A Study And Simulation For Marine Boiler Water Level Control System

Marine boiler is an important part of the ship whose water level control call for a non-linear, mutative and multi-variable system and the phenomenon of "false level" also lead to the puzzle of boiler level control. The cascade PID control system of boiler water level is prevalent used in industry. However, the boiler water level control can’t achieve the best results because of the limitation by technology development at that time. Marine boiler water level models were accurate modeling based on the marine boiler operation mechanism; We give a theoretical analysis to the dynamic character of’false level"according to the knowledge of the related field and operation experience on site, pointing out the deficiency of the cascade PID control system subsequently:1.An inaccuracy in steam flow measurement under low load conditions2.Vapor-liquid two-phase transformation should pay the responsibility to the phenomena of’false level"which is occurred in marine boiler and indelible, and it can’t be measured by conventional method. Based on the fact that the phenomenon of’false level"take place at instant state of non-harmony of gas and water, this article aims not only at measuring the pertinence of the flux of steam and water but also at giving "false level"qualitative predictions by applying the theory of correlation function. Thus, we use the concept of system identification to design the state estimator based on knowledge of Kalman filter, which can be used to observe and find the"false"component of boiler level. After eliminating those components from feedback of cascade PID control system, this design marine boiler level control system is confirmed and validated on the simulation software MATLAB.