A medium-high temperature heat power conversion working medium for high-speed aircraft and a preparation method and application thereof

Abstract

The application discloses a medium-high temperature heat power conversion working medium for high-speed aircrafts and a preparation method and application thereof, and comprises the following components in percentage by mass: 10-90% of ammonia, 10-70% of multi-component alcohol, and the rest of water; the multi-component alcohol comprises at least two of ethanol, isopropyl alcohol, ethylene glycol, n-propanol and n-butanol; and the mass of each alcohol in the multi-component alcohol accounts for 5-40% of the total mass of the medium-high temperature heat power conversion working medium. The ammonia, multi-component alcohol and water are combined for the first time, and a double-bed catalyst is combined, so that not only the physical heat absorption can be utilized, but also the heat absorption can be strengthened through chemical reaction, the heat sink can reach more than 7.0 MJ / kg, the application can be used for the aerodynamic heat absorption of the high-speed aircrafts with the speed higher than 5 Mach, the cooling capacity is high, the application is suitable for the heat protection system of the components with higher heat flow density and continuous long-time aerodynamic heating; meanwhile, the high-temperature high-pressure small-molecule gas is generated, the thrust can be generated to do work, and the maneuverability of the high-speed aircrafts is effectively strengthened.

Description

Technical Field

[0001] The present invention relates to the technical field of high-speed aircraft, and more specifically, to a medium- and high-temperature heat-to-power conversion working fluid for high-speed aircraft, and a preparation method and application thereof. Background Art

[0002] High-speed aircraft, with their rapid response, quick strike, and easy penetration, have become a crucial tool in transforming future warfare and combat modes. When high-speed aircraft fly at high speeds, shock wave compression, viscous friction, and other factors cause the temperature of their outer walls and surrounding areas to rise rapidly. To ensure that internal components operate within the permitted temperature range and maintain their aerodynamic shape, effective structural thermal protection design is essential.

[0003] Thermal protection technology can be mainly divided into passive and active thermal protection technologies. Passive thermal protection that uses thermal insulation materials or phase change of ablative materials to absorb heat is the most widely used aerodynamic heat treatment measure and is used in many high-speed aircraft (such as the US X-30 and X-47). This type of thermal protection technology has a relatively simple structure, but the preparation process is complex and the cost is high. When the ablative thermal protection system is flying at high speed, the material will gradually be ablated as the temperature rises, which can easily change the overall aerodynamic shape and cause accidents. At the same time, due to the weak heat absorption capacity of the passive thermal protection system, the thickness and weight of the materials required for long-duration applications are large, which seriously compresses the payload of the aircraft.

[0004] In contrast, active thermal protection uses cooling fluids to remove or block heat from the structure through various cooling methods. Compared with passive thermal protection, active thermal protection has the advantages of strong cooling capacity, the ability to withstand long-term heating with high-density heat flow, and the ability to achieve closed-loop temperature control. Active thermal protection technologies are mainly divided into two categories: sweat cooling and convection cooling. The commonly used cooling fluid for sweat cooling is water. It draws on the way organisms dissipate heat through sweating, using the latent heat of vaporization of water to absorb heat and form a thermal insulation barrier, but the system reliability is poor. Convection cooling is often used in aerospace vehicles or aircraft. Generally, circulating liquid hydrocarbon fuel is used as a coolant, and the physical heat capacity of the fuel's heating is used to remove heat from the surface of the structure. Due to the limitation of fuel coking, this heat absorption mode is only suitable for supersonic flight at speeds below Mach 5. Summary of the Invention

