Study On Hydrodynamic Characteristics Of Water Wall In A 600MW Supercritical Once-through Boiler

Water wall is one of the most important parts in supercritical once-through boiler. its structure is mainly divided into spiral tube and vertical tube times two. Spiral water wall and vertical water wall are two types of water wall. There are many advantages of spiral water wall, such as small heat deviation, flexible selection of pipe diameter, good fuel adaptability and can meet the large mass flow rate, etc. The focus of this work is based on the theory of network, and the hydrodynamic characteristics of spiral water wall in a 600 MW supercritical boiler were studied. And computing program was developed.First of all, the development of hydrodynamic calculation model and mathematical method were studied. The water wall system was divided into circuits, pressure grids, and connecting pipes based on the theory of pipe network calculation. The mathematical model for calculating the flow rate distribution and metal temperature in water wall is developed based on the mass, momentum and energy conservations equations. Secondly, according to the pipe network model of hydrodynamic calculation and fluid network theory, the nonlinear equations of water wall flow distribution and pressure distribution were established. And the establishment principles were grids mass conservation law and circuit energy balance law. The quasi-newton method was chosen to solve nonlinear equations. Metal wall temperature distribution was calculated in the tube of high flux. Finally, hydrodynamic calculation of spiral water wall in a 600 MW supercritical boiler were calculated and analyzed. The calculating program was developed too.Using the calculation procedure in this paper, the hydrodynamic characteristics of 600 MW supercritical once-through boiler water wall system was calculated under Boiler Maximum Continuous Rating(BMCR), 75%BMCR, 50%BMCR and 30%BMCR. The results show that the water wall in lower furnace can support larger mass velocity than the water wall in upper furnace, and the flow deviation is small. Outlet fluid temperature deviation of each water wall tube at different loads is small, the maximum temperature deviation is about 6 ℃. The highest metal temperature of water wall is 467.8 ℃, which appears in the spiral water wall by effects of heat flux rate distribution. It is lower than the allowable temperature of the pipe. The boiler can operate safely.Operation data of a 600 MW supercritical once-through boiler was collected. According to the main factors influencing the hydrodynamic instability of once-through boiler, the pressure drop, metal temperature and the curve of hydrodynamic characteristic were verified. Compared the calculated results and operation data, it can be found that calculation results are in conformity with operation data. The pulsation, heat transfer deterioration and the phenomenon of water wall explosion were not going to occur.