Numerical calculation and experimental study on fluidized airflow of circulating fluidized bed boiler

Abstract The circulating fluidized bed boiler has problems with clogging of the return feeder and poor fluidization of the bed material after co-firing biomass fuel. The change in fluidized air volume directly reflects the fluidized state of the bed material in the return feeder, and the fluidized air volume cannot be accurately measured, which makes it difficult to detect blockages in the return feeder in a timely manner and has a certain lag. In order to achieve an accurate measurement of fluidized air volume, numerical calculation, and on-site experimental research methods were applied to study the measurement of air volume in the outlet duct of the fluidized fan based on the forced vortex theory. The pressure distribution law at the bend was obtained through numerical calculation, which is consistent with the forced eddy current theory. The variation between the flow rate and pressure difference is approximately linear. According to the forced vortex theory, the calculated total flow coefficient increases with the increase of flow rate at low flow rates. At high flow rates, the total flow correction coefficient remains unchanged, and the critical Reynolds number is between 1.15×105 and 1.31×105. Using the average flow coefficient method for coefficient correction can achieve a flow measurement deviation between 0.299% and 0.567%. On site experimental research has verified the accuracy of numerical calculation methods and the feasibility of using forced eddy current theory to measure flow rate. The measurement error obtained on site is between −0.57% and 0.77%, which meets the requirements of engineering applications. Compared with traditional flow measurement devices, its measurement results have a strong linear variation law and have certain engineering application prospects.