Energy-saving method and system for central cooling water system of cable laying ship based on PID (Proportion Integration Differentiation) control

Abstract

The invention relates to the technical field of cooler energy saving, in particular to an energy-saving method and system for a central cooling water system of a cable laying ship based on PID (Proportion Integration Differentiation) control. According to the method, the temperature of a seawater outlet on the seawater side of the central cooler, the pressure parameter of the water outlet end of the seawater pump and the temperature of fresh water inlet equipment on the fresh water side are monitored, the frequency conversion control technology is adopted, the minimum seawater pressure and the minimum cooling seawater amount serve as the target, and the seawater heat exchange effect is improved to the maximum degree. In a control strategy, the temperature of fresh water entering equipment at the fresh water side of the cooler is used as a main control quantity, the opening degree of a three-way temperature control valve is used as a secondary control quantity, and the temperature of a seawater outlet at the seawater side of the cooler is used as a safety control quantity, so that the efficient and energy-saving cooling effect is realized on the premise of not depending on additional equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of cooler energy saving, and in particular to an energy saving method and system for a central cooling water system of a cable-laying vessel based on PID control. Background Art

[0002] The cooling water system of modern ship equipment is usually designed as a central cooling system, that is, seawater is used to cool the closed-circulation low-temperature fresh water through an intercooler, and then the cooled low-temperature fresh water is transported to various auxiliary equipment for cooling. Through the analysis of existing ships, it is found that the main problems are: the capacity of each component of the system is too large, the design is unreasonable, and the configuration of the entire system cannot timely and effectively adjust the cooling water flow according to the changes in the operating conditions of the cable-laying ship. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides the following technical solutions: an energy-saving method for a central cooling water system of a cable-laying ship based on PID control, applied to a ship central cooler with a pressure sensor and a temperature sensor, comprising the steps.

[0004] S1. Set preset parameters for the PLC controller, including the set value of the seawater pump outlet pressure, the set value of the seawater outlet temperature, and the set value of the cooling fresh water outlet temperature, and execute the next step.

[0005] S2. The PLC controller monitors the actual value corresponding to the preset parameter in real time through the pressure sensor and the temperature sensor, and executes the next step when the actual value corresponding to the preset parameter changes.

[0006] S3. When the actual value of the seawater pump outlet pressure is greater than the set value of the seawater pump outlet pressure, the PLC controller controls the seawater pump to reduce the seawater flow until the actual value of the seawater pump outlet pressure is equal to the set value of the seawater pump outlet pressure, and executes the next step, otherwise directly executes the next step.

[0007] S4. When the actual value of the seawater outlet temperature is greater than the set value of the seawater outlet temperature, the PLC issues a high temperature alarm, otherwise it executes the next step.

[0008] S5. When the actual value of the cooling fresh water outlet temperature is equal to the set value of the cooling fresh water outlet temperature, return to execute step S2; when the actual value of the cooling fresh water outlet temperature is greater than the set value of the cooling fresh water outlet temperature, the PLC sends out a high temperature alarm and controls the seawater pump to increase the seawater flow rate until the actual value of the cooling fresh water outlet temperature is equal to the set value of the cooling fresh water outlet temperature, and then returns to execute step S2; when the actual value of the cooling fresh water outlet temperature is less than the set value of the cooling fresh water outlet temperature, the PLC controller controls the seawater pump to reduce the seawater flow rate and executes the next step.

[0009] S6. When the actual value of the cooling fresh water outlet temperature is equal to the set value of the fresh water outlet temperature before the seawater flow rate controlled by the seawater pump is reduced to the minimum value, return to execute step S2; when the seawater flow rate controlled by the seawater pump is reduced to the minimum value and the actual value of the cooling fresh water outlet temperature is still less than the set value of the fresh water outlet temperature, the PLC controller controls the opening of the three-way valve to reduce the flow rate of high-temperature fresh water input from the fresh water pump to the central cooler until the actual value of the cooling fresh water outlet temperature is equal to the set value of the fresh water outlet temperature, and return to execute step S2.