[0005] In order to overcome the problems of low heat sink and easy carbon deposition of cooling fluids in existing active thermal protection technologies, the present invention provides a medium- and high-temperature heat-to-work conversion fluid for high-speed aircraft, and its preparation method and application, which can absorb heat by coupling physical (sensible heat, latent heat) and chemical reactions to improve the heat sink and thermal protection performance of the working fluid. In addition, the high-temperature and high-pressure gas small molecules (hydrogen, nitrogen, carbon monoxide, etc.) produced by the reaction can be used to do external work. Therefore, based on this green working fluid, not only can the heat absorption capacity of the system be improved, but also aerodynamic heat can be converted into chemical energy to realize waste heat utilization, thereby reducing the thickness of the aircraft's thermal insulation layer, increasing the system's payload, and improving the aircraft's maneuverability.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A medium- and high-temperature heat-to-power conversion working fluid for high-speed aircraft, comprising the following components in percentage by mass: 10% to 90% ammonia, 10% to 70% multi-component alcohol, and the remainder water;

[0008] The multi-component alcohol comprises at least two of ethanol, isopropanol, ethylene glycol, n-propanol and n-butanol;

[0009] The mass of each alcohol in the multi-component alcohol is 5% to 40% of the total mass of the medium- and high-temperature heat-to-power conversion working medium.

[0010] Preferably, the multi-component alcohol is ethanol and isopropanol.

[0011] Optionally, when the multi-component alcohol is ethanol and isopropanol, the medium- and high-temperature heat-to-power conversion working fluid includes the following components in percentage by mass: 10% to 90% ammonia, 5% to 40% ethanol, 5% to 30% isopropanol, and the rest is water.

[0012] Preferably, the medium- and high-temperature heat-to-power conversion working fluid comprises the following components in percentage by mass: 10% to 90% ammonia, 10% to 30% ethanol, 5% to 20% isopropanol, and the remainder is water.

[0013] The present invention also discloses a method for preparing the above-mentioned medium- and high-temperature heat-to-power conversion working medium for high-speed aircraft, comprising the following steps:

[0014] Ammonia gas is introduced into water to obtain an ammonia solution, and then multi-component alcohol is added and mixed at 0° C. to 20° C. to obtain the medium- and high-temperature heat-to-power conversion working fluid.

[0015] The present invention also discloses a medium-high temperature heat-to-power conversion working fluid for high-speed aircraft as described above, or the use of the medium-high temperature heat-to-power conversion working fluid for high-speed aircraft prepared by the above preparation method in a heat-to-power conversion system of a high-speed aircraft;

[0016] The application includes: subjecting the medium- and high-temperature heat-to-work conversion medium to a chemical endothermic reaction under the action of high-temperature aerodynamic heat and a catalyst to generate high-temperature and high-pressure gas small molecules.

[0017] Optionally, the temperature of the chemical endothermic reaction is 500°C to 900°C.

[0018] Optionally, the catalyst is silicic-calcium alumina and an active component supported on the silicic-calcium alumina.

[0019] Optionally, the catalyst is a dual-bed catalytic system comprising a front-bed catalyst and a rear-bed catalyst, wherein the front-bed catalyst accounts for 10% to 100% of the total catalyst mass, and the rear-bed catalyst accounts for 0% to 90% of the total catalyst mass.

[0020] Optionally, the forebed catalyst includes siliceous calcium alumina and an active component supported on the siliceous calcium alumina.

[0021] Optionally, in the fore-bed catalyst, the active components in the fore-bed catalyst include at least two of Ru, Cu, Ni, and Pt.

[0022] Optionally, in the fore-bed catalyst, the mass of the active component accounts for 5% to 30% of the total mass of the fore-bed catalyst; in the active component, the molar amount of each metal element is 10% to 90% of the total molar amount of the active component.

[0023] Optionally, the rear bed catalyst is porous activated carbon loaded with active metals.

[0024] Optionally, the specific surface area of ​​the rear bed catalyst is 200m 2 / g~2000m 2 / g.

[0025] Optionally, the active metal in the rear bed catalyst includes one or more of Ba, La and Ca.

[0026] Optionally, in the rear bed catalyst, the mass of the active metal accounts for 1% to 5% of the total mass of the rear bed catalyst.

