Pure oxygen combustion system and combustion method for Stirling engine

Abstract

The invention discloses a Stirling engine pure oxygen combustion system and method, and the Stirling engine pure oxygen combustion system comprises a Stirling engine body which is used for converting heat energy into mechanical energy; the reformer is connected with the exhaust hole of the Stirling engine body through a waste heat recovery pipeline, so that diesel oil in the reformer can be subjected to steam reforming through exhaust waste heat; the metal monolithic catalytic system is a monolithic catalyst which takes FeCrAl honeycomb as a matrix and is arranged in the reformer; the direct blowing type swirl nozzle is connected with the Stirling engine body and the reformer and is used for mixing and combusting diesel oil, reformed gas and pure oxygen; and the ejector is connected with the Stirling engine body and the direct blowing type swirl nozzle and is used for adjusting the flue gas recirculation proportion. According to the system, through the coupling design of fuel reforming and pure oxygen combustion, deep utilization of exhaust waste heat is achieved, and the combustion efficiency and the efficiency of an external combustion system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal engines, and further to a Stirling engine pure oxygen combustion system and a combustion method. Background Art

[0002] Stirling engines, with their strong fuel adaptability and low operating noise, offer unique advantages in underwater vehicle propulsion. However, existing Stirling engines using pure oxygen combustion systems still face several technical challenges in practical application. First, the substantial amount of heat energy carried in the engine exhaust is not fully utilized, resulting in significant energy waste. Second, the traditional diesel-to-oxygen combustion process suffers from uneven temperature distribution and low heat exchange efficiency, hindering further improvements in combustion efficiency. Finally, the energy matching mechanism between the engine system and the fuel reformer is still imperfect, making it difficult to maintain the reforming reaction at its optimal operating state.

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

[0004] In response to the above technical problems, the purpose of the present invention is to provide a pure oxygen combustion system and combustion method for a Stirling engine, which, through the coupling design of fuel reforming and pure oxygen combustion, can achieve deep utilization of exhaust waste heat and improve combustion efficiency and external combustion system efficiency.

[0005] In order to achieve the above object, the present invention provides a Stirling engine pure oxygen combustion system, comprising: The Stirling engine body, used to convert thermal energy into mechanical energy; a reformer connected to the exhaust port of the Stirling engine body via a waste heat recovery pipeline so that waste heat from the exhaust gas can steam reform the diesel in the reformer; Metal monolithic catalytic system, Pt-Rh / Ce based on FeCrAl honeycomb 0.75 Zr 0.25 An O2 / Al2O3 monolithic catalyst is disposed in the reformer; a direct-blowing swirl nozzle connected to the Stirling engine body and the reformer, for mixing diesel and reformed gas with pure oxygen for combustion; The ejector is connected to the Stirling engine body and the direct-blowing swirl nozzle to adjust the flue gas recirculation ratio.

[0006] 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°C.

[0007] In some embodiments, the nozzle outlet diameter of the direct-blowing swirl nozzle is 17 mm to 21 mm, and the swirl blade angle is 30° to 50°; The direct-blowing swirl nozzle is coaxially arranged with the fuel nozzle, and the reformed gas injection speed matches the oxygen injection speed to form a recirculation zone.

[0008] In some embodiments, the ejector is a Venturi ejector, and the Venturi ejector controls the ejection ratio to be 5-9.

[0009] In some embodiments, further comprising: The steam generator is connected to the reformer through a heat exchange pipeline, uses the waste heat of the exhaust gas from the reformer to convert water into steam, inputs the steam into the reformer, and discharges the low-temperature gas after heat exchange.

[0010] According to another aspect of the present invention, the present invention further provides a combustion method using any one of the above-mentioned Stirling engine pure oxygen combustion systems, characterized in that it comprises the steps of: The exhaust waste heat of the Stirling engine is used to steam reform the diesel in the reformer to generate reformed gas; Diesel and reformed gas are mixed with pure oxygen and burned through a direct-blowing swirl nozzle; The flue gas recirculation ratio is adjusted by the ejector.

[0011] In some embodiments, the steam reforming of diesel in the reformer by utilizing the exhaust waste heat of the Stirling engine to generate reformed gas specifically comprises the following steps: The fuel distribution ratio in the reformer is controlled to be 21%-38%, the water-carbon ratio is 1.5-2.25, the reaction pressure is 3-5MPa, the reaction temperature is 550-650℃, and the Pt-Rh / Ce based on FeCrAl honeycomb is used. 0.75 Zr 0.25 O2 / Al2O3 integral catalyst is used to steam reform diesel to generate hydrogen-rich reformed gas.

