CN103021253A - Open-type hot water boiler heating experimental system - Google Patents

Abstract

An open hot water boiler heating experiment system, including a measurement and control instrument panel, a programmable controller, multiple relays, a hot water boiler, a circulation pump, a water supply pump, a frequency converter, a one-piece water tank, a radiator, and a host computer; its features In that: the programmable controller is connected with the control output terminal through the system analog input terminal on the measurement and control instrument panel, and then connected with the hardware of the whole system; the programmable controller is connected with the upper computer through the serial interface RS485; The hot water boiler mentioned above is connected with the radiator through the hot water pipeline, the radiator is connected with the circulation pump through the heat follower pipeline, and the circulation pump is connected with the hot water boiler through the pipeline. The invention has few consumables, long service life, low cost, stable and reliable performance, and convenient maintenance, and is suitable for popularization and use in teaching and experiment links.

Description

An open hot water boiler heating experimental system

technical field

The present invention is mainly based on the S7-200 series programmable controller of Siemens Company and the open experiment object platform of the furnace temperature control system of KingView, the configuration software of Yakong Company. Development and design are carried out according to the professional situation to ensure the organic connection with the experiments of related courses.

Background technique

In recent years, the research on temperature controllers at home and abroad has become more and more extensive and in-depth. Especially with the development of computer technology, the research and development of temperature controllers has made great leaps and bounds, and a number of commercial temperature regulators have been formed. At the same time, intelligent PID, fuzzy control, adaptive control, etc., are widely used in the technological transformation of temperature control systems and related equipment in enterprises due to their good performance and control effects.

In the field of automation, PLC (programmable logic controller) is widely used in the automatic control of modern industry due to its high reliability, strong anti-interference ability, simple programming, powerful functions, high cost performance, small size, and low energy consumption. middle. In the current industrial control, PLC is often selected as the on-site control equipment for data acquisition and processing, logic judgment, and output control; while the upper computer uses configuration software to complete the display of industrial control status, process and parameters, and realize Monitoring, management, analysis and storage functions. This monitoring system makes full use of the respective characteristics of PLC and computer, and has been widely used.

In colleges and universities, the laboratory is the basic support platform to realize the two major functions of training talents, scientific research, and the two major functions. There are many disadvantages in the traditional experimental teaching platform, which is not conducive to cultivating students' innovative ability. "Open" laboratories can be used in limited resources. To provide students with a place to display their intelligence and develop their individuality, to stimulate students' interest in experiments, and to cultivate students' innovative consciousness and innovative ability. Make students change from "want me to do the experiment" to "I want to do the experiment". The implementation of laboratory opening is a necessary condition for university laboratories to truly play a role. In recent years, our laboratory has gradually moved from partial opening to full opening. In practice, we have gradually improved the opening mechanism of the laboratory and achieved good results in cultivating innovative talents.

Contents of the invention

The object of the present invention is to provide a kind of open-type hot water boiler heating experiment system, which is based on "sensor and detection technology", "computer process control technology", "intelligent instrumentation", To meet the teaching needs of courses such as "Networked Measurement and Control System" and "Process Control System and Instrumentation", a set of equipment developed and developed takes the hot water heating boiler as the measurement and control object, combines water storage tanks, heaters, water supply pumps, thermal instruments, and various The networked measurement and control experimental equipment composed of various valves and circulation systems is used to improve the quality of practical teaching, improve experimental teaching methods, improve laboratory technology, and enhance undergraduates' professional comprehensive design and application capabilities.

The technical solutions adopted are:

An open hot water boiler heating experiment system, including a measurement and control instrument panel, a programmable controller, multiple relays, a hot water boiler, a circulation pump, a water supply pump, a frequency converter, a one-piece water tank, a radiator, and a host computer; its features In that: the programmable controller is connected to the control output terminal through the system analog input terminal on the measurement and control instrument panel, and then connected to the hardware of the whole system; the programmable controller is connected to the upper computer through the serial interface RS485; The hot water boiler mentioned above is connected with the radiator through the hot water pipeline, the radiator is connected with the circulation pump through the heat follower pipeline, and the circulation pump is connected with the hot water boiler through the pipeline.

Working principle and operating procedure of the present invention:

The present invention is a set of simulated modern industrial control process, the experimental platform of the boiler heating system, its hardware structure diagram is shown in Figure 1, the main controller adopts PLC (programmable controller) of German Siemens, The digital-to-analog conversion module EM235 is used to collect the on-site analog quantities. EM235 realizes the functions of 4 analog inputs and 1 analog output. Use the DIP switch to set the EM235 expansion module, and the different settings of the 6 switches can select the unipolar/bipolar, gain and attenuation of the input analog.