[0010] Preferably, the data monitored in real time in step S2 also includes the actual value of the seawater pump inlet pressure. The seawater pump is controlled by PLC so that the actual value of the seawater pump outlet pressure is equal to the seawater pump outlet pressure set value. When the pressure value of the seawater pump inlet exceeds the set threshold, an alarm is issued.

[0011] Preferably, the data monitored in real time in step S2 also includes the actual value of the temperature at the outlet of the seawater pump. When the actual value of the temperature at the outlet of the seawater pump exceeds a set threshold, the PLC issues an alarm.

[0012] A central cooling system for a cable-laying vessel based on PID control executes the above method, comprising a central cooler, wherein the seawater inlet of the central cooler is connected to a seawater pump, the seawater outlet of the central cooler is connected to a seawater outlet, the freshwater inlet of the central cooler is connected to a freshwater pump, the freshwater outlet of the central cooler is connected to a three-way valve, the other inlet of the three-way valve is connected to the outlet of the freshwater pump, the inlet and outlet of the seawater pump are both provided with pressure sensors, the seawater outlet is provided with a temperature sensor, the outlet of the three-way valve is provided with a temperature sensor, and also comprises a PLC controller, the PLC controller is electrically connected to the seawater pump, the freshwater pump, the temperature sensor of the seawater outlet, the pressure sensor and the temperature sensor of the outlet of the three-way valve.

[0013] Preferably, the three-way valve and the temperature sensor at the water outlet of the three-way valve are combined into a three-way temperature control valve.

[0014] Preferably, a first one-way valve is provided between the water outlet of the seawater pump and the seawater inlet of the central cooler.

[0015] Preferably, a second one-way valve is provided at the water outlet of the fresh water pump to prevent the fresh water from flowing back to the fresh water pump.

[0016] Compared with the prior art, the present invention has the following beneficial effects: by monitoring the outlet temperature of seawater on the seawater side of the central cooler, the temperature of the freshwater inlet equipment on the freshwater side, and the main engine load, the frequency conversion control technology is adopted to meet the minimum seawater pressure and cooling seawater volume, and the freshwater inlet equipment temperature on the freshwater side of the cooler is used as the main control quantity, the opening of the three-way temperature control valve is used as the secondary control quantity, and the seawater outlet temperature on the seawater side of the cooler is used as the safety control quantity. After adding a temperature control valve to the central cooling water system, the amount of freshwater participating in the heat exchange is adjusted by adjusting the temperature control valve opening PID to maintain the temperature of the freshwater inlet of the equipment within the deviation range allowed by the set value. Even if there is a small amount of scale inside the heat exchanger, the temperature of the freshwater inlet of the equipment can be controlled by adjusting the amount of freshwater participating in the heat exchange by the temperature control valve.

[0017] Other advantages, objectives and features of the present invention will be set forth in part in the following description and, in part, will be apparent to those skilled in the art based on an examination of the following or may be taught from the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the process of the present invention; Figure 2 It is a functional structure schematic diagram of the present invention; Figure 3 It is a control flow diagram of the present invention.

[0019] Description of the drawings: 1. Central cooler; 2. Seawater pump; 3. Fresh water pump; 4. Seawater outlet; 5. Seawater pump outlet temperature sensor; 6. Seawater outlet pressure sensor; 7. Three-way temperature control valve; 8. First one-way valve; 9. Second one-way valve. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] See also Figure 1-Figure 3The present invention provides a central cooling water system for a cable-laying vessel based on PID control. The system comprises a central cooler, a seawater inlet of the central cooler is connected to a seawater pump, a seawater outlet of the central cooler is connected to a seawater outlet, a freshwater inlet of the central cooler is connected to a freshwater pump, a freshwater outlet of the central cooler is connected to a three-way valve, another water inlet of the three-way valve is connected to a water outlet of the freshwater pump, a pressure sensor is provided at the water inlet and the water outlet of the seawater pump, a temperature sensor is provided at the seawater outlet, and a temperature sensor is provided at the water outlet of the three-way valve.

[0022] The temperature sensor can be set at the water outlet of the three-way valve. In this embodiment, the three-way valve and the temperature sensor at the water outlet of the three-way valve are directly combined into a three-way temperature control valve, and the technical effects of the three-way valve and the temperature sensor are achieved through the three-way temperature control valve.

