Infrared suppression device and method for ship exhaust plume

Abstract

The application discloses a ship exhaust plume infrared suppression method, which adopts radiation participating cooling gas to wrap high-temperature exhaust of a ship, and uses strong absorption of the radiation participating cooling gas to high-temperature exhaust infrared radiation to realize reduction of infrared radiation characteristics. The application also provides a ship exhaust plume infrared suppression device. The application uses the radiation participating cooling gas to wrap the high-temperature exhaust of the ship, so as to weaken the characteristic signal and achieve the purpose of suppressing the infrared radiation of the ship exhaust plume.

Description

Technical Field

[0001] This invention belongs to the field of infrared technology, specifically relating to an infrared suppression device and method for ship exhaust plumes of cooling gas with induced radiation participation, used for infrared suppression of high-temperature exhaust gas from chimneys. Background Technology

[0002] Modern ships primarily use large diesel engines, steam turbines, and gas turbines as their power plants. Their propulsion systems have high output power, and their exhaust temperatures are significantly higher than the ambient temperature. This results in the exhaust plume's infrared radiation (3μm~5μm band) accounting for a significant portion of the ship's overall infrared radiation. Suppressing the infrared radiation of ship exhaust plumes is crucial for improving a ship's camouflage and concealment capabilities. Government vessels, when performing official duties, sometimes need to conceal their movements to track and monitor target vessels; therefore, controlling the exhaust plume—the largest source of infrared radiation from government vessels—is essential.

[0003] Currently, the main measure to suppress infrared radiation from ship exhaust plumes is to install infrared suppression devices (or exhaust ejector infrared suppressors) on the ship's exhaust system. The principle is to use the high-speed exhaust from the engine to eject and mix with the surrounding low-temperature air to cool the mainstream flue gas, forming an air film to cool the flue gas wall, reducing the temperature of the exhaust system and flue gas, and eliminating high-intensity mid-wave infrared radiation. This changes the ship's infrared characteristics from a high-intensity localized radiation point heat source to a uniformly distributed weak radiation surface heat source. Alternatively, water mist can be sprayed into the exhaust pipe, where the water droplets undergo evaporation and phase change, absorbing a large amount of heat and significantly reducing infrared radiation in the 3μm~5μm band.

[0004] The two methods described above each have the following problems: For the method using engine exhaust ejection: due to limited specific heat capacity and flow rate, the air cooling effect is insufficient, and the device's suppression effect on plume infrared radiation is limited. If the plume temperature is further reduced by increasing the ejection ratio, this will lead to a significant increase in exhaust resistance, increasing engine fuel consumption and deteriorating both economic and power performance. For the method of spraying water mist into the exhaust pipe: spraying water mist into high-temperature flue gas makes the exhaust pipe susceptible to corrosion from moisture, especially salt water.

[0005] Therefore, it is necessary to design a new infrared suppression device and method. Summary of the Invention

[0006] The main objective of this invention is to provide a device and method for suppressing infrared radiation from ship exhaust plumes. This device and method utilize radiation-participating cooling gas to envelop the high-temperature exhaust gas from the ship, thereby reducing its characteristic signals and suppressing the infrared radiation from the ship exhaust plumes.

[0007] The technical solution adopted in this invention is: A method for suppressing infrared emissions from ship exhaust plumes involves using radiation-participating cooling gas to envelop the high-temperature exhaust gas from the ship, thereby reducing the infrared radiation characteristics by utilizing the strong absorption of infrared radiation from the high-temperature exhaust gas by the radiation-participating cooling gas.

[0008] According to the above scheme, the method includes the following steps: 1) The high-temperature flue gas mainstream of the ship is ejected through the converging nozzle. Under the action of gas viscosity, it undergoes a violent momentum exchange with the cooling air in the surrounding environment of the converging nozzle outlet. The cooling air (low-temperature gas) in the cooling gas environment is entrained and injected into the high-temperature flue gas mainstream, which cools down the high-temperature flue gas mainstream and forms a mixed exhaust mainstream. 2) The mixed exhaust mainstream enters the ejector diffuser ring of the gas film cooling diffuser mixing tube and continues to mix, and flows towards the outlet along the gas film cooling diffuser mixing tube; during the flow of the mixed exhaust mainstream, the radiation-participating cooling gas in the ejector cavity is drawn in by the slits on the gas film cooling diffuser mixing tube body, forming a highly absorbent gas layer around the mixed exhaust mainstream (high temperature flue gas), that is: the radiation-participating cooling gas forms a cooling gas film layer on the inner wall of the gas film cooling diffuser mixing tube to wrap the mixed exhaust mainstream; 3) The strong absorption of infrared rays by the cooling gas film layer causes a large amount of the strong infrared energy generated by the mainstream of high-temperature flue gas to be absorbed and attenuated.

