Improved ship engine SCR device ventilation implementation method

Abstract

The invention discloses an improved ship engine SCR (Selective Catalytic Reduction) device ventilation implementation method, which relates to the technical field of ship engines, and comprises the following steps: signal acquisition: acquiring a pressure difference signal of a pressure difference sensor PDT501 in front of and behind an SCR stop valve; a step of boosting time processing: when the ventilation function is executed for the first time, setting the number of the auxiliary air supply channels according to the pressure difference rise time, and determining an air supply strategy corresponding to the target boosting time; a ventilation execution step: controlling a urea spray gun to atomize air and purge air and a plurality of soot blowing pipelines to inject compressed air into an SCR pipeline according to the air supply strategy, and performing circulation control based on the upper and lower limits of the pressure difference; and a differential pressure monitoring and alarming step: monitoring a differential pressure value in real time. Ventilation and air supply are achieved through an original SCR urea spray gun and a soot blowing pipeline, pressure rising time self-adaption setting and pressure difference closed-loop control are combined, an independent ventilation pipeline and an electromagnetic valve are not needed, positive pressure can be stably maintained, devices of different specifications can be adapted, cost is reduced, and reliability is improved.

Description

Technical Field

[0001] This invention relates to the field of marine engine technology, and in particular to an improved method for achieving ventilation in a marine engine SCR device. Background Technology

[0002] Selective catalytic reduction (SCR) systems are widely used in marine diesel engines and dual-fuel engines as an important exhaust aftertreatment device to meet IMO emission regulations. When the main engine of a ship is operating under Tier II conditions, undergoing maintenance, or when there is a potential risk of leakage in the dual-fuel system, ventilation of the SCR system is usually required to prevent exhaust gases or combustible gases from remaining inside the SCR reactor and pipelines.

[0003] Ventilation functions in marine SCR systems are typically achieved using independent ventilation air supply pipelines and dedicated ventilation solenoid valves. This independent ventilation system is controlled by the SCR controller, which opens and closes the ventilation solenoid valves. Flow is limited by a fixed orifice plate, and the ventilation pressure status is determined based on signals from differential pressure sensors before and after the SCR shut-off valve. When insufficient positive pressure is detected inside the SCR, the ventilation solenoid valves are opened to inject compressed air into the pipeline to maintain a certain positive pressure.

[0004] However, existing technologies have low system integration in practical applications. Independent ventilation ducts and valves usually need to be installed separately in the shipyard. This can easily lead to installation errors, omissions, or difficulties in commissioning due to differences in site layout or insufficient construction coordination. The existing ventilation flow rate is predetermined by the orifice plate. When the volume of the SCR pipeline varies due to ship type, layout, or modifications, the fixed flow rate is difficult to match different volume requirements, resulting in excessive pressure rise time deviation or unstable ventilation effect. Traditional ventilation control often adopts a single threshold start-stop method, which lacks optimization of pressure rise time and alarm delay logic design, and is prone to frequent start-stop or false alarms. Therefore, we propose an improved ventilation implementation method for marine engine SCR devices. Summary of the Invention

[0005] The purpose of this invention is to provide an improved ventilation method for a marine engine SCR device to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an improved method for ventilation implementation of a marine engine SCR device, comprising: Step 1: Signal acquisition. Acquire the differential pressure signal from the differential pressure sensor PDT501 before and after the SCR shut-off valve, and receive the ventilation command signal from the main unit. Step 2, Pressure Rise Time Processing Step: When the ventilation function is executed for the first time, the number of auxiliary air supply channels is adjusted according to the pressure difference rise time, and the air supply strategy corresponding to the target pressure rise time is determined. Step 3: Ventilation execution step. According to the air supply strategy, control the urea spray gun atomized air, purging air and several soot blowing pipes to inject compressed air into the SCR pipeline, and perform cyclic control based on the upper and lower limits of pressure difference. Step 4: Differential pressure monitoring and alarm procedure. Monitor the differential pressure value in real time, activate the low pressure alarm logic when the ventilation command is valid, and deactivate the alarm when the ventilation command is invalid.

