How to increase firepower when the jinyu box furnace is small?

There is a switch adjustment knob on the side of the box furnace, which is adjusted to one side to become larger and to the other side to become smaller. Barrel furnace, also known as portable butane gas furnace, refers to non-fixed cooking utensils with butane gas as the main fuel and liquefied gas as the fuel, which are directly heated by fire, and are mostly used for family outdoor leisure and hotel supplies.