[0009] According to the above scheme, in step 2), during the mainstream flow of the mixed exhaust gas, the radiation-participating cooling gas in the injection cavity is drawn in by all the slits on the gas film cooling diffuser mixing pipe; the radiation-participating cooling gas forms a cooling gas film layer on the inner wall of the gas film cooling diffuser mixing pipe to wrap the mainstream of the mixed exhaust gas; or, in step 2), during the mainstream flow of the mixed exhaust gas, the cooling air around the gas film cooling diffuser mixing pipe is drawn in by the slits at the front and middle of the gas film cooling diffuser mixing pipe for further mixing; the radiation-participating cooling gas in the injection cavity is drawn in by the slits at the tail of the gas film cooling diffuser mixing pipe; the radiation-participating cooling gas forms a cooling gas film layer on the inner wall of the gas film cooling diffuser mixing pipe to wrap the mainstream of the mixed exhaust gas.

[0010] According to the above scheme, the radiation-participating cooling gas is CO2, CO, or HC (hydrocarbon gas).

[0011] According to the above scheme, the flow rate of the radiation-participating cooling gas... for: (1) In the formula, The flow rate of the radiation-involved cooling gas; The mainstream flow rate of flue gas; This is the entrainment coefficient; when using full-stage entrainment, Take a value of 0.6~0.72; when using a final stage ejector, Take a value of 0.12 to 0.14.

[0012] According to the above scheme, the radiation-participating cooling gas is ejected in the final stage through the final ejector diffuser ring at the tail of the gas film cooling diffuser mixing tube in the ejector cavity; or, the radiation-participating cooling gas is ejected in the entire stage through all the ejector diffuser rings of the gas film cooling diffuser mixing tube in the ejector cavity.

[0013] In this invention, different types of gases, such as CO2, CO, and HC, can be selected to be introduced through different slits to meet the actual needs, thereby reducing economic costs while meeting the actual infrared suppression requirements.

[0014] An apparatus used in a method for suppressing infrared exhaust plumes from ships includes a tapered nozzle, a film-cooled diffuser mixing pipe, an ejector cavity, and a radiation-participating cooling gas supply unit. The tapering nozzle is installed at the stern of the ship's exhaust pipe, and its stern gradually narrows. The film cooling diffuser mixing tube is placed after the converging nozzle, with its central axis coinciding with the central axis of the converging nozzle. The front end of the film cooling diffuser mixing tube is a certain distance from the rear end of the converging nozzle, so that the high-speed, high-temperature flue gas stream ejected from the converging nozzle undergoes a violent momentum exchange with the cooling air surrounding the converging nozzle outlet due to the viscosity of the gas. This entrains and injects the cooling air into the high-temperature flue gas stream, forming a mixed exhaust stream. The film cooling diffuser mixing tube includes a mixing tube and an ejector diffuser ring assembly. The ejector diffuser ring assembly includes multiple sequentially connected, gradually increasing in size ejector diffuser rings. The first-stage ejector diffuser ring is connected to the rear end of the mixing tube. Slits are provided between adjacent ejector diffuser rings and between the first-stage ejector diffuser ring and the mixing tube. The ejector cavity is a closed cavity placed outside the film cooling diffuser mixing tube. Its tail end is connected to the tail end of the last stage ejector diffuser ring of the film cooling diffuser mixing tube, and its front end is connected to the mixing tube below the first stage ejector diffuser ring of the film cooling diffuser mixing tube. The cavity of the ejector cavity is connected to the film cooling diffuser mixing tube through a slit. A radiation-involved cooling gas supply unit provides radiation-involved cooling gas to the ejector cavity. The radiation-involved cooling gas supply unit includes a gas storage tank, a vacuum pump, a valve, and a controller. The gas storage tank is connected to one end of the valve via the vacuum pump, and the other end of the valve is connected to the injection port of the ejector cavity via a gas pipe. A flow meter is installed on the gas pipe between the valve and the ejector cavity. The flow meter transmits the collected data to the controller, which controls the opening degree of the valve and the operation of the vacuum pump, thereby controlling the flow rate of the radiation-involved cooling gas entering the ejector cavity.

