No Spark Plugs…..Better Gas Mileage?
Our Guest Blogger, George Delozier, is from Pennsylvania and recently joined the U.S. Air Force. Growing up with all types of machines, George wanted to share the newest innovations on all things motor with the readers of InventorSpot.com.
Here's his article:
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The idea seems almost backwards, unless you are MIT. A team from the Massachusetts Institute of Technology is currently working on a engine that, under certain conditions, can move into a spark free combustion state. According to their testing, this can lead to less pollution and more miles per gallon.
In a traditional Internal Combustion (IC) Engine, once the mixture of fuel and air has been compressed, it is ignited by the spark plug and the rapid expansion inside the cylinder forces the piston back down. The expansion is caused by the single flame front traveling through the mixture, burning it as it moves, and causing the gas to expand. This is called the “Power Stroke.” After this is complete, the piston moves back up, forcing the spent mixture out of the engine. This completes one full cycle of an IC engine.
The new design works in the exact same way, with 2 exceptions. The first of which is the lack of a spark from the spark plug at the beginning of the power stroke. The second difference comes from the multiple flame fronts present during combustion. They are generated by the combination of heat and compression with the motor. This kind of engine is known as a "homogeneous charge compression ignition" (HCCI) engine. The HCCI engine has 2 main benefits. The first of which is producing a more complete burn of the mixture, due to the multiple flame fronts. This produces more power and raises the efficiency of the motor. The second is the ability to use roughly the same amount of air in the combustion, regardless of how much fuel is being utilized.
When driving with an IC engine, as you lower the amount of fuel being forced into the chamber, the amount of air is lowered as well. This is a huge waste of energy. In the HCCI Engine, the amount of air does not have to be precise to allow for a clean burn to occur, effectively raising the efficiency of the fuel, as well as reducing the amount of carbon and nitrogen expelled.
Currently, the engine has only been tested under “ideal” conditions in the laboratory. Due to ever-changing driving conditions, it is unclear how well it will perform during everyday use. A prototype is expected soon, with production models estimated at 2 to 3 years. MIT has also developed a cheap, simple “switch” used to go from IC to HCCI modes. This is vital for operation because of the temperature required to operate the HCCI mode. The engine will start in IC mode to heat the interior walls of the cylinder and eventually the entire engine block. Once the proper temperature is reached, the engine can move into the HCCI mode.
All of this has one bottom line, which is efficiency. It is estimated that the HCCI mode would improve gas mileage by anywhere from 3 to 6 miles per gallon. "That may not seem like an impressive improvement," said Professor William H. Green Jr., of the Department of Chemical Engineering. "But if all the cars in the US today improved that much, it might be worth a million barrels of oil per day--and that's a lot." This is also without mentioning the money saved everyday by drivers around the world and the improvement in air quality within densely populated areas.