Rheology is the study of how fluids -- usually liquids -- flow in response to certain stimuli. Electrorheology studies how fluids react to applied electricity. In the case of an invention out of Temple University, introduced in September 2008, the fluid is fossil fuel.
The innovation relies on what's actually a fairly new physics principle -- that applying electricity to fuel can reduce its viscosity not only by imparting negative charges, but also by altering the position of fuel molecules [source: Tao]. In the new invention, this second effect is more important than the first.
The electrorheological theory at work goes something like this: When you zap fuel with electricity, the molecules tend to realign. But fuel is made up of lots of different types of molecules, and the different types respond differently to the voltage. Larger molecules group together into little bunches, while smaller particles don't cluster as much. The result is a less viscous fluid, because the largest molecules are more spread out. Thinner fuel breaks up into a finer mist when it hits the injector nozzle.
Why is this so important? First, because the smaller the injected fuel particles, the more surface area comes into direct contact with oxygen. The particles burn more completely, allowing the engine to create more energy out of each serving of fuel. Second, it reduces the amount of pollution pouring out of our cars, because most harmful emissions result from the fuel not burning completely [source: Tao].
The big deal about this invention is how easy it would be to add it to our cars. The voltage, 1 kV/mm, is applied within the fuel injector by two pieces of metallic mesh, one positively charged, the other negatively, spaced 1 centimeter apart [source: GCC]. The pieces of mesh can simply be inserted into an existing fuel injector, positioned before the fuel hits the nozzle. The cost, then, would be relatively low. The other big plus is that it uses very little power to create the voltage, so it doesn't detract much from the car's battery.
So we can pop this into our cars without too much trouble. But how much improvement are we looking at? It's pretty significant, up to a 20 percent jump in fuel efficiency when tested on a diesel-fuel engine. Researchers have found up to a 15 percent increase on regular gasoline [source: Tao].
For such a recent development, it looks like we might not be waiting too long for a chance to try it out. The Temple researchers have already leased the patent to Save the World Inc. The people at Save the World are working on development, with plans to mass-test the part in conjunction with a Pennsylvania-based trucking company. They're expecting a fuel-efficiency increase of up to 12 percent, which could have the added benefit of lowering the prices of all the stuff those trucks carry to a store near you [source: ScienceDaily].
For lots more information on electrorheology, fuel efficiency, car engines and related topics, look over the links on the next page.