[0015] Alternatively, an apparatus used in a method for infrared suppression of ship exhaust plumes, comprising a tapered nozzle, a film-cooled diffuser mixing pipe, an ejector cavity, and a radiation-participating cooling gas supply unit; The tapering nozzle is installed at the stern of the ship's exhaust pipe, and its stern gradually narrows. The film cooling diffuser mixing tube is placed after the converging nozzle, with its central axis coinciding with the central axis of the converging nozzle. The front end of the film cooling diffuser mixing tube is a certain distance from the rear end of the converging nozzle, so that the high-speed, high-temperature flue gas stream ejected from the converging nozzle undergoes a violent momentum exchange with the cooling air surrounding the converging nozzle outlet due to the viscosity of the gas. This entrains and injects the cooling air into the high-temperature flue gas stream, forming a mixed exhaust stream. The film cooling diffuser mixing tube includes a mixing tube and an ejector diffuser ring assembly. The ejector diffuser ring assembly includes multiple sequentially connected, gradually increasing in size ejector diffuser rings. The first-stage ejector diffuser ring is connected to the rear end of the mixing tube. Slits are provided between adjacent ejector diffuser rings and between the first-stage ejector diffuser ring and the mixing tube. The ejector cavity is a closed cavity placed outside the gas film cooling diffuser mixing tube. Its tail end is connected to the tail end of the last stage ejector diffuser ring of the gas film cooling diffuser mixing tube, and its front end is connected to the tube body of the next last stage ejector diffuser ring of the gas film cooling diffuser mixing tube. A radiation-involved cooling gas supply unit provides radiation-involved cooling gas to the ejector cavity. The unit includes a gas storage tank, a pump, a valve, and a controller. The gas storage tank is connected to one end of the valve via the pump, and the other end of the valve is connected to the ejector cavity via a gas pipe. A flow meter is installed on the gas pipe between the valve and the ejector cavity. The flow meter transmits the collected data to the controller, which adjusts the flow rate of the radiation-involved gas accordingly. The calculation formula, the controller controls the valve opening and the operation of the air pump, thereby adjusting the flow rate of the radiation-involved cooling gas into the ejector cavity to match the ejection requirements of the radiation-involved gas.

[0016] According to the above scheme, each stage of ejector diffuser ring is connected by a rod-shaped connector, and each stage of ejector diffuser ring has a slit.

[0017] The principle of this invention is that the main infrared emitter in the plume—the gaseous medium—has strong absorption radiation characteristics within its distinct emission wavelength range. Based on this principle, this method wraps a low-temperature radiation-participating gaseous medium at the end of the exhaust gas, utilizing the strong absorption of infrared radiation from the high-temperature exhaust gas by the radiation-participating gaseous medium to further reduce the infrared radiation characteristics.

[0018] The beneficial effects of this invention are as follows: Based on the fact that radiation-participating cooling gases (such as CO2, CO, or HC) have strong radiation absorption characteristics in the obvious emission band, the infrared radiation of the ship's exhaust plume is reduced by inducing radiation-participating cooling gases to form an envelope around the ship's exhaust plume. This invention makes reasonable use of the radiation characteristics of gas medium. By changing the type of ejector gas to a radiation-participating gas, it can suppress the infrared radiation of ship exhaust plumes, reduce the infrared radiation of ship exhaust plumes, and effectively improve the ship's infrared characteristic control capability. The tapered nozzle is used to accelerate the mainstream flue gas and improve the ejection capability; the slit of the film-cooled diffuser mixing tube provides a channel for the entrainment of radiation-involved gases; the ejection cavity is used to provide a radiation-involved gas environment and is the "container" for ejecting radiation-involved cooling gases. The cooling gas film layer has a strong absorption effect on the infrared radiation generated by the high-temperature flue gas inside, thus forming a shielding layer that blocks the high-temperature infrared radiation source inside. Through shielding, the maximum detectable radiance of the plume can be reduced by nearly 50%. Choosing CO2 as a radiation-participating cooling gas is a superior choice in terms of preparation cost, environmental impact, and safety. Compared to ejected air, ejected radiation-participating cooling gas can significantly reduce the infrared radiation intensity of the exhaust plume, with the maximum radiation brightness reduced by nearly 50%. At the same time, this invention does not cause problems such as equipment corrosion and increased exhaust resistance caused by seawater spraying. This invention can improve the infrared suppression effect by changing the type of excitation gas based on the existing excitation structure. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of an ejector structure that does not employ radiation-participating cooling gas; Figure 2 This is a schematic diagram of the structure of the ship exhaust plume infrared suppression device in Example 4; Figure 3 This is a schematic diagram of the full-stage CO2 ejection process in Example 1; Figure 4 This is a schematic diagram of the structure of the ship exhaust plume infrared suppression device in Example 5; Figure 5 This is a schematic diagram of the final stage CO2 ejection system in Example 2; Figure 6 These are comparison images, in which: (a) is an infrared radiation image of the ship's exhaust plume when all stages eject air, with the green box area in the image representing the main plume region; (b) is an infrared radiation image of the ship's exhaust plume when the last stage ejects CO2 (temperature 300K) and other stages eject air; (c) is an infrared radiation image of the ship's exhaust plume when all stages eject CO2 (temperature 300K).

