Following up on three men and a tiny engine: MIT's efficient ethanol injection ICE
While Derrick covered the news of this new engine, I wanted to point readers to this article in Science Daily, which explains a bit more about the ethanol injection system on the itty-ICE and how it would affect the gasoline economy in the U.S. If all cars on the road today had the MIT engine, the team, made up of Leslie Bromberg, principal research engineer at the Plasma Science and Fusion Center, Daniel Cohn, division head and senior research scientist at the PSFC, and John Heywood, director of the Sloan Automotive Lab and professor of mechanical engineering, says America would use 30 billion fewer gallons of gas a year. The research was conducted using computer models at MIT and engine tests at Ford Motor Company. I've included a long quote from Science Daily about how the ethanol injection eliminates knock and improves performance after the jump, and I recommend the entire article, which you can find at the "Read" link below.
From Science Daily:
"For decades, efforts to improve the efficiency of the conventional spark-ignition (SI) gasoline engine have been stymied by a barrier known as the "knock limit": Changes that would have made the engine far more efficient would have caused knock--spontaneous combustion that makes a metallic clanging noise and can damage the engine. Now, using sophisticated computer simulations, the MIT team has found a way to use ethanol to suppress spontaneous combustion and essentially remove the knock limit.
When the engine is working hard and knock is likely, a small amount of ethanol is directly injected into the hot combustion chamber, where it quickly vaporizes, cooling the fuel and air and making spontaneous combustion much less likely. According to a simulation developed by Bromberg, with ethanol injection the engine won't knock even when the pressure inside the cylinder is three times higher than that in a conventional SI engine. Engine tests by collaborators at Ford Motor Company produced results consistent with the model's predictions.
With knock essentially eliminated, the researchers could incorporate into their engine two operating techniques that help make today's diesel engines so efficient, but without causing the high emissions levels of diesels. First, the engine is highly turbocharged. In other words, the incoming air is compressed so that more air and fuel can fit inside the cylinder. The result: An engine of a given size can produce more power.
Second, the engine can be designed with a higher compression ratio (the ratio of the volume of the combustion chamber after compression to the volume before). The burning gases expand more in each cycle, getting more energy out of a given amount of fuel.
The combined changes could increase the power of a given-sized engine by more than a factor of two. But rather than seeking higher vehicle performance--the trend in recent decades--the researchers shrank their engine to half the size. Using well-established computer models, they determined that their small, turbocharged, high-compression-ratio engine will provide the same peak power as the full-scale SI version but will be 20 to 30 percent more fuel efficient."
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