[0027] Optionally, the front bed catalyst is used to catalyze the ammonia decomposition reaction of ammonia in the medium- and high-temperature heat-to-power conversion working fluid to produce nitrogen and hydrogen, and at the same time catalyze the reforming reaction of multi-component alcohols in the medium- and high-temperature heat-to-power conversion working fluid with water to produce hydrogen and carbon monoxide; the rear bed catalyst is used to catalyze the water component in the medium- and high-temperature heat-to-power conversion working fluid to undergo a water-carbon vaporization reaction (H2O+C→H2+CO) to produce hydrogen and carbon monoxide.

[0028] Specifically, the water in the medium- and high-temperature heat-to-work conversion working fluid acts as a solvent, which can not only liquefy ammonia (forming ammonia water) and form a uniform mixed solution with multi-component alcohols, but also significantly enhance aerodynamic heat absorption through chemical endothermic reactions, and can produce high-temperature and high-pressure gas small molecules (hydrogen, nitrogen and carbon monoxide, etc.), which are particularly suitable for aerodynamic heat absorption of high-speed aircraft. In addition, by performing external work through the small gas molecules, the attitude and speed of the aircraft can be controlled, and the heat-to-work conversion process from "harmful aerodynamic heat" to "useful work" is realized, thereby ensuring long-term stable flight of the high-speed aircraft.

[0029] The implementation of the present invention will have the following beneficial effects:

[0030] 1. Compared with traditional passive insulation methods, the medium- and high-temperature heat-to-work conversion working fluid provided in this application belongs to active thermal protection technology, which has the advantages of strong cooling capacity, ability to withstand long-term heating with high-density heat flow, and realization of closed-loop temperature control.

[0031] 2. Compared with the active thermal insulation method of water sweating, the medium- and high-temperature heat-to-work conversion working fluid provided by this application combines ammonia, multi-component alcohol, and water for the first time, utilizing the synergistic effect between the components and combining with a dual-bed catalyst. This not only achieves physical heat absorption of the usable working fluid, but also enhances heat absorption through chemical reactions. The maximum heat absorption capacity of the system is more than doubled (>7.0 MJ / kg) compared with water sweating heat absorption (~3 MJ / kg), and can be used for aerodynamic heat absorption of high-speed aircraft with speeds exceeding Mach 5. Compared with traditional passive thermal protection methods based on ablative materials, it has the advantage of strong cooling capacity and is suitable for thermal protection systems of aerodynamic heating components with high heat flux density and long duration, and can effectively alleviate the problems of high cost and large thickness of passive thermal protection materials. Compared with active thermal protection technology based on water sweating, this application can more than double the system's heat absorption capacity through chemical reactions, while generating high-temperature and high-pressure small molecule gases (hydrogen, carbon monoxide, and nitrogen, etc.) for work, effectively enhancing the maneuverability of high-speed aircraft. In addition, it has the advantages of low cost, large heat sink, high stability and strong working ability, and has broad application prospects.

[0032] 3. Compared with single hydrocarbon fuel (such as aviation kerosene) endothermic working fluid, the medium and high temperature heat-to-work conversion working fluid provided by this application has high endothermic performance, is not prone to carbon deposition in chemical reactions, and has strong system stability.

[0033] 4. Compared with hydrocarbon fuel and water two-phase endothermic working fluids, the medium- and high-temperature heat-to-work conversion working fluid provided in this application is a mixed solution of a uniform single phase, which is easier to store, has a simple system, easy to control chemical reactions, and is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a comparison chart of the heat absorption performance of ethanol steam reforming and water in Example 1 of the present invention.

[0035] Figure 2 This is a comparison chart of the heat absorption performance of isopropyl alcohol steam reforming and water in Example 2 of the present invention.

[0036] Figure 3 1 is a comparison chart of the heat absorption performance of ammonia decomposition and water in Example 3 of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific examples, but the present invention is not limited thereto in any way.

