A method for eliminating interference of ship flue gas on shipborne atmospheric sampling

Abstract

The application provides a method for eliminating the interference of ship flue gas on shipborne atmospheric sampling, and relates to the technical field of marine environment monitoring. The application comprises the following steps: based on the investigation and measurement results, the sampling port is set; based on the flue gas lifting model and the Gaussian diffusion model, the flue gas diffusion path and the flue gas lifting height are calculated in combination with the ship structure, the sailing speed, the wind direction and the wind speed parameters; and whether the setting of the sampling port is reasonable is verified based on the calculation results. The sampling rod is arranged in a safe area, the sampling port layout is optimized, the flue gas diffusion path and the influence range are accurately calculated in combination with the flue gas lifting model and the Gaussian diffusion model, the shortcomings of the traditional method, such as the dependence on fixed wind direction and manual intervention, are overcome, the all-weather, real-time and automatic sampling data protection is realized, the accuracy and reliability of the marine environment monitoring data are significantly improved, the position of the sampling port is determined through the verification of the embodiments, the flue gas interference is avoided, the monitoring data is normal, and the effectiveness and practicability of the application are proved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of marine environment monitoring, in particular to a method for eliminating interference of ship smoke on shipborne atmospheric sampling. BACKGROUND

[0002] Shipborne underway observation is an important means to obtain marine atmospheric composition data, but in the actual sampling process, the smoke emitted by the ship itself is easy to pollute the sampling gas, resulting in abnormal monitoring data. Especially when the wind direction is consistent with the heading and the wind speed is greater than the ship speed, the sampling port is easy to inhale smoke, which seriously affects the data quality.

[0003] At present, the means to eliminate ship smoke is to permanently install the sampling port at the highest point or the front end of the ship, which will greatly depend on the fixed prevailing wind assumption, and will be invalid once the wind direction changes. Or use manual judgment and interrupt sampling, this sampling method has poor real-time performance and cannot respond to instantaneous changes. The above methods cannot improve the representativeness of the sample and the accuracy of the monitoring data.

[0004] Therefore, it is very necessary to design a method for eliminating interference of ship smoke on shipborne atmospheric sampling. SUMMARY

[0005] In order to overcome the shortcomings of the prior art, the purpose of the present application is to provide a method for eliminating interference of ship smoke on shipborne atmospheric sampling.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] The present application provides a method for eliminating interference of ship smoke on shipborne atmospheric sampling, comprising:

[0008] Step 1: based on the investigation and measurement results, the sampling port is set;

[0009] Step 2: based on the smoke lifting model and the Gaussian diffusion model, combined with the ship structure, the speed, the wind direction and the wind speed parameters, the smoke diffusion path and the smoke lifting height are calculated;

[0010] Step 3: based on the calculation results, it is verified whether the setting of the sampling port is reasonable.

[0011] Preferably, in step 1, based on the investigation and measurement results, the sampling port is set, specifically:

[0012] Based on the investigation and measurement results, the sampling rod is set in the ship smoke plume shadow area, and the sampling port is set at the top end of the sampling rod.

[0013] Preferably, the distance between the sampling rod and the smoke exhaust port is less than 20 cm.

[0014] Preferably, the height of the sampling rod is more than 2 times the height of the smoke outlet.

[0015] Preferably, the smoke lifting height is calculated based on the smoke lifting model combined with the ship structure, speed, wind direction and wind speed parameters, specifically:

[0016] Obtain the ship structure, speed, wind direction and wind speed parameters;

[0017] The maximum height of the vertical rising of the ship smoke, i.e. the smoke lifting height, is calculated based on the Holland formula combined with the ship structure, speed, wind direction and wind speed parameters, which is:

[0018] (1)

[0019] In the formula, T s , T a are the temperatures of the smoke and air respectively, with the unit of K, is the smoke lifting height, with the unit of m, Q H is the heat of the discharged smoke, with the unit of KJ / s, V s is the speed of the smoke outlet, with the unit of m / s, d is the diameter of the smoke outlet, with the unit of m, is the average wind speed at the height of the smoke outlet, with the unit of m / s.

