fluid also allows for understanding the critical conditions of these systems that come into or may come into contact with the SAF. The disclosed JRF is a fluid made from simple, controllable and reproducible materials, providing a means for easy data comparison using simple compositions and test methods that use reproducible fluids and techniques. For systems with aggressive environmental vision or plans to achieve 100% SAF capability within several years, it is important to be able to evaluate the suitability of any materials or systems that the candidate SAF will come into contact with.

[0022] The disclosed JRF is designed to test the extreme compositional limits of actual SAFs, even if their compositions may be known, proposed for use in a system or exposure to a component. The resulting knowledge and methods can be shared and compared with industry partners as standardized test methods. While a distribution of compositions may exist when an SAF is manufactured, the JRF represents molecules that can be isolated from the SAF composition. Clearly, if a system or component can pass a test method using the JRF, problems will be reduced or eliminated when the SAF is actually used. Aerospace vehicle components may include a range of materials, such as sealants, thermoplastics, thermosets, finishes, materials, and associated fuel systems and / or components. The use and methods of the JRF described herein are not limited to assessing exposure to a specific fuel, which further benefits from the implication that the manufacturer or provider of the SAF is not important.

[0023] Compatibility testing and additional testing methods ensure that SAFs can be safely used in existing aircraft engines without causing unexpected operational problems. Examples of existing compatibility tests include material compatibility tests, engine performance tests, fuel system tests, storage and handling tests, additive compatibility tests, and cold flow characteristics tests. Material compatibility tests involve exposing materials used in fuel systems, such as seals, hoses, and gaskets, to SAFs to assess their compatibility, thereby determining or confirming that the SAFs will not degrade or corrode the materials over time. Engine performance tests can evaluate the impact of SAFs on engine performance, including efficiency, thrust, and emissions. Verification that SAFs meet the specifications required for aircraft engine combustion can also be an accompanying test. Fuel system tests can examine the behavior of SAFs in fuel systems, taking into account factors such as flow characteristics and filtration, to ensure that the SAFs are sufficiently atomized in the combustion chamber without clogging or damaging fuel system components. Storage and handling tests estimate and investigate the effects of long-term storage on SAF properties, providing insight into SAF handling procedures and ensuring that these handling or storage procedures are similar to those of conventional jet fuel. Cold-flow property tests can evaluate SAF performance under colder conditions, such as those at high altitudes, to avoid issues such as fuel freezing or component precipitation. Additional tests or evaluations of response to JRF exposure include system response to fuel composition, such as fuel quality indicator systems (FQIS), which may use capacitance or ultrasonic information where properties such as dielectric constant versus density and bulk modulus are important indicators of performance. Additional tests of physical properties such as tensile strength, elongation, and modulus of elastomers can also be employed, as well as paint adhesion tests and metal corrosion tests.

[0024] Examples of sustainable aviation fuel (SAF) compositions or production methods include HEFA (hydrogenated esters and fatty acids), SIP (synthetic isoparaffins from hydrotreated fermented sugars), ATJ (alcohol-to-jet), and HLB (hydrotreated lignocellulosic biomass). Examples of HEFA (hydrogenated esters and fatty acids) include vegetable oil or animal fat-derived materials, which are chemically similar to conventional jet fuel but contain less sulfur. SIP (synthetic isoparaffins from hydrotreated fermented sugars) can be produced by fermentation of sugars followed by hydroprocessing, achieving a high energy density similar to that of conventional aviation fuel. Examples of fuels produced by ATJ (alcohol-to-jet) include those derived from alcohols such as ethanol or butanol, which are converted into jet fuel through a series of additional chemical processes. HLB (hydrotreated lignocellulosic biomass) fuel can be obtained from non-edible plant materials such as wood, grass, and agricultural residues by further hydroprocessing lignocellulosic biomass. These are some examples of pathways, feedstocks, and final compositions for producing synthetic blend components or fuels, although these categories are interrelated and may overlap to some extent. HEFA, SIP, and ATJ are all examples of pathways for producing fuels. HLB is a specific category of feedstock that can be utilized via various routes depending on the processing method. Fuel compositions include 100% synthetic paraffinic kerosene (SPK), which can be produced via the HEFA, SIP, and ATJ routes. However, the composition of SPK can vary based on the feedstock and route, including the specific route conditions, such as temperature, catalyst, catalyst life, and fractionation. Other major categories of synthetic blend components contain aromatics, and are currently under development: 100% cycloparaffinic fuel (CPK) and 100% synthetic aromatic kerosene (SAK). SAK is unlikely to be used as a standalone fuel but could be used as a synthetic blend component.Examples of synthetic blends include synthetic paraffinic kerosene plus aromatics (Annex 5) and ATJ-SKA (ASTM D7566 Annex 8). These synthetic blend components may also be combined to create fully synthetic "drop-in" fuels that fall within the range of petroleum-derived Jet A (e.g., blends of HEFA and SAK).

