Nano-fluid fuel taking metal carbide as additive and preparation method of nano-fluid fuel

Abstract

The invention provides a nanofluid fuel with metal carbide as an additive and a preparation method thereof.The nanofluid fuel comprises liquid fuel, the metal carbide and a surfactant, the metal carbide and the surfactant are evenly dispersed in the liquid fuel, the mass percent of the metal carbide is 1%-40%, the mass percent of the surfactant is 1%-20%, and the mass percent of the liquid fuel is 1%-20%. The mass percent of the surfactant is 1%-15%, and the balance is liquid fuel. By applying the technical scheme, the technical problems that in the prior art, the energy density of liquid fuel is insufficient, and the combustion heat release process of fuel is affected by surface oxidation and combustion products of traditional energy-containing nano metal particles or metal oxide particles are solved.

Description

Technical Field

[0001] The invention relates to the technical field of nanofluid fuel, and in particular to a nanofluid fuel with metal carbide as an additive and a preparation method thereof. Background Art

[0002] High-performance liquid fuels are widely used in aerospace and defense fields. Their energy properties such as mass calorific value and density have a significant impact on the performance of engines and aircraft. Using artificial chemical synthesis and fuel compounding, researchers have successfully prepared a series of high-density liquid hydrocarbon fuels such as JP-10, RJ-4, and RJ-5 (density reaches 0.9g / mL). However, with the development of aerospace technology, traditional liquid hydrocarbon fuels are facing the bottleneck problem of further improving energy density. Adding high-energy nanoparticles with high volumetric calorific value to liquid hydrocarbon fuels to form nanofluid fuels is considered to be one of the most promising solutions.

[0003] At present, nanofluid fuels mostly use nano metals or metal oxides such as boron (B), aluminum (Al), and magnesium (Mg) as solid phase additives. Metals as high-energy additives have the advantages of high calorific value (high energy density), high thermal conductivity (short ignition delay time), and wide sources. Chinese patent CN108456558A discloses a nano energy storage fuel with nano Al powder as an additive and a preparation method thereof, and proposes to use high-energy organic boron compounds with special structures to improve the ignition and combustion performance of fuels. Chinese patent CN116891765A discloses a technical solution to solve the poor stability and ignition and combustion performance of existing nanofluids by using magnesium diboride as an additive. Chinese patent CN111117712A invented a method that can significantly improve the energy density of liquid bioethanol fuel. The prepared nanofluid fuel has high stability and good ignition and combustion performance. The nanofluid fuel includes 1-20% by mass of solid energetic nanoparticles, 1-3% by mass of surfactants, and the rest is liquid fuel. The solid energetic nanoparticles are one or both of nano aluminum and nano boron.

[0004] Although high-energy nano-metal particles have been widely used to significantly increase the energy density of liquid fuels and improve the combustion characteristics of liquid fuels such as ignition delay time, metal nanofluid fuels also have obvious defects, that is, due to the non-energy oxide passivation layer on the particles and the solid oxide reaction products produced during the combustion process, the combustion heat release process of the fuel is seriously affected. Therefore, it is urgent to develop a nanofluid fuel with a new type of high-energy solid particles as an additive and a preparation method thereof to improve the combustion efficiency and work capacity of the fuel. Summary of the invention

[0005] The present invention provides a nanofluid fuel with metal carbide as additive and a preparation method thereof, which can solve the technical problems in the prior art of insufficient energy density of liquid fuel and the influence of surface oxidation and combustion products of traditional energetic nanometal particles or metal oxide particles on the fuel combustion heat release process.

[0006] According to one aspect of the present invention, a nanofluid fuel with metal carbide as an additive is provided, the nanofluid fuel comprising liquid fuel, metal carbide and a surfactant, the metal carbide and the surfactant being uniformly dispersed in the liquid fuel, wherein the mass percentage of the metal carbide is 1% to 40%, the mass percentage of the surfactant is 1% to 15%, and the rest is liquid fuel.

[0007] Furthermore, the particle size of the metal carbide is 50 to 500 nm.

