Research Of Variable Frequency And Constant Pressure Technology Used In Large-bore Low-speed Two-stroke Diesel Engine Shop Test System

In the past, it is possible to keep the pressure of fuel, lubricating oil and cooling water constant in large-bore low-speed two-stroke diesel engine shop test system through changing the number of pumps and the position of valves. But this method is inconvenient, unreliable and waste. With the rapid development of power electronic, automation and control technology, it is possible to design one kind of constant-pressure control system which is more convenient, reliable and energy saving.Direct towards the mentioned problem, this paper designed a constant-pressure control system which is mainly consist pump, frequency converter, soft starter, PLC, pressure transducer, PID controller. The method of this system is that: first of all pressure transducer sends the value of pressure to PID controller; then PID controller performs calculation according to the set point and the actual value; at last change the flow of system through changing the number of pumps by PLC and the speed of pump by frequency converter and keep the pressure constant.This paper explained the principle of constant-pressure control, at the same time listed different designs of constant-pressure control system and made a choice. On the basis of the choice this paper also explained the running process. Then the design of constant-pressure control system's hardware and software was introduced and analyzed in this paper.This constant-pressure control system is designed for large-bore low-speed two-stroke diesel engine shop test system. After on-site commissioning and operation shows the control performance was proved to be all-right and the method of constant-pressure control also can be used for constant-temperature control and constant-level control.