Red Flag 1
08-24-2008, 14:35
Hemmings Motor News carried a short article in it's 8/08 issue. The article presented a brief report on a GM demonstration of a "new" approach to the internal combustion engine. This "new" approach is Homogeneous Charge Compression Ignition (HCCI). I say "new" because this was explored in the 1970's as a lab curosity only. The plan is to bring diesel fired power plant efficency to gasoline power plants, to include all present conventional gas engines. This would include Ethanol, or E85, as well.
Given the race for cheaper, more efficent and cleaner fuels, many things are being revisited. HCCI can produce greater fuel efficency by a claimed 25-30%. Byproducts of this combustion will be much cleaner, needing less, if any, post combustion treatment of exhaust gasses.
HCCI works much like diesel, in that the mixture of air/gasoline in the combustion chamber is being ignited by compression only. As with diesel power plants, the cylinders must be warm enough to help support ignition. Glow plugs, as used in diesel applications, would be a problem with the potential of pre ignition, and/or multiple ignitions; impressive sound but catastrophic. The GM approach to this problem is to use conventional spark plug ignition until the cylinders are warm enough to supply the needed sustained heat. Spark plugs, in the GM prototype, are also used at speeds above 55 MPH.
The GM Saturn Aura demo was driven by reporters to test drivability, fuel effeiecny, and low emission. The demos were driven on public streets. While the article does not speak to the emission findings, it does relate an observed 15% increase in real world fuel economy.
There are things that need to be addressed, some of these include:
A robust and reliable powerplant.
Stratified charge of injected fuel mixtures.
Reuse of exhaust gasses to reduce post ignition treatment,ie. to remove the looming problem of diesel requiring injection of Urea into exhaust gases.
Greater sophistication of sensors and feedback to control systems.
We are not there yet, however, this technology could be a big part of the answer for fuel efficency in the near future. Driving habits will probably not be impacted much if at all. It does not require reinvention of the wheel. Because of better combustion in the combustion chamber, emissions will be much less.
There are several signing on for HCCI. Dr. Rolf Leonhard of Bosch sees HCCI as a very workable idea:
http://www.autobloggreen.com/cataegory/hcci
Popular Mechanics has looked at HCCI:
http://www.popularmechanics.com/automotive/new_cars/42611288.html
Also:
http://www.greencarcongress.com/2008/05/gm-continues-to.html
Anyone heard anything pro or con?
RF 1
Given the race for cheaper, more efficent and cleaner fuels, many things are being revisited. HCCI can produce greater fuel efficency by a claimed 25-30%. Byproducts of this combustion will be much cleaner, needing less, if any, post combustion treatment of exhaust gasses.
HCCI works much like diesel, in that the mixture of air/gasoline in the combustion chamber is being ignited by compression only. As with diesel power plants, the cylinders must be warm enough to help support ignition. Glow plugs, as used in diesel applications, would be a problem with the potential of pre ignition, and/or multiple ignitions; impressive sound but catastrophic. The GM approach to this problem is to use conventional spark plug ignition until the cylinders are warm enough to supply the needed sustained heat. Spark plugs, in the GM prototype, are also used at speeds above 55 MPH.
The GM Saturn Aura demo was driven by reporters to test drivability, fuel effeiecny, and low emission. The demos were driven on public streets. While the article does not speak to the emission findings, it does relate an observed 15% increase in real world fuel economy.
There are things that need to be addressed, some of these include:
A robust and reliable powerplant.
Stratified charge of injected fuel mixtures.
Reuse of exhaust gasses to reduce post ignition treatment,ie. to remove the looming problem of diesel requiring injection of Urea into exhaust gases.
Greater sophistication of sensors and feedback to control systems.
We are not there yet, however, this technology could be a big part of the answer for fuel efficency in the near future. Driving habits will probably not be impacted much if at all. It does not require reinvention of the wheel. Because of better combustion in the combustion chamber, emissions will be much less.
There are several signing on for HCCI. Dr. Rolf Leonhard of Bosch sees HCCI as a very workable idea:
http://www.autobloggreen.com/cataegory/hcci
Popular Mechanics has looked at HCCI:
http://www.popularmechanics.com/automotive/new_cars/42611288.html
Also:
http://www.greencarcongress.com/2008/05/gm-continues-to.html
Anyone heard anything pro or con?
RF 1