[0008] Furthermore, the metal carbide is boron carbide, aluminum carbide or a combination of both.

[0009] Furthermore, the surfactant is one or more of stearic acid, oleic acid, citric acid ricinoleic acid, sorbitan fatty acid ester, sorbitan trioleate, and Tween-80.

[0010] Furthermore, the mass ratio of the metal carbide to the surfactant is 1:a, wherein the value of a ranges from 1 to 3.

[0011] Furthermore, the liquid fuel is hydrocarbon liquid fuel.

[0012] Furthermore, the liquid fuel is tetrahydrodicyclopentadiene.

[0013] According to another aspect of the present invention, there is provided a method for preparing the nanofluid fuel proposed in the present invention, the method comprising:

[0014] S1, determine the types of liquid fuel, metal carbide and surfactant;

[0015] S2, adding a surfactant to the liquid fuel and mixing them evenly to obtain a mixed base liquid of the nanofluid fuel;

[0016] S3, adding metal carbide to the mixed base liquid obtained in S2, and mixing them evenly to obtain uniformly dispersed nanofluid fuel.

[0017] Furthermore, the mixing method in S2 is ultrasonic oscillation mixing under constant temperature conditions, the ultrasonic oscillation mixing temperature is 15±5° C., and the ultrasonic oscillation mixing time is 20-30 min.

[0018] Furthermore, the mixing method in S3 is ultrasonic oscillation mixing under constant temperature conditions, the ultrasonic oscillation mixing temperature is 15±5° C., and the ultrasonic oscillation mixing time is 20-30 min.

[0019] The beneficial effects of the present invention compared with the prior art are as follows:

[0020] (1) The carbon dioxide generated by the metal carbide additive in the nanofluid fuel of the present invention during combustion can effectively destroy the oxide thin layer on the particle surface, exposing more active surfaces, making it easier for them to react with oxygen, thereby accelerating the combustion reaction rate and improving the combustion efficiency. It can not only enhance the combustion performance of the fuel, but also effectively improve the thermal efficiency of the combustion chamber, reduce energy loss, and thus increase the engine thrust;

[0021] (2) The gas generated by the combustion of the metal carbide additive in the nanofluid fuel of the present invention will trigger micro-explosion, secondary atomization and other processes, which greatly promotes the release of droplet energy. The droplets are broken into a large number of sub-droplets, which increases the specific surface area of ​​the droplet evaporation and accelerates the evaporation rate of the fuel. At the same time, the micro-explosion process also allows more nanoparticles to contact with the air, causing oxidation reactions and releasing a large amount of heat. The heat released by the combustion further accelerates the droplet evaporation and combustion rate.

[0022] (3) Compared with existing high-energy nano-metal particles, metal carbides have stronger antioxidant capacity and chemical stability, which can avoid oxidation in high-temperature environments and ensure the continuous reactivity of particles during combustion. At the same time, during fuel storage, metal carbides can maintain a higher content of effective components, reduce the occurrence of oxidation or sedimentation, and extend the storage life of the fuel;

[0023] (4) Compared with liquid fuel, the nanofluid fuel of the present invention has significantly improved energy density and significantly enhanced combustion heat release performance, and the fuel preparation method is simple and can be prepared in large quantities. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0025] Figure 1 A schematic diagram of a single droplet combustion test device provided according to a specific embodiment of the present invention is shown;

[0026] FIG. 2( a ) shows a normalized curve of aluminum carbide droplet diameter provided according to a specific embodiment of the present invention;

[0027] FIG2( b ) shows a normalized curve of boron carbide droplet diameter provided according to a specific embodiment of the present invention;

[0028] Figure 3 The combustion process of 30wt% Al4C3 / OA / JP-10 nanofluid fuel droplets provided according to a specific embodiment of the present invention is shown;

[0029] Figure 4 The combustion process of 30wt% B4C / OA / JP-10 nanofluid fuel droplets provided according to a specific embodiment of the present invention is shown;

[0030] FIG5( a ) shows a temperature distribution diagram of secondary atomization and micro-explosion of B4C / OA / JP-10 provided according to a specific embodiment of the present invention;