[0038] Working fluid heat sink test method:

[0039] The heat sink of the working fluid is evaluated by the current heating reaction, and the heat sink of the endothermic process is calculated using the energy conservation method.

[0040] Q sink =Q in -Q loss (Equation 1)

[0041] ΔH sink =Q sink / m feed (Equation 2)

[0042] Q sink is the heat absorption power of the working medium (kW), Q in is the input power (kW) on the reactor during steady-state operation, Q loss is the heat dissipation power of the reactor and electrodes (kW), ΔH sink is the total heat sink generated by the heat absorbing medium (MJ·kg -1 ), m feed is the feed mass rate of the endothermic working fluid (g·s -1 ).

[0043] Example 1

[0044] Calculate the maximum theoretical heat sink of an ethanol / water solution with a molar ratio of ethanol to water of 1:1, an initial temperature of room temperature (25°C), and a pressure of 1 MPa. The heat absorbed by the solution at different temperatures for complete decomposition into H2 and CO (Equation 3) is as follows: Figure 1 shown.

[0045] C2H6O(l,25℃)+H2O(l,25℃)→2CO(g,T)+4H2(g,T) (Equation 3)

[0046] Example 2

[0047] Calculate the maximum theoretical heat sink of an isopropanol / water solution with a molar ratio of isopropanol to water of 1:2, an initial temperature of room temperature (25°C), and a pressure of 1 MPa. The heat absorbed by the solution at different temperatures for complete decomposition into H2 and CO (Equation 4) is as follows: Figure 2 shown.

[0048] C3H8O(l,25℃)+2H2O(l,25℃)→3CO(g,T)+6H2(g,T) (Equation 4)

[0049] Example 3

[0050] Calculate the maximum theoretical heat sink for ammonia decomposition, where the initial temperature of ammonia is room temperature (25°C) and the pressure is 1 MPa. The corresponding heat absorption for its complete decomposition into N2 and H2 at different temperatures (Equation 5) is as follows: Figure 3 shown.

[0051] 2NH3(l,25℃)→N2(g,T)+3H2(g,T) (Equation 5)

[0052] The calculation results show that for ethanol and isopropanol, the theoretical maximum heat sink is equivalent to the physical heat absorption of water at around 250℃ and 300℃ respectively. As the temperature increases, the theoretical heat sink increases rapidly. The reason is that as the temperature increases, the maximum conversion rate can be significantly improved. At 500℃, the maximum heat sink of ethanol / water is 6.6MJ / kg, and the maximum heat sink of isopropanol / water is 7.0MJ / kg. For liquid ammonia, its theoretical maximum heat sink at 500℃ is 5.6MJ / kg, which is slightly lower than that of alcohol-water solution. However, at 200℃, the theoretical maximum heat sink can reach 3.8MJ / kg, which exceeds the physical heat absorption of water (2.9MJ / kg). This shows that ammonia has a stronger low-temperature heat absorption capacity than alcohol-water solution, but its high-temperature heat absorption performance is lower than that of alcohol-water solution. In addition, compared with alcohol-water solution, the ammonia decomposition reaction is simple and does not undergo exothermic side reactions such as water vapor shift reaction (CO+H2O→CO2+H2) or methanation (CO+3H2→CH4+H2O; CO2+4H2→CH4+2H2O). Therefore, in order to make the endothermic working fluid exhibit a large heat sink over a wide temperature range, its formula needs to be optimized.

[0053] Example 4

[0054] The heat-to-work conversion system of this embodiment includes an upper, medium, and high-temperature heat-to-work conversion working medium and a double-bed catalyst.

[0055] The medium- and high-temperature heat-to-power conversion working fluid for high-speed aircraft of this embodiment includes the following components in percentage by mass:

[0056] The medium and high temperature heat-to-work conversion working fluid includes the following components in mass percentage:

[0057] 10% ammonia, 30% ethanol, 20% isopropyl alcohol, and the rest is water.

