A pure oxygen combustion system and combustion method for stirling engine

Abstract

The application discloses a Stirling engine pure oxygen combustion system and a combustion method, and relates to the technical field of Stirling engines. The Stirling engine pure oxygen combustion system comprises a Stirling engine body, a reformer, a metal integrated catalytic system and a direct injection swirl nozzle. The reformer is connected with an exhaust hole of the Stirling engine body through a waste heat recovery pipeline, so that exhaust waste heat can be used for steam reforming of diesel in the reformer. The metal integrated catalytic system is an integrated catalyst with a FeCrAl honeycomb as a base body and is arranged in the reformer. The direct injection swirl nozzle is connected with the Stirling engine body and the reformer and is used for mixing and combusting diesel and reforming gas with pure oxygen. The ejector is connected with the Stirling engine body and the direct injection swirl nozzle and is used for adjusting a smoke gas recirculation ratio. In the application, the coupling design of fuel reforming and pure oxygen combustion is adopted, the exhaust waste heat is deeply utilized, and the combustion efficiency and the external combustion system efficiency are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat engines, and further relates to a Stirling engine pure oxygen combustion system and a combustion method. BACKGROUND

[0002] The Stirling engine has unique advantages in the field of underwater vehicle power due to its strong fuel adaptability and low operating noise. However, the existing Stirling engine with a pure oxygen combustion system still faces several technical challenges in practical application. First, a large amount of heat energy carried in the engine exhaust is not fully utilized, resulting in significant energy waste. Second, the traditional diesel pure oxygen combustion process has problems of uneven temperature distribution and low heat exchange efficiency, which restricts the further improvement of combustion efficiency. In addition, the energy matching mechanism between the engine system and the fuel reformer is not perfect, which makes it difficult to maintain the reforming reaction in the best working state.

[0003] Therefore, it is urgent to design a Stirling engine pure oxygen combustion system and a combustion method to solve the above problems. SUMMARY

[0004] In view of the above technical problems, the purpose of the present application is to provide a Stirling engine pure oxygen combustion system and a combustion method, which realizes the deep utilization of exhaust heat and improves the combustion efficiency and external combustion system efficiency through the coupling design of fuel reforming and pure oxygen combustion.

[0005] In order to achieve the above purpose, the present application provides a Stirling engine pure oxygen combustion system, comprising:

[0006] A Stirling engine body for converting heat energy into mechanical energy;

[0007] A reformer connected to the exhaust hole of the Stirling engine body through a waste heat recovery pipeline, so that the exhaust heat can perform steam reforming on diesel in the reformer;

[0008] A metal monolithic catalytic system, a Pt-Rh / Ce 0.75 Zr 0.25 O2 / Al2O3 monolithic catalyst arranged in the reformer;

[0009] A straight-through swirl nozzle connected to the Stirling engine body and the reformer for mixing and burning diesel and reforming gas with pure oxygen;

[0010] An ejector connected to the Stirling engine body and the straight-through swirl nozzle for adjusting the smoke gas recirculation ratio.

[0011] In some embodiments, the fuel distribution ratio in the reformer is 21%-38%, the water-carbon ratio is 1.5-2.25, the reaction pressure is 3-5 MPa, and the reaction temperature is 550-650℃.

[0012] In some embodiments, the straight-injection swirl nozzle has a nozzle outlet diameter of 17-21 mm and a swirl vane angle of 30-50°.

[0013] The straight-injection swirl nozzle is coaxially arranged with the fuel nozzle, and the reforming gas injection speed is matched with the oxygen injection speed to form a backflow area.

[0014] In some embodiments, the ejector is a Venturi ejector, and the control ejector ratio is 5-9.

[0015] In some embodiments, the application further comprises:

[0016] A steam generator is connected to the reformer through a heat exchange pipeline, and uses the waste heat of the exhaust gas from the reformer to convert water into steam which is input into the reformer, and the low-temperature gas after heat exchange is discharged.