[0012] In some embodiments, the mixing and burning of diesel and reformed gas with pure oxygen through a direct-blowing swirl nozzle specifically comprises the following steps: A straight-blowing swirl nozzle with an outlet diameter of 17mm-21mm is used, and the swirl blade angle is set to 30°-50°. The straight-blowing swirl nozzle is coaxially arranged with the fuel nozzle to match the reformed gas injection velocity with the oxygen injection velocity, forming a stable reflux zone.

[0013] In some embodiments, the step of adjusting the flue gas recirculation ratio by the ejector specifically comprises the following steps: A Venturi ejector is used to control the ejection ratio to 5-9.

[0014] In some embodiments, the steps are further included: The waste heat of the exhaust gas from the reformer is used to convert water into steam and input it into the reformer; The low-temperature gas after heat exchange is discharged from the system.

[0015] Compared with the prior art, the Stirling engine pure oxygen combustion system and combustion method provided by the present invention have at least one of the following beneficial effects: In the present invention, the Stirling engine body and the reformer are connected through a waste heat recovery pipeline, which fully utilizes the waste heat of the engine exhaust to reform diesel steam, significantly improving energy utilization efficiency; the specific component metal integral catalyst set in the reformer ensures the efficient conversion of diesel and improves fuel utilization; the direct-blowing swirl nozzle realizes the full mixing and combustion of diesel, reformed gas and pure oxygen, ensuring the stability of the combustion process; the configuration of the ejector can flexibly adjust the flue gas recirculation ratio, which not only optimizes the combustion temperature field distribution, but also effectively controls pollutant emissions; the entire system, through the coordinated cooperation between the various components, takes into account environmental protection performance and operational reliability while ensuring efficient energy conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following will explain optional implementation methods in a clear and easy-to-understand manner with reference to the accompanying drawings to further illustrate the above-mentioned characteristics, technical features, advantages and implementation methods of the present invention.

[0017] Figure 1 is a schematic structural diagram of a pure oxygen combustion system of a Stirling engine according to an optional embodiment of the present invention; Figure 2 2 is a schematic structural diagram of a direct-blowing swirl nozzle according to an optional embodiment of the present invention; Figure 3 1 is a bottom view of a direct-blowing swirl nozzle according to an optional embodiment of the present invention; Figure 4 is a cross-sectional view of a direct-blowing swirl nozzle according to an optional embodiment of the present invention; Figure 5 This is a cross-sectional SEM image of a metal monolithic catalyst according to an optional embodiment of the present invention; Figure 6 It is a cloud diagram of the temperature field of the combustion chamber under different injection ratios of an optional embodiment of the present invention.

[0018] Description of Figure Numbers: Stirling engine body 1, combustion chamber 11, heating pipe 111, recirculating flue gas pipeline 112, waste heat recovery pipeline 113, reformer 2, reformed gas pipeline 21, heat exchange pipeline 22, reformed diesel pipeline 23, metal integral catalytic system 3, direct-blowing swirl nozzle 4, diesel delivery pipeline 41, reformed gas inlet 42, fuel nozzle 43, nozzle outlet 44, swirl blade 45, ejector 5, oxygen delivery pipeline 51, ejector output pipeline 52, steam generator 6, water inlet pipeline 61, steam pipeline 62, low-temperature exhaust pipeline 63. DETAILED DESCRIPTION

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the specific embodiments of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other embodiments can be obtained based on these drawings without inventive work.

[0020] To simplify the drawings, only portions relevant to the invention are schematically depicted in each figure; they do not represent the actual structure of the product. Furthermore, to simplify the drawings and facilitate understanding, in some figures, only one component with the same structure or function is schematically depicted or labeled. In this document, "one" not only means "only one" but also "more than one."

[0021] It should be further understood that the term "and / or" used in this specification and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0022] It should be noted that, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they can refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0023] In addition, in the description of the present application, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0024] In one embodiment, the reference Figure 1The present invention provides a Stirling engine pure oxygen combustion system, comprising: a Stirling engine body 1, used to convert thermal energy into mechanical energy; a reformer 2, connected to the exhaust port of the Stirling engine body 1 via a waste heat recovery pipe 113, so that the waste heat of the exhaust can steam reform the diesel in the reformer 2; a metal integral catalytic system 3, a Pt-Rh / Ce based on FeCrAl honeycomb 0.75 Zr 0.25 An O2 / Al2O3 integral catalyst is arranged in the reformer 2; a direct-blowing swirl nozzle 4 is connected to the Stirling engine body 1 and the reformer 2, and is used to mix diesel and reformed gas with pure oxygen for combustion; an ejector 5 is connected to the Stirling engine body 1 and the direct-blowing swirl nozzle 4 to adjust the flue gas recirculation ratio.

