Static Electric Charge and Fuel

By Christopher A. Sawyer

The recent pit fire in Spain that destroyed the Williams pit after Pastor Maldonado’s inaugural Grand Prix win may have been caused by static electricity setting off fuel vapor. And while the fire has become a political hot potato in F1 circles, it points to a problem that plagues race cars and passenger cars alike. The volatility of fuel vapors are the reason patrons are warned to not get in and out of their vehicle while refueling, and to not use their cell phone while filling up.

However, the problem of static electricity and its effect on fuel goes much deeper than this. Though nearly charge-free at rest, fuel (gasoline or diesel) carries a charge while in motion. That is, every time it sloshes around inside the tank or moves through the fuel lines and into the engine, it holds a charge. Enough of a charge that I personally know of one instance where a prominent fuel injector maker experienced the effect static electricity can have: the accumulated charged destroyed an injector during a dyno test.

What’s missing is all of this is what happens inside the combustion chamber. No matter how finely atomized, charged fuel will be attracted to the walls, valves and pistons, and this minute amount of fuel will be cooked onto these surfaces and adsorb and desorb charged fuel. Might this, in fact, be where carbon deposits come from?

As engineers move closer to plasma induction (a portion of the atomized fuel, I am told, is in the form of plasma today), this situation will become even more critical. As scientists working on America’s hyper space plane discovered, plasma, by its nature, carries a static electric charge, and this affects the way it combusts as well as how much of the charge is ignited. Some of the plasma is attracted to the surrounding walls.

If this theory as applied to passenger vehicle engines is correct, how much energy is being wasted by this phenomena? How does it degrade fuel economy and performance over time? And what is the ultimate cost to the consumer? It’s worth thinking about.