I’ve always been a little embarrassed to ask, but when I have, say, a propane torch, how come the flame doesn’t go back through the line and blow up the can?
In: Engineering
Also the propane is pressurized, so when you open the valve, it really wants to spurt out that little nozzle like air blown it into a balloon, and that energy pushes the flame outward, hence the direction of the flame you see. If it weren’t pressurized, it would just dribble out as a liquid like gasoline from a gas pump which does happen as the propane exhausts itself and so the pressure drops a lot — it dribbles out. Without pressure of some kind, the ignition could burn back down the hose into the tank. Not a pretty sight.
It’s the same with plastic cigarette lighters which are filled with butane and then a shot of pressured gas (?) added. When you flick your Bic, the spark ignites a gas coming out of the lighter under pressure. And you hear a rushing of gas. This is unlike on an older style zippo lighter which operates by an older method much like a kerosene lantern. A gas-soaked cotton pad with a cotton wick attached releases gas fumes when you open the top of the lighter. Flick the friction device to create a spark, and it ignites the end of a wick surrounded by those fumes. That’s why a zippo lighter flame is lazy and wavering like a candle while a Bic lighter flame operates more like a blowtorch.
Puncture a kid’s blow-up swimming pool and you watch the water in the pool, under gravity pressure, pushing the water out very fast. The likelihood of the burning flame going into the container is pretty close to zero due to that pressure. It’s like a punctured tire . . . [Oh,shut up!] . . . .
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