[0025] In this embodiment, the Stirling engine body 1 and the reformer 2 are connected through the waste heat recovery pipeline 113, which fully utilizes the waste heat of the engine exhaust to reform the diesel steam, thereby significantly improving the energy utilization efficiency; the specific component metal integral catalyst arranged in the reformer 2 ensures the efficient conversion of diesel and improves the fuel utilization rate; the direct-blowing swirl nozzle 4 realizes the full mixing and combustion of diesel, reformed gas and pure oxygen, ensuring the stability of the combustion process; the configuration of the ejector 5 can flexibly adjust the flue gas recirculation ratio, which not only optimizes the combustion temperature field distribution, but also effectively controls pollutant emissions; the entire system, through the coordinated cooperation between the various components, takes into account both environmental protection performance and operational reliability while ensuring efficient energy conversion.

[0026] In one embodiment, the reference Figure 1 The Stirling engine body 1 has a combustion chamber 11, in which a heating pipe 111 is provided. The Stirling engine body 1 is connected to the reformer 2 through a waste heat recovery pipeline 113, and diesel steam is reformed using the waste heat of the engine exhaust; the Stirling engine body 1 is connected to the ejector 5 through a recirculating flue gas pipeline 112, which not only optimizes the combustion temperature field distribution, but also effectively controls pollutant emissions.

[0027] Reformer 2 adopts shell and tube structure with built-in Pt-Rh / Ce 0.75 Zr 0.25O2 / Al2O3 integral catalyst tube; reformer 2 is connected to a reformed diesel pipeline 23 for diesel fuel. After entering reformer 2, diesel fuel is steam-reformed using waste heat from the engine exhaust. The reformed gas is then delivered to the direct-blowing swirl nozzle 4 via a reformed gas pipeline 21. Within reformer 2, the fuel distribution ratio is 21%-38%, the water-to-carbon ratio is 1.5-2.25, the reaction pressure is 3-5 MPa, and the reaction temperature is 550-650°C. This fuel distribution ratio ensures an optimal energy balance between diesel fuel and reformed gas. The optimized water-to-carbon ratio ensures sufficient steam reforming reaction while effectively preventing carbon deposition on the catalyst. The reaction pressure and temperature within this range maximize the activity of the Pt-Rh-based catalyst, achieving efficient diesel conversion while ensuring long-term stable operation of the reforming system.

[0028] Reference Manual Figures 2 to 4 The direct-blowing swirl nozzle 4 is a straight cylindrical structure. A diesel delivery pipeline 41 is connected to the top of the direct-blowing swirl nozzle 4. A reformed gas inlet 42 is provided on the sidewall of the direct-blowing swirl nozzle 4, which is connected to the reformed gas pipeline 21. The nozzle outlet 44 of the direct-blowing swirl nozzle 4 has a diameter of 17mm-21mm, and the swirl blade 45 has an angle of 30°-50°. The direct-blowing swirl nozzle 4 is coaxial with the fuel nozzle 43. The reformed gas injection velocity matches the oxygen injection velocity to form a recirculation zone, preventing the flame from scouring the bottom of the combustion chamber. By precisely controlling the diameter of the nozzle outlet 44 and the angle of the swirl blades 45, efficient mixing of the fuel and oxidant is achieved, and an ideal flow field structure can be generated, ensuring the formation of a stable recirculation zone in the combustion chamber; the coaxial arrangement of the nozzle and the fuel and the precise matching of the injection speeds of the reformed gas and oxygen not only optimize the stability of the combustion process but also significantly improve the combustion efficiency; this enables the fuel to be fully burned while effectively avoiding the formation of local high-temperature zones, ensuring a more uniform temperature distribution in the combustion chamber.

[0029] Ejector 5 is a Venturi ejector connected to an oxygen delivery line 51 and an ejection output line 52. Recirculated flue gas and oxygen enter the Venturi ejector, which controls the ejection ratio between 5 and 9. The Venturi ejector efficiently ejects the recycled flue gas. The precisely controlled gas mixture ratio ensures a uniform temperature distribution within the combustion chamber while effectively suppressing the formation of localized high-temperature zones.

