Modified boron-based phase change heat absorption nanofluid hydrocarbon fuel and preparation method thereof

Abstract

According to the modified boron-based phase change heat absorption nanofluid hydrocarbon fuel and the preparation method thereof, RP-3 kerosene is used as matrix fuel, paraffin (PW) is used as a phase change fuel additive, nano boron (NBK) coated and modified by a silane coupling agent (KH550) is used as a high-energy nano particle additive, and the matrix fuel, the PW and the NBK are uniformly mixed to form the modified boron-based phase change heat absorption nanofluid hydrocarbon fuel. By combining the molecular confinement of the phase change paraffin and the boron nanoparticle catalytic cracking strategy, the prepared boron-based heat absorption phase change nanofluid fuel has the advantages of stable physical form, no layering, super-long dispersion stability in a normal temperature environment and the like, and the preparation process has the characteristics of simplicity in operation, high practicability and the like.

Description

Technical Field

[0001] This invention relates to a technology in the field of aviation fuel, specifically a modified boron-based phase change endothermic nanofluid hydrocarbon fuel for high Mach number scramjet engines and its preparation method. Background Technology

[0002] During the high-speed cruise of hypersonic vehicles, the peak heat flux density of the engine combustion chamber can reach 3 MW / m², and the wall temperature ranges from 2500 K to 3000 K, far exceeding the safety limits of existing materials. Under higher flight Mach number conditions, the heat absorption energy and calorific value of existing hydrocarbon fuels are insufficient in high Mach number scenarios, and nanoparticles cannot be stably dispersed for a long time, resulting in problems such as low combustion efficiency, long ignition delay, incomplete combustion, and unstable thrust output. Summary of the Invention

[0003] This invention addresses the shortcomings of existing traditional hydrocarbon fuels in terms of endothermic energy and calorific value by proposing a modified boron-based phase change endothermic nanofluid hydrocarbon fuel and its preparation method. By combining the molecular confinement of phase change paraffin with the catalytic cracking strategy of boron nanoparticles, the prepared boron-based endothermic phase change nanofluid fuel has advantages such as physical morphological stability, no stratification, and ultra-long dispersion stability at room temperature. The preparation process is simple to operate and highly practical.

[0004] This invention addresses the aforementioned shortcomings of the prior art.

[0005] This invention is achieved through the following technical solution:

[0006] This invention relates to a method for preparing a modified boron-based phase change endothermic nanofluid hydrocarbon fuel. The method uses RP-3 kerosene as the base fuel, paraffin (PW) as the phase change fuel additive, and silane coupling agent (KH550)-coated modified boron nanoparticles (NBK) as the high-energy nanoparticle additive. The base fuel, PW, and NBK are uniformly mixed to form the modified boron-based phase change endothermic nanofluid hydrocarbon fuel.

[0007] The high-energy nanoparticle additive accounts for 5%-25% of the total mass of the phase change fuel, i.e., the base fuel and the phase change fuel additive.

[0008] The phase change fuel additives account for 2%-10% of the mass of the base fuel.

[0009] The silane coupling agent (KH550)-coated modified boron nanoparticles (NBK) are obtained by dispersing micron-sized amorphous boron powder (MB) in an aqueous ethanol solution, adding an aqueous solution of silane coupling agent (KH550) modified with glacial acetic acid (AR), and centrifuging after sufficient reaction.

[0010] The complete reaction refers to the reaction being carried out at 60 °C with magnetic stirring for 6 h, followed by washing with ethanol and deionized water three times each after the reaction is completed.

[0011] The centrifugal separation refers to: after the fully reacted product is centrifuged, it is freeze-dried at -60 ℃ for 72 hours.

[0012] Technical effect

[0013] This invention utilizes sliced ​​paraffin as a macromolecular segment to spatially confine the movement of kerosene molecules and nanoparticles, preparing endothermic, ultra-stable nanofluid hydrocarbon fuels. Simultaneously, a novel KH550-modified boron-coated nanoparticle is synthesized using the silane coupling agent KH550 (γ-aminopropyltriethoxysilane) through ultrasonic nanostructuring. This strategy enables the formation of boron nanoparticles-KH55 (NBK) for catalytic cracking of hydrocarbon fuels. The phase-change nanofluid fuel prepared by this invention exhibits a flowable state at low temperatures, enabling ultra-long-term storage; at high temperatures, it transforms into a nanofluid state, increasing the fuel's physical endothermic energy. Furthermore, the high-energy boron nanofluid fuel possesses both flow stability and catalytic cracking performance in its fluid state. This invention provides theoretical support for solving the design of endothermic fuels and nanofluid combustion problems in high-Mach number hypersonic vehicles, and also offers innovative ideas and theoretical references for research on other related issues in the fields of endothermic fuel design and high-energy nanoparticle catalytic combustion chemistry. Attached Figure Description

[0014] Figure 1 The images show (a) a schematic diagram of the molecularly confined nanofluid fuel of the present invention; and (b) a physical image of RP-3 fuel containing 0-10% PW.