[0021] In the diagram: 1. Injector diffuser ring, 2. Converging nozzle, 3. Injector cavity, 4. Inlet, 5. Valve, 6. Air pump, 7. Air tank, 8. Flow meter. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] A method for suppressing infrared radiation from ship exhaust plumes involves encapsulating the high-temperature exhaust gas with a radiation-participating cooling gas. The strong absorption of infrared radiation from the high-temperature exhaust gas by the radiation-participating cooling gas reduces its infrared radiation characteristics. The radiation-participating cooling gas can be gases that strongly absorb infrared radiation from high-temperature exhaust gas, such as CO2, CO, or HC. The following embodiments use CO2 as the radiation-participating cooling gas.

[0024] Example 1 A method for suppressing infrared emissions from ship exhaust plumes includes the following steps: 1) The high-temperature flue gas mainstream (high-speed mainstream) of the ship is ejected through the converging nozzle. Under the action of gas viscosity, it undergoes a violent momentum exchange with the cooling air (low-temperature gas) in the surrounding environment of the converging nozzle outlet. The cooling air (low-temperature gas) in the cooling gas environment is entrained and injected into the high-temperature flue gas mainstream, which cools down the high-temperature flue gas mainstream and forms a mixed exhaust mainstream. 2) The mixed exhaust gas mainstream enters the ejector diffuser ring of the gas film cooling diffuser mixing tube and continues to mix, and flows towards the outlet along the gas film cooling diffuser mixing tube; during the flow of the mixed exhaust gas mainstream, the radiation-participating cooling gas CO2 in the ejector cavity is drawn in by the slits on the gas film cooling diffuser mixing tube body, forming a highly absorbent CO2 gas layer around the mixed exhaust gas mainstream (high temperature flue gas), that is: the radiation-participating cooling gas CO2 forms a CO2 cooling gas film layer on the inner wall of the gas film cooling diffuser mixing tube to wrap the mixed exhaust gas mainstream; 3) The strong absorption of infrared rays by the CO2 cooling gas film layer causes a large amount of the strong infrared energy generated by the high-temperature flue gas mainstream to be absorbed and attenuated.

[0025] In step 2), the radiation-participating cooling gas is fully ejected through all the ejector diffuser rings of the gas film cooling diffuser mixing tube in the ejector cavity; that is, during the mainstream flow of the mixed exhaust gas, the radiation-participating cooling gas CO2 in the ejector cavity is drawn in through all the slits on the gas film cooling diffuser mixing tube; the radiation-participating cooling gas CO2 forms a CO2 cooling gas film layer on the inner wall of the gas film cooling diffuser mixing tube to wrap the mainstream of the mixed exhaust gas.

[0026] Among them, the flow rate of radiation-participating cooling gas for: (1) In the formula, The flow rate of the radiation-involved cooling gas; The mainstream flow rate of flue gas; The gravitation coefficient is taken as 0.6~0.72.

