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.
The acrylic version made me very happy :)
On Sat, Jul 25, 2020 at 9:24 AM Theo McDonald <theo.mcdonald@xxxxxxxxx>
wrote:
Very clever use of integrating the swagelok front ferrule design.
Machining looks a bit complicated, but good on you. In the college
environment, I'm impressed you were able to make the diffuser cone angle.
Any suggestions for other schools / groups attempting this on a budget?
The acrylic version is VERY neat.
On Fri, Jul 24, 2020 at 2:55 AM roxanna Mason <rocketmaster.ken@xxxxxxxxx>
wrote:
Yeah Daniel, you brought up old memories.
I made many venturis on my lathe over the years using a tapped hand
reamer for the diffuser portion of the venturi. The trick is to achieve
repeatable results by controlling the Cd which is highly dependent on the
throat conture. A Cd near unity is possible. I was first introduced to
cavitation venturis by Mr. Fox of Fox valve back in 1982 or 3. He just
introduced the motorized variable geometry venturi to the industry. I used
a pair in a GOx/JP-8 water cooled rocket engine used as a heat standard for
testing ablative materials for solid rockets and solid and liquid fuel
ramjets at United Technologies/ Chemical Systems Div.in San Jose,CA.I was
hooked once the venturis utility became apparent to the extent I learned to
machine my own to save $1000's. Usually made them from aluminum for ease of
machining. The manually adjustable venturi was my all time favorite as you
can dial a mixture ratio by setting the stem length calibrated with water
and referenced to a calibration chart.
Indeed many old and good memories.
Ken
On Thu, Jul 23, 2020 at 11:00 PM Daniel Dyck <daniel.dyck.379ba@xxxxxxxxx>
wrote:
I figured now would be a good time to share something neat I worked on
in college.
For my capstone project our team built a permanent liquid rocket engine
testing facility, as well as a 1,000 lbf liquid rocket engine.
My job was designing/building the feed system. I built the feed system
using Swagelok, and to set the mass flow rates of our pressure fed engine,
I decided to use cavitating venturis.
I designed the venturi to be a slide in replacement for the front
ferrule, as shown in the cross section below.
(Straight barrel section fits in I.D of tube)
[image: image.png]
I believe this might be the only slide-in Swagelok compatible cavitating
venturi?
I got them machined out of stainless steel, photo of the finished
product below.
[image: image.png]
Before doing this, I made a little -6 AN cavitating venturi that ran on
water and shop air as a proof of concept. It worked great.
[image: image.png]
With the demo venturi I made the plot below. Apologies for the pixely
photo, digging through old college media:
[image: image.png]
And finally, I made an acrylic venturi where you could throttle
downstream pressure and see the results. I attempted to turn it into a GIF
to share, so hopefully this comes through alright.
https://giphy.com/gifs/dY0Cq7jWzo96ZEwT3O
<https://giphy.com/gifs/dY0Cq7jWzo96ZEwT3O>
Hope some folks found this interesting.
Daniel
--
Theodore B. McDonald