This steel pipe placed inside the smoke generator can significantly improve airflow when burning fine wood chips or wood pellets.  The pipe creates an open-air channel through the fuel, preventing the chips or pellets from packing too tightly together and allows oxygen to reach the burning ember more consistently, resulting in a steadier burn, more reliable smoke production and fewer flameouts.
This is especially beneficial when using smaller fuel sizes that naturally settle and restrict airflow. By maintaining an open passage for air, it promotes a cleaner, more efficient burn while reducing the need to relight the smoke generator.