[0027] Example 2 Unlike Example 1, in step 2), the radiation-participating cooling gas is ejected through the final stage ejector diffuser ring at the tail of the gas film cooling diffuser mixing tube in the ejector cavity. That is, during the mainstream flow of the mixed exhaust gas, the cooling air around the gas film cooling diffuser mixing tube is entrained and further mixed through the slits at the front and middle of the tube body; the radiation-participating cooling gas CO2 in the ejector cavity is entrained through the slits at the tail of the gas film cooling diffuser mixing tube, and the radiation-participating cooling gas CO2 forms a CO2 cooling gas film layer on the inner wall of the gas film cooling diffuser mixing tube to wrap the mainstream of the mixed exhaust gas.

[0028] Among them, the flow rate of CO2, a radiation-participating cooling gas. In the calculation formula, Take a value of 0.12 to 0.14.

[0029] Example 3 Unlike Example 1, in step 2), different types of gases are selected to be ejected through different slits depending on the actual needs. Specifically, during the mainstream flow of the mixed exhaust gas, the radiation-participating cooling gas CO in the first ejection cavity is entrained through the slits at the front and middle of the gas film cooling diffuser mixing pipe; the radiation-participating cooling gas CO2 in the second ejection cavity is entrained through the slit at the tail of the gas film cooling diffuser mixing pipe. The radiation-participating cooling gases CO2 and CO form a CO2 and CO cooling gas film layer on the inner wall of the gas film cooling diffuser mixing pipe, which envelops the mainstream of the mixed exhaust gas.

[0030] Example 4 See Figure 2The device used in the infrared suppression method for ship exhaust plumes in Example 1 includes a tapered nozzle 2, a film-cooled diffuser mixing pipe, an ejector cavity 3, and a radiation-participating cooling gas supply unit.

[0031] A tapered nozzle 2 is installed at the stern of the ship's exhaust pipe, with its stern gradually narrowing. A film-cooled diffuser mixing pipe is positioned aft of the tapered nozzle 2, with its central axis coinciding with the central axis of the tapered nozzle 2. The front end of the film-cooled diffuser mixing pipe is a certain distance from the stern of the tapered nozzle 2, allowing the high-speed, high-temperature flue gas stream ejected from the tapered nozzle 2 to undergo a violent momentum exchange with the cooling air surrounding the exit of the tapered nozzle 2 due to the viscosity of the gas. This entrains and injects the cooling air into the high-temperature flue gas stream, forming a mixed exhaust stream. The film-cooled diffuser mixing pipe includes a mixing pipe and an ejector diffuser ring assembly. The ejector diffuser ring assembly includes multiple sequentially connected, progressively larger ejector diffuser rings 1. The first-stage ejector diffuser ring 1 is connected to the stern of the mixing pipe. Slits are provided between adjacent ejector diffuser rings 1 and between the first-stage ejector diffuser ring 1 and the mixing pipe.

[0032] The ejector cavity 3 is placed outside the film-cooled diffuser mixing tube. To facilitate the ejection of CO2 gas, the ejector cavity 3 is connected to the film-cooled diffuser mixing tube to form a closed cavity structure, which serves as a "container" for CO2. The ejector cavity 3 is a cylindrical structure welded to the outside of the film-cooled diffuser mixing tube. Its tail end is connected to the tail end of the last stage ejector diffuser ring 1 of the film-cooled diffuser mixing tube, and its front end is connected to the mixing tube below the first stage ejector diffuser ring 1 of the film-cooled diffuser mixing tube. Its interior is connected to the interior of the film-cooled diffuser mixing tube through a slit.

[0033] The radiation-participating cooling gas supply unit provides radiation-participating cooling gas to the ejector cavity 3. It includes a gas storage tank 7, a vacuum pump 6, a valve 5, and a controller. The gas storage tank 7 is connected to one end of the valve 5 via the vacuum pump 6, and the other end of the valve 5 is connected to the injection port 4 of the ejector cavity 3 via a gas pipe. A flow meter 8 is installed on the gas pipe between the valve 5 and the ejector cavity 3. The flow meter 8 transmits the collected data to the controller, which controls the opening degree of the valve 5 and the operation of the vacuum pump 6, thereby controlling the flow rate of the radiation-participating cooling gas entering the ejector cavity 3.

[0034] Example 5 See Figure 4 The device used in the infrared suppression method for ship exhaust plumes in Example 2 includes a tapered nozzle 2, a film-cooled diffuser mixing pipe, an ejector cavity 3, and a radiation-participating cooling gas supply unit.