[0031] FIG5( b ) shows a temperature distribution diagram of secondary atomization and micro-explosion of Al4C3 / OA / JP-10 according to a specific embodiment of the present invention;

[0032] FIG. 6( a ) shows a maximum temperature curve of a B4C / OA / JP-10 droplet combustion process according to a specific embodiment of the present invention;

[0033] FIG6( b ) shows a maximum temperature curve of the Al4C3 / OA / JP-10 droplet combustion process according to a specific embodiment of the present invention;

[0034] Figure 7 A schematic flow chart of a method for preparing nanofluid fuel according to a specific embodiment of the present invention is shown. DETAILED DESCRIPTION

[0035] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0037] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0038] According to a specific embodiment of the present invention, a nanofluid fuel with metal carbide as an additive is provided. The nanofluid fuel includes liquid fuel, metal carbide and surfactant. The metal carbide and surfactant are uniformly dispersed in the liquid fuel, wherein the mass percentage of the metal carbide is 1% to 40%, the mass percentage of the surfactant is 1% to 15%, and the rest is liquid fuel.

[0039] By using this configuration, a nanofluid fuel with metal carbide as an additive is provided. The nanofluid fuel uses metal carbide as an additive, which can significantly enhance the energy release process (evaporation, combustion process) of the base liquid fuel by regulating combustion products, micro-explosion, secondary atomization and other phenomena while greatly improving the energy density of the liquid fuel, and inhibit the influence of metal carbide particle surface oxidation and combustion products on the heat release process, thereby significantly improving the combustion efficiency and work capacity of the fuel. Compared with the prior art, the technical solution of the present invention can solve the technical problems of insufficient energy density of liquid fuel and the influence of surface oxidation and combustion products of traditional energetic nano metal particles or metal oxide particles on the fuel combustion heat release process in the prior art.

[0040] Furthermore, in an embodiment of the present invention, the liquid fuel is a hydrocarbon liquid fuel, such as JP-10. The surfactant is one or more of stearic acid, oleic acid, citric acid ricinoleic acid, sorbitan fatty acid ester, sorbitan trioleate, and Tween-80. The stability of the nanofluid fuel can be improved by adding a surfactant. In addition, in an embodiment of the present invention, the metal carbide is nanoscale, and its particle size is 50 to 500 nm. As a specific embodiment of the present invention, the metal carbide is one or a combination of two of boron carbide and aluminum carbide, and the mass ratio of the metal carbide to the surfactant is 1:a, wherein the value range of a is 1 to 3. Boron carbide (B4C), aluminum carbide (Al4C3) and other metal carbides have high calorific value (B4C volume calorific value 130.6MJ / L, Al4C3 volume calorific value 70.7MJ / L) and excellent thermophysical properties (B4C thermal conductivity 300 ~ 500W / (m·K)), which can significantly improve the energy density of existing liquid JP-10 fuel (39.4MJ / L); at the same time, using them as additives can help shorten the ignition delay time of liquid fuel, accelerate the evaporation process of liquid fuel, and increase the fuel combustion rate. In other words, nanofluid fuels with metal carbides as additives have the advantages of increasing combustion speed, increasing combustion stability, increasing volumetric energy density, improving catalytic activity, and reducing ignition delay, thereby improving engine thrust and efficiency.

[0041] Please refer to Figure 7 According to another aspect of the present invention, a method for preparing the nanofluid fuel proposed in the present invention is provided, the method comprising:

[0042] S1, determine the types of liquid fuel, metal carbide and surfactant;

[0043] S2, adding a surfactant to the liquid fuel and mixing them evenly to obtain a mixed base liquid of the nanofluid fuel;

[0044] S3, adding metal carbide to the mixed base liquid obtained in S2, and mixing them evenly to obtain uniformly dispersed nanofluid fuel.

[0045] Furthermore, in the embodiment of the present invention, the mixing methods in S2 and S3 are both ultrasonic oscillation mixing under constant temperature conditions, the ultrasonic oscillation mixing temperature is 15±5°C, and the ultrasonic oscillation mixing time is 20-30 minutes. In this way, it can be ensured that the nanofluid fuel has the best dispersion stability.