[0017] According to another aspect of the application, the application further provides a combustion method using the pure-oxygen combustion system of the Stirling engine as described in any one of the above embodiments, characterized in that it comprises the steps of:

[0018] Steam reforming diesel in the reformer by the exhaust waste heat of the Stirling engine body to generate reforming gas;

[0019] Mixing and combusting diesel and reforming gas with pure oxygen through a straight-injection swirl nozzle;

[0020] Adjusting the flue gas recirculation ratio through an ejector.

[0021] In some embodiments, the steam reforming diesel in the reformer by the exhaust waste heat of the Stirling engine body to generate reforming gas specifically comprises the steps of:

[0022] Controlling the fuel distribution ratio in the reformer to be 21%-38%, the water-carbon ratio to be 1.5-2.25, the reaction pressure to be 3-5 MPa, and the reaction temperature to be 550-650℃, and using a Pt-Rh / Ce 0.75 Zr 0.25 O2 / Al2O3 monolithic catalyst to steam reform diesel to generate hydrogen-rich reforming gas.

[0023] In some embodiments, the mixing and combusting diesel and reforming gas with pure oxygen through a straight-injection swirl nozzle specifically comprises the steps of:

[0024] The straight-blowing type rotational flow nozzle with an outlet diameter of 17mm-21mm is arranged coaxially with the fuel nozzle, the rotational flow blade angle is 30°-50°, the jet speed of the reforming gas is matched with the jet speed of the oxygen, and a stable backflow area is formed.

[0025] In some embodiments, the adjusting the flue gas recirculation ratio by the ejector specifically comprises the steps of:

[0026] The Venturi ejector is used to control the jet ratio to be 5-9.

[0027] In some embodiments, the method further comprises the steps of:

[0028] The water is converted into steam by using the waste heat of the reformer exhaust gas and input into the reformer;

[0029] The low-temperature gas after heat exchange is discharged from the system.

[0030] Compared with the prior art, the pure oxygen combustion system and the combustion method of the Stirling engine have at least one of the following beneficial effects:

[0031] In the application, the Stirling engine body and the reformer are connected through a waste heat recovery pipeline, the exhaust gas waste heat of the engine is fully utilized for diesel steam reforming, the energy utilization efficiency is significantly improved, the specific component metal monolithic catalyst arranged in the reformer ensures the efficient conversion of diesel, and the fuel utilization rate is improved; the straight-blowing type rotational flow nozzle realizes the sufficient mixing and combustion of diesel, reforming gas and pure oxygen, and ensures the stability of the combustion process; the configuration of the ejector can flexibly adjust the flue gas recirculation ratio, optimizes the combustion temperature field distribution, and effectively controls the pollutant emission; the whole system is cooperated through the cooperation between the components, and the environmental protection performance and the operation reliability are considered while the efficient energy conversion is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0032] The above characteristics, technical features, advantages and implementation modes of the application will be further described in the following in a clear and understandable manner in combination with the optional embodiments and the accompanying drawings.

[0033] Figure 1 is a structural schematic diagram of the optional embodiment of the pure oxygen combustion system of the Stirling engine of the application;

[0034] Figure 2 is a structural schematic diagram of the straight-blowing type rotational flow nozzle of the optional embodiment of the application;

[0035] Figure 3 is a bottom view of the straight-blowing type rotational flow nozzle of the optional embodiment of the application;

[0036] Figure 4 is a sectional view of the straight-blowing type rotational flow nozzle of the optional embodiment of the application;

[0037] Figure 5 is a SEM image of a metal monolith catalytic section of an optional embodiment of the present application;

[0038] Figure 6 is a temperature field cloud image of a combustion chamber at different entrainment ratios of an optional embodiment of the present application.

[0039] BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Stirling engine body 1, combustion chamber 11, heating pipe 111, recirculation flue gas pipe 112, waste heat recovery pipe 113, reformer 2, reforming gas pipe 21, heat exchange pipe 22, reforming diesel pipe 23, metal monolith catalytic system 3, direct injection swirl nozzle 4, diesel delivery pipe 41, reforming gas inlet 42, fuel nozzle 43, nozzle outlet 44, swirl vane 45, ejector 5, oxygen delivery pipe 51, ejector output pipe 52, steam generator 6, water inlet pipe 61, steam pipe 62, low-temperature exhaust pipe 63. DETAILED DESCRIPTION

[0041] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the specific embodiments of the present application will be described below with reference to the drawings. Obviously, the drawings described below are only some of the embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor, and other embodiments can also be obtained by those skilled in the art.

