Wednesday, December 10, 2008

Changing the Internal Combustion Engine

There's been a lot of talk about the automotive industries these days and changing the way they do business, including looking at alternative fuel sources. But while alternative fuels often get all the attention, there is another area of research that has long been overlooked by the general public. Namely, can we change the internal combustion engine itself?

In some ways, it'd be nice to think that we could end our dependence on oil altogether and find some other way of power our vehicles but that isn't going to happen anytime soon. In the meantime, can we do something to the internal combustion engine to make it more fuel efficient?

Most fuel saving methods that people generally think of involve changing aspects of the car rather than the engine itself. Using plastic rather than steel, making the car more aerodynamic, making the vehicles smaller and so on. But the US government, working together with scientists from around the world have been examining how we can change the engine itself.

The article "Research Needs for Future Internal Combustion Engines" published in the November 2008 edition of Physics Today discussed some of the challenges and opportunities that exist as researchers continue in their attempts to reform the traditional internal combustion engine. In particular they discuss the potential for homogeneous charge-compression ignition (HCCI) to increase the efficiency of the engine by 50%.

A traditional engine relies on a spark plug to ignite the fuel but in an HCCI engine the mixture of fuel and air is compressed to the point at which it auto-ignites as shown in this diagram from an article in the January 2006 edition of New Scientist magazine.

Because the fuel combusts at a lower temperature it means that emissions of chemicals like nitrous oxides and soot are reduced. As well, HCCI engines have higher energy conversion efficiencies than standard engines so they require less fuel. Compressing the fuel to the point of auto-ignition means however that the cylinder must be capable of withstanding extremely high pressures and since you are relying on auto-ignition rather than an active spark to initiate the reaction you have much less control over it. Moreover, HCCI engines are subject to a great deal of wear and tear and would need more maintenance than a traditional engine.

In any case, the proponents for HCCI engines have a long ways to go in promoting their new vision of the internal combustion engine to the public at large, which has largely been looking to discard it completely. If the internal combustion engine can be reformed and improved we should not hesitate to support the initiative and should examine the possibilities in as unbiased manner as possible.

As the case of ethanol has shown, politicians are too eager to jump on some bandwagons without seriously thinking about the scientific pros and cons of a technology or advance or the problems that might arise. Until a true alternative fuel is found, its best to keep your options open.

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