[0030] In one embodiment, the reference Figure 1The Stirling engine pure oxygen combustion system also includes a steam generator 6, which is connected to the reformer 2 via a heat exchange line 22. The steam generator 6 is connected to a water inlet line 61 and a low-temperature exhaust line 63. The steam generator 6 utilizes the residual heat of the exhaust gas from the reformer 2 to convert water into steam, which is then fed into the reformer 2 via a steam line 62. The low-temperature gas, after heat exchange, is then discharged from the low-temperature exhaust line 63. The steam generator 6 converts the residual heat energy of the exhaust gas from the reformer 2 into steam, which is then fed back into the reformer 2 to participate in the reaction process. This achieves cascaded energy utilization, significantly improving the overall thermal efficiency of the system and ensuring a continuous and stable supply of steam required for the reforming reaction. The discharge of the low-temperature gas after heat exchange avoids energy waste and maintains system thermal balance. This heat recovery mechanism enables the entire system to form a self-sufficient energy cycle, further improving fuel utilization and the economic efficiency of system operation, while reducing dependence on external energy sources.

[0031] According to another aspect of the present invention, Figures 1 to 6 The present invention further provides a combustion method using any one of the above-mentioned Stirling engine pure oxygen combustion systems, characterized in that it comprises the steps of: The exhaust waste heat of the Stirling engine body 1 is used to steam reform the diesel in the reformer 2 to generate reformed gas; Diesel and reformed gas are mixed with pure oxygen and burned through a direct-blowing swirl nozzle 4; The flue gas recirculation ratio is adjusted by the ejector 5.

[0032] Specifically, the fuel distribution ratio in the reformer 2 is controlled to be 21%-38%, the water-carbon ratio is 1.5-2.25, the reaction pressure is 3-5MPa, the reaction temperature is 550-650℃, and the Pt-Rh / Ce based on FeCrAl honeycomb is used. 0.75 Zr 0.25 O2 / Al2O3 integral catalyst is used to steam reform diesel to generate hydrogen-rich reformed gas.

[0033] A direct-blowing swirl nozzle 4 with an outlet diameter of 17mm-21mm is used, and the angle of the swirl blade 45 is set to 30°-50°. The direct-blowing swirl nozzle 4 and the fuel nozzle 43 are coaxially arranged to match the injection velocity of the reformed gas with the oxygen injection velocity, forming a stable reflux zone; a Venturi ejector is used to control the injection ratio to 5-9; the combustion heat is transferred to the Stirling cycle working medium through the heater, and the exhaust waste heat is preferentially supplied to the reformer 2, and the remaining heat is used for steam generation.

[0034] In this embodiment, the waste heat from the engine exhaust is used to drive the diesel steam reforming reaction, converting part of the fuel into high-quality reformed gas rich in hydrogen, thereby recovering the waste heat and improving the fuel quality; the diesel and reformed gas are fully mixed and burned with pure oxygen through the direct-blowing swirl nozzle 4, ensuring that the combustion process is both sufficient and stable; the flue gas recirculation ratio 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, and while ensuring high thermal efficiency, it significantly reduces pollutant emissions, making the operation of the entire system more environmentally friendly and efficient; the introduction of reformed gas changes the characteristics of traditional pure oxygen combustion, maintaining the advantages of high-temperature combustion while avoiding the problem of local overheating.

[0035] Furthermore, the combustion method also includes the steps of utilizing the waste heat from the exhaust gas of reformer 2 to convert water into steam, which is then fed into reformer 2; and discharging the low-temperature gas after heat exchange. The waste heat contained in the exhaust gas of reformer 2 is recovered for steam production, which then re-enters the reforming reaction, forming a self-sufficient closed-loop thermal energy utilization loop. This significantly improves the overall thermal efficiency of the system while ensuring a continuous and stable supply of steam required for the reforming process. Discharging the low-temperature gas after sufficient heat exchange avoids energy waste and maintains the system's optimal thermal balance.

[0036] For example, taking a certain type of underwater Stirling engine as an example, the reformer adopts a shell-and-tube structure with a built-in 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%; direct-blowing swirl nozzle outlet diameter 19mm, swirl blade 30°, coaxial arrangement with pressure vortex fuel nozzle, reformed gas to diesel flow ratio 1:3; ejector adopts Venturi structure, when the ejection ratio is 8, the average temperature of the heating tube is 750℃, and the temperature difference is 15℃.

[0037] Implementation steps of the pure oxygen combustion method: Startup phase: water-carbon ratio 2.0, steam is used to adjust the temperature difference of the heating tube to 9°C to avoid thermal stress damage; stable operation: fuel distribution ratio 38%, injection ratio 8, forming a uniform temperature field of 1800-2000K in the combustion chamber, and convective heat transfer increased by 20.5%; load regulation: through the coordinated control of fuel distribution ratio and injection ratio, the efficiency fluctuation within the load range of 30%-100% is achieved. ≤2%.

