Prechamber Mod "Flame" Front

OM616

10mm MW

572

01-28-2011, 01:06 PM #88

The link is describing a DI diesel operation. I didn't see any references to a prechamber affects / function anywhere. The entire reason for the prechamber is to change the combustion process buy braking it up into smaller processes that better refine the total combustion, resulting in a “quieter” operation instead of "diesel knock."

Keep in mind that this discussion is about producing more power, not a quieter operation. I agree that smaller holes = quieter operation, I am interested in more power. From my perspective, to get more power, more fuel will need to be burnt in the prechamber, and the expanding gasses will need to be able to escape faster as well. Fortunately both are aided from increasing the hole diameter.

If the size of the holes were increased to allow more air into the prechamber, the prechamber air temperature, (before, and at the time of injection), would be higher from the additional pressure, (increasing the conditioning of the fuel), aiding in combustion.

Also, if more air is allowed to enter the prechamber, then the pressure differential during compression would be lower, if the prechamber pressure is always higher than the cylinder pressure during combustion with the small holes, (high pressure differential during compression), then with a lower compression pressure differential, the prechamber combustion pressure would be even higher than the cylinder pressure, blowing out its contents even faster and with more vigor.

The faster the engine is running the less time there is for air to make it into the prechamber, lowering the prechamber pressure and reducing the amount of vigor. Less vigor, bad, more vigor, good.

If more air is allowed to flow into the prechamber then the swirl in the prechamber will be increased, again more vigorous, and the fuel/air mixture conditioning would be improved, resulting in a more vigorous combustion. (more power)

If larger elements are used, then the length of time that the fuel is injected in is reduced, and the holes will need to flow at an increased rate to keep up. With small holes the restriction would reduce efficiency as the holes would hold up the works.

Any extra air that is allowed to enter the prechamber, and is not used up, will be expelled, if the holes will flow enough that is, and the pressure will push on the piston.

The closer the prechamber and cylinder pressures are during compression, the less energy that is used to raise the prechamber pressure above the cylinder pressure during combustion. (poorly worded I know, but I hope everyone gets my point).

All in all, I see larger holes as a win win. And the reports, from other members besides me, support larger holes.

I think that ¼ to 2/3 (or more) of the fuel should be burnt in the prechamber, and the wrest in the cylinder in a two part process. The difference in my thinking is that the holes be very large to allow a large amount of air to flow in and out of the prechamber, raising the compressed air temperature in the prechamber, and reaching ignition temperatures sooner, allowing for advanced injection timing.

The increased air entering the prechamber will create a stronger swirl improving the mix of gasses and fuel. Due to the lower cylinder / prechamber pressure differential, the result of larger holes, more pressure will be exerted on the piston sooner, and a grater amount of pressure will be used to push on the piston, instead of being needed to maintain a higher prechamber pressure because of the high cylinder / prechamber pressure differential.

Got to go.

This post was last modified: 01-28-2011, 04:19 PM by OM616.