[0015] Figure 2 The diagram shows (a) the preparation of NBK and (b) its reaction mechanism.

[0016] Figure 3 FTIR spectra of MB, NB, KH550 and NBK;

[0017] Figure 4 SEM images of (a)MB, (b)NB, and (c)NBK, and EDS analysis of B and Si elements in NBK;

[0018] Figure 5 TG-DSC curves for MB and NBK particles;

[0019] Figure 6 The dispersion stability of MB / RP-3, NBK / RP-3 and NBK / PW-RP-3 at different times;

[0020] Figure 7DSC curves (a) and corresponding physical endothermic energy (b) for RP-3, PW-RP-3 and NBK / PW-RP-3;

[0021] Figure 8 The GC-MS spectra of RP-3, PW-RP-3 and NBK / PW-RP-3 fragmentation under nitrogen conditions at 900℃ are shown.

[0022] Figure 9 Ignition delay time for PW-RP-3 with different contents and PW-RP-3 containing MB, NB, and NBK;

[0023] Figure 10 The ignition process of PW-RP-3 fuel containing MB and NBK under the action of a pulse igniter;

[0024] Figure 11 SEM image (a) and EDS analysis diagram (b) of the combustion products of MB / PW-RP-3 and NBK / PW-RP-3. Detailed Implementation Example

[0025] This embodiment includes the following steps:

[0026] Step 1: Preparation of phase change hydrocarbon fuels, specifically including:

[0027] 1.1 Add 1 g of kerosene RP-3 to a beaker;

[0028] 1.2 Add PW to a beaker with a mass percentage of 0-10%, where 0% is the comparative example;

[0029] 1.3 PW and RP-3 were uniformly mixed by magnetic stirring for 30 min (80 ℃, 500 rpm) to form phase change hydrocarbon fuel PW-RP-3.

[0030] like Figure 1 As shown in (a), this embodiment demonstrates the physical morphology of fuel formed by adding 0-10% sliced ​​paraffin (PW) to RP-3 fuel according to the molecular confinement nanofluid fuel construction strategy. The phase change fuel is formed by confining kerosene molecules within the paraffin slice macromolecules, achieving long-term stability of the nanofluid fuel and enhancing its physical endothermic energy.

[0031] like Figure 1 (b) shows images of RP-3 fuel containing 0-10% PW, which was prepared by mixing at 80 °C for 30 min and then cooling. As the PW content increases, the fuel gradually changes from colorless to milky white; when the PW content reaches 10%, the fuel can maintain a gel state (it is still flowable when the PW content is 8%).

[0032] Step 2: Synthesize KH550 modified coated B nanoparticles (NBK), specifically including:

[0033] 2.1 Add 200 mL of a mixed solvent of anhydrous ethanol and deionized water (mass ratio 1:1) to the flask;

[0034] 2.2 Two g of micron-sized amorphous boron powder MB was ultrasonically dispersed (25℃, 300 W, 4 h) in a mixed solvent of anhydrous ethanol and deionized water for nano-sizing.

[0035] 2.3 Dissolve 0.8 g of silane coupling agent KH550 in 4 g of deionized water, then add 0.3 g of glacial acetic acid (AR) to prepare a KH550 modified solution;

[0036] 2.4 Add KH550 modification solution to the flask to perform surface modification of boron nanoparticles (NB);

[0037] 2.5 The surface modification reaction was carried out in the above flask at 60 °C for 6 h by magnetic stirring (1000 r / min);

[0038] 2.6 After the reaction is complete, wash three times each with ethanol and deionized water;

[0039] 2.7 The above products were separated by centrifugation (10000 r / min, 15 min);

[0040] 2.8 The separated product was freeze-dried at -60 °C for 72 h to obtain the solid product, NBK.

[0041] like Figures 2-5 As shown, the NBK sample synthesized in this embodiment is a NB sample modified with KH550. It retains the BB bond stretching vibration peak of NB at 1380 cm⁻¹ and exhibits the Si-OB stretching vibration peak at 1050 cm⁻¹, indicating successful surface modification of NB by the KH550 coupling agent. The NBK nanoparticles have a diameter of approximately 434.3–664.8 nm, and the Si element in the NB treated with KH550 is uniformly dispersed on the NB surface. The initial oxidation temperatures (Ti) of MB and NBK boron particles are essentially the same, at 783.4 °C and 784.3 °C, respectively. Compared to MB, NBK shows an 8% increase in TG (the increased mass of oxygen in the boron oxide produced by the reaction of boron and oxygen), indicating that under the same testing conditions, the oxidation degree of NBK is 3.6% higher than that of MB (the proportion of B bound by 8% oxygen). Comparing the calorific values ​​of MB and NBK, the calorific value of MB increases from 13.9 kJ / g to 17.6 kJ / g, attributed to the improved oxidation performance of NBK.