[0035] The tapered nozzle 2 is installed at the stern of the ship's exhaust pipe, and the stern of the tapered nozzle 2 gradually narrows.

[0036] A film-cooled diffuser mixing tube is placed after the converging nozzle 2, with its central axis coinciding with the central axis of the converging nozzle 2. The front end of the film-cooled diffuser mixing tube is a certain distance from the rear end of the converging nozzle 2, so that the high-speed, high-temperature flue gas stream ejected from the converging nozzle 2 undergoes a violent momentum exchange with the cooling air surrounding the outlet of the converging nozzle 2 due to the viscosity of the gas. This entrains and injects the cooling air into the high-temperature flue gas stream, forming a mixed exhaust stream. The film-cooled diffuser mixing tube includes a mixing tube and an ejector diffuser ring assembly. The ejector diffuser ring assembly includes multiple sequentially connected, gradually increasing in size ejector diffuser rings 1. The first-stage ejector diffuser ring 1 is connected to the rear end of the mixing tube. Slits are provided between adjacent ejector diffuser rings 1 and between the first-stage ejector diffuser ring 1 and the mixing tube.

[0037] The ejector cavity 3 is a closed cavity placed outside the gas film cooling diffuser mixing tube. Its tail end is connected to the tail end of the last stage ejector diffuser ring 1 of the gas film cooling diffuser mixing tube, and its front end is connected to the tube body of the second-last stage ejector diffuser ring 1 of the gas film cooling diffuser mixing tube.

[0038] A radiation-participating cooling gas supply unit provides radiation-participating cooling gas to the ejector cavity 3. It includes a gas storage tank 7, a vacuum pump 6, a valve 5, and a controller. The gas storage tank 7 is connected to one end of the valve 5 via the vacuum pump 6, and the other end of the valve 5 is connected to the injection port 4 of the ejector cavity 3 via a gas pipe. A flow meter 8 is installed on the gas pipe between the valve 5 and the ejector cavity 3. The flow meter 8 transmits the collected data to the controller, which adjusts the flow rate of the radiation-participating gas accordingly. The calculation formula, the controller controls the valve opening and the operation of the air pump, thereby adjusting the flow rate of the radiation-involved cooling gas into the ejector cavity to match the ejection requirements of the radiation-involved gas.

[0039] The final-stage CO2 entrainment scheme is similar to the full-stage CO2 entrainment scheme. During the process of entraining external cooling gas through slits in the mixing tube to form a cooling gas film on the inner wall of the pipe, different slits can be selected to entrain different types of cooling gas. In this embodiment, CO2 is selected to be entrained in the final-stage slit, while air is entrained in other stages; that is, CO2 is entrained in the final stage. Its effect on suppressing infrared radiation is as follows: Figure 6 As shown in (b).

[0040] In this invention, each stage of ejector diffuser ring 1 is connected by a rod-shaped connector, and each stage of ejector diffuser ring has a slit.

[0041] Compared to exhaust ejector cooling methods (see...) Figure 1 This invention utilizes a method of introducing a radiation-participating medium (such as CO2) into a gas film cooling diffuser mixing tube to form an infrared-high absorption coating layer for high-temperature exhaust gas, thereby shielding the outward transmission of strong infrared radiation signals generated by the high-temperature flue gas. See details... Figures 2-5 .

[0042] The converging nozzle 2 accelerates the flow of the main exhaust stream, enhancing its ejection capability. Under the action of gas viscosity, it undergoes a violent momentum exchange with the cooling gas in the surrounding environment of the converging nozzle 2 outlet, thus providing primary cooling to the main exhaust stream.

[0043] The ejector chamber 3 is filled with CO2. Due to the secondary ejection of the main exhaust stream, the CO2 in the ejector chamber 3 enters the main flue gas region (inside the film-cooled diffuser mixing tube) through the slit of the film-cooled diffuser mixing tube, forming a CO2 coating layer at the edge of the main flue gas stream. The CO2 coating layer is mainly composed of CO2 with a lower temperature and higher concentration. Due to the strong absorption of infrared radiation by CO2, the strong infrared energy generated by the high-temperature main flue gas stream is largely absorbed and attenuated, thereby weakening the detectable infrared characteristic signal generated by the plume.

