While the race to find the next alternative fuel dominates much of the green automobile conversation, there are significant efforts being made to improve existing technologies. Ethanol direct injection (ethanol DI) is one such development that could dramatically improve fuel efficiency in traditional internal combustion engines.
How ethanol DI works
Ethanol direct injection technology refers to the process of injecting a small amount of ethanol alcohol directly into the engine’s combustion chamber. The presence of ethanol in the hot combustion chamber lowers the internal temperature, making unwanted spontaneous combustion, or “engine knock,” unlikely.
The problem ethanol DI solves
What is engine knock, and why is it important to eliminate? In traditional internal combustion engines, pockets of unburned gas can form in the combustion chamber. The pressure exerted by the pistons during high-torque operation can produce temperatures high enough to cause these pockets of unburned gas to ignite out of sync with normal combustion. This spontaneous explosion (engine knock) creates a shockwave inside the engine that can stress and damage the pistons, combustion cylinder and engine block. For this reason, modern internal combustion engines can handle combustion chamber pressures only below a certain point, a threshold known as the “knock limit.”
How eliminating engine knock improves fuel efficiency
Eliminating engine knock by itself will not make an engine more efficient. The benefit comes from the possibility of producing engines that can handle pressures that exceed the knock limit. When the knock limit is surpassed, engineers can incorporate more fuel efficient attributes into the engine, such as turbo charging and higher compression ratios. According to researchers at MIT, an engine that can withstand a higher compression ratio will produce the same peak power as a typical engine but at a rate that is 30 percent more operationally efficient.
Why ethanol DI is a big deal
While due emphasis is being placed on next-generation fuel technologies, incremental advancements such as ethanol DI technology will help propel engine design to the next level. The model that is made possible by ethanol DI technology uses existing engine designs and very small amounts of ethanol alcohol. The ethanol tank in a vehicle using this system would have to be refilled five to 10 times as infrequently as the gas tank. And since an ethanol tank costs a relatively inexpensive $600, the fuel savings of ethanol DI technology can be earned back in much less time than with current hybrid vehicles. A 30 percent increase in fuel efficiency with minimal design overhaul is a great next step in designing the engine of tomorrow.
Article by Dale Cooper
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