Yes and yes, they maintain exact and precise M-dot at a given/fixed
upstream pressure regardless of downstream pressure fluxuations upto ~85%
of
upstream pressure at which cavitation ceases and M-dot drops in
accordance to the square/square root law/Bernoulli's equation.
K
On Sun, Jul 26, 2020 at 1:17 PM 1bcjolly <1bcjolly@xxxxxxxxxxxxx> 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?
Barry
Sent from my Sprint Tablet.
-------- Original message --------
From: roxanna Mason <rocketmaster.ken@xxxxxxxxx>
Date: 7/26/20 14:26 (GMT-05:00)
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Re: My Cavitating Venturi
Attached is a link to Fox Valve Co., Larry Fox introduced me to the
cavitating venturi back in 1982 at our test facility at United Technologies
in San Jose. Fixed and variable area venturis became part of my rocket
carrer ever since. Prevents hard starts which propellant valves are
slammed open at zero chamber pressure and maintain constant M-dot and O/F
through a burn even with throat erosion and other downstream pressure
perturbations. As long as the tank pressure remains constant so will flow
rate up to 85% upstream pressure, somewhat less for variable area venturis.
https://www.foxvalve.com/venturi-flow-controls/cavitating-venturi/
Ken
On Sun, Jul 26, 2020 at 2:25 AM Peter Fairbrother <peter@xxxxxxxxxx>
wrote:
On 25/07/2020 18:45, Terry McCreary wrote:
14 degree (full angle) carbide burrs are a standard item and
inexpensive. Long shank tools are available, as well as those with
wider flutes for cutting aluminum. >
Best -- Terry
On 7/25/2020 11:24 AM, Daniel Dyck wrote:
Thanks Theo. Machining was definitely complicated. For a college team
w/ limited resources I would highly suggest going AN, aluminum, and
designing it to slide into the flare, w/ no curves (like my waterflow
demo venturi). Additionally if your diffuser half angle is 7 deg, you
can buy 7 deg tapered end mills.
For other angles and shapes, if you have a lathe you can make and use a
D bit.
Turn the exact inside shape you want on the lathe in tool steel,
harden/temper/polish (or grind a bit of broken HSS tool to shape). Then
grind just less than half of it away so the remainder is a thou or two
greater than half diameter and has a D profile.
The end and the corners of the D form the cutting edge(s). Should be
used in the biggest lathe you can find rather than in a drill, if at all
possible. Use drill bits to rough out the shape before using the D bit.
Can get very accurate holes.
Works well in aluminium, stainless less so but in a bigger lathe with
coolant it is possible. Can even be done in copper for eg chamber
throats, but then the straight part of the D should be noticeably more
concave - this takes practice to get right, and should be done before
you turn the outside of the chamber.
It is of course possible to buy teeny boring bars and braze/solder/hold
them in the end of some suitable stock.
Peter Fairbrother