An Efficient Inlet Design for Enhancing Temperature Uniformity in a Laboratory MILD Furnace: A Numerical Study

The purpose of the present study is to design the fuel and air inlet to enhance the performance of a MILD furnace. The effect of changing the diameter of the fuel and air inlet in both nonpremixed and premixed conditions on the inlet flow momentum and MILD combustion performance has been examined numerically. To simulate the turbulent flow field, the standard k‐ε model with modified coefficients was adopted. The interaction between turbulence and chemistry was modeled using the Eddy Dissipation Concept (EDC) approach, also with modified coefficients. The results showed that in the nonpremixed condition, reducing the air inlet diameter and increasing the inlet flow momentum cause the two vortices formed inside the furnace to merge, creating a larger and stronger vortex. In both nonpremixed and premixed conditions, reducing the inlet diameter increases the internal recirculation ratio by 2.51 and 4.09 times the base furnace, respectively. Additionally, increasing the inlet flow momentum reduces the maximum furnace temperature by 52 and 117 K in the premixed and nonpremixed conditions, respectively. With increased inlet flow momentum, the temperature gradient inside the furnace decreases, and the maximum heat release is reduced by approximately 0.9 W. A decrease in the temperature gradient and maximum heat release further underscores the novel thermal management strategy introduced by this work. Premixed conditions demonstrated better NO emission control, with the best case achieving 1.57 ppm. Carbon monoxide (CO) emissions remained constant in nonpremixed cases, but in premixed conditions decreased from 12.86 to 3.79 ppm, then rose to 10.51 ppm; case 5 had the best CO performance. The results of the present numerical investigation provide valuable insights for heat treatment applications.