Kirk:
Ahh, I see..Sorry I was thinking of the casing. ( You right click the blower in the tree to build a casing..)
In most cases a seal isnt necessary, in fact its very typical to have a relief instead to stop lockup, many makers
professionally make a small tube in the case from the center of the case ( left and right) to the low pressure side
to allow flow to "slip" by when the pressure peaks in the rotation. Generally though the slippage is considered
to be a small percentage of the total volume being moved. It IS possible of course to make a seal on the rotors
apex to make it tighter , but I left that up to the user as it seems making a small slit ( or alteratively a small
tube to allow more slippage) is defined more by the roots usage than by its intrinsic design.
Take note that a roots blower does not in any way drive its mate, in fact it always rubs its mate ( the wrong way..
)
so adding a seal also increases the power necessary to turn it and would wear on that spot. To me the best roots
blower implementation ( mathematically) has enough clearance so that when expanded by maximum heat it has
zero clearance to its mate. But since thats hard to figure there really should be just an allowance for looseness
with the understanding that speed vs slip will result in a bit of loss that can be computed in its operational spec.
( But I could easily be wrong, Ive never used one I just studied them a bit to implement them, so as always
we "book experts" can be found wrong anytime by experienced field users.
)
Art
