A hot primary-air pipe system is the bridge connecting an air-preheater with a coal mill in power generation stations. The effective geometrical configuration of the pipe network greatly affects the air flow distribution and consequently influences the safe and economic operation of milling systems in power stations. In order to improve the properties of the air flow, in the present work the SIM-PLEC method is used to simulate numerically the flow field for the original layout of the system. As a result, the internal mechanisms influencing the uneven pressure drop in each branch are explored and three optimization schemes are proposed accordingly. The numerical results indicate that, for the original layout, the local pressure drop of the tee section accounts for approximately 74% of the total drop of the system, with other pressure drops depending on the specific branch considered. It is shown that after optimization, a roughly balanced flow resistance and flow rate can be obtained. Compared with the original layout, the pressure drop relating to different branches is significantly reduced.
The pressure losses of the hot primary-air pipe system have a great influence on the economic operation of a pulverizing system. To balance the flow resistance for different branches, Fluent was applied to simulate flow dynamics and pressure drop for a hot primary-air pipe system, and two improvement schemes were proposed. Numerical simulation reveals that for the original configuration, the flow losses of each branch are quite different, and the large resistance of some branches is mainly caused by pipe tees. After improvement, the flow regime has been significantly polished, and the total pressure drop of different branches is greatly reduced. Compared with the original configuration, the total pressure loss of branch B and branch D in case 2 is reduced by 65% and 53%, respectively, then an approximately equal pressure drop of each branch is achieved after structure improvement.
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