Modeling And Simulation Of The Working Fluid Dynamics In A 300MW Once-through Boiler

In the energy and electricity field, the dynamic and static characters of the large capacity power-generating devices have been the focus of the researchers native and abroad for decades. Boiler has complex systems, large cubage and highly cost. The characteristic of the working fluid in the tube (including the single-phase section and two-phase section) is especially complex. It is hard to study working fluid in the boiler directly by experiments. An effective way is to build its mathematical model to calculate the characteristics through computer simulation.The problems about modeling on working fluid in the 300MW subcritical once-through boiler installed in Henan Yaomeng Power Plant are discussed in detail and working fluid dynamics are studied by digital simulation. The main contents are as followings:(1)For the single-phase sections of the boiler, this paper takes the secondary superheater of 300MW once-through boiler installed in Yaomeng Power Plant as the research object, analyses and compares the insertion structure modeling method, the chain structure modeling method and the moving parameter modeling method presented by researchers in recent years. Their dynamic responses under different disturbances are obtained. Because the liner distributed-parameter model contains many simplifications and assumptions, so here does not directly follow the traditional way of comparing the transitive functions with the liner distributed-parameter model while analyzing, and introduces the popular CFD/NHT software—Fluent to build the model of a single-phase tube instead. Compared with the liner distributed parameter model, the k-εturbulent model is adopted in this model, to further develop the working fluid dynamics, the simulation results are much more approaching to actual conditions, and are taken as the criterion for model comparing.(2)For the two-phase sections, this paper concludes the methods of how to establish a mathematical model and the development of modeling. Take the evaporation section of 300MW subcritical once-through boiler installed in Yaomeng Power Plant as the research object and establish its dynamic mathematical model through theoretical analysis method. The simulation of the model on digital computer is presented and the rationality of the model is also proved. This model is able to withstand large disturbances and simulate transformation between different states of the working fluid in the boiler evaporation section. The simulation results show that the model can reflect the distribution parameter characters correctly and could provide reference for the later research works.Based on the model of evaporation section, the responses of main parameters under different disturbance are investigated, also the responses of main parameters when the boiler is operating between different loads. The results are then compared to the dates calculated by the APROS simulation system. The rationality of the model is proved.The dynamic responses of parameters of evaporation section under main disturbance of control variables are presented by simulation. The results are referable for the explanation of physical phenomena in evaporation section as well as the designing and setting of the control systems.Finally, some problems which need further research are pointed out.