[0042] In order to make the drawing simple, only the parts related to the present application are shown in each drawing, and they do not represent the actual structure of the product. In addition, in order to make the drawing simple and easy to understand, in some drawings, only one of the parts with the same structure or function is shown, or only one of them is marked. In this paper, "one" not only means "only one", but also means "more than one".

[0043] It should be further understood that the term "and / or" used in the specification and claims of the present application means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0044] In this paper, it should be noted that unless otherwise specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0045] In addition, in the description of the present application, the terms "first", "second" and the like are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0046] In one embodiment, referring to the drawings attached Figure 1 The pure oxygen combustion system of the Stirling engine provided by the present application comprises: a Stirling engine body 1 for converting heat energy into mechanical energy; a reformer 2 connected with an exhaust hole of the Stirling engine body 1 through a waste heat recovery pipeline 113, so that exhaust waste heat can perform steam reforming on diesel in the reformer 2; a metal monolithic catalyst system 3 with a Pt-Rh / Ce 0.75 Zr 0.25 O2 / Al2O3 monolithic catalyst arranged in the reformer 2; a direct injection swirl nozzle 4 connected with the Stirling engine body 1 and the reformer 2, for mixing and combusting diesel and reforming gas with pure oxygen; and an ejector 5 connected with the Stirling engine body 1 and the direct injection swirl nozzle 4, for adjusting the proportion of flue gas recirculation.

[0047] In the embodiment, the Stirling engine body 1 is connected with the reformer 2 through the waste heat recovery pipeline 113, so that the exhaust waste heat of the engine is fully utilized to perform steam reforming on diesel, and the energy utilization efficiency is significantly improved; the specific component metal monolithic catalyst arranged in the reformer 2 ensures efficient conversion of diesel, and improves fuel utilization rate; the direct injection swirl nozzle 4 realizes sufficient mixing and combustion of diesel, reforming gas and pure oxygen, and ensures the stability of the combustion process; the configuration of the ejector 5 can flexibly adjust the proportion of flue gas recirculation, which not only optimizes the combustion temperature field distribution, but also effectively controls pollutant emissions; the entire system is cooperated through the components, and ensures efficient energy conversion, and takes into account environmental performance and operation reliability.

[0048] In one embodiment, referring to the drawings attached Figure 1 The Stirling engine body 1 has a combustion chamber 11, a heating pipe 111 is arranged in the combustion chamber 11, the Stirling engine body 1 is connected with the reformer 2 through the waste heat recovery pipeline 113, and the exhaust waste heat of the engine is utilized to perform steam reforming on diesel; the Stirling engine body 1 is connected with the ejector 5 through a recirculated flue gas pipeline 112, which not only optimizes the combustion temperature field distribution, but also effectively controls pollutant emissions.

[0049] The reformer 2 adopts a shell-and-tube structure, and a Pt-Rh / Ce 0.75 Zr 0.25O2 / Al2O3 monolithic catalyst tube; reformer 2 is connected with a reforming diesel pipeline 23 for conveying diesel, after diesel enters the reformer 2 and is subjected to diesel steam reforming by using engine exhaust waste heat, the reforming gas is conveyed to the direct injection swirl nozzle 4 through the reforming gas pipeline 21. The fuel distribution ratio in the reformer 2 is 21%-38%, the water-carbon ratio is 1.5-2.25, the reaction pressure is 3-5 MPa, and the reaction temperature is 550-650℃. This fuel distribution ratio ensures the optimal energy ratio of diesel and reforming gas, and the optimal water-carbon ratio not only ensures the full implementation of the steam reforming reaction, but also effectively prevents the problem of catalyst carbon deposition; the reaction pressure and temperature range in this range enable the Pt-Rh-based catalyst to exhibit optimal activity, while realizing efficient conversion of diesel and ensuring long-term stable operation of the reforming system.