[0058] The method for preparing the medium- and high-temperature heat-to-work conversion working medium of this embodiment includes the following steps:

[0059] Ammonia gas is introduced into water to obtain an ammonia solution, and then multi-component alcohol is added and mixed at 20° C., and then cooled to room temperature to obtain a medium- and high-temperature heat-to-power conversion working fluid.

[0060] The double-bed catalyst includes 10 g of the front-bed catalyst and 10 g of the rear-bed catalyst.

[0061] The front bed catalyst is a silicon-modified alumina carrier and an active component Ru-Cu supported on the carrier, and the active component accounts for 10% of the total mass of the front bed catalyst;

[0062] The rear bed catalyst is Ba-loaded activated carbon, and the mass fraction of Ba loaded thereon accounts for 5% of the total mass of the rear bed catalyst.

[0063] Example 5

[0064] The medium- and high-temperature heat-to-power conversion working fluid for high-speed aircraft of this embodiment includes the following components in percentage by mass:

[0065] The medium and high temperature heat-to-work conversion working fluid includes the following components in mass percentage:

[0066] 20% ammonia, 30% ethanol, 15% isopropyl alcohol, and the rest is water.

[0067] The medium- and high-temperature heat-to-work conversion working fluid of this embodiment was prepared according to the preparation method of Example 4.

[0068] Example 6

[0069] The medium- and high-temperature heat-to-power conversion working fluid for high-speed aircraft of this embodiment includes the following components in percentage by mass:

[0070] The medium and high temperature heat-to-work conversion working fluid includes the following components in mass percentage:

[0071] 30% ammonia, 30% ethanol, 10% isopropyl alcohol, and the rest is water.

[0072] The medium- and high-temperature heat-to-work conversion working fluid of this embodiment was prepared according to the preparation method of Example 4.

[0073] Example 7

[0074] The only difference between this embodiment and embodiment 4 is that the medium- and high-temperature heat-to-work conversion working fluid includes the following components in percentage by mass:

[0075] 30% ammonia, 40% ethanol, 10% isopropyl alcohol, and the rest is water.

[0076] Example 8

[0077] The only difference between this embodiment and embodiment 4 is that the rear bed catalyst is activated carbon loaded with Ca.

[0078] Example 9

[0079] The only difference between this embodiment and embodiment 4 is that the rear bed catalyst is La-loaded activated carbon.

[0080] Comparative Example 1

[0081] The heat absorbing medium in this comparative example is water.

[0082] Comparative Example 2

[0083] The only difference between this comparative example and Example 4 is that no ethanol, isopropanol and water are added to the medium- and high-temperature heat-to-work conversion working fluid.

[0084] Comparative Example 3

[0085] The only difference between this comparative example and Example 4 is that no ammonia is added to the medium- and high-temperature heat-to-work conversion working medium, as follows:

[0086] The endothermic working fluid in this comparative example is a mixed solution of water / ethanol / isopropanol with a molar ratio of 4:1:1, and the corresponding mass fractions are 40.4%, 25.8% and 33.8%, respectively.

[0087] Comparative Example 4

[0088] The only difference between this comparative example and Example 4 is that ethanol and ammonia are not added to the medium- and high-temperature heat-to-work conversion working fluid, as follows:

[0089] The endothermic working fluid in this comparative example is a mixed solution of isopropyl alcohol and water, with a molar ratio of isopropyl alcohol to water of 1:3.

[0090] Comparative Example 5

[0091] The only difference between this comparative example and Example 4 is that no isopropyl alcohol and ammonia are added to the medium- and high-temperature heat-to-work conversion working fluid. The details are as follows:

[0092] The endothermic working fluid in this comparative example is a mixed solution of ethanol and water, with a molar ratio of ethanol to water of 1:1.

[0093] Comparative Example 6

[0094] The only difference between this comparative example and comparative example 6 is that the molar ratio of ethanol to water is 1:2.

[0095] Comparative Example 7

[0096] The only difference between this comparative example and Example 4 is that the medium- and high-temperature heat-to-power conversion working fluid only includes a mixed solution of ethylene glycol and water in a molar ratio of 1:1.

