Numerical simulation of premixed n-heptane/air combustion in micro tube with internal channel optimization

In military and aerospace fields, petrol and aviation kerosene are the preferred fuels for micro power systems due to their reduced carrying load and convenient fuel source. Therefore, n-heptane, an alternative to petrol and aviation paraffin, was chosen as the fuel. A micro quartz glass tube was used as the combustor, and the premixed combustion characteristics of n-heptane/air were investigated using numerical simulations. The method used to improve the internal flow channel includes a built-in cross baffle and scaled backward-facing step. The resulting optimized combustion characteristics, such as internal flow line, wall temperature, CO emission, and wall radiation, have been analyzed. The results indicate that, with a fixed equivalence ratio of 1.0 and a n-heptane mass flow rate of 2.70 mg/s, the built-in cross baffle concentrates and stabilizes the high temperature zone of the flame, resulting in a significant increase in wall temperature. Conversely, the use of the micro tube with scaled backward-facing step creates a reflux zone due to the sudden expansion of the inlet cross-section, which promotes better fuel mixing and flame anchoring. Furthermore, after comparing the output efficiencies of micro tube with different internal structures, it was discovered that enhancing the internal channel of the micro tube is crucial for increasing the wall radiation efficiency.