[0050] With reference to the drawings accompanying the specification Figures 2 to 4 The direct injection swirl nozzle 4 has a straight cylindrical structure, the top of the direct injection swirl nozzle 4 is connected with a diesel conveying pipeline 41, and the side wall of the direct injection swirl nozzle 4 is provided with a reforming gas inlet 42 connected with the reforming gas pipeline 21. The nozzle outlet 44 of the direct injection swirl nozzle 4 has a diameter of 17mm-21mm, and the angle of the swirl vane 45 is 30°-50°; the direct injection swirl nozzle 4 is coaxially arranged with the fuel nozzle 43, the reforming gas injection speed is matched with the oxygen injection speed to form a backflow area, thereby avoiding flame flushing the bottom of the combustion chamber. By precisely controlling the diameter of the nozzle outlet 44 and the angle of the swirl vane 45, efficient mixing of fuel and oxidant is realized, and an ideal flow field structure is generated, thereby ensuring the formation of a stable backflow area in the combustion chamber; the coaxial arrangement of the nozzle and the fuel, as well as the precise matching of the reforming gas and oxygen injection speeds, not only optimizes the stability of the combustion process, but also significantly improves the combustion efficiency; thereby enabling the fuel to be fully combusted, while effectively avoiding the formation of local high-temperature areas, thereby ensuring more uniform temperature distribution in the combustion chamber.

[0051] The ejector 5 is a Venturi ejector, the Venturi ejector is connected with an oxygen conveying pipeline 51 and an ejecting output pipeline 52, the recirculated flue gas and oxygen enter the Venturi ejector, and the Venturi ejector controls the entrainment ratio to be 5-9. The Venturi ejector can efficiently entrain the recirculated flue gas, and the precisely controlled gas mixing ratio not only ensures the uniform distribution of the temperature field in the combustion chamber, but also effectively suppresses the formation of local high-temperature areas.

[0052] In one embodiment, with reference to the drawings accompanying the specification Figure 1The pure-oxygen combustion system of the Stirling engine further comprises a steam generator 6 connected with the reformer 2 through a heat exchange pipeline 22, the steam generator 6 being connected with an inlet water pipeline 61 and a low-temperature exhaust pipeline 63, water being converted into steam by the residual heat of the exhaust gas of the reformer 2, the steam being input into the reformer 2 through a steam pipeline 62, and the low-temperature gas after heat exchange being discharged from the low-temperature exhaust pipeline 63. The steam generator 6 converts the residual heat energy of the exhaust gas of the reformer 2 into steam and re-inputs the steam into the reformer 2 to participate in the reaction process, so that the energy is utilized in stages, the overall thermal efficiency of the system is significantly improved, and the continuous and stable supply of steam required by the reforming reaction is ensured; the low-temperature gas after heat exchange is discharged, so that energy waste is avoided and the system heat balance is maintained; the heat energy recovery mechanism makes the whole system form a self-sufficient energy cycle, further improves the fuel utilization rate and the economy of system operation, and reduces the dependence on external energy.

[0053] According to another aspect of the present application, with reference to the drawings attached hereto Figures 1 to 6 The present application further provides a combustion method using the pure-oxygen combustion system of the Stirling engine as described in any one of the above, characterized in that comprising the steps of:

[0054] The diesel in the reformer 2 is steam-reformed by the exhaust heat of the Stirling engine body 1 to generate reforming gas;

[0055] The diesel and the reforming gas are mixed and combusted with pure oxygen through the direct injection swirl nozzle 4.

[0056] The flue gas recirculation ratio is adjusted through the ejector 5.

[0057] Specifically, the fuel distribution ratio in the reformer 2 is 21%-38%, the water-carbon ratio is 1.5-2.25, the reaction pressure is 3-5 MPa, the reaction temperature is 550-650℃, the Pt-Rh / Ce 0.75 Zr 0.25 O2 / Al2O3 monolithic catalyst is used to steam-reform the diesel to generate hydrogen-rich reforming gas.