[0097] Comparative Example 8

[0098] The only difference between this comparative example and Example 4 is that the medium- and high-temperature heat-to-power conversion working fluid only includes a mixed solution of n-propanol and water in a molar ratio of 1:3.

[0099] Comparative Example 9

[0100] The only difference between this comparative example and Example 4 is that the medium- and high-temperature heat-to-power conversion working fluid only includes a mixed solution of n-butanol and water in a molar ratio of 1:4.

[0101] Comparative Example 10

[0102] The only difference between this comparative example and Example 4 is that the medium- and high-temperature heat-to-work conversion working fluid includes the following components in percentage by mass:

[0103] 5% ammonia, 30% ethanol, 35% isopropyl alcohol, and the rest is water.

[0104] Comparative Example 11

[0105] The only difference between this comparative example and Example 4 is that the catalyst is only the front bed catalyst.

[0106] Comparative Example 12

[0107] The only difference between this comparative example and Example 4 is that the catalyst is only the rear bed catalyst.

[0108] Test Case

[0109] The heat absorption of the heat absorbing medium was measured for Examples 4-9 and Comparative Examples 1-12. The test process included:

[0110] The initial temperature of the solution was set at 25°C, and the flow rate was set at 30 g / min. The medium- and high-temperature heat-to-work conversion fluid underwent a chemical endothermic reaction under the action of high-temperature aerodynamic heat and a catalyst. The reaction temperature was controlled by adjusting the heating power and was set to 500°C, 700°C, and 900°C, respectively. The reaction pressure was set to 1.0 MPa. The heat absorption of the endothermic working fluid was measured, and the results are shown in Table 1.

[0111] Table 1 Comparison of actual heat absorption of different components of heat absorbing working fluids in Examples 4-9 and Comparative Examples 1-12

[0112]

[0113] According to the results of Examples 4-7 and Comparative Example 10, for a water / ethanol / isopropanol / ammonia mixed solution, by adjusting its composition, the solution can maintain excellent heat absorption performance over a wide temperature range of 500°C to 900°C. Above 900°C, its maximum heat sink value exceeds 7.0 MJ / kg.

[0114] According to Example 4, Examples 8-9 and Comparative Examples 11-12, when the catalytic bed is changed from a single bed to a double bed, at a temperature greater than 700°C, due to the water-carbon vaporization reaction, further heat is absorbed. It can be seen that the heat sink of the system is significantly improved (greater than 7.0 MJ / kg); compared with La and Ca, Ba-modified activated carbon has the highest activity.

[0115] According to Example 4 and Comparative Examples 1-9, the heat absorption performance of the cooling medium can be significantly improved by changing the components and composition relationship of the cooling medium. Relatively speaking, at a low temperature of 500°C, the heat absorption capacity of ammonia is greater than that of a mixed solution of ethanol and water, and greater than that of a mixed solution of isopropanol and water. After the temperature exceeds 700°C, the heat absorption capacity is reversed; the heat absorption capacity of n-propanol is slightly lower than that of isopropanol, while the heat absorption performance of n-butanol is only good above 700°C, and is far inferior to ethanol and isopropanol at low temperatures.

[0116] In summary, the present invention combines ammonia, ethanol, isopropanol and water for the first time, utilizes the synergistic effect between the components, and combines a dual-bed catalyst, wherein the front-bed catalyst is used to catalyze the ammonia decomposition reaction of ammonia in the medium- and high-temperature heat-power conversion working fluid to produce nitrogen and hydrogen, and simultaneously catalyzes the reforming reaction of multi-component alcohols in the medium- and high-temperature heat-power conversion working fluid with water to produce hydrogen and carbon monoxide; the rear-bed catalyst is used to catalyze the water component in the medium- and high-temperature heat-power conversion working fluid to undergo a water-carbon vaporization reaction to produce hydrogen and carbon monoxide, so that it can not only utilize the physical heat absorption of the working fluid, but also enhance heat absorption through chemical reactions. The maximum heat absorption capacity of the system is more than doubled (>7.0MJ / kg) compared to the heat absorption of water sweating (~3MJ / kg), which can further enhance the heat absorption performance of the system.