[0023] A first one-way valve is provided between the water outlet of the seawater pump and the seawater inlet of the central cooler to prevent the seawater from flowing back to the seawater pump.

[0024] A second one-way valve is provided at the water outlet of the fresh water pump to prevent the fresh water from flowing back to the fresh water pump, thereby preventing the fresh water from the central cooler or the three-way valve from flowing to the fresh water pump.

[0025] The control method of the above system comprises the steps of: S1. Set preset parameters for the PLC controller, including the set value of the seawater pump outlet pressure, the set value of the seawater outlet temperature, and the set value of the cooling fresh water outlet temperature, and execute the next step. The present invention mainly monitors the outlet temperature of the seawater on the seawater side of the central cooler, the temperature of the freshwater inlet equipment on the freshwater side, and the main engine load, etc., and adopts frequency conversion control technology to meet the minimum seawater pressure and cooling seawater volume. The temperature of the freshwater inlet equipment on the freshwater side of the cooler is used as the main control quantity, the opening of the three-way temperature control valve is used as the secondary control quantity, and the seawater outlet temperature on the seawater side of the cooler is used as the safety control quantity. The preset parameters are set according to the actual situation. In this embodiment, the freshwater inlet temperature of the cable-laying ship operation system is usually set to 36°C, that is, the set value of the cooling fresh water outlet temperature is 36°C; to prevent the precipitation of seawater salt, the safety value of the seawater outlet temperature is set to 45°C, and the set value of the pressure value is set according to the actual situation based on the different sea areas.

[0026] S2. The PLC controller monitors the actual values ​​corresponding to the preset parameters in real time through pressure sensors and temperature sensors, and executes the next step when the actual values ​​corresponding to the preset parameters change, so as to adjust the cooling effect of the entire cooling system in time.

[0027] S3. When the actual value of the seawater pump outlet pressure is greater than the set value of the seawater pump outlet pressure, the PLC controller controls the seawater pump to reduce the seawater flow rate, otherwise it executes the next step. The actual value of the seawater pump outlet pressure determines the flow rate of seawater, and the flow rate of seawater directly determines the cooling effect of the central cooling system. Therefore, the first step is to control the flow rate of seawater so that the flow rate of seawater becomes a quantitative value, thereby making the entire system enter a stable and controllable state.

[0028] S4. When the actual value of the seawater pump outlet temperature is greater than the set value of the seawater pump outlet temperature, the PLC issues a high temperature alarm, otherwise it executes the next step. Since the temperature of seawater in each sea area is different when the cable-laying ship sails in each sea area, the high seawater temperature at the seawater outlet may be caused by the high temperature of the seawater itself. In this case, manual intervention and control are required to avoid affecting the heat exchange effect of the central cooler. When the temperature of the seawater outlet is not higher than the set value of the seawater outlet temperature, it means that the parameters of each device on the seawater side of the central cooler are normal, and the equipment on the freshwater side of the central cooler can be controlled according to the heat exchange capacity of the existing seawater flow, that is, proceed to the next step.

[0029] S5. When the actual value of the cooling fresh water outlet temperature is equal to the set value of the cooling fresh water outlet temperature, the process returns to step S2 for execution, that is, the temperature of the cooling fresh water outlet meets the requirements, and the process returns to step S2 for continuous monitoring so as to re-automate the operation for subsequent temperature changes. When the actual value of the cooling fresh water outlet temperature is greater than the set value of the cooling fresh water outlet temperature, the PLC issues a high temperature alarm and controls the seawater pump to increase the seawater flow rate until the actual value of the cooling fresh water outlet temperature is equal to the set value of the cooling fresh water outlet temperature, and the heat exchange effect of the central cooler is enhanced by increasing the seawater flow rate to reduce the temperature of the cooling fresh water outlet, and then returns to step S2 for subsequent continuous monitoring. When the actual value of the cooling fresh water outlet temperature is less than the set value of the fresh water outlet temperature, the PLC controller controls the seawater pump to reduce the seawater flow rate and executes the next step, and reduces the heat exchange effect of the central cooler by reducing the seawater flow rate, thereby limiting the cooling effect of fresh water in the central cooler, thereby increasing the temperature of the cooling fresh water. However, in this step, the cooling fresh water temperature is increased by controlling the seawater pump to reduce the seawater flow rate, and the reduction in seawater flow rate will inevitably lead to an increase in the actual value of the seawater outlet temperature. Based on the set value of the seawater outlet temperature, the actual value of the seawater outlet temperature cannot continue to increase when it reaches the set value of the seawater outlet temperature. And based on the mechanical performance limit of the seawater pump, the seawater pump also has a speed that cannot be further reduced. Therefore, there is a limit value for the seawater flow rate controlled by the seawater pump. When the seawater flow rate reaches this limit value, the seawater pump can no longer be controlled to continue to reduce the seawater flow rate. Therefore, the next step is to increase the actual value of the cooling fresh water outlet temperature by regulating the freshwater side of the central cooler.