[0058] The direct injection swirl nozzle 4 with an outlet diameter of 17mm-21mm is used, the swirl vane 45 angle is set to 30°-50°, the direct injection swirl nozzle 4 is coaxially arranged with the fuel nozzle 43, the reforming gas injection speed is matched with the oxygen injection speed, a stable backflow area is formed; the Venturi ejector is used to control the injection ratio to be 5-9; the combustion heat is transferred to the Stirling cycle working medium through a heater, the exhaust heat is preferentially supplied to the reformer 2, and the remaining heat is used for steam generation.

[0059] In this embodiment, the diesel steam reforming reaction is driven by the exhaust heat of the engine to convert part of the fuel into high-quality reforming gas rich in hydrogen, thereby recovering waste heat and improving fuel quality; the diesel, reforming gas, and pure oxygen are fully mixed and combusted through the straight-through swirl nozzle 4, ensuring that the combustion process is both sufficient and stable; the proportion of flue gas recirculation is accurately controlled with the help of an ejector to form an ideal combustion environment; this combustion method combines waste heat recovery, fuel reforming, and combustion control, ensuring high thermal efficiency while significantly reducing pollutant emissions, making the entire system more environmentally friendly and efficient; the introduction of reforming gas changes the characteristics of traditional pure oxygen combustion, maintaining the advantages of high-temperature combustion while avoiding local overheating.

[0060] Further, the combustion method further includes the steps of: using the waste heat of the exhaust gas from the reformer 2 to convert water into steam input into the reformer 2; and discharging low-temperature gas after heat exchange from the system. The waste heat contained in the exhaust gas from the reformer 2 is recovered for steam production, and the steam is reused in the reforming reaction, forming a self-sufficient closed loop of heat energy utilization; not only significantly improving the overall thermal efficiency of the system, but also ensuring the continuous and stable supply of steam required for the reforming process; the low-temperature gas discharged after sufficient heat exchange not only avoids energy waste, but also maintains the optimal thermal balance state of the system.

[0061] For example, taking a certain type of underwater Stirling engine as an example, the reformer adopts a shell-and-tube structure, with a Φ16mm Pt-Rh / Ce 0.75 Zr 0.25 O2 / Al2O3 catalyst tube, water-carbon ratio 1.75, reaction temperature 650℃, pressure 3MPa, diesel conversion rate 94.5%; straight-through swirl nozzle outlet diameter 19mm, swirl blade 30°, coaxially arranged with the pressure vortex fuel nozzle, reforming gas to diesel flow ratio 1:3; the ejector adopts a Venturi structure, with an average heating pipe temperature of 750℃ and a temperature difference of 15℃ at an entrainment ratio of 8.

[0062] The implementation steps of the pure oxygen combustion method are as follows: start-up stage: water-carbon ratio 2.0, adjust the heating pipe temperature difference to 9℃ through steam to avoid thermal stress damage; stable operation: fuel distribution ratio 38%, entrainment ratio 8, form a uniform temperature field of 1800-2000K in the combustion chamber, increase the convective heat transfer by 20.5%; load regulation: realize efficiency fluctuation ≤2% within 30%-100% load range through coordinated regulation of fuel distribution ratio and entrainment ratio.

[0063] The performance of the above-mentioned combustion system and combustion method is verified, and compared with the traditional pure oxygen combustion system under a combustion pressure of 2.2MPa: the exhaust heat utilization rate is increased from 50% to 82%; NOx emissions are reduced by 12%, and CO emissions are ≤0.013%; the external combustion system efficiency is increased by 12.9%, meeting the long-time demand of underwater vehicles.