[0007] Preferably, the differential pressure signal acquisition and processing in step 1 includes: The analog signal of the differential pressure sensor PDT501 before and after the SCR shut-off valve is cyclically sampled at a frequency of 1 time / 0.5 seconds. Perform maximum and minimum value rejection processing on multiple consecutively collected sample values; A sliding window averaging filter model is constructed for the remaining sampled values ​​to obtain a stable differential pressure value; The stable differential pressure value is transmitted to the SCR controller in real time and displayed on the operation interface; The PDT501 has a measurement range of -1 bar to 1 bar.

[0008] Preferably, the ventilation command logic control in step 1 includes: When the host ventilation command switches from invalid to valid, the ventilation mode is activated and the low pressure alarm logic is enabled. When the main unit ventilation command changes from valid to invalid, the air supply solenoid valve is closed and an alarm shielding signal is sent to the controller. At the same time, the function of continuously acquiring and displaying differential pressure values ​​should be maintained without interruption.

[0009] Preferably, the boost time processing in step 2 includes: When the ventilation command is executed for the first time, the urea spray gun atomizing air solenoid valve, the purging air solenoid valve and the soot blowing branch pipe solenoid valve are opened simultaneously. The initial pressurization time required when the monitoring pressure difference reaches the set upper limit; After the differential pressure drops back to the set lower limit, reduce the input of one soot blowing branch solenoid valve and measure the pressure rise time again. Repeat the adjustment until the pressurization time is close to the target pressurization time, thereby determining the number of soot blowing pipes to be put into ventilation operation.

[0010] Preferably, the target boost time satisfies: The target pressurization time is less than the low ventilation pressure alarm trigger time; Furthermore, the target boost time is 50%-60% of the alarm trigger delay time.

[0011] Preferably, step 3 includes: Upon receiving the ventilation command, the corresponding solenoid valve is opened according to the air supply strategy determined in step 2. When the differential pressure value of PDT501 is higher than the upper limit value, the gas supply solenoid valve is closed. When the differential pressure value of PDT501 is lower than the lower limit, the gas supply solenoid valve is opened to maintain positive pressure inside the SCR pipeline.

[0012] Preferably, the upper limit of the pressure difference is 0.12 bar, and the lower limit of the pressure difference is 0.02 bar.

[0013] Preferably, in step 3, the solenoid valves of the soot blowing branch pipes participating in ventilation adopt a polling opening mode. When the total number of soot blowing branch pipes is N and the number of pipes put into ventilation operation is m, each round of ventilation sequentially selects solenoid valves of different numbers of soot blowing branch pipes to participate in air supply until all branch pipes participate in polling.

[0014] Preferably, step 4 includes: When the ventilation command is active, if the differential pressure is lower than the set value and the duration exceeds the alarm trigger time, a low ventilation pressure alarm signal will be output. When the ventilation command is invalid, only the differential pressure value is displayed and no alarm is triggered.

[0015] Preferably, the ventilation air supply channel adopts the original urea spray gun atomizing air channel, purging air channel and soot blowing air pipeline; the independent ventilation air supply pipeline and ventilation solenoid valve are eliminated.

[0016] The technical effects and advantages of this invention are as follows: This invention utilizes the existing urea spray gun atomizing air channel, purging air channel, and soot blowing air pipeline of the SCR system as ventilation supply channels. Combined with adaptive pressure rise time setting and differential pressure upper and lower limit closed-loop control, it enables SCR ventilation function to be completed without independent ventilation pipelines and dedicated solenoid valves. This not only improves the system integration and standardization, but also adapts to different specifications of SCR devices, stably maintains positive pressure and avoids false alarms, reduces hardware costs and construction workload, and improves system reliability and maintenance convenience. Attached Figure Description

[0017] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0018] 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.

[0019] This invention provides, for example Figure 1 An improved method for implementing ventilation in a marine engine SCR device is shown, comprising: Step 1: Signal acquisition. Acquire the differential pressure signal from the differential pressure sensor PDT501 before and after the SCR shut-off valve, and receive the ventilation command signal from the main unit. The differential pressure signal acquisition and processing in step 1 includes: The analog signal of the differential pressure sensor PDT501 before and after the SCR shut-off valve is cyclically sampled at a frequency of 1 time / 0.5 seconds. Perform maximum and minimum value rejection processing on multiple consecutively collected sample values; A sliding window averaging filter model is constructed for the remaining sampled values ​​to obtain a stable differential pressure value; The stable differential pressure value is transmitted to the SCR controller in real time and displayed on the operation interface; The PDT501 has a measurement range of -1 bar to 1 bar.