[0046] In order to further understand the present invention, the following Figure 1 6 and FIG. 6 illustrate in detail the preparation method and combustion performance of the nanofluid fuel of the present invention.

[0047] 1. Sample preparation

[0048] The types of liquid fuel, metal carbide and surfactant were determined, and nanofluid fuel was prepared by a two-step method. JP-10 was used as the base liquid and oleic acid (OA) was used as the surfactant. First, a certain amount of JP-10 and OA were weighed and ultrasonically oscillated for 20 minutes at a constant temperature (15±5℃). Then, a certain amount of boron carbide and aluminum carbide metal powders were weighed according to the ratio of OA: metal powder = 1:3, placed in a reagent bottle, and ultrasonically oscillated again for 20 minutes. During the ultrasonic treatment, in order to prevent overheating, an ice bath was used to ensure that the temperature was around 15℃. This ensures that the fuel has the best dispersion stability. Table 1 lists the components and names of each group of samples.

[0049] Table 1 Composition and name of fuel

[0050]

[0051] 2. Combustion test device

[0052] Figure 1 The schematic diagram of the experimental device for the combustion characteristics of a single droplet includes an ignition module, a droplet suspension and positioning module, a high-speed imaging and temperature measurement module, an illumination module, and a flame emission spectrum detection module. In the ignition module, a high-temperature zone is formed around the nickel-chromium wire coil by electric heating, and the power of the nickel-chromium wire coil is controlled by an external voltage-stabilized power supply. The high-temperature zone is distributed in a gradient along the direction perpendicular to the heating wire, and the maximum temperature can reach 800°C. In the droplet suspension and positioning module, in order to ensure the precise positioning of the droplet and keep the ignition position consistent in multiple experiments, this experiment uses a robotic arm with an accuracy of 20μm to position the droplet to the high-temperature zone to eliminate the difference in ambient temperature caused by droplet positioning in multiple experiments. A quartz fiber with a diameter of 125μm and a low thermal conductivity (1.4W / mK) is fixed at the end of the robotic arm. The micro-syringe produces droplets and transfers them to the quartz fiber, which is suspended at the end of the fiber. Because the droplets are affected by gravity, suspended fibers, and surface tension, the droplets are elliptical. In order to minimize the influence of droplet size and morphology on the experiment, the droplets in each group of experiments maintained the same morphology, and the equivalent diameter was almost constant at 1.1±0.1mm. After setting the starting and ending points of the quartz optical fiber, the automatic positioning of the droplets was completed by controlling the robotic arm. In the high-speed imaging and temperature measurement module, a high-speed camera (Phantom Micro M310) with a lens was used to record the droplet combustion process at a frame rate of 10,000fps and a resolution of 512×512 pixels. In the illumination module, the backlight source is located on the same axis as the high-speed camera to provide a uniform bright field of view and measure the droplet size and flame profile.

[0053] The flame emission spectrum detection module consists of a fiber optic spectrometer (Aurora4000) to record the emission spectrum of the droplet flame. The spectral range is 200nm to 1100nm, and the spectral resolution of the spectrometer is 0.75nm. The integration time in all experiments was kept at 400ms. In order to accurately measure and verify the repeatability of the experiment, each set of experiments was repeated 5 times.

[0054] Figure 2(a) and Figure 2(b) show the normalized and compared results of the droplet combustion process between different samples repeated 5 times. It should be noted that in order to eliminate the influence of droplet size differences, the time and instantaneous diameter are divided by Ensure the results are normalized. Figure 2(a) is a normalized graph of the droplet size of 30wt.% aluminum carbide. In the initial combustion stage of the droplets, the droplet size shows a slow downward trend. As the pressure inside the droplets accumulates and the temperature rises, the droplets begin to undergo micro-explosions of varying degrees. At this time, the fourth group of samples was observed to have the highest micro-explosion intensity. Due to the droplet fragmentation caused by the micro-explosion, the mother droplet was destroyed, resulting in a sharp drop in the droplet size.