[0117] The above-described embodiments merely represent several implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A medium-high temperature heat-to-power conversion system for high-speed aircraft, characterized in that: The medium-high temperature heat-to-work conversion system includes a medium-high temperature heat-to-work conversion medium and a catalyst; The medium- and high-temperature heat-to-power conversion working fluid comprises the following components in percentage by mass: 10% to 90% ammonia, 10% to 70% multi-component alcohol, and the remainder water; The multi-component alcohol comprises at least two of ethanol, isopropanol, ethylene glycol, n-propanol and n-butanol; The mass of each alcohol in the multi-component alcohol is 5% to 40% of the total mass of the medium- and high-temperature heat-to-power conversion working fluid; The catalyst is a dual-bed catalytic system consisting of a front-bed catalyst and a rear-bed catalyst, wherein the front-bed catalyst accounts for 10% to 100% of the total catalyst mass, and the rear-bed catalyst accounts for 0% to 90% of the total catalyst mass; The front bed catalyst comprises silicic-calcium alumina and an active component supported on the silicic-calcium alumina; The rear bed catalyst is porous activated carbon loaded with active metals.

2. The medium-high temperature heat-to-work conversion system for high-speed aircraft according to claim 1, characterized in that: The multi-component alcohol is ethanol and isopropanol; The medium- and high-temperature heat-to-work conversion working fluid includes the following components in percentage by mass: 10%~90% ammonia, 5%~40% ethanol, 5%~30% isopropyl alcohol, and the rest is water.

3. The medium-high temperature heat-to-work conversion system for high-speed aircraft according to claim 2, characterized in that: The medium- and high-temperature heat-to-work conversion working fluid includes the following components in percentage by mass: 10%~90% ammonia, 10%~30% ethanol, 5%~20% isopropyl alcohol, and the rest is water.

4. The medium-high temperature heat-to-work conversion system for high-speed aircraft according to claim 1, characterized in that: The medium-high temperature heat-to-work conversion medium is subjected to a chemical endothermic reaction under the action of high temperature aerodynamic heat and a catalyst to generate high temperature and high pressure gas small molecules; The front bed catalyst is used to catalyze the ammonia decomposition reaction of ammonia in the medium- and high-temperature heat-power conversion working fluid to produce nitrogen and hydrogen, and at the same time catalyze the reforming reaction of multi-component alcohol and water in the medium- and high-temperature heat-power conversion working fluid to produce hydrogen and carbon monoxide; the rear bed catalyst is used to catalyze the water component in the medium- and high-temperature heat-power conversion working fluid to undergo a water-carbon vaporization reaction to produce hydrogen and carbon monoxide.

5. The medium-high temperature heat-to-work conversion system for high-speed aircraft according to claim 4, characterized in that: The temperature of the chemical endothermic reaction is 500°C to 900°C.

6. The medium-high temperature heat-to-work conversion system for high-speed aircraft according to claim 5, characterized in that: In the fore-bed catalyst, the active components in the fore-bed catalyst include at least two of Ru, Cu, Ni, and Pt; The mass of the active component accounts for 5% to 30% of the total mass of the front bed catalyst; In the active component, the molar amount of each metal element is 10% to 90% of the total molar amount of the active component.

7. The medium-high temperature heat-to-work conversion system for high-speed aircraft according to claim 5, characterized in that: The specific surface area of ​​the rear bed catalyst is 200 m 2 / g~2000 m 2 / g; The active metal in the rear bed catalyst includes one or more of Ba, La and Ca; In the rear bed catalyst, the mass of the active metal accounts for 1% to 5% of the total mass of the rear bed catalyst.

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