[0020] Preferably, the calculation process of the heat of the discharged smoke is:

[0021] Q = m fuel ×LHV× η comb (2)

[0022] In the formula, Q is the heat release rate of the smoke, with the unit of kJ / s or kW, m fuel is the mass flow of the fuel, with the unit of kg / s, LHV is the low heat value of the fuel, with the unit of kJ / kg, η comb is the combustion efficiency, with the value of 85-95%.

[0023] Preferably, in step 2, the smoke diffusion path is calculated based on the Gaussian diffusion model combined with the ship structure, speed, wind direction and wind speed parameters, specifically:

[0024] The smoke diffusion path of the ship is simulated through the Gaussian diffusion model based on the ship structure, speed, wind direction and wind speed parameters, and the smoke concentration diffusion distance is obtained.

[0025] Preferably, in step 3, it is verified whether the setting of the sampling port is reasonable based on the calculation result, specifically:

[0026] The height of the flue gas rise and the height of the sampling rod are obtained. If the height of the sampling rod is greater than the height of the flue gas rise, it is determined that the vertical position of the sampling port is set reasonably.

[0027] The maximum distance of flue gas concentration diffusion is obtained. If the maximum distance of flue gas concentration diffusion is greater than the distance between the sampling rod and the flue gas emission port, it is determined that the sampling horizontal plane position is set reasonably.

[0028] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0029] This invention provides a method for eliminating interference from ship exhaust fumes on shipborne atmospheric sampling. The method includes setting up sampling ports based on survey and measurement results; calculating the exhaust gas diffusion path and exhaust gas rise height based on exhaust gas rise and Gaussian diffusion models, combined with ship structure, speed, wind direction, and wind speed parameters; and verifying the rationality of the sampling port setup based on the calculation results. This invention optimizes the sampling port layout and accurately calculates the exhaust gas diffusion path and impact range by combining exhaust gas rise and Gaussian diffusion models, thereby placing the sampling rod in a safe area. This method overcomes the shortcomings of traditional methods that rely on fixed wind direction and manual intervention, achieving all-weather, real-time, and automatic sampling data protection, significantly improving the accuracy and reliability of marine environmental monitoring data. In specific implementation, through verification by examples, the sampling port location (15m height from the deck and 3.5m horizontal distance from the chimney) completely avoids exhaust gas interference, and no abnormalities were observed in the monitoring data, proving the effectiveness and practicality of this invention. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the sampling layout structure;

[0032] Figure 2 This is a schematic diagram simulating ship exhaust gas.

[0033] Figure 3 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] The purpose of this invention is to provide a method for eliminating interference from ship exhaust gas on shipborne atmospheric sampling. By optimizing the sampling port layout and combining exhaust gas rise and Gaussian diffusion models, the exhaust gas diffusion path and influence range are accurately calculated, thereby allowing the sampling rod to be placed in a safe area. This method overcomes the shortcomings of traditional methods that rely on fixed wind direction and manual intervention, achieving all-weather, real-time, and automatic sampling data protection, and significantly improving the accuracy and reliability of marine environmental monitoring data. In specific implementation, through aerial survey verification of an example, the sampling port location (15m above the deck and 3.5m horizontal distance from the chimney) completely avoids exhaust gas interference, and no abnormalities were found in the monitoring data, proving the effectiveness and practicality of this invention.

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 3 As shown, the present invention provides a method for eliminating interference from ship exhaust gas on shipborne atmospheric sampling, comprising:

[0038] Step 1: Based on the survey and measurement results, set up the sampling port;

[0039] Step 2: Based on the flue gas rise model and Gaussian diffusion model, and combined with ship structure, speed, wind direction and wind speed parameters, calculate the flue gas diffusion path and flue gas rise height;

[0040] Step 3: Verify whether the sampling port settings are reasonable based on the calculation results.

[0041] In step 1, based on the survey and measurement results, the sampling port is set up as follows:

[0042] Based on the survey and measurement results, the sampling rod was set in the shadow area of ​​the ship's smoke plume, and a sampling port was set at the top of the sampling rod.

[0043] The distance between the sampling rod and the flue gas emission outlet is less than 20cm.