[0025] An example method for testing aviation fuel compatibility may include providing a predetermined amount of evaluation jet fuel surrogate fluid (JRF), evaluating one or more components or systems of an aerospace vehicle, exposing the predetermined amount of evaluation jet fuel surrogate fluid (JRF) to the one or more components or systems of the aerospace vehicle for a predetermined period of time, and evaluating the one or more components or systems of the aerospace vehicle after exposing the one or more components or systems of the aerospace vehicle to the evaluation jet fuel surrogate fluid (JRF). The method for testing aviation fuel compatibility may include evaluating the one or more components or systems of the aerospace vehicle by weighing or visually inspecting the one or more components or systems of the aerospace vehicle. The method for testing the compatibility of an aviation fuel may include evaluating one or more components or systems of an aerospace vehicle after exposing the one or more components of the aerospace vehicle to an evaluation jet fuel surrogate fluid (JRF), which may include weighing or visually inspecting the one or more components or systems of the aerospace vehicle. In some examples, the predetermined period of time may be from about 1 hour to about 10,000 hours. In other examples, the one or more components or systems of the aerospace vehicle may include a thermoset, a thermoplastic, a sealant, an elastomer, a metal, a finish, a coating, or a combination thereof. In alternative examples, the one or more components or systems of the aerospace vehicle may include wiring, which may incorporate one or more conductive metals or insulating or coating materials. The one or more components or systems of the aerospace vehicle may include a fuel system. The evaluation jet fuel surrogate fluid (JRF) used in the method may include any of the JRFs described in this disclosure. Fluid exposure parameters, such as time and temperature, may vary depending on the material, and the evaluation of the material after fluid exposure may also vary. For example, test exposure conditions may include times up to 10,000 hours, which may be referred to as a "long term soak," and temperatures from room temperature, assumed to be about 25°C, to about 75°C.Additionally, part of the test protocol may include "switch-loading," in which the sample is alternately exposed to a high-aromaticity jet fuel surrogate fluid and a low-aromaticity jet fuel surrogate fluid over time for certain materials. Previous testing of nitrile butadiene rubber (NBR) O-rings has shown that this can have a different impact on material performance than using a single test fluid alone. In the case of NBR, aromatic compounds from the jet fuel can displace plasticizers within the material. When the test is subsequently switched to a non-aromatic fuel, the aromatic compounds absorbed within the material dissociate into the fuel, causing the O-ring to shrink in volume. This can potentially lead to leakage. Switch-loading may also have a similar effect of extracting individual components of the material formulation, and it is important to understand whether this phenomenon could degrade material performance over time.