[0020] The ventilation command logic control in step 1 includes: When the host ventilation command switches from invalid to valid, the ventilation mode is activated and the low pressure alarm logic is enabled. When the main unit ventilation command changes from valid to invalid, the air supply solenoid valve is closed and an alarm shielding signal is sent to the controller. At the same time, the function of continuously acquiring and displaying differential pressure values ​​should be maintained without interruption; In the implementation of this invention, step 1 is the basic link of ventilation control, and its core lies in achieving stable acquisition of differential pressure data and reliable triggering of ventilation control logic; First, at the hardware level, a differential pressure sensor PDT501 is installed before and after the SCR shut-off valve to measure the pressure difference between the two sides of the SCR shut-off valve in real time. The range of the differential pressure sensor is set to -1 bar to 1 bar, which can cover the entire pressure change range of the SCR system in both ventilated and non-ventilated states. The PDT501 outputs an analog signal to the PLC analog input module of the SCR controller. During signal acquisition, the PLC control unit performs cyclic sampling at a fixed sampling frequency of 1 time / 0.5 seconds, that is, it collects the differential pressure value twice per second. This sampling frequency can ensure the dynamic response capability of the voltage boosting process, and also avoid the controller load from being increased due to excessive sampling frequency. To avoid the impact of abnormal data caused by compressed air pulsation, sensor transient disturbances, or electromagnetic interference on the judgment accuracy, the continuously sampled data is preprocessed at the software level. Specifically, the maximum and minimum values ​​of a set of continuously collected differential pressure sample data are removed to eliminate sudden peak interference. Then, a sliding window average filtering model is constructed for the remaining data. The sliding window can be set to a fixed length (e.g., 5 to 10 sampling points). The window slides and updates over time. By performing an arithmetic average calculation on the data within the window, a stable differential pressure value is obtained. The filtered and stable differential pressure value is transmitted to the human-machine interface (HMI) of the SCR controller in real time for display, so that the operator can intuitively observe the pressure difference changes during the ventilation process. At the same time, the stable differential pressure value serves as the basis for subsequent pressurization time calculation and ventilation control logic judgment. Regarding the ventilation command logic, the SCR controller continuously receives ventilation command signals from the ship's main engine control system. These ventilation commands are switch signals used to indicate whether to enter the SCR ventilation mode. When the controller detects that the ventilation command has switched from an invalid state to an effective state, it immediately starts the ventilation mode preparation process, including allowing the execution of ventilation supply logic, starting the low pressure alarm monitoring timer, and disabling the relevant alarm shielding function. When the ventilation command switches from an active state to an inactive state, the controller immediately closes the currently open air supply solenoid valve and sends a low pressure alarm shielding signal to the alarm management module to avoid triggering false alarms due to the natural drop in pressure difference during non-ventilation. It should be noted that during the alarm shielding period, the pressure difference acquisition and interface display functions continue to operate, only the alarm output logic is disabled, and the data recording and monitoring functions are not affected. This logical design ensures the decoupling of ventilation control and alarm functions: data acquisition and display are always continuous, while the alarm function only takes effect during the effective ventilation period, thereby avoiding false alarms from affecting the ship's operational judgment. Through the above-described signal acquisition and logic control methods, the present invention demonstrates the following effects during implementation: First, the signal stability is significantly improved. Through the dual processing method of "maximum and minimum value elimination + sliding window averaging", the compressed air pulsation and instantaneous noise interference of the sensor are effectively suppressed, making the differential pressure curve smooth and stable, providing a reliable basis for subsequent pressure rise time Tu calculation. Second, the system response is reasonable and controllable. The sampling frequency of 1 time / 0.5 seconds can accurately capture the entire process of pressure difference rising from 0.02 bar to 0.12 bar, while avoiding oversampling that would waste PLC resources. Third, to avoid false alarms, by binding the alarm logic to the ventilation command, the low pressure alarm function is automatically blocked when the ventilation command is invalid. This solves the problem of false alarms being triggered by the natural decrease in pressure difference in non-ventilated states in traditional systems, and improves the reliability of system operation. Fourth, improve the system's continuous monitoring capability. Even when the alarm is blocked, the differential pressure value continues to be collected and displayed, enabling operators to fully understand the internal pressure changes of the SCR system and enhancing system transparency. Fifth, it provides a data foundation for subsequent adaptive tuning. Stable differential pressure data provides an accurate basis for calculating the pressurization time during the first ventilation, making the adaptive adjustment of the number of sootblowing pipes more accurate and improving the overall ventilation matching degree. In summary, the signal acquisition and logic control in step 1 not only achieves highly stable acquisition of differential pressure data, but also improves the system reliability and intelligence through reasonable software logic design, providing an important foundation for the present invention to achieve the improvement goal of eliminating the need for independent ventilation ducts.

