A gas burner blends fuel with air before it burns. Use the buttons to look inside, then follow the gas from the jet, through the throat, and out of the ports as a clean flame.
A venturi mixer is the part of many gas burners that blends the fuel with air before it is burned. Gas speeds through a narrowing passage and, by the venturi effect, pulls primary air in with it, so a ready-mixed gas and air flow reaches the burner head.
From outside, a burner is just a metal tube leading to a row of flame ports. The mixing that decides whether the flame is clean and blue or smoky and yellow happens out of sight, inside the throat and mixing tube.
Fuel gas flows along the inlet pipe under pressure and is squeezed through a small jet, or orifice. Forcing it through this narrow opening turns the steady supply into a fast, concentrated stream.
As the jet shoots across the throat, its high speed lowers the pressure in that region. Because the pressure there is now below the surrounding air, atmospheric pressure pushes primary air in through the air shutter to join the gas.
Gas and air travel on together down the mixing tube. The turbulence of the fast, narrow flow keeps blending them, so by the time the mixture reaches the end of the tube, it is thoroughly combined.
The mixed gas and air fill the burner head. It spreads out and is pushed through a row of small ports, which shape the flow into an even sheet ready to burn.
Because the fuel and oxygen are already mixed, the gas lights cleanly at the ports and burns hot and blue. To trim the flame, the air shutter is opened or closed to change how much primary air is drawn in.
The gas jet leaves the orifice at high speed. As it crosses the narrowed throat, that fast flow lowers the local pressure, and ordinary atmospheric pressure pushes primary air in through the shutter to join it.
The throat is the point where the passage is narrowest. Narrowing speeds the gas up and strengthens the drop in pressure, which is what draws in and thoroughly mixes the air.
Flame needs fuel and oxygen together. Pre-mixing them in the tube gives a clean, hot, blue flame; if air only meets gas at the flame, it burns unevenly and makes soot.
It is an adjustable opening that sets how much primary air is entrained. Open it for more air and a leaner flame, close it for less, to suit the gas and the burner setting.
A blue flame shows that gas and air are well mixed and burning completely. A yellow, flickering flame usually means too little air, so unburnt carbon glows and makes soot.