[0030] S6. When the actual value of the cooling fresh water outlet temperature before the seawater flow rate controlled by the seawater pump is reduced to the minimum value is equal to the set value of the cooling fresh water outlet temperature, then it is normal to return to step S2 for continuous monitoring. When the seawater flow rate controlled by the seawater pump is reduced to the minimum value and the actual value of the cooling fresh water outlet temperature is still less than the set value of the fresh water outlet temperature, the PLC controller controls the opening of the three-way valve to reduce the flow of high-temperature fresh water input from the fresh water pump to the central cooler, so that more high-temperature fresh water is directly bypassed and mixed with the cooling fresh water until the actual value of the cooling fresh water outlet temperature is equal to the set value of the fresh water outlet temperature, that is, when the seawater flow rate on the seawater side of the central cooler has been reduced to the uncontrollable minimum value, the high-temperature fresh water output from the outlet end of the fresh water pump is increased through the three-way valve to directly enter the three-way valve and flow out from the cooling fresh water outlet, thereby increasing the actual temperature of the cooling fresh water outlet that is too low. When the actual value of the cooling fresh water outlet temperature is equal to the set value of the cooling fresh water outlet temperature, it returns to step S2 for subsequent continuous monitoring.

[0031] The data monitored in real time in step S2 also includes the actual value of the pressure at the water inlet of the seawater pump. The seawater pump is controlled by PLC so that the actual value of the pressure at the outlet of the seawater pump is equal to the set value of the pressure at the outlet of the seawater pump. When the pressure value at the water inlet of the seawater pump exceeds the set threshold, an alarm is issued. In this method, the actual value of the outlet pressure of the seawater pump is first determined to reach the set value of the outlet pressure of the seawater pump, and then the quantity is determined. Based on the different seawater pressures when the cable-laying ship sails in various sea areas, a pressure sensor is set at the water inlet end of the seawater pump to determine the pressure of seawater in each sea area in advance, so as to control the seawater pump in advance to ensure that the actual value of the outlet pressure of the seawater pump can reach a stable state, thereby ensuring the stability of the entire cooling system when running this method.

[0032] The data monitored in real time in step S2 also includes the actual value of the temperature at the outlet of the seawater pump. When the actual value of the temperature at the outlet of the seawater pump exceeds the set threshold, the PLC issues an alarm to determine in advance whether the seawater temperature in the current sea area is appropriate. When the seawater temperature in the current sea area is too high, an alarm is issued and manual intervention is required to adjust it.

[0033] On the basis of the above implementation scheme, the processors, modules, corresponding control programs, algorithm programs and other supporting technologies mentioned in the present invention can be implemented in combination with existing electrical technology, information technology, software technology and general protocols. They are not within the scope of protection required by the present invention and will not be described in detail in this application.

[0034] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered as exemplary and non-restrictive in all respects.