[0021] Step 2, Pressure Rise Time Processing Step: When the ventilation function is executed for the first time, the number of auxiliary air supply channels is adjusted according to the pressure difference rise time, and the air supply strategy corresponding to the target pressure rise time is determined. Step 2, the boost time processing, includes: When the ventilation command is executed for the first time, the urea spray gun atomizing air solenoid valve, the purging air solenoid valve and the soot blowing branch pipe solenoid valve are opened simultaneously. The initial pressurization time required when the monitoring pressure difference reaches the set upper limit; After the differential pressure drops back to the set lower limit, reduce the input of one soot blowing branch solenoid valve and measure the pressure rise time again. Repeat the adjustment until the pressurization time is close to the target pressurization time, thereby determining the number of soot blowing pipes to be put into ventilation operation.

[0022] The target boost time satisfies the following: The target pressurization time is less than the low ventilation pressure alarm trigger time; Furthermore, the target boost time is 50%-60% of the alarm trigger delay time; In the implementation of this invention, step 2 is a key step to achieve adaptive matching of the ventilation system. Its core purpose is to dynamically adjust the number of auxiliary air supply channels involved in ventilation by measuring and comparing the actual pressurization time inside the SCR pipeline without having to pre-set a fixed throttling flow rate, thereby obtaining the optimal air supply strategy to adapt to SCR pipelines of different volumes. When the SCR system receives the ventilation command from the host for the first time, the controller automatically determines whether the current system is in the "first ventilation execution" state. If it is the first execution, it enters the pressure rise time setting mode. During the initial setup phase, the controller simultaneously opens the urea spray gun atomizing air solenoid valve and the purging air solenoid valve, allowing compressed air to be injected into the SCR pipeline through the urea spray gun channel as the main air supply channel. At the same time, a preset number of n soot blowing branch solenoid valves are opened by default (for example, the initial value can be set to 3) as auxiliary air supply channels, allowing compressed air to enter the SCR pipeline through the soot blowing nozzle. At the moment the gas supply is turned on, the system starts the pressure rise time timer and monitors the stable pressure difference value as described in step 1 in real time. When the stable pressure difference value rises from the set lower limit value (e.g., 0.02 bar) to the set upper limit value (e.g., 0.12 bar), the first pressure rise time is recorded. Then the gas supply solenoid valve is closed, allowing the system pressure to drop naturally. Once the stable differential pressure value drops to the lower limit, the controller reduces the number of solenoid valves activated on one soot blowing branch pipe, for example, from 3 to 2, and executes the gas supply process again, recording the second pressurization time. By gradually reducing the number of auxiliary gas supply channels and repeatedly measuring the pressurization time, the system obtains pressurization response curves under different gas supply combinations. When a certain pressurization time value is close to the target pressurization time, it is considered that the number of soot blowing branch pipes m currently put into use is the optimal value to match the pipeline volume of the current SCR system. The target boost time is set according to the following principles: The target pressurization time must be less than the low ventilation pressure alarm trigger time to ensure that effective pressurization can be completed before the alarm delay time arrives, thus avoiding false alarm triggering. For example, when the alarm delay time is 10 seconds, the target boost time is preferably between 5 and 6 seconds. This ratio range has been verified through engineering tests to achieve a balance between boost stability and the operating frequency of the actuator. Through the above-described adaptive pressure rise time tuning method, this invention achieves the following significant effects in practical applications: It enables automatic matching of ventilation flow. Different models of SCR devices have significantly different pipeline volumes. Traditional designs using fixed orifice plates are difficult to adapt to subsequent pipeline layout adjustments. This invention determines the number of air supply channels by measuring the actual pressure rise time, achieving automatic adaptation to systems with different volumes. It avoids false alarm triggering. By limiting the target pressure rise time to less than the alarm trigger time, preferably set to 50%–60% of the alarm delay time, it ensures that the system remains within a safe margin during pressure rise, effectively preventing low-pressure alarms due to excessively slow pressure rise. It reduces frequent operation of actuators. If the pressure rise time is too short, the system will frequently reach its upper limit, causing repeated opening and closing of the solenoid valve, affecting its lifespan. By controlling the target pressure rise time within a reasonable range, the solenoid valve's operating frequency is kept within a controllable range, extending its service life.