[0038] Performance verification was carried out on the above-mentioned combustion system and combustion method. Under a combustion pressure of 2.2MPa, compared with the traditional pure oxygen combustion system: the exhaust waste heat utilization rate increased from 50% to 82%; NOx emissions decreased by 12%, CO emissions ≤0.013%; the efficiency of the external combustion system increased by 12.9%, meeting the long-endurance requirements of underwater vehicles.

[0039] In this invention, the exhaust heat recovery rate reaches 82% through fuel reforming, and the efficiency of the external combustion system is increased from 87.4% to 92.3%. The direct-blowing swirl nozzle reduces the temperature fluctuation of the heating tube to 7°C and increases the heat flux density by 20.5%. 0.75 Zr 0.25 The O2 / Al2O3 catalyst achieves a diesel conversion rate of 94.5% and has excellent anti-carbon deposition performance; it requires little additional equipment and is suitable for space-constrained scenarios such as underwater vehicles.

[0040] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0041] It should be noted that the above embodiments can be freely combined as needed. The above are only optional implementations of the present invention. It should be pointed out that those skilled in the art can make several improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A pure oxygen combustion system for a Stirling engine, characterized in that: include: The Stirling engine body, used to convert thermal energy into mechanical energy; a reformer connected to the exhaust port of the Stirling engine body via a waste heat recovery pipeline so that waste heat from the exhaust gas can steam reform the diesel in the reformer; Metal monolithic catalytic system, Pt-Rh / Ce based on FeCrAl honeycomb 0.75 Zr 0.25 An O2 / Al2O3 monolithic catalyst is disposed in the reformer; a direct-blowing swirl nozzle connected to the Stirling engine body and the reformer, for mixing diesel and reformed gas with pure oxygen for combustion; The ejector is connected to the Stirling engine body and the direct-blowing swirl nozzle to adjust the flue gas recirculation ratio.

2. The Stirling engine pure oxygen combustion system according to claim 1, characterized in that: 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°C.

3. The Stirling engine pure oxygen combustion system according to claim 1, characterized in that: The nozzle outlet diameter of the direct-blowing swirl nozzle is 17mm-21mm, and the swirl blade angle is 30°-50°; The direct-blowing swirl nozzle is coaxially arranged with the fuel nozzle, and the reformed gas injection speed matches the oxygen injection speed to form a recirculation zone.

4. The Stirling engine pure oxygen combustion system according to claim 1, characterized in that: The ejector is a Venturi ejector, and the Venturi ejector controls the ejection ratio to be 5-9.

5. The Stirling engine pure oxygen combustion system according to claim 1, characterized in that: Also includes: The steam generator is connected to the reformer through a heat exchange pipeline, uses the waste heat of the exhaust gas from the reformer to convert water into steam, inputs the steam into the reformer, and discharges the low-temperature gas after heat exchange.

6. A combustion method using the Stirling engine pure oxygen combustion system according to any one of claims 1 to 5, characterized in that: Including steps: The exhaust waste heat of the Stirling engine is used to steam reform the diesel in the reformer to generate reformed gas; Diesel and reformed gas are mixed with pure oxygen and burned through a direct-blowing swirl nozzle; The flue gas recirculation ratio is adjusted by the ejector.

7. The combustion method according to claim 6, characterized in that: The method of steam reforming the diesel in the reformer by utilizing the exhaust waste heat of the Stirling engine to generate reformed gas specifically includes the following steps: The fuel distribution ratio in the reformer is controlled to be 21%-38%, the water-carbon ratio is 1.5-2.25, the reaction pressure is 3-5MPa, the reaction temperature is 550-650℃, and the Pt-Rh / Ce based on FeCrAl honeycomb is used. 0.75 Zr 0.25 O2 / Al2O3 integral catalyst is used to steam reform diesel to generate hydrogen-rich reformed gas.

8. The combustion method according to claim 6, characterized in that: The method of mixing diesel and reformed gas with pure oxygen through a direct-blowing swirl nozzle and burning the mixture specifically comprises the following steps: A straight-blowing swirl nozzle with an outlet diameter of 17mm-21mm is used, and the swirl blade angle is set to 30°-50°. The straight-blowing swirl nozzle is coaxially arranged with the fuel nozzle to match the reformed gas injection velocity with the oxygen injection velocity, forming a stable reflux zone.

9. The combustion method according to claim 6, characterized in that: The method of adjusting the flue gas recirculation ratio by the ejector specifically includes the following steps: A Venturi ejector is used to control the ejection ratio to 5-9.

10. The combustion method according to claim 6, characterized in that: Also includes the steps: The waste heat of the exhaust gas from the reformer is used to convert water into steam and input it into the reformer; The low-temperature gas after heat exchange is discharged from the system.

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