[0026] One or more evaluation jet fuel surrogate fluid (JRF) compositions of the present disclosure can include a first hydrocarbon and a second hydrocarbon, wherein the first hydrocarbon and the second hydrocarbon are free of aromatic compounds. The first hydrocarbon can be or include isooctane, for example. The second hydrocarbon can include n-heptane. These hydrocarbons can also include cyclohexane, heptane, or any of the hydrocarbons described herein. Examples of evaluation jet fuel surrogate fluid (JRF) compositions include those in which the first hydrocarbon is present in an amount of about 1% to about 20% by weight based on the total weight of the evaluation jet fuel surrogate fluid, or those in which the second hydrocarbon is present in an amount of about 50% to about 90% by weight based on the total weight of the evaluation jet fuel surrogate fluid. Either the first hydrocarbon or the second hydrocarbon fluid, or any additional fluids added thereto, may be present in an amount of about 1 wt. % to about 99 wt. %, or about 10 wt. % to about 90 wt. %, or about 20 wt. % to about 80 wt. %, or about 30 wt. % to about 70 wt. %, or about 40 wt. % to about 60 wt. %, or about 50 wt. % to about 75 wt. In some examples, the evaluation jet fuel surrogate fluid (JRF) composition may also include one or more additives, such as glycol monomethyl ether (DiEGME). The additive or other additives may be present in an amount of about 0.1 wt. % to about 10 wt. %, or 1 wt. % to about 20 wt. %, or 2 wt. % to about 5 wt. % based on the total weight of the evaluation jet fuel surrogate fluid. In some examples, the evaluation jet fuel surrogate fluid (JRF) composition includes a case where one of the first hydrocarbon and the second hydrocarbon includes one or more aromatic compounds, such as toluene.

[0027] The examples shown below are representative compositions of jet fuel surrogate fluid mixtures for evaluation. [Table 1] [Table 2] [Table 3] [Table 4]

[0028] The evaluation jet fuel surrogate fluids listed in the table represent various applicable limit cases of fuel chemistry for evaluating material compatibility. These evaluation jet fuel surrogate fluid recipes are intentionally designed to include readily available materials. Therefore, these fluids should be reusable and scalable. These materials are also compatible with a variety of fuel types. While existing testing is simplified, it uses expensive and variable fluids, such as AMS2629. AMS2629 requires extensive laboratory testing to produce and is based on Jet A fuel, whose composition can vary from batch to batch. AMS2629 has a limited shelf life, and extending its shelf life requires additional testing, which is not readily available in most laboratories. Using the test fluid compositions disclosed herein eliminates the need for materials such as AMS2629, resulting in cost savings over the testing required for various material specifications. Because DiEGME is a required additive in military fuel specifications, demonstrating that materials used in aircraft fuel tanks (particularly primers) are compatible with DiEGME could have a significant impact on military aircraft. While required for military aircraft, DiEGME is also permitted in civilian fuels. If operators determine that DiEGME has advantages (e.g., biostatic properties), it may be used more frequently in the commercial fuel sector.

[0029] Additional test fluids for assessing metal and inorganic finish exposure may include naphthenic and sulfur species, known impurities in crude oil that may be present in finished jet fuel and that are known to affect metal corrosion. Examples of such fluids include "synthetic sump" materials, such as those shown in Tables 5, 6, and 7 below.

Table 5

Table 6

Table 7

[0030] While the present disclosure has been illustrated with respect to one or more embodiments, changes and / or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. For example, while the processes of the present disclosure are described as a series of acts or events, it will be understood that the present disclosure is not limited by the order of these acts or events. Some acts may occur in a different order and / or concurrently with other acts or events other than those described herein. Also, not all process steps may be required to implement a methodology in accordance with one or more aspects or embodiments of the present disclosure. It will be understood that structures and / or process steps may be added, or existing structures and / or process steps may be deleted or modified. Furthermore, one or more of the acts described herein may be performed in one or more separate acts and / or steps. The term "at least one" means that one or more of the listed items may be selected. Furthermore, in the description and claims herein, the term "on," when used with respect to two materials "on" one another, means that there is at least some contact between the materials; the term "over" means that the materials are proximate to one another, but that one or more additional intervening materials may be present, and that contact is possible but not required. Additionally, the terms "on" and "above" as used herein do not imply any directional orientation. The term "conformal" refers to a coating material in which the angle of the underlying material is maintained by the conformal material. The term "about" indicates that a stated value may be modified somewhat without resulting in incompatibility of the process or structure with the illustrated embodiment. The terms "couple," "coupled," "connect," "connected," "connecting," "connecting," and "connected" mean "directly connected" or "connected via one or more intermediate elements or members." Finally, the terms "representative" and "exemplary" indicate that the description is not intended to be ideal, but is used as an example.Other embodiments of the present disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure described herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the present disclosure being indicated by the following claims.