[0023] Step 3: Ventilation execution steps. According to the air supply strategy, control the atomized air of the urea spray gun, the purging air and several soot blowing pipelines to inject compressed air into the SCR pipeline, and perform circulation control based on the upper and lower limits of the pressure difference. Step 3 includes: Upon receiving the ventilation command, the corresponding solenoid valve is opened according to the air supply strategy determined in step 2. When the differential pressure value of PDT501 is higher than the upper limit value, the gas supply solenoid valve is closed. When the differential pressure value of PDT501 is lower than the lower limit, the gas supply solenoid valve is opened to maintain positive pressure inside the SCR pipeline. The upper limit of the differential pressure is 0.12 bar, and the lower limit is 0.02 bar. In step 3, the solenoid valves of the soot blowing branch pipes involved in ventilation adopt a polling opening mode. When the total number of soot blowing branch pipes is N and the number of ventilation operation is m, each round of ventilation sequentially selects solenoid valves of different numbers of soot blowing branch pipes to participate in air supply until all branch pipes participate in polling. In the implementation of this invention, step 3 is the normal operation stage of the ventilation function. Its core is to maintain the SCR pipeline in a stable positive pressure state through closed-loop control based on the air supply strategy determined in step 2. When the SCR controller receives the ventilation command from the ship's main engine and the pressurization time setting in step 2 is completed, the system enters the ventilation execution mode. The controller opens the urea spray gun atomizing air solenoid valve, the purging air solenoid valve, and the m-way soot blowing branch pipe solenoid valve according to the determined air supply strategy. At this time, compressed air is injected into the SCR pipeline through the urea spray gun channel and the selected soot blowing branch pipe channel, forming a ventilation structure in which the main air supply and auxiliary air supply work together. During the gas supply process, the controller reads the filtered differential pressure value in real time and compares it with the set upper and lower limits of differential pressure. In this embodiment, the upper limit of differential pressure is set to 0.12 bar and the lower limit of differential pressure is set to 0.02 bar. This range has been verified by engineering and can ensure that the SCR pipeline maintains positive pressure while avoiding excessive pressure from causing additional load on the sealing structure and catalyst carrier. When the differential pressure value is detected to be ≥0.12 bar, the controller immediately closes the currently open air supply solenoid valve, stopping the injection of compressed air. Subsequently, the internal pressure of the SCR pipeline gradually decreases under the buffering effect of natural leakage and system volume. When the differential pressure value is ≤0.02 bar, the controller reopens the corresponding solenoid valve, allowing compressed air to be injected again. Through the above-mentioned dual threshold control logic of "closing when the upper limit is reached and opening when the lower limit is reached", a periodic closed-loop regulation is formed to achieve stable fluctuation of the internal pressure of the SCR pipeline between 0.02 bar and 0.12 bar. This control method is essentially a closed-loop control mode with hysteresis characteristics. Because upper and lower limit ranges are set, it can effectively avoid the solenoid valve from frequently opening and closing near a single threshold, thereby reducing the wear of the actuator. Considering that marine compressed air systems generally have high moisture content, if a certain soot blowing branch pipe is used for air supply for a long time, the catalyst in the corresponding area of ​​the branch pipe may be damp for a long time, thus affecting the catalytic efficiency and lifespan. Therefore, this invention adopts a polling opening mode for the soot blowing branch pipe solenoid valve involved in ventilation during the ventilation process. Specifically, when the total number of soot blowing branch pipes in the SCR unit is N (e.g., 9 to 36), and step 2 determines that the number of pipes put into ventilation operation is m (usually m ≤ 2), the controller sequentially selects solenoid valves of m soot blowing branch pipes with different numbers to participate in air supply in each ventilation execution cycle, for example: If N=24 and m=2, then in the first round of ventilation, branch pipes numbered 1 and 2 will be opened; in the second round, branch pipes numbered 3 and 4 will be opened; in the third round, branch pipes numbered 5 and 6 will be opened... and so on. When the number reaches 24, the cycle will start again from number 1. This polling logic is implemented by the PLC's internal counter and index variable. The polling strategy can be progressively based on the number of ventilation cycles, rather than switching in real time with pressure fluctuations, in order to avoid frequent changes in the gas supply channel during a single pressurization process.