[0064] In the present application, the exhaust gas waste heat recovery rate reaches 82% by fuel reforming, and the external combustion system efficiency is improved from 87.4% to 92.3%; the temperature fluctuation of the heating pipe is reduced to 7℃ by the direct blowing type swirl nozzle, and the heat flux density is increased by 20.5%; the Pt-Rh / Ce 0.75 Zr 0.25 The O2 / Al2O3 catalyst achieves 94.5% diesel conversion rate and has excellent anti-carbon deposition performance; the additional equipment is less, and it is suitable for space-limited scenes such as underwater vehicles.

[0065] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in detail in a certain embodiment can be referred to the related description of other embodiments.

[0066] It should be noted that the above embodiments can be freely combined as needed. The above are only optional embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can also be made, which should be considered as the protection scope of the present application.

Claims

1. A pure oxygen combustion system for a Stirling engine, characterized by, Comprising: a Stirling engine body for converting thermal energy into mechanical energy; a reformer connected with an exhaust hole of the Stirling engine body through a waste heat recovery pipeline, so that exhaust waste heat can steam reform diesel in the reformer; Metallic monolithic catalytic system with a Pt-Rh / Ce on a FeCrAl honeycomb as a base 0.75 Zr 0.25 O2 / Al2O3 monolithic catalyst arranged in said reformer; a direct-fired swirl nozzle connected with the Stirling engine body and the reformer for mixing and burning diesel and reforming gas with pure oxygen; an ejector connected with the Stirling engine body and the direct-fired swirl nozzle for adjusting the proportion of flue gas recirculation.

2. The Stirling engine pure oxygen combustion system according to claim 1, wherein the fuel distribution ratio in the reformer is 21%-38%, the water-carbon ratio is 1.5-2.25, the reaction pressure is 3-5 MPa, and the reaction temperature is 550-650℃.

3. The Stirling engine pure oxygen combustion system according to claim 1, wherein the nozzle outlet diameter of the direct-fired swirl nozzle is 17mm-21mm, and the swirl vane angle is 30°-50°.

4. The Stirling engine pure oxygen combustion system according to claim 1, wherein the ejector is a Venturi ejector, and the control of the ejector ratio is 5-9. Further comprising: a steam generator connected with the reformer through a heat exchange pipeline, which converts water into steam using the waste heat of the exhaust gas of the reformer and inputs the steam into the reformer, and discharges low-temperature gas after heat exchange. Comprising steps: steam reforming diesel in the reformer by exhaust waste heat of the Stirling engine body to generate reforming gas; 5. The Stirling engine pure oxygen combustion system of claim 1, wherein, mixing and burning diesel and reforming gas with pure oxygen through a direct-fired swirl nozzle; adjusting the proportion of flue gas recirculation by an ejector.

6. A combustion method using the pure oxygen combustion system of the Stirling engine according to any one of claims 1 to 5, characterized by, The steam reforming diesel in the reformer by exhaust waste heat of the Stirling engine body to generate reforming gas specifically comprises steps of: The mixing and burning diesel and reforming gas with pure oxygen through a direct-fired swirl nozzle specifically comprises steps of: adopting a direct-fired swirl nozzle with an outlet diameter of 17mm-21mm, setting a swirl vane angle of 30°-50°, arranging the direct-fired swirl nozzle coaxially with the fuel nozzle, matching the reforming gas injection speed with the oxygen injection speed, and forming a stable backflow area. The adjusting the proportion of flue gas recirculation by an ejector specifically comprises steps of:

7. The combustion method of claim 6, wherein, adopting a Venturi ejector to control the ejector ratio to be 5-9. The fuel distribution ratio in the control reformer is 21%-38%, the water-carbon ratio is 1.5-2.25, the reaction pressure is 3-5 MPa, the reaction temperature is 550-650 DEG C, and the Pt-Rh / Ce 0.75 Zr 0.25 O2 / Al2O3 monolithic catalyst, steam reforming diesel to generate hydrogen-rich reforming gas.

8. The combustion method of claim 6, wherein, Further comprising steps of: converting water into steam using the waste heat of the exhaust gas of the reformer and inputting the steam into the reformer; 9. The combustion method of claim 6, wherein, discharging low-temperature gas after heat exchange from the system. ​ 10. The combustion method of claim 6, wherein, ​ ​ ​

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