Experimental study of airflow thermal fluctuation properties induced by liquid metal pouring based on schlieren and proper orthogonal decomposition

Abstract

Understanding the thermal fluctuation characteristics of the induced airflow during liquid metal pouring processes aids in effective control of emissions from metallurgical plants. This study used schlieren and proper orthogonal decomposition (POD) to analyze the thermal fluctuation characteristics of induced airflow during continuous and discontinuous liquid column flow, within the range of Grashof numbers from 2.64 × 105–3.19 × 105, and liquid column discharge rates ranging from 2500 to 3000 mL/min. The results show that the induced airflow exhibited weak turbulence in both continuous liquid column flow (CLCF) and discontinuous liquid column flow (DLCF). Higher Grashof numbers predominantly elevate the induced airflow thermal fluctuation in CLCF, whereas increased liquid column flow rates primarily enhance the induced airflow thermal fluctuation in DLCF. The primary spatial fluctuation region of induced airflow is within a dimensionless distance (X/r') of 1 at the front side of the pouring cup; the dimensionless horizontal thermal fluctuation diameter (d') of the induced airflow around the liquid column is approximately 2.5. The fluctuation frequency of the induced airflow was mainly within the range of 0–5 Hz. The main frequency during the CLCF was greater than 1 Hz; during the DLCF it was less than 1 Hz. Additionally, the root-mean-square values of the schlieren image grayscale demonstrated the potential advantage of identifying regions with pronounced turbulence characteristics. In summary, identifying the primary location and frequency of the induced airflow with different pouring processes is beneficial for developing novel smoke-control technologies, and the experimental methods and induced airflow details are good references for further studies.