[0024] Step 4: Differential pressure monitoring and alarm procedure. Monitor the differential pressure value in real time, activate the low pressure alarm logic when the ventilation command is valid, and deactivate the alarm when the ventilation command is invalid. Step 4 includes: When the ventilation command is active, if the differential pressure is lower than the set value and the duration exceeds the alarm trigger time, a low ventilation pressure alarm signal will be output. When the ventilation command is invalid, only the differential pressure value is displayed and no alarm is triggered; The method utilizes the existing urea spray gun atomizing air channel, purging air channel and soot blowing air pipeline of the SCR system as ventilation and air supply channels. Eliminate independent ventilation air supply pipelines and ventilation solenoid valves; In the implementation of this invention, step 4 is an important part of ensuring the safety of ventilation function. Its core lies in real-time monitoring of the internal pressure difference of the SCR pipeline and implementing differentiated alarm logic control according to the ventilation command status, thereby ensuring the reliability of the system during ventilation operation and avoiding false alarms in non-ventilation states. In terms of hardware structure, the present invention does not add an additional differential pressure detection device. It still uses the differential pressure sensor PDT501 configured in the original SCR system to measure the differential pressure across the SCR shut-off valve in real time. The output signal of PDT501 is filtered and processed as described in step 1 to form a stable differential pressure value, which serves as the basis for alarm logic judgment. During ventilation, the controller continuously monitors the status of ventilation commands issued by the host. When the ventilation command is valid, the system enters the alarm monitoring mode. At this time, the controller compares the current differential pressure value ΔP with the set alarm lower limit value. In this embodiment, the alarm judgment benchmark value is preferably the differential pressure lower limit value of 0.02 bar. If the differential pressure is lower than the set value, the controller will not immediately trigger an alarm. Instead, it will start an alarm delay timer. Only when the differential pressure remains lower than the set value for a duration exceeding the alarm trigger time will the system output a "low ventilation pressure" alarm signal. This alarm signal can be displayed through an audible and visual alarm device or on the SCR controller operating interface, and can also be uploaded to the ship's main engine monitoring system. The aforementioned delayed judgment mechanism is designed to avoid false alarms caused by instantaneous pressure fluctuations or sampling errors. Since there may be minor leaks or pressure fluctuations in the SCR pipeline during actual operation, using instantaneous values ​​for judgment can easily generate false alarms, thereby affecting the judgment of ship operation. When the ventilation command is invalid, the system automatically enters the alarm shielding mode. At this time, although the differential pressure acquisition and display function continues to run and the differential pressure value is still displayed in real time on the control interface, the alarm logic is disabled, and the alarm signal will not be triggered even if the differential pressure value is lower than the set value. The reason for this logic design is that, under non-ventilated conditions, it is normal for the internal pressure of the SCR pipeline to naturally drop to near zero. If the low pressure alarm continues to be activated, meaningless alarms will be triggered frequently. Therefore, this invention achieves intelligent start and stop control of the alarm function by binding the ventilation command with the alarm logic. In addition, at the overall structural level, this invention utilizes the original urea spray gun atomizing air channel, purging air channel, and soot blowing air pipeline of the SCR system as ventilation and air supply channels, completely eliminating the independent ventilation and air supply pipeline and ventilation solenoid valve in the traditional design. The ventilation and air supply function is completed by the above-mentioned existing channels in coordination, and the alarm logic is only based on the existing differential pressure sensor signal. This structural optimization requires no new sensors or valves; it achieves ventilation monitoring and alarm functions solely through improvements to the control logic. It is a system-level optimization design based on existing hardware resources.