[0044] The height of the sampling rod is more than twice the height of the flue gas emission outlet.

[0045] Based on the flue gas rise model and combined with ship structure, speed, wind direction, and wind speed parameters, the flue gas rise height is calculated as follows:

[0046] Obtain parameters such as ship structure, speed, wind direction, and wind speed;

[0047] Based on Holland's formula and combined with parameters of ship structure, speed, wind direction, and wind speed, the maximum vertical rise height of ship exhaust, i.e., the exhaust rise height, is calculated as follows:

[0048] (1)

[0049] In the formula, T s T a These are the temperatures of the flue gas and the air, respectively, in Kelvin (K). Q represents the height of the flue gas rise, measured in meters (m). H The heat released from the flue gas is expressed in kJ / s, V. s d represents the emission velocity of the flue gas at the emission outlet, in m / s, and d represents the diameter of the flue gas emission outlet, in m. The average wind speed at the height of the flue gas emission outlet is expressed in m / s.

[0050] The calculation process for the heat of the discharged flue gas is as follows:

[0051] Q H = m fuel ×LHV× η comb (2)

[0052] In the formula, Q H The heat removed from the flue gas is expressed in kJ / s or kW. m fuel The fuel mass flow rate is expressed in kg / s, and LHV is the lower heating value of the fuel, expressed in kJ / kg. η comb For combustion efficiency, the value is 85-95%.

[0053] In step 2, based on the Gaussian diffusion model and combined with ship structure, speed, wind direction, and wind speed parameters, the smoke diffusion path is calculated, specifically as follows:

[0054] (1) Establish a dynamic calculation coordinate system

[0055] A three-dimensional moving coordinate system is established with the center of the ship's exhaust outlet as the origin O. This coordinate system moves synchronously with the ship. The positive direction of the X-axis is defined as the direction of the effective wind direction (i.e., the combined wind direction of the ambient wind vector and the ship's heading vector), the Y-axis is the direction perpendicular to the X-axis on the horizontal plane, and the Z-axis is the vertical direction (pointing towards the sky).

[0056] (2) Determine the key input parameters of the model

[0057] Calculate the wind speed: Use the average wind speed at the height of the flue gas outlet (i.e., the same wind speed parameter used in the Holland formula) as the input wind speed in the Gaussian diffusion model.

[0058] Effective wind direction: By combining the ambient wind direction and speed with the ship's heading and speed through vector operations, the effective wind direction is calculated. This direction is the downwind direction (X-axis direction) in the Gaussian diffusion model.

[0059] Atmospheric stability: Based on real-time measurements of solar radiation intensity, cloud cover, and average wind speed at the height of the flue gas emission outlet, and referring to the Pasqual stability classification method in the "Technical Guidelines for Environmental Impact Assessment: Atmospheric Environment", the current atmospheric stability level is determined (e.g., A-extremely unstable, B-unstable, C-slightly unstable, D-neutral, etc.).

[0060] (3) Select diffusion parameters and perform simulation.

[0061] Based on the atmospheric stability level determined in the previous step, the corresponding Briggs diffusion parameter formula is selected. Based on this, the horizontal diffusion parameter σy and the vertical diffusion parameter σz are calculated at different downwind distances X.

[0062] Subsequently, the emission source strength, calculated wind speed, effective source height (chimney physical height + flue gas rise height), and diffusion parameters σy and σz are substituted into the Gaussian diffusion model formula to perform numerical calculations, simulating the flue gas concentration field distribution under the entire moving coordinate system, thereby clearly depicting the flue gas diffusion path.

[0063] (4) Obtain the diffusion distance of flue gas concentration

[0064] The flue gas concentration diffusion distance is specifically defined as: the maximum horizontal straight-line distance between the flue gas concentration distribution contour line and the flue gas emission outlet (coordinate origin O) when the contour line decays to a preset safety threshold on a horizontal plane (Z=0).

[0065] The preset safety threshold can be determined comprehensively based on the detection limit of the shipborne atmospheric sampling instrument and the ambient background concentration value. For example, it can be set as the lowest concentration limit that does not interfere with the target monitored gas components. By scanning the concentration field obtained through simulation calculation, the diffusion distance of this flue gas concentration can be automatically identified and output.