[0055] Figure 2(b) is a normalized graph of the particle size of 30wt.% boron carbide droplets. Unlike aluminum carbide, the stable combustion stage of the droplets is shorter, and several groups of droplets successively experience micro-explosions of varying degrees at around 0.3s. In the 0.5-1.6s stage, the droplets undergo multiple micro-explosions, and the micro-explosions of several groups of droplets have similar intensities and occur in the same time range. After the micro-explosion ends, the droplets have a relatively long period of stable combustion, and the droplet particle size changes tend to be stable until they are finally extinguished.

[0056] In a comprehensive comparison, boron carbide droplets have good combustion characteristics, similar droplet combustion conditions, and more micro-explosions. The micro-explosions of aluminum carbide samples vary in strength, and the combustion conditions vary greatly. Only one strong micro-explosion occurs, and the number of times is less than that of boron carbide. This is consistent with the experimental conclusion that the spectral intensity of boron carbide is higher than that of aluminum carbide. This shows that boron carbide has better combustion performance during the combustion process.

[0057] 3. Combustion evolution process and characteristics

[0058] Figure 3The combustion process of 30wt% aluminum carbide (chemical formula Al4C3) is shown. The three-stage combustion process of Al4C3 / OA / JP-10 nanofluid fuel droplets can be clearly observed, namely, stage I (Figures a1, a2), stage II (Figures a3-a6) and stage III (Figures a7, a8). During the first stage, the secondary flame or flame oscillation has not yet been determined, and the flame is orange, which should be attributed to the combustion of JP-10, and the droplets maintain a constant combustion rate; in the second stage, the droplets undergo a micro-explosion, the stable flame is interrupted, the flame height rises rapidly, the outer front of the flame changes continuously, and a bubble-like flame can be observed (Figures a3-a6), which indicates that dense concentrations of bubbles have been formed in the nanofluid droplets. When the bubble pressure exceeds the surface tension, secondary atomization and micro-explosion will occur, and the secondary droplets will be ejected from the primary droplets, participate in the combustion, and micro-explosion will occur; when the liquid fuel is almost exhausted, the Al4C3 nanoparticle agglomerates participate in the combustion and last for a long time, which is the third stage.

[0059] Figure 4 The combustion process of 30wt% boron carbide (chemical formula B4C) also observed the three-stage combustion process of B4C / OA / JP-10 nanofluid fuel droplets. After ignition, an envelope flame began to form, and the stable flame length was slightly smaller than that of the Al4C3 fuel droplets. After a short period of stable combustion, the combustion quickly entered the second stage, the flame height rose and fluctuated uninterruptedly, and a bubble-like flame was also identified, and a micro-explosion phenomenon occurred. However, a comparison found that the start time of stage II of the fuel droplets with added B4C was advanced, but the duration was shortened, and the intensity was significantly less than that of the Al4C3 fuel droplets.

[0060] 4. Temperature distribution diagram of secondary atomization and micro-explosion

[0061] Figures 5(a) and 5(b) show the two-dimensional distribution images of flame temperature during the micro-explosion and secondary atomization process of B4C / OA / JP-10 and Al4C3 / OA / JP-10, respectively. It can be seen that after the micro-explosion occurs, the stable combustion state of the flame ends and the flame morphology changes significantly. The temperature of the flame surface increases significantly and the width of the high-temperature area increases, which shows that the micro-explosion and secondary atomization process greatly promote the release of droplet energy. The droplets break up to form a large number of sub-droplets, which increases the specific surface area of ​​droplet evaporation and accelerates the evaporation rate of the fuel. At the same time, the micro-explosion process also allows more nanoparticles to come into contact with the air, undergoing oxidation reactions and releasing a large amount of heat. The heat released by these combustions further accelerates the droplet evaporation and combustion rate.

