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Working models

Working models

Working models

(OP)
I invented a different sort of pressure vessel (the patent was approved last week) and I want to build a see-thru working model. The approach I want to take is:
  • Design a dynamically valid scale model (i.e., with the same Reynolds Numbers and Weber Numbers as the full-size unit) on a desktop scale (maybe 14 inches tall, 3 inches ID for the big diameter, the similitude analysis will lock those values down, but I don't want the length much longer an a foot to represent a 9 ft tall vessel)
  • Generate a 3-D AutoCAD model of the scale-model
  • Find a rapid prototyping company that can build it
  • Add level control, solenoid valves, a scale model eductor to let the water flow suck in air (to simulate entrained gas), and a pump (capacity to be determined in the similitude analysis)
I have no problem the first two, but have no idea where to start picking a prototyping company for the vessel and the eductor, locating 1/8" solenoid valves, locating similar scale level controllers, little bitty pump, etc. Anyone have any feeling for how to start down any of these roads?

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

RE: Working models

Small solenoid valves should not be hard to come by. If you are able to use (polymer) tube, you may be able to use a pinch type valve. If you require rigid connections, perhaps consider having the smallest metallic valve you can find and using bushings/reducers as necessary.

I am sure others have ideas on your other concerns.

RE: Working models

What kind of pressure? Most RP materials have poor mechanical properties.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Working models

(OP)
I haven't gotten that far in my arithmetic yet, I'm shooting for something under 15 psig (1 barg, 100 kPa) at room temp. Getting the Reynolds Number of the gas side right will dictate the pressure, but I don't think it will have to be really high.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

RE: Working models

I'll back up with dgallup says on the properties of what many folk think of when talking 'rapid prototype' (additive processes like SLA & FDM etc). Also on the 'see through' front I believe that will limit you some on what rapid prototype materials are available to you.

This company has some information https://www.solidconcepts.com/ on a range of different processes they do, I've used them for some FDM parts.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

RE: Working models

We used a company that makes SLA parts for our last rapid prototype (of a regulating valve). We asked for, and received a water-clear transparent valve shell, with enough thickness (about 3/16") to withstand 50 psi water pressure during flow testing (max. body diameter was around 2.25"). There are a lot of places that can do this, we used www.quickparts.com because they quoted the best price/delivery for our needs at the time.

Eductor - this will likely be the toughest one, as you may need to tweak the throat diameter to get the flow conditions you want. I'd get a local machine shop to cut the part in aluminum, or out of acrylic if you want it clear. Wipe a film of silicone grease across the machined surface to get a reasonably clear view.

Small pumps - google is your friend. What kind of pump, what head and delivery? Small diaphragm pumps are a dime a dozen. A little flexible impeller pump is out there, somewhere. You know the pump affinity laws as well as I do, and know you won't be able to get the head, flow and NPSH you likely need from a scaled centrifugal pump.

Level control...simplest and most easily scaled would be a set conductive probes along the wall.

RE: Working models

Not entirely sure if this would work with off the shelf components, but

Instead of a pump and an eductor to suck in air how about re-purposing a a vacuum ejector as the fluid mover and the air comes along for the ride as a byproduct.

http://www.smcpneumatics.ie/pages/products.php?ite...

RE: Working models

Not the transparent ones.......

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Working models

the patent was approved last week

well come on then, don't hold out on us, let us go see the patent/diagrams online!

RE: Working models

(OP)
I got notice last week that the patent had been "allowed". That triggers a registration fee which causes a patent number to be issued and (within 3 months of receipt of payment) the patent to be issued. It probably won't be in the databases until summer. There is an animation at GasBuster Animation that shows how it works.

I went to a couple of the rapid prototyping sites referenced above and both look like they'll work well, thanks for the leads.

MintJulep,
Some great sites. I could look at Clipard for hours. The ejectors at the SMC site all have convergent/divergent power nozzles that are designed for air and usually have about 45% efficiency with a gaseous power fluid. I've used supersonic ejectors as eductors (i.e., with a liquid power fluid) a couple of times and there is a huge efficiency hit (down to around 10-15%), they still move suction fluids. Since micro-size pumps are more available than micro-size compressors I still think pumping makes more sense, but the SMC ejectors are probably the direction I'm going to go to get the air into the system.


David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

RE: Working models

David,

Agree that small compressors are tougher to find, especially if you need a fairly decent delivery/pressure. They also tend to be noisy, which doesn't help when you are trying to talk to your audience during the demo. Alternatively, why not use a small pressure bottle for demos (I'm thinking of the kind that can be attached to paintball guns and recharged to ~