2. Efficient integrated dedicated controller
Complete the above monitoring and display functions, there are many parameters to be controlled due to processing. It is difficult to implement the data acquisition and logic control circuit composed of ordinary relays or discrete electronic components. Therefore, two systems are usually adopted internationally:
1> Special control module;
2> Programmable controller. At present, the programmable logic controller ( PLC ) is widely used in China to collect and control multi-channel analog quantity ( sensor – transmitter ) and switch quantity data. The advantage of adopting PLC is that it is free from development and quick to start, can change programs at any time, and is easy to expand, but the system is still complex and relatively expensive. The developed countries basically adopt the special controller developed by the door ( high integration, small size, few integrated connections, and high reliability, the direct input of sensors makes the peripheral circuit simple, although the development cycle is long / the cost is high, the cost in mass production is very low ).
At present, according to the special control of diesel engine water pump, a special fire pump control system has been developed according to the intelligent requirements, and a series of special controllers have been successfully developed, and a national invention and utility patent has been declared. The diesel engine fire pump control system adopts an integrated modular design, and the panel operation and peripheral wiring are very simple. The controller meets the above-mentioned intelligent requirements.
3. Advanced diesel pump set
The rotation speed of the pump group of the rotation speed regulation system can be optimally controlled by a special controller. It has excellent steady-state and transient speed adjustment rate. and achieves a better regulating effect. The slip rate of asynchronous motor is generally 2 % – 3 %, while the steady-state rate of the normal diesel engine is 5 % – 10 % and the transient rate is 10 % – 30 %, so it is difficult to meet the control accuracy requirements of motor fire pump with the normal diesel engine. Moreover, high-performance fire pumps are often designed with the most energy-saving ( high efficiency ) and as small volume/mass as possible according to users’ head and flow requirements. So the speed is according to the head, flow, the requirements of pump efficiency, pump speed characteristics, engine power-torque/speed characteristics, etc., make it more difficult for the mechanical speed control device of ordinary diesel engines to meet the requirements (the engine is only available on the premise of large-volume orders, It is possible to improve the steady-state and transient regulation rate by modifying/adjusting the fuel pump at a specific speed by the production industry.
Therefore, the diesel engine water pump must be equipped with an electronic speed regulation system if it is to reach or approach the level of the electric pump. The improved special electronic speed regulation system for diesel engine water pump can execute the instructions issued by the special controller, and it is very convenient to realize constant speed or constant pressure control for the water supply system.
Constant speed: by detecting the rotation speed of the water pump, the fuel supply of the engine will be continuously corrected to ensure the constant speed operation of the engine ( speed closed loop control ).
Constant pressure: continuously change the fuel supply of the engine by detecting the change of the outlet pressure of the pump, and change the running speed of the engine to the constant outlet pressure of the pump (pressure closed-loop variable speed constant pressure control). The improved diesel engine fire pump control system cooperates with the electronic speed reducer to realize soft start control of the engine. By setting the system to the user, the idle running time and the slope of the rising speed can be arbitrarily set.
In addition, it also has the following advantages:
( 1 ) slowly increasing the torque of the engine can save the intermediate buffer connection between the engine and the water pump; The hydraulic coupling is adopted, and the torque is transmitted to the water pump after the engine speed is raised.
( 2 ) Reduce the emission of starting (high-speed starting of the cold engine will damage the engine and increase the emission of black smoke).
( 3 ) Slow down before stopping, then idle for a period of time, and stop after the engine cools down. The above-mentioned electronic speed regulation system can ideally solve the speed control problem of a diesel fire pump. With the electric control system, however, how to refit the mechanical and electronic accelerator is a difficult problem. Original speed control system only adjusts the oil quantity for the acceleration and deceleration of the engine ( car ). For example, when the speed control lever is fixed at a certain angle ( position ) and the load changes, the engine speed will also change greatly at the same time, and cannot stabilize the speed. The steady-state speed adjustment is usually 5 % to 20 %.
Through the speed sensor, PID process controller and electromagnetic drive actuator, the rotating speed can be set by the user to work stably at the set point regardless of the load change, and the adjusting speed can be 0. This is very important for the pump to work stably at a certain speed. Due to the application of the above two technologies, the whole system has a simple structure and only one control component, which can easily realize the full-automatic control of the unit and quickly restore the mechanical speed.