Vortex mechanisms for flow measurement in nonstandard elbows with transverse mixing

With the growing share of renewable energy, peak shaving of coal-fired units has become critical, making accurate primary air flow measurement of coal mills essential for safe and economic unit operation. Traditional methods face large errors and poor adaptability due to the complex inlet pipeline geometry and flow disturbances from cold and hot primary air mixing. Using vortex theory, this study combined experiments, numerical simulations, and nonlinear regression, focusing on the MPS190-HP-II coal mill of a 350 MW unit. The research scope was divided into three regions, and flow rate-to-parameter relationships were established. Results show the power-law model fits Regions 1 and 2 optimally with no systematic deviation. The 3P PL model in Region 3 has a maximum error of 2.57%, meeting engineering needs, while the 4P Poly model has a maximum error of 0.81%, which suits high-precision scenarios. Increased cold primary air velocity distorts the hot primary air elbow's secondary flow and vortices, expands the low-pressure zone, and creates a transverse pressure gradient, increasing elbow differential pressure, consistent with regression model trends. This study overcomes limitations of traditional single-medium measurement, providing theoretical and technical support for flow monitoring and optimization in industrial cold-hot fluid transport.