[0042] Step 3: Prepare boron-based nanofluid fuel and boron-based phase change nanofluid fuel, specifically including:

[0043] 3.1 Add RP-3 or PW-RP-3 (10%) to a beaker, with a mass of 1 g;

[0044] 3.2 Add NBK (MB) to the beaker, accounting for 20% of the mass of the above fuel;

[0045] 3.3 The nanofluid fuel was uniformly dispersed by ultrasonic dispersion for 10 min (100 W, 20 ℃) ​​and magnetic stirring for 30 min (80 ℃, 600 rpm).

[0046] In this embodiment, a digital camera was used to measure the dispersion stability characteristics of MB / RP-3, NBK / RP-3, and NBK / PW-RP-3, respectively. Cases with a 20% content are listed below.

[0047] like Figure 6 As shown, in this embodiment, MB began to settle in RP-3 after 2 minutes during the preparation process; NBK modified by nano-sizing and KH550 treatment settled in RP-3 after 60 minutes, and due to the nano-sizing and modification treatment of NBK, its agglomeration volume was much smaller than that of unmodified MB. For NBK / PW-RP-3 fuel, thanks to the molecular confinement effect, the fuel could maintain stable dispersion throughout the entire test period, and no sedimentation occurred even after 180 days. Example

[0048] In this embodiment, boron-based phase change nanofluid fuel is prepared in the following proportions:

[0049] Step 1: Add 1 g of PW-RP-3 (10%) to a beaker;

[0050] Step 2: Add NBK to the beaker, accounting for 20% of the mass of the fuel mentioned above;

[0051] Step 3: Disperse the nanofluid fuel uniformly by ultrasonic dispersion for 10 min (100 W, 20 ℃) ​​and magnetic stirring for 30 min (80 ℃, 600 rpm).

[0052] In this embodiment, DSC and pyrolysis GC-MS were used to measure the physical and chemical endothermic properties of RP-3, PW-RP-3, and NBK / PW-RP-3 fuels, respectively. Cases with a 20% content are listed.

[0053] like Figure 7 and 8As shown, the physical endothermic energies of RP-3, PW-RP-3, and NBK / PW-RP-3 fuels in this embodiment are 400.02 J / g, 506.85 J / g, and 529.72 J / g, respectively. Adding PW increased the physical endothermic energy of RP-3 by 26.7%; adding NBK to PW-RP-3 fuel to form a confined nanofluid fuel further increased the physical endothermic energy by an additional 4.5%. Compared with pure RP-3, the total physical endothermic energy of NBK / PW-RP-3 increased by 32.4%. Adding PW to RP-3 forms a confined fluid fuel, further increasing the phase change heat storage (i.e., the transition from confined fluid to liquid fluid fuel). Comparing the spectra of PW-RP-3 and NBK / PW-RP-3 shows that the addition of NBK promoted the conversion of short-chain alkanes to olefins in RP-3, indicating that NBK has a very significant catalytic effect on the olefin cracking of RP-3. The addition of NBK promoted the catalytic cracking of short-chain and long-chain alkanes into olefins, increasing the olefin content from 19.89% in PW-RP-3 (of which RP-3 accounted for 21.16%) to 66.74% (the sum of short-chain and long-chain olefins). For uncracked pure RP-3 fuel, the olefin content is approximately 3.06% of the total fuel; while at 900°C, the olefin contents in the cracking products of RP-3, PW-RP-3, and NBK / PW-RP-3 fuels are 18.10%, 16.83%, and 63.68%, respectively. Therefore, the olefin yield of NBK / PW-RP-3 fuel increased from 16.83% in PW-RP-3 to 63.68%, which is 378.4% of that of PW-RP-3 fuel without NBK. Adding NBK to PW-RP-3 increases the fuel's chemical endothermic energy by 468.50–702.75 kJ / kg. The chemical endothermic energy of pure RP-3 is approximately 1300 kJ / kg (under supercritical conditions and at 5 MPa pressure). The chemical endothermic energy of the fuel was increased by approximately 36.04%–54.06% through olefin catalytic cracking. Example

[0054] In this embodiment, boron-based phase change nanofluid fuel is prepared in the following proportions:

[0055] Step 1: Add 1 g of PW-RP-3 (10%) to a beaker;

[0056] Step 2: Add NBK (MB or NB) to the beaker, with a mass percentage of 0-25%;

[0057] Step 3: Disperse the nanofluid fuel uniformly by ultrasonic dispersion for 10 min (100 W, 20 ℃) ​​and magnetic stirring for 30 min (80 ℃, 600 rpm).

