> I can't see how you can get the airflow you want from air
> > trying to make it through a spinning ball like that.
>
>Well, if the "ball" was basically a hemisphere, and of
>reasonable size, it could provide for a large open gap
>when perpindicular to the piston. At that moment, air
>could get in much more directly than in current designs,
>where it has to flow around a valve. The hemishpere
>could also be vaned to help reduce weird aerodynamics.
True, it has to flow around a valve now, but when the valve opens there is
air already directly behind it to be pulled in. And when a conventional
valve is open, if you look at the airflow, it really doesn't block any air
from getting in. With the hemispherical ball just before it opens (if I
understand the way it would need to be designed) the port side is also
blocked. So when the ball opens, it would have to pull air through the
diameter of the ball, not just from the other side of the valve like it
does now. And it would be difficult to design this vaning system that
would work over the incredibly large rpm range they are talking about.
> > That means the air would basically be spinning as it entered the
> > combustion chamber, and would be aimed at different points as
> > the ball spins.
>
>Not necessarily. The spinning ball could in fact act as a
>mini supercharger, forcing air in as it closes. In that case,
>flow would not be laminar, bout would at least be chaotic.
Possibly, but the effect would be negigible at best.
> > Also, how do you seal against combustion chamber pressure
> > with a spinning ball?
>
>The same way you do with valves. The ball is *inside* the
>cylinder, so pressire just forces it against the head and
>therefore helps to seal the cylinder. Sure, there'd be a
>trick to keeping that mating lubricated (err...), but that's
>not all that difficult if you can guarantee tolerances and
>know the materials that you're working with.
The difference is that a valve is not spinning. When it closes, it is
pulled up against the seat by the spring and stays put. The combustion
pressure may help, but the spring has to seal it first. If it is not
sealed, combustion pressure can not build to seal it. (Kind of like a
chicken or egg thing). And then, if the combustion pressure did seal it
enough to allow combustion pressure to build, I find it hard to believe
that the ball would be able to rotate.
> > And remember it will change temperatures rapidly
> > as well, and will have a large temperature gradient in the
> > ball itself. Also, how would you oil it to keep the oil out
> > of the combustion chamber?
>
>That all sounds pretty similar to the problems with valves.
The valve seat is a good heat sink, so the heat of combustion can flow from
the valve into the cylinder head, and the water flowing through the head
can cool the valve when it is against the seat. There would not be this
good metal to metal contact for heat flow with a spinning ball.
>I agree that we're years away, and I personally think that
>computer (rather than drivetrain) controlled iris-type
>solenoids may be a more promising future, but this is
>certainly an interesting design.
It is interesting to think about, and perhaps all the issues could be
addressed. I agree that solenoid controlled valves are more likely to be
implemented however.
-Matt
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