Claims

1. a first hydrocarbon; and a second hydrocarbon; An evaluation jet fuel substitute fluid (JRF) composition, wherein the first hydrocarbon and the second hydrocarbon are aromatic-free.

2. 10. The evaluation jet fuel substitute fluid (JRF) composition of claim 1, wherein the first hydrocarbon comprises isooctane.

3. 10. The evaluation jet fuel substitute fluid (JRF) composition of claim 1, wherein the second hydrocarbon comprises n-heptane.

4. 10. The evaluation jet fuel surrogate fluid (JRF) composition of claim 1, wherein the first hydrocarbon is present in an amount of about 1 wt. % to about 20 wt. %, based on a total weight of the evaluation jet fuel surrogate fluid.

5. 10. The evaluation jet fuel surrogate fluid (JRF) composition of claim 1, wherein the second hydrocarbon is present in an amount of about 50 wt. % to about 90 wt. % based on a total weight of the evaluation jet fuel surrogate fluid.

6. The evaluation jet fuel substitute fluid (JRF) composition according to any one of claims 1 to 5, further comprising glycol monomethyl ether (DiEGME).

7. 7. The evaluation jet fuel surrogate fluid (JRF) composition of claim 6, wherein the glycol monomethyl ether (DiEGME) is present in an amount of about 0.1 wt. % to about 10 wt. %, based on the total weight of the evaluation jet fuel surrogate fluid.

8. a first hydrocarbon; and a second hydrocarbon; An evaluation jet fuel substitute fluid (JRF) composition, wherein one of the first hydrocarbon and the second hydrocarbon comprises one or more aromatic compounds.

9. 9. The evaluation jet fuel substitute fluid (JRF) composition of claim 8, wherein the first hydrocarbon comprises toluene.

10. 9. The evaluation jet fuel substitute fluid (JRF) composition of claim 8, wherein the second hydrocarbon comprises isooctane.

11. 10. The evaluation jet fuel substitute fluid (JRF) composition of claim 8, further comprising cyclohexane.

12. 9. The evaluation jet fuel substitute fluid (JRF) composition of claim 8, further comprising n-heptane.

13. 1. A method for testing the suitability of aviation fuel, comprising: Preparing a predetermined amount of the jet fuel substitute fluid (JRF) for evaluation according to any one of claims 1 to 12; evaluating one or more components or systems of an aerospace vehicle; exposing the predetermined amount of the evaluation jet fuel surrogate fluid (JRF) to one or more components or systems of an aerospace vehicle for a predetermined period of time; and evaluating the one or more components or systems of an aerospace vehicle after exposing the one or more components or systems of the aerospace vehicle to the evaluation jet fuel surrogate fluid (JRF).

14. 14. The method for testing aviation fuel compatibility of claim 13, wherein evaluating one or more components or systems of the aerospace vehicle comprises weighing or visually inspecting the one or more components or systems of the aerospace vehicle.

15. 14. The method of testing aviation fuel compatibility as described in claim 13, wherein evaluating one or more components or systems of an aerospace vehicle after exposing the one or more components of the aerospace vehicle to the evaluation jet fuel surrogate fluid (JRF) comprises weighing or visually inspecting the one or more components or systems of the aerospace vehicle.

16. 14. The method of testing aviation fuel compatibility as set forth in claim 13, wherein the predetermined period of time is from about 1 hour to about 72 hours.

17. 14. The method of testing aviation fuel compatibility as described in claim 13, wherein the one or more components or systems of an aerospace vehicle include a thermoset, a thermoplastic, a sealant, an elastomer, a metal, a finish, a coating, or a combination thereof.

18. The method of testing aviation fuel compatibility as set forth in claim 13 , wherein the one or more components or systems of an aerospace vehicle include wiring.

19. 14. The method of testing aviation fuel compatibility as set forth in claim 13, wherein the one or more components or systems of an aerospace vehicle include a fuel system.

20. 14. The method of testing aviation fuel compatibility as set forth in claim 13, wherein the evaluation jet fuel surrogate fluids (JRF) include isooctane and n-heptane.

21. 21. The method for testing the suitability of aviation fuels according to any one of claims 13 to 20, wherein the evaluation jet fuel surrogate fluid (JRF) comprises toluene and cyclohexane.

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