[0058] This embodiment uses a suspended droplet pulse ignition experimental device and a high-speed camera to measure the ignition and combustion characteristics of 5-25% CPZS@B-0.5 / RP-3 nanofluid fuels. The ignition and combustion results for fuels containing 20% ​​CPZS@B-0.5 / RP-3 are also listed.

[0059] like Figure 9 , 10 and Figure 11 As shown, at a low addition level of 5%, the ignition delay times were slightly shorter than those of PW-RP-3 after adding MB, NB, and NBK, respectively, to 21.0 ms, 15.5 ms, and 14.6 ms. When the addition level increased to 10%, the ignition delay times for MB, NB, and NBK were 49.4 ms, 31.0 ms, and 26.6 ms, respectively. The ignition delay time was 11.9 ms when 25% NBK was added. The combustion process of PW-RP-3 is mainly based on the evaporation combustion of hydrocarbon fuels, while the combustion process of fuels with added nano-boron consists of two stages: the hydrocarbon fuel evaporation combustion stage (Stage I) and the nanoparticle combustion stage (Stage II). Comparison of SEM micrographs of the combustion products of MB / PW-RP-3 and NBK / PW-RP-3 revealed that the combustion products of MB / PW-RP-3 consisted of particles with non-uniform size and still contained unburned boron particles. In contrast, the combustion products of NBK / PW-RP-3 exhibited a porous structure composed of interconnected, uniform nanoscale particles. Furthermore, Si (as in the KH550 combustion products) was detected in the combustion products of NBK / PW-RP-3. Combining the elemental distributions of B, O, and Si in the combustion products of MB / PW-RP-3 and NBK / PW-RP-3, the oxidation performance of NBK was significantly enhanced, increasing from 10.77% to 31.83%. The increased O content indicates that NBK can generate more B2O3 compared to unmodified boron, thus improving the degree of boron oxidation (consistent with TG-DSC analysis results).

[0060] In summary, this invention utilizes sliced ​​paraffin as a macromolecular segment to spatially confine the movement of kerosene molecules and nanoparticles to prepare endothermic, ultra-stable nanofluid hydrocarbon fuels. Simultaneously, based on the ultrasonic nanostructuring of the silane coupling agent KH550 (γ-aminopropyltriethoxysilane), a novel KH550-modified boron-coated nanoparticle is synthesized. This strategy can form boron nanoparticles-KH55 (NBK) for catalytic cracking of hydrocarbon fuels.

[0061] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A method for preparing a modified boron-based phase change heat-absorbing nanofluid hydrocarbon fuel, characterized in that, A modified boron-based phase change endothermic nanofluid hydrocarbon fuel is formed by uniformly mixing a base fuel, a paraffin wax (PW) as a phase change fuel additive, and a nanometer boron (NBK) coated with a silane coupling agent (KH550) as a high-energy nanoparticle additive.

2. The method for preparing modified boron-based phase change endothermic nanofluid hydrocarbon fuel according to claim 1, characterized in that, The high-energy nanoparticle additive accounts for 5%-25% of the total mass of the phase change fuel, i.e., the base fuel and the phase change fuel additive.

3. The method of claim 1 or 2, wherein the modified boron-based PCN nanofluid hydrocarbon fuel is prepared by the steps of: (a) mixing the boron-based PCN nanofluid with the hydrocarbon fuel; (b) adding the surfactant to the mixture; and (c) mixing the mixture. The phase change fuel additive accounts for 2%-10% of the mass of the base fuel.

4. The method for preparing modified boron-based phase change endothermic nanofluid hydrocarbon fuel according to claim 1, characterized in that, The nanometer boron (NBK) coated with the silane coupling agent (KH550) is obtained by dispersing micro-sized amorphous boron powder (MB) in an ethanol aqueous solution, adding a silane coupling agent (KH550) aqueous solution modified by glacial acetic acid (AR), and centrifugally separating the product after sufficient reaction.

5. The method for preparing modified boron-based phase change endothermic nanofluid hydrocarbon fuel according to claim 1, characterized in that, The sufficient reaction refers to magnetic stirring reaction at 60 ℃ for 6 h, and washing with ethanol and deionized water for 3 times respectively after the reaction.

6. The method for preparing modified boron-based phase change endothermic nanofluid hydrocarbon fuel according to claim 1, characterized in that, The centrifugal separation refers to freezing and drying the product after centrifugal separation at-60 ℃ for 72 h.

7. The modified boron-based PCHE nanofluid hydrocarbon fuel prepared by the method according to any one of claims 1-6, characterized in that, The modified boron-based phase change endothermic nanofluid hydrocarbon fuel is in a flowable state and a nanofluid state at different temperatures.

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