[0062] Figure 6(a) and Figure 6(b) show the changes in the maximum temperature of the flame surface during the combustion process of B4C / OA / JP-10 and Al4C3 / OA / JP-10, respectively. It can be seen that the micro-explosion and secondary atomization process significantly increase the maximum temperature of the flame. Compared with the stable combustion temperature (about 1600℃), the maximum temperature of the flame increases by more than 15%, and its maximum temperature can even reach about 2200℃. Comparing the combustion flame temperatures of the samples with two different particles of B4C and Al4C3, it is found that the temperature of the fuel with the B4C sample is higher during the combustion process. It proves that compared with Al4C3 particles, the addition of B4C samples can promote the release of more energy from the fuel. At the same time, the temperature of the fuel droplets with the B4C sample rises earlier during the combustion process, proving that it can greatly advance the time of the micro-explosion phenomenon. It is worth noting that there is a peak temperature at the ignition moment (B4C 1831℃, Al4C3 1753℃), which is about 230℃ and 150℃ higher than the stable combustion temperature, respectively. This is because the oxidation reaction results in a large amount of heat release, raising the temperature of the system, which is then lost to the surrounding air after ignition causing the temperature in the system to drop.

[0063] In summary, the present invention provides a nanofluid fuel with metal carbide as an additive and a preparation method thereof. The nanofluid fuel uses metal carbide as an additive, and while greatly improving the energy density of liquid fuel, by regulating combustion products and micro-explosions, secondary atomization and other phenomena, it can significantly enhance the energy release process (evaporation, combustion process) of the base liquid fuel, and inhibit the influence of metal carbide particle surface oxidation and combustion products on the heat release process, thereby significantly improving the fuel's combustion efficiency and work capacity. Compared with the prior art, the technical solution of the present invention can solve the technical problems of insufficient energy density of liquid fuel and the influence of traditional energetic nano metal particles or metal oxide particles' surface oxidation and combustion products on the fuel combustion heat release process in the prior art.

[0064] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0065] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A nanofluid fuel with metal carbide as an additive, characterized in that: The nanofluid fuel comprises liquid fuel, metal carbide and surfactant, wherein the metal carbide and the surfactant are uniformly dispersed in the liquid fuel, wherein the mass percentage of the metal carbide is 1% to 40%, the mass percentage of the surfactant is 1% to 15%, and the rest is the liquid fuel.

2. The nanofluid fuel according to claim 1, characterized in that: The particle size of the metal carbide is 50 to 500 nm.

3. The nanofluid fuel according to claim 2, characterized in that: The metal carbide is boron carbide, aluminum carbide or a combination of both.

4. The nanofluid fuel according to claim 1, characterized in that: The surfactant is one or more of stearic acid, oleic acid, citric acid ricinoleic acid, sorbitan fatty acid ester, sorbitan trioleate, and Tween-80.

5. The nanofluid fuel according to claim 4, characterized in that: The mass ratio of the metal carbide to the surfactant is 1:a, wherein the value range of a is 1-3.

6. The nanofluid fuel according to claim 1, characterized in that: The liquid fuel is hydrocarbon liquid fuel.

7. The nanofluid fuel according to claim 6, characterized in that: The liquid fuel is tetrahydrodicyclopentadiene.

8. A method for preparing the nanofluid fuel according to any one of claims 1 to 7, characterized in that: The method comprises: S1, determine the types of liquid fuel, metal carbide and surfactant; S2, adding a surfactant to the liquid fuel and mixing them evenly to obtain a mixed base liquid of the nanofluid fuel; S3, adding metal carbide to the mixed base liquid obtained in S2, and mixing them evenly to obtain uniformly dispersed nanofluid fuel.

9. The preparation method according to claim 8, characterized in that: The mixing method in S2 is ultrasonic oscillation mixing under constant temperature conditions, the ultrasonic oscillation mixing temperature is 15±5°C, and the ultrasonic oscillation mixing time is 20-30min.

10. The preparation method according to claim 8, characterized in that: The mixing method in S3 is ultrasonic oscillation mixing under constant temperature conditions, the ultrasonic oscillation mixing temperature is 15±5°C, and the ultrasonic oscillation mixing time is 20-30min.

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