THE WORLD'S SIMPLEST 'PULSE JET' HEATER!

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For a small price, then, and some occasional maintenance, you can enjoy heat where you thought you couldn't afford to . . . and that's a warm feeling.

HOW IT WORKS

Our downspout heater is a scaled-down and considerably simplified version of the earliest form of jet engine, which was merely a reinforced cylinder with a flap-equipped inlet, a combustion chamber, and an exhaust duct. Like the jet, our stove relies upon a continuous airflow through its corrugated steel cylinder to function; cool combustion air is drawn through the outside inlet and past the burner, where it mixes with droplets of fuel introduced to the combustion area by way of the small channels cut into the wick washers. The ignition of this mixture heats and rapidly expands the gases, which are forced out the flue stack, entraining afresh supply of air behind them to continue the process.

Because a precise fuel/air ratio is difficult to maintain with this design, combustion is intermittent, resulting in a rhythmic pulsation of thrust . . . hence the name pulse jet. The engine's drawbacks-inconsistent fuel consumption, noise, and a cogent vibrationmake it impractical for aviation but perfectly acceptable for other purposes, such as a space heater . . . especially since it takes its combustion air from outside the living area. The fuel-control question is eased somewhat with our restricted double feed design: With the auxilliary needle valve closed, only a small amount of fluid is absorbed by the burner wick; with both needles open, the full amount of fuel is available to the burner. The main shutoff valve blocks the fuel flow entirely to turn the heater off.

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