[0025] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An improved method for achieving ventilation in a marine engine SCR device, characterized in that, include: Step 1: Signal acquisition. Acquire the differential pressure signal from the differential pressure sensor PDT501 before and after the SCR shut-off valve, and receive the ventilation command signal from the main unit. Step 2, Pressure Rise Time Processing Step: When the ventilation function is executed for the first time, the number of auxiliary air supply channels is adjusted according to the pressure difference rise time, and the air supply strategy corresponding to the target pressure rise time is determined. Step 3: Ventilation execution step. According to the air supply strategy, control the urea spray gun atomized air, purging air and several soot blowing pipes to inject compressed air into the SCR pipeline, and perform cyclic control based on the upper and lower limits of pressure difference. Step 4: Differential pressure monitoring and alarm procedure. Monitor the differential pressure value in real time, activate the low pressure alarm logic when the ventilation command is valid, and deactivate the alarm when the ventilation command is invalid.

2. The improved ventilation method for a marine engine SCR device according to claim 1, characterized in that, The differential pressure signal acquisition and processing in step 1 includes: The analog signal of the differential pressure sensor PDT501 before and after the SCR shut-off valve is cyclically sampled at a frequency of 1 time / 0.5 seconds. Perform maximum and minimum value rejection processing on multiple consecutively collected sample values; A sliding window averaging filter model is constructed for the remaining sampled values ​​to obtain a stable differential pressure value; The stable differential pressure value is transmitted to the SCR controller in real time and displayed on the operation interface; The PDT501 has a measurement range of -1 bar to 1 bar.

3. The improved ventilation method for a marine engine SCR device according to claim 1, characterized in that, The ventilation command logic control in step 1 includes: When the host ventilation command switches from invalid to valid, the ventilation mode is activated and the low pressure alarm logic is enabled. When the main unit ventilation command changes from valid to invalid, the air supply solenoid valve is closed and an alarm shielding signal is sent to the controller. At the same time, the function of continuously acquiring and displaying differential pressure values ​​should be maintained without interruption.

4. The improved ventilation method for a marine engine SCR device according to claim 1, characterized in that, The boost time processing in step 2 includes: When the ventilation command is executed for the first time, the urea spray gun atomizing air solenoid valve, the purging air solenoid valve and the soot blowing branch pipe solenoid valve are opened simultaneously. The initial pressurization time required when the monitoring pressure difference reaches the set upper limit; After the differential pressure drops back to the set lower limit, reduce the input of one soot blowing branch solenoid valve and measure the pressure rise time again. Repeat the adjustment until the pressurization time is close to the target pressurization time, thereby determining the number of soot blowing pipes to be put into ventilation operation.

5. The improved ventilation method for a marine engine SCR device according to claim 4, characterized in that, The target boost time satisfies: The target pressurization time is less than the low ventilation pressure alarm trigger time; Furthermore, the target boost time is 50%-60% of the alarm trigger delay time.

6. The improved ventilation method for a marine engine SCR device according to claim 1, characterized in that, Step 3 includes: Upon receiving the ventilation command, the corresponding solenoid valve is opened according to the air supply strategy determined in step 2. When the differential pressure value of PDT501 is higher than the upper limit value, the gas supply solenoid valve is closed. When the differential pressure value of PDT501 is lower than the lower limit, the gas supply solenoid valve is opened to maintain positive pressure inside the SCR pipeline.

7. The improved ventilation method for a marine engine SCR device according to claim 6, characterized in that, The upper limit of the differential pressure is 0.12 bar. The lower limit of the differential pressure is 0.02 bar.

8. The improved ventilation method for a marine engine SCR device according to claim 1, characterized in that, In step 3, the solenoid valves of the soot blowing branch pipes participating in ventilation adopt a polling opening mode. When the total number of soot blowing branch pipes is N and the number of pipes put into ventilation operation is m, each round of ventilation sequentially selects solenoid valves of different numbers of soot blowing branch pipes to participate in air supply until all branch pipes participate in polling.

9. The improved ventilation method for a marine engine SCR device according to claim 1, characterized in that, Step 4 includes: When the ventilation command is active, if the differential pressure is lower than the set value and the duration exceeds the alarm trigger time, a low ventilation pressure alarm signal will be output. When the ventilation command is invalid, only the differential pressure value is displayed and no alarm is triggered.

10. The improved ventilation method for a marine engine SCR device according to claim 1, characterized in that, The ventilation and air supply channels adopt the existing urea spray gun atomizing air channel, purging air channel, and soot blowing air pipeline of the SCR system.

Images