|
Here are two of the charts from the Naca report. The
one on the left shows diffuser resistance without a resistance (radiator) behind
it and the one on the right shows the diffuser with a radiator core behind
it.
Note the considerably increase in diffuser
efficiency with a core. It appears that the while the pressure
that builds up in front of a core eventually leads to boundary layer separation
due to the adverse pressure gradient,.
It in fact actually helps the resistance diffuser
pressure recovery efficiency over the open diffuser by preventing the separation
until much later. The one on the right also shows that a shorter length
L/D also helps efficiency as that apparently causes the expansion before the
boundary layer has grown too thick with the tendency to separate.
Of course you could always get the report and do your own
interpretation {:>)
|