The PLC (Programmable Logic Controller) is connected with the upper computer through the serial interface RS485, and the configuration software Kingview of Yakong Company is used on the upper computer to compile the monitoring interface to detect and control the implementation of the whole invention. The whole of the present invention can be divided into three hierarchical structures of control layer, monitoring layer and management layer. Among them, the monitoring layer is connected to the lower control layer and the upper management layer. It not only realizes real-time monitoring and control of the site, but also plays an important role in uploading and downloading and configuration development in the automatic control system. It is beneficial for experimenters to monitor on-site in real time. It includes alarm window, real-time trend curve, etc., which can easily generate various reports.

In the present invention, a closed-loop control method is used to control continuously changing analog quantities such as temperature, pressure, and flow. The mathematical model of the control system has strong flexibility and adaptability, and the structure of the PID controller is typical, the program design is simple, the engineering is easy to realize, and the parameter adjustment is convenient. The control volume (temperature, pressure, liquid level, flow) is stable at the expected value.

Steps:

1. After the equipment is powered on, observe the "measurement and control instrument panel". The measurement and control instrument panel is shown in Figure 2. Whether the display status of each instrument is normal and whether the water level of the water tank is normal. When the equipment is normal, first set the "control mode" switch to "manual", and close the system drain valve V4. Then manually adjust the water supply control voltage (maximum value 5VDC), so that the inverter controls the water supply pump to run at full speed; adjust the heating voltage, and observe the speed of temperature change; at the same time, you can observe the changes of various quantities in the monitoring interface of the host computer. Through the instrument control panel, the supplementary water pump, heating module, circulating water pump, etc. of the heating system can be controlled, combined with the data collection and display of sensors and instruments, so as to understand the process of heating production. When there is no "low pressure" or "high pressure" alarm for the supplementary water pressure, start the circulating pump and record the changes of the instruments in each part of the system. During this step, the speed of the circulation pump can be adjusted to gradually decrease to 0, and the value changes of the pressure gauges B1, B2, B4, B5 and the B-phase ammeter can be recorded.

2. Set the "control mode" switch to "terminal", add 5VDC voltage through the water supply control terminal "BSK+ and GND", adjust the water supply pump to the maximum output; start the circulation pump. The V4 valve is closed. The boiler outlet water temperature is collected through the terminals "T1+ and GND". After the digital-to-analog conversion of the EM235 module of the controller PLC, the output 0~5VDC adjustment value is input to the pressure regulation module of the experimental system through "JRK+ and GND" to change the boiler AC. voltage, and then control the boiler outlet temperature to be constant, and detect the return water temperature and circulation pipeline flow to understand the heating situation. Flow rate and ambient temperature are the main disturbances. Controlled variable: boiler outlet temperature; adjusted variable: trigger voltage of pressure regulating module; detection sensor: K-type thermocouple for S1 boiler temperature measurement.

3. Adjust the frequency of the frequency converter of the water replenishment pump to change the speed of the motor of the water replenishment pump, so as to control the pressure of the return water (water replenishment) to be constant. Check the outlet pressure to understand the relationship between water replenishment and circulation. Controlled variable: boiler return water (water supply) pressure; adjusted variable: frequency converter of water supply pump; detection sensor: B4 remote pressure gauge.

4. Water tank liquid level control: stop heating, use the A and B parts of the one-piece water tank, use the replenishment pump to drain water from the A water tank, open the V4 drain valve, and fill water into the one-piece water tank B (open the middle of the one-piece water tank Connecting holes to ensure that the water level on side A is lower than the connecting hole, and the water level on side B is higher than the connecting hole), adjust the inverter frequency of the water replenishing pump to change the motor speed of the water replenishing pump, that is, change the drainage flow, so as to control the liquid level of the water tank on the right side to be constant. Controlled variable: liquid level of the water tank on the right side; Adjusting variable: frequency converter of water supply pump; detection sensor: S3 liquid level sensor. After the control is stable, the opening of the system drain valve V4 can be moderately changed to observe the control effect. This control process stops heating.

