Featured Homogeneous Charge Compression Ignition

Just another attempt at making a diesel engine that uses gasoline.

And since when does a leaner mixture equal LOWER combustion temperatures ??
Seems like I remember that just the opposite is true.

 

It's nuanced. Slightly lean can be hotter, but go more lean and cylinder temps drop. Perhaps a little less fuel leads to less cylinder cooling, and the temperature spikes, but it sounds like the real culprit is detonation, or knocking. This increases the pressures in the cylinder, and that increases the heat.

I'm remaining skeptical on the emissions for now. Mazda is claiming that the temperatures remain low enough to keep NOx and particle emissions low enough to only need normal emission controls.

 

Low enough...too lean mixture equals cooler combustion.

 

Mazda looks like it will be the first to put an hcci in a car.

The mazda system uses super charging and cooled egr to manage compression and oxygen levels in the cylinder, and a spark plug to manage the engine in higher power and at start up stages.

A key to lower temperatures in hcci is the homogeneous part of H(cci). This eliminates many of the hot spots associated with a moving flame front in a lean burn gasoline engine and provides for more complete combustion. My guess is mazda engine when in hcci mode will use a miller cycle with aggressive cooled egr, which will run cooler exhaust temperatures just like the prius atkinson cycle with aggressive cooled egr. This allows for hotter compressed temperature before combustion even with slightly lean mixtures.

During heavier loads or high rpms, it looks like the mazda engine will use a spark plug and slightly rich of stoich to provide better acceleration while keeping the engine size small.