Claims

1. A method for energy saving of a central cooling water system of a cable-laying ship based on PID control, applied to a ship central cooler with a pressure sensor and a temperature sensor, characterized in that: Includes steps: S1. Set preset parameters for the PLC controller, the preset parameters include the set value of the seawater pump outlet pressure, the set value of the seawater outlet temperature, the set value of the cooling fresh water outlet temperature, and execute the next step; S2. The PLC controller monitors the actual value corresponding to the preset parameter in real time through the pressure sensor and the temperature sensor, and executes the next step when the actual value corresponding to the preset parameter changes; S3. When the actual value of the seawater pump outlet pressure is greater than the set value of the seawater pump outlet pressure, the PLC controller controls the seawater pump to reduce the seawater flow rate until the actual value of the seawater pump outlet pressure is equal to the set value of the seawater pump outlet pressure, and executes the next step, otherwise directly executes the next step; S4. When the actual value of the seawater outlet temperature is greater than the set value of the seawater outlet temperature, the PLC issues a high temperature alarm, otherwise executes the next step; S5. When the actual value of the cooling fresh water outlet temperature is equal to the set value of the cooling fresh water outlet temperature, return to step S2; when the actual value of the cooling fresh water outlet temperature is greater than the set value of the cooling fresh water outlet temperature, the PLC issues a high temperature alarm and controls the seawater pump to increase the seawater flow rate until the actual value of the cooling fresh water outlet temperature is equal to the set value of the cooling fresh water outlet temperature, and then returns to step S2; when the actual value of the cooling fresh water outlet temperature is less than the set value of the cooling fresh water outlet temperature, the PLC controller controls the seawater pump to reduce the seawater flow rate and executes the next step; S6. When the actual value of the cooling fresh water outlet temperature is equal to the set value of the fresh water outlet temperature before the seawater flow rate controlled by the seawater pump is reduced to the minimum value, return to execute step S2; when the seawater flow rate controlled by the seawater pump is reduced to the minimum value and the actual value of the cooling fresh water outlet temperature is still less than the set value of the fresh water outlet temperature, the PLC controller controls the opening of the three-way valve to reduce the flow rate of the high-temperature fresh water input from the fresh water pump to the central cooler until the actual value of the cooling fresh water outlet temperature is equal to the set value of the fresh water outlet temperature, and return to execute step S2.

2. The energy-saving method for the central cooling water system of a cable-laying vessel based on PID control according to claim 1 is characterized in that: The data monitored in real time in step S2 also includes the actual value of the seawater pump inlet pressure. The seawater pump is controlled by PLC so that the actual value of the seawater pump outlet pressure is equal to the seawater pump outlet pressure setting value. When the pressure value of the seawater pump inlet exceeds the set threshold, an alarm is issued.

3. The energy-saving method for the central cooling water system of a cable-laying vessel based on PID control according to claim 1 is characterized in that: The data monitored in real time in step S2 also includes the actual value of the temperature at the outlet of the seawater pump. When the actual value of the temperature at the outlet of the seawater pump exceeds a set threshold, the PLC issues an alarm.

4. A central cooling water system for a cable-laying vessel based on PID control, executing the method according to any one of claims 1 to 3, characterized in that: The invention comprises a central cooler, wherein the seawater inlet of the central cooler is connected to a seawater pump, the seawater outlet of the central cooler is connected to a seawater outlet, the freshwater inlet of the central cooler is connected to a freshwater pump, the freshwater outlet of the central cooler is connected to a three-way valve, the other inlet of the three-way valve is connected to the outlet of the freshwater pump, the inlet and outlet of the seawater pump are both provided with pressure sensors, the seawater outlet is provided with a temperature sensor, the outlet of the three-way valve is provided with a temperature sensor, and a PLC controller is also included, wherein the PLC controller is electrically connected to the seawater pump, the freshwater pump, the temperature sensor of the seawater outlet, the pressure sensor and the temperature sensor of the outlet of the three-way valve.

5. The central cooling water system of the cable-laying vessel based on PID control according to claim 4 is characterized in that: The three-way valve and the temperature sensor at the water outlet of the three-way valve are combined into a three-way temperature control valve.

6. The central cooling water system of a cable-laying vessel based on PID control according to claim 4 is characterized in that: A first one-way valve is provided between the water outlet of the seawater pump and the seawater inlet of the central cooler.

7. The central cooling water system of a cable-laying vessel based on PID control according to claim 4 is characterized in that: A second one-way valve is provided at the water outlet of the fresh water pump to prevent high-temperature fresh water from flowing back to the fresh water pump.

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