Posted by LJD on November 19, 2011 at 14:17:07 from (72.171.0.144):
A few years ago several companies had new versions of diesel engines that ran on gasoline. Since gas today here in NY is $3.65 and diesel is $4.30 - seems a diesel engine that runs on gasoline might be nice to have. Of course, it would have to be 20 years old before I'd pay for one.
GM was the leader - but once the US and Canadian governments took control of GM - never heard another word about it. Last I heard of it was in 2009.
2007 article . . .
GM unveils diesel-like gasoline engines Drivable concept versions of General Motors cars that use efficient new engines with HCCI technology revealed Friday. August 24 2007: 3:07 PM EDT
NEW YORK (CNNMoney.com) -- General Motors revealed two drivable concept cars with new engines that burn gasoline in virtually the same way that a diesel engine burns diesel fuel.
The engines will get 15-percent better fuel economy than ordinary gasoline engines, GM estimates, but will not need the expensive exhaust treatment that diesel engines require. 2007_saturn_aura.03.jpg GM is revealing the fuel saving diesel-like gasoline engine in a version of the Saturn Aura.
Several car companies have been working on this type of engine technology, commonly known as homogeneous charge compression ignition, or HCCI. The technology promises the fuel economy of a diesel engine, which is typically much more efficient than a gasoline engine, but with the much cleaner exhaust of a gasoline engine.
In an HCCI engine, gasoline is ignited inside the cylinder using compression and the engine's own heat without the need of a spark. This is the same way that a diesel engine ignites diesel fuel. (When the engine is first started, and until it warms up, GM's HCCI engine still uses a spark to ignite the fuel.)
This type of ignition results in more energy to propel the vehicle because the fuel burns with less heat and light, which wastes energy, and because there is more compression when the fuel is ignited and, therefore, more of a push when the fuel and air expand.
"I remember debating the limits of combustion capability when I was in college," Tom Stephens, group vice president, GM Powertrain and Quality, said in a company statement. "HCCI was just a dream then. Today, using math-based predictive analysis and other tools, we are beginning to see how we can make this technology real."
The vehicles GM showed Friday are a Saturn Aura and an Opel Vectra, two virtually identical mid-sized sedans, both equipped with 180-horsepower 2.2-liter four cylinder HCCI engines.
They can drive at up to roughly 55 miles per hour using diesel-like ignition but will have to rely on traditional spark ignition at higher speeds or under heavy loads, GM said.
"Perhaps the biggest challenge of HCCI is controlling the combustion process," said Dr. Uwe Grebe, executive director for GM Powertrain Advanced Engineering.
Engineers hope to increase operating range under HCCI and improve performance under cold weather and high-altitude conditions, the company said.
2009 article . . .
Since our first encounter with General Motors' HCCI (homogeneous charge compression ignition) engines in August 2007, the powertrain research engineers at the GM Tech Center in Warren, MI have continued plugging away at the technology, trying to turn it into a marketable reality. The basic premise of compression ignition is simple. Based on the Ideal gas law (PV=nRT), if you decrease the volume of a particular quantity of air, the temperature rises to the point where fuel will spontaneously combust.
The hard part is controlling the pressure, temperature and air/fuel mixtures precisely enough to manage that combustion without causing excess noise and engine damage. When we first tried the HCCI prototypes a couple of years ago, the engines had a fairly narrow band of HCCI operation with the engine running in basic spark ignition mode the rest of the time. Thanks to a newly developed mixed-mode HCCI feature and external EGR, the engines can now run in HCCI from idle all the way to 60 mph!
We had a chance to drive a Saturn Aura with an HCCI engine based on the 2.2-liter EcoTec four-cylinder around the streets near the Tech Center. The engine ran smoothly and transitions between HCCI and spark ignition really couldn't be felt. The only indication of a transition was a slight ringing sound over the first couple of power cycles after transition.
The basic hardware for a production HCCI engine is in place now, with the only new piece of hardware being a combustion chamber pressure sensor. GM is continuing to work on the control software to make this a robust system and even adapting the homogeneous charge and pressure sensors to diesel engines to reduce NOx emissions. The HCCI engine achieves about a 15% improvement in fuel efficiency compared to a similar spark ignition engine at a much lower cost than a hybrid. GM hopes to have HCCI engines in production in about five years.
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