Pulsejet Engine / Mr. Denjiro's Happy Energy!

DENJIRO: Let me show you an interesting phenomenon using this jar. There is an opening on the lid, and there is alcohol inside. When you put fire through the hole...
Let's look at it in slow-motion. There are explosions occurring in short intervals. Why does this occur? Inside the bottle, alcohol vapor gets mixed with air. When it is lit on fire, an explosion occurs, and gas comes out of the bottle. Then, the pressure within the bottle decreases, causing air to come in the bottle. Once that happens, that air mixes with the alcohol vapor in the bottle, and another explosion occurs from the remaining fire. What you saw was a repetition of this cycle.
If you put this bottle on a car, it can act as a driving force. An engine that use this principle is called a pulsejet engine. This is a pulsejet engine for model airplanes. This side is the intake, and the other side is the exhaust. When you send air into the engine, fuel also enters the engine. An electric spark causes it to catch fire. Now, let's try it out.
It's quite powerful! Once this engine starts moving, air is sucked in through the intake, so even if you stop sending air inside, fuel is sent in, and the engine continues to run.
I hope energy will bring you all happiness. Our magic word is "Happy Energy!"