Quote:
Originally Posted by t vago
Sorry, no.
Available work has not changed, but produced work has gone up to cover the deadbeat cylinder.
It's really very simple - with DCD, you're running an internal combustion engine at stoich (or rich due to the engine computer going into limp-in mode), with what amounts to an air compressor that gets its air supply from the intake manifold, which then discharges into the exhaust stream.
Yah, pumping work will go down as compared to a normally operating otherwise identical engine, but the DCD engine will still consume more fuel than the normally operating one, because you just added an extra load to it, all other things being equal. That load is the pumping work associated with the deadbeat cylinder.
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I don't agree. The way I setup the problem, starting in #251 and not before, is to move the fuel from the deadbeat cylinder to the other 3 so that the total fuel per cycle, and hence the produced work per cycle (#239 by you), is unchanged. At that step it is an assumption, not an assertion, or I should say it is an approach to the setup rather than a derived parameter. (Because assumptions are always part of the setup, not a method for jumping to conclusions. ... in real derivations that is.)
Afterwards I balance AFR and then re-analyze losses still without changing fuel quantity per cycle, and hence not changing produced work. Again, an assumption, not an assertion.
There are three parameters that are derived, rather than assumed in the setup. The first is manifold vacuum, next is pumping loss, and the last is available work.
As additional commentary; loss for the deadbeat cylinder exists before the cylinder is deactivated, so there is no need to add a loss at this step. It is much easier to analyze pumping loss for the whole cycle rather than for each cylinder. The engine displacement does not change with DCD, which is a restatement of the cylinder's pumping loss existing before and after, but manifold vacuum does change after DCD, a necessity to re-balance AFR. So only the change in the manifold vacuum can have an effect on per-cycle pumping loss after DCD is activated. (#224 by you)