Study On Flow Field In The Furnace And Characteristics Of Fuel Air Of 670t/h Boiler In Jingneng Power Plant

After the alteration of the 200MW boiler of Jingneng thermal power, the cold field test and numerical simulation study on the characteristics of air-dynamics field in the furnace and fuel air device have been done in the dissertation, by which correlative conclusions of the air-flow rules and characteristics of fuel air device were drawn, respectively.Study of the industrial experiments shows that the air-phase flow field is basically rational. On this basis, the Realizable k-εtwo equations turbulent model is applied in the numerical simulation of the turbulent flow in the furnace. The results of the simulation are consistent with those of the industrial experiments. The counterclockwise strong air-ring is formed with a large diameter. The fullness of the air in the furnace is good enough to ensure the combustion and the surfaces inside the furnace aren't washed by air clearly, which can avoid the formation of slag. The static pressure is negative in the quasi-solid region and the value of the static pressure increases obviously with the increase of the distance from the center of the furnace; the rotary flame is surrounded by the airflow in order to keep it in the certain form and position, making the pulverized coal burn stably. The result of numerical simulation shows that the turbulent fluctuation is stronger near the combustion device than that in the center of the furnace.The same simulation method is applied to study the characteristics of fuel air device. The results ,basically rational by comparing with those gotten in the experiments ,indicate that the average velocity of fuel air at the outlet is higher than that of secondary air under the same inlet pressure and air-baffle opening. And the adjustment characteristic of the air-baffle is perfect when the air-baffle opening is less than 50%.Also the numerical simulation studies on four influencing factors of the characteristics of fuel air device were done in the dissertation. It was found that with the increase of the inlet pressure of fuel air device, average velocity of fuel air at the outlet is higher and the responsivity of the air-baffle is more sensitive when the air-baffle opening is less than 50%. The outlet area is an important influencing factor .As the air thickness of the outlet increases, the mass flow rate also increases, with decreasing velocity and the almost same adjustment characteristics of the air-baffle. The air-baffle size should be suitable, or the adjustment characteristic of the air-baffle will be bad when the size is too big and the mass flow rate and velocity will decrease when the size is too small. And adjustment characteristic of the air-baffle is the best when the width is half of original width. Average velocity of the side arranged secondary air at the outlet will decrease obviously compared with that of the fuel air, and the velocity of left side will decrease more. So the fuel air should be assigned a priority according to the local situation.The study results have theoretical guiding significance for the thermal state adjustment of NO.4 boiler and the upgrade of the combustion equipment on the NO.3 and NO.4 boilers.