5. Outlet flow control: stop heating, water tank A drains water outwards with the replenishment pump, open the V4 drain valve, and fill water into the one-piece water tank A. Adjust the frequency of the water supplement pump inverter to change the speed of the water supplement pump motor, that is, to change the drainage flow, so as to control the flow (speed) to be constant. Controlled variable: pipeline flow rate; adjusted variable: frequency converter of water supply pump; detection sensor: S4 pipeline flowmeter. After the control is stable, the opening of the system drain valve V4 can be moderately changed to observe the control effect. This control process stops heating.

Advantages of the invention

1) Practicality: The present invention is developed and designed for the situation of theoretical teaching to ensure the organic connection with the experiments of related courses. Provide students with a place to display their intelligence and develop their individuality, stimulate students' interest in experiments, and cultivate students' innovative consciousness and ability.

2) Engineering: The present invention organically combines Siemens PLC (Programmable Logic Controller), a commonly used software for industrial control, with configuration software Kingview. And it should be as complete as possible.

3) Openness: open experimental object platform. The invention leads out various analog terminals on the control panel, so besides being able to complete various experiments, it also provides a good test platform for the design and development of the thermal unit instrument of the process control system. Instruments that can support testing, such as the development of pipeline flow totalizers, the development of single-loop pressure displays, the development of single-loop pressure controllers, the development of single-loop temperature display instruments based on thermocouples, and the single-loop temperature control based on thermocouples Instrument development, PT100-based single-loop temperature display instrument development, PT100-based single-loop temperature control instrument development, and pressure transmitter-based light column liquid level display instrument development.

The design of the invention is scientific, reasonable and full of creativity, and fully embodies the advantages of flexibility, convenience, easy operation and running accuracy of PLC (programmable logic controller). The efficiency of electricity sales is improved, the practicability is strong, the overall structure is compact, the consumables are few, the service life is long, the cost is low, the performance is stable, reliable, and maintenance is convenient. The present invention is suitable for popularization and use in teaching and experiment links.

Description of drawings

Fig. 1 is a schematic diagram of the hardware structure of the present invention.

Fig. 2 is a schematic diagram of the system control structure of the present invention.

Fig. 3 is a schematic diagram of the open terminal structure of the present invention.

Detailed ways

An open hot water boiler heating experiment system, including a measurement and control instrument panel 1, a PLC (programmable logic controller) 2, multiple relays 3, a hot water boiler 4, a circulation pump 5, a water supply pump 7, a frequency converter 6, and a conjoined body Water tank 8, radiator 9, as shown in Figure 1, hot water boiler 4 is the controlled object of the whole invention system, after hot water is heated, it circulates, passes through radiator 9, simulates heat dissipation, and cold water returns to hot water boiler through circulation pump 5 The one-piece water tank is used as the object of replenishing water and controlling the liquid level, and the frequency converter 6 controls the voltage of the replenishing water pump 7 to control the flow, pressure and liquid level. The control part of an open hot water boiler heating experiment system is shown in Figure 2, and the CPU of PLC (Programmable Logic Controller) 2 uses 222 as shown in Figure 2 10, and the temperature in the boiler is collected through the digital-to-analog conversion module 11 (EM235) , displayed on the measurement and control instrument panel 1, and at the same time, after being processed by the host computer 12, the heating voltage of the hot water boiler 4 is controlled by PLC (programmable logic controller) 2, and then the temperature is controlled.

The measurement and control instrument panel 1 has lead-out terminals 13 for each analog quantity and control quantity, an alarm indicator light 14, a display module 15, and a working mode switch 16. When each quantity is in the alarm area, the control relay 3 is turned on, and the alarm light is on at this time start to show an alarm; the working mode is used to switch between manual mode and terminal control mode.

The lead-out terminal 13 of each analog quantity and control quantity includes the lead-out terminal 17 of analog quantity temperature, liquid level, pressure, flow rate, heating control and water replenishment control terminal 18; Development provides a good testbed for experimentation.

Claims (1)

1. An open hot water boiler heating experiment system, including measurement and control instrument panel (1), programmable controller (2), multiple relays (3), hot water boiler (4), circulation pump (5), water supply pump (7), frequency converter (6), one-piece water tank (8), radiator (9), and upper computer (12); ) on the system analog input terminal (17) is connected to the control output terminal (18), and then connected to the hardware of the entire system; the programmable controller (2) is connected to the host computer (12) through the serial interface RS485; the The hot water boiler (4) is connected with the radiator (9) through the hot water pipe, the radiator (9) is connected with the circulating pump (5) through the hot water pipe, and the circulating pump (5) is connected with the hot water through the pipeline. Boiler (4) is connected.

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