On the topic of pressure loss that is the main/only drawback of
cavitation venturi's
is they do add about 15% additional feed pressure to a hydraulic system
which usually is not an issue on a test stand but can be prohibitive in a
flight rocket except sub systems like the aforementioned Apollo LM
descent engine that Henry just mentioned. They were also used in the Titan
ICBM Gas Generator propellant control system.
K
On Sun, Jul 26, 2020 at 2:41 PM Henry Spencer <hspencer@xxxxxxxxxxxxx>
wrote:
On Sun, 26 Jul 2020, 1bcjolly wrote:
Ken,
Not being a liquid man there is a lot that I don't know. Are these
cavitating ventures used as metering orifices for the purpose of o/f
mixture control or do they serve some other purpose?
As Ken said, they're for maintaining constant flow despite changes in
downstream conditions (within limits). Controlling mixture ratio is one
application -- the Apollo LM descent engine had (variable) cavitating
venturis as part of its throttling system. They can help suppress
low-frequency oscillations by breaking feedback loops, since a surge in
back pressure doesn't reduce the flow rate through a C.V. They can hold a
catalyst's flow rate constant even as chamber pressure builds up. They
can stabilize performance in an engine with an ablative throat (or a
throat with a soot layer that occasionally flakes off) whose exact
throat-area history isn't fully predictable. Etc. They do this without
nearly as much pressure loss as a plain orifice.
Henry