[0044] from Figure 6 As shown in (a)-(c), compared to entrained air, entrained CO2 significantly reduces the infrared radiation intensity of the exhaust plume. This is due to the absorption of infrared radiation from the high-temperature plume by the low-temperature CO2 envelope formed around it. Comparing (b) and (c), it can be seen that because the CO2 gas envelope formed by full-stage entrainment is thicker, full-stage entrained CO2 has a better suppression effect on the infrared radiation at the center of the plume, reducing the maximum radiation temperature by approximately 24°C compared to entrained air. In other words, full-stage entrainment has a better suppression effect on the maximum infrared radiation of the plume compared to the final-stage entrainment, resulting in a greater reduction in the maximum infrared radiation intensity. Even the final-stage entrainment of CO2 has a good suppression effect on the mainstream infrared radiation of the plume. In practical applications, the appropriate method can be chosen based on actual needs.

[0045] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0046] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for suppressing infrared emissions from ship exhaust plumes, characterized in that: The ship's high-temperature exhaust gas is wrapped with radiation-participating cooling gas, and the infrared radiation characteristics are reduced by utilizing the strong absorption of infrared radiation from the high-temperature exhaust gas by the radiation-participating cooling gas.

2. The method for suppressing infrared emissions from ship exhaust plumes according to claim 1, characterized in that: The method includes the following steps: 1) The main stream of high-temperature flue gas from the ship is ejected through a converging nozzle. Due to the viscosity of the gas, it undergoes a violent momentum exchange with the cooling air in the surrounding environment of the converging nozzle outlet, entraining and injecting the cooling air into the main stream of high-temperature flue gas, forming a mixed exhaust stream. 2) The mixed exhaust gas mainstream enters the ejector diffuser ring of the film cooling diffuser mixing tube and continues to mix, and flows towards the outlet along the film cooling diffuser mixing tube; during the flow of the mixed exhaust gas mainstream, the radiation-participating cooling gas in the ejector cavity is drawn in by the slits on the film cooling diffuser mixing tube body, and the radiation-participating cooling gas forms a cooling gas film layer on the inner wall of the film cooling diffuser mixing tube to wrap the mixed exhaust gas mainstream; 3) The strong absorption of infrared rays by the cooling gas film layer causes a large amount of the strong infrared energy generated by the mainstream of high-temperature flue gas to be absorbed and attenuated.

3. The method for suppressing infrared emissions from ship exhaust plumes according to claim 2, characterized in that: In step 2), during the mainstream flow of the mixed exhaust gas, the radiation-participating cooling gas in the injection cavity is drawn in by all the slits on the gas film cooling diffuser mixing pipe; the radiation-participating cooling gas forms a cooling gas film layer on the inner wall of the gas film cooling diffuser mixing pipe to wrap the mainstream of the mixed exhaust gas.

4. The method for suppressing infrared emissions from ship exhaust plumes according to claim 3, characterized in that: In step 2), different slits entrain different types of gas.

5. The method for suppressing infrared emissions from ship exhaust plumes according to claim 2, characterized in that: In step 2), during the mainstream flow of the mixed exhaust gas, the cooling air around the gas film cooling diffuser mixing pipe body is further mixed by the slits at the front and middle of the pipe body; the radiation-participating cooling gas in the injection cavity is drawn in by the slits at the tail of the gas film cooling diffuser mixing pipe body, and the radiation-participating cooling gas forms a cooling gas film layer on the inner wall of the gas film cooling diffuser mixing pipe to wrap the mainstream of the mixed exhaust gas.

6. The method for suppressing infrared exhaust plumes from ships according to any one of claims 1-5, characterized in that: The radiation-participating cooling gas is CO2, CO, or HC.

7. The method for suppressing infrared emissions from ship exhaust plumes according to claim 6, characterized in that: The flow rate of the radiation-participating cooling gas for: （1） In the formula, The flow rate of the radiation-involved cooling gas; The mainstream flow rate of flue gas; This is the entrainment coefficient; when using full-stage entrainment, Take a value of 0.6~0.72; when using a final stage ejector, Take a value of 0.12 to 0.

14.

8. The method for suppressing infrared emissions from ship exhaust plumes according to claim 1, characterized in that: The radiation-participating cooling gas is ejected in the final stage through the ejector diffuser ring at the tail end of the gas film cooling diffuser mixing tube in the ejector cavity; or, the radiation-participating cooling gas is ejected in the full stage through all the ejector diffuser rings of the gas film cooling diffuser mixing tube in the ejector cavity.