[0066] In step 3, the setting of the sampling port is verified based on the calculation results to determine whether it is reasonable. Specifically:

[0067] The height of the flue gas rise and the height of the sampling rod are obtained. If the height of the sampling rod is greater than the height of the flue gas rise, it is determined that the vertical position of the sampling port is set reasonably.

[0068] The maximum distance of flue gas concentration diffusion is obtained. If the maximum distance of flue gas concentration diffusion is greater than the distance between the sampling rod and the flue gas emission port, it is determined that the sampling horizontal plane position is set reasonably.

[0069] This invention provides an embodiment to verify the accuracy of the above method:

[0070] With a ship length / width of 43.8 / 7.5m, a draft of 3.0m, a flue gas outlet diameter of approximately 40cm, a displacement of 500 tons, a speed of 10 knots, and the center height of the outlet approximately 4.5 meters above the deck, the estimated maximum average wind speed at the flue gas outlet is 6.2m / s, the ship's speed is 4.1m / s, the emission speed at the outlet is 3.0m / s, and the average wind speed at the outlet is 6.2m / s. The purpose of this estimation is to use Holland's formula to calculate the maximum plume lift, determine whether the sampling port is affected by the ship's flue gas, and thus verify the rationality of the sampling port layout.

[0071] The calorific value of flue gas emission is calculated according to formula (2). When the fuel is marine diesel under low load conditions, the fuel is approximately 42700 kJ / kg, the fuel flow rate is 0.0082 kg / s, and the combustion efficiency is 90%. The calorific value of flue gas emission under low load conditions is approximately 315 kJ / s.

[0072] When the calorific value of the flue gas emission is 315 kJ / s, the heat QH of the emitted flue gas is substituted into the flue gas rise height formula to calculate the expected rise height of the flue gas after leaving the chimney is about 1m, that is, 5.5m from the deck.

[0073] Under full load conditions, heavy oil is used as fuel, with a lower heating value of approximately 40,000 kJ / kg, a fuel flow rate of 0.026 kg / s, and a combustion efficiency of 85%. The calculated calorific value of flue gas emissions under full load conditions is approximately 884 kJ / s.

[0074] When the calorific value of the flue gas emission is 884 kJ / s, the calculated expected rise height of the flue gas after leaving the chimney is about 2m, and 6.5m from the deck.

[0075] When the ship is in operation (low load and full load), the maximum rise height of the flue gas after leaving the chimney is estimated to be 2m, that is, 6.5m from the deck. If the sampling port is higher than 6.5m, the vertical direction will not be affected by the flue gas. In this experiment, the height of the sampling rod is 15m from the deck, which meets the vertical height requirement.

[0076] The sampling rod was set 3.5m from the chimney exhaust outlet, and the sampling port was 15m from the deck. See details below. Figure 1The flue gas diffusion process was simulated using a Gaussian diffusion model. The simulation showed that the maximum concentration of flue gas was 5m horizontally, which exceeded the distance between the sampling rod and the chimney outlet. This means that the sampling outlet was located outside the core diffusion area of ​​the plume, which met the horizontal distance requirement.

[0077] As can be seen, during normal ship navigation, when the sampling port is 15m above the deck and 3.5m horizontally from the chimney exhaust, it will not be affected by the flue gas. (See details...) Figure 2 ;

[0078] The above embodiments show that the analysis of flue gas diffusion during ship navigation indicates that the setting of the sampling port (see details) is important. Figure 1 This effectively avoids flue gas interference. According to the Holland formula, under low-load operating conditions (flue gas heat release rate 315 kJ / s), the plume rises to a height of 1 m, and the plume is 5.5 m above the deck; under high-load operating conditions (flue gas heat release rate 884 kJ / s), the plume rises to a height of 2 m, and the top is 6.5 m above the deck. Through Gaussian diffusion model simulation, the maximum plume concentration area is located 5 m downwind of the chimney, with a diffusion diameter of approximately 0.5 m.

[0079] The sampling port is positioned 15m above the deck and 3.5m horizontally from the chimney. This placement meets the following safety requirements:

[0080] 1. In the vertical direction, the sampling port extends 8.5 meters beyond the maximum influence range of the plume;

[0081] 2. In the horizontal direction, the sampling port is located outside the core diffusion region of the plume;

[0082] 3. In addition, the measured data in the embodiment showed that the average uncorrected wind speed during navigation was 8.1 m / s, which was higher than the average wind speed of 6.2 m / s at the flue gas emission outlet. According to the Holland formula, the higher ambient wind speed would further suppress the rise of the plume, thereby reducing the potential interference to the sampling port.

[0083] Based on the above analysis, it can be confirmed that the location of the sampling port in the embodiment can completely avoid the interference of ship exhaust gas on the sampling work, ensuring the accuracy and reliability of the monitoring data.

[0084] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0085] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for eliminating interference from ship exhaust gas on shipborne atmospheric sampling, characterized in that, include: Step 1: Based on the survey and measurement results, the sampling port is set up as follows: Based on the survey and measurement results, the sampling rod was set in the shadow area of ​​the ship's flue gas plume, and a sampling port was set at the top of the sampling rod. The distance between the sampling rod and the flue gas emission port was less than 20cm, and the height of the sampling rod was more than twice the height of the flue gas emission port. Step 2: Based on the smoke rise model and the Gaussian diffusion model, and combined with ship structure, speed, wind direction, and wind speed parameters, calculate the smoke diffusion path and smoke rise height. The smoke rise model is based on Holland's formula combined with ship structure, speed, wind direction, and wind speed parameters to calculate the ship's smoke rise height; the Gaussian diffusion model, combined with ship structure, speed, wind direction, and wind speed parameters, calculates the smoke diffusion path, specifically as follows: Establish a moving coordinate system with the flue gas emission outlet as the origin, and determine the effective wind direction as the downwind direction of the Gaussian diffusion model based on the ambient wind in the wind direction and wind speed parameters and the ship's heading in the speed parameters. The average wind speed at the height of the flue gas emission outlet is obtained as the calculation wind speed for the Gaussian diffusion model; The atmospheric stability level is determined based on real-time meteorological conditions, and the corresponding horizontal and vertical diffusion parameters are selected based on the atmospheric stability level. Based on horizontal and vertical diffusion parameters, the smoke concentration distribution at each point downwind is simulated and calculated using a Gaussian diffusion model to determine the smoke diffusion path. Step 3: Verify the rationality of the sampling port settings based on the calculation results, specifically: Obtain the flue gas rise height and the sampling rod height. If the sampling rod height is greater than the flue gas rise height, it is determined that the vertical position of the sampling port is set reasonably. The maximum distance of flue gas concentration diffusion is obtained. If the maximum distance of flue gas concentration diffusion is greater than the distance between the sampling rod and the flue gas emission port, it is determined that the sampling horizontal plane position is set reasonably.

2. The method according to claim 1, characterized in that, Based on the flue gas rise model and combined with ship structure, speed, wind direction, and wind speed parameters, the flue gas rise height is calculated as follows: Obtain parameters such as ship structure, speed, wind direction, and wind speed; Based on Holland's formula and combined with parameters of ship structure, speed, wind direction, and wind speed, the maximum vertical rise height of ship exhaust, i.e., the exhaust rise height, is calculated as follows: （1） In the formula, T s T a These are the temperatures of the flue gas and the air, respectively, in Kelvin (K). Q represents the height of the flue gas rise, measured in meters (m). H The heat released from the flue gas is expressed in kJ / s, V. s d represents the emission velocity of the flue gas at the emission outlet, in m / s, and d represents the diameter of the flue gas emission outlet, in m. The average wind speed at the height of the flue gas emission outlet is expressed in m / s.

3. The method according to claim 2, characterized in that, The calculation process for the heat of the discharged flue gas is as follows: Q = m fuel ×LHV× η comb (2) In the formula, Q is the flue gas heat release rate, with units of kJ / s or kW. m fuel The fuel mass flow rate is expressed in kg / s, and LHV is the lower heating value of the fuel, expressed in kJ / kg. η comb For combustion efficiency, the value is 85-95%.

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