9. An apparatus used in the infrared suppression method for ship exhaust plumes according to claim 3, characterized in that: Includes a tapered nozzle, a film-cooled diffuser mixing tube, an ejector cavity, and a radiation-participating cooling gas supply unit; The tapering nozzle is installed at the stern of the ship's exhaust pipe, and its stern gradually narrows. The film cooling diffuser mixing tube is placed after the converging nozzle, with its central axis coinciding with the central axis of the converging nozzle. The front end of the film cooling diffuser mixing tube is a certain distance from the rear end of the converging nozzle, so that the high-speed, high-temperature flue gas stream ejected from the converging nozzle undergoes a violent momentum exchange with the cooling air surrounding the converging nozzle outlet due to the viscosity of the gas. This entrains and injects the cooling air into the high-temperature flue gas stream, forming a mixed exhaust stream. The film cooling diffuser mixing tube includes a mixing tube and an ejector diffuser ring assembly. The ejector diffuser ring assembly includes multiple sequentially connected, gradually increasing in size ejector diffuser rings. The first-stage ejector diffuser ring is connected to the rear end of the mixing tube. Slits are provided between adjacent ejector diffuser rings and between the first-stage ejector diffuser ring and the mixing tube. The ejector cavity is a closed cavity placed outside the gas film cooling diffuser mixing tube. Its tail end is connected to the tail end of the last stage ejector diffuser ring of the gas film cooling diffuser mixing tube, and its front end is connected to the mixing tube below the first stage ejector diffuser ring of the gas film cooling diffuser mixing tube. A radiation-involved cooling gas supply unit provides radiation-involved cooling gas to the ejector cavity. The radiation-involved cooling gas supply unit includes a gas storage tank, a vacuum pump, a valve, and a controller. The gas storage tank is connected to one end of the valve via the vacuum pump, and the other end of the valve is connected to the ejector cavity via a gas pipe. A flow meter is installed on the gas pipe between the valve and the ejector cavity. The flow meter transmits the collected data to the controller, which controls the opening degree of the valve and the operation of the vacuum pump, thereby controlling the flow rate of the radiation-involved cooling gas entering the ejector cavity.

10. An apparatus used in the infrared suppression method for ship exhaust plumes according to claim 5, characterized in that: Includes a tapered nozzle, a film-cooled diffuser mixing tube, an ejector cavity, and a radiation-participating cooling gas supply unit; The tapering nozzle is installed at the stern of the ship's exhaust pipe, and its stern gradually narrows. The film cooling diffuser mixing tube is placed after the converging nozzle, with its central axis coinciding with the central axis of the converging nozzle. The front end of the film cooling diffuser mixing tube is a certain distance from the rear end of the converging nozzle, so that the high-speed, high-temperature flue gas stream ejected from the converging nozzle undergoes a violent momentum exchange with the cooling air surrounding the converging nozzle outlet due to the viscosity of the gas. This entrains and injects the cooling air into the high-temperature flue gas stream, forming a mixed exhaust stream. The film cooling diffuser mixing tube includes a mixing tube and an ejector diffuser ring assembly. The ejector diffuser ring assembly includes multiple sequentially connected, gradually increasing in size ejector diffuser rings. The first-stage ejector diffuser ring is connected to the rear end of the mixing tube. Slits are provided between adjacent ejector diffuser rings and between the first-stage ejector diffuser ring and the mixing tube. The ejector cavity is a closed cavity placed outside the gas film cooling diffuser mixing tube. Its tail end is connected to the tail end of the last stage ejector diffuser ring of the gas film cooling diffuser mixing tube, and its front end is connected to the tube body of the next last stage ejector diffuser ring of the gas film cooling diffuser mixing tube. A radiation-involved cooling gas supply unit provides radiation-involved cooling gas to the ejector cavity. The radiation-involved cooling gas supply unit includes a gas storage tank, a vacuum pump, a valve, and a controller. The gas storage tank is connected to one end of the valve via the vacuum pump, and the other end of the valve is connected to the ejector cavity via a gas pipe. A flow meter is installed on the gas pipe between the valve and the ejector cavity. The flow meter transmits the collected data to the controller, which controls the opening degree of the valve and the operation of the vacuum pump, thereby controlling the flow rate of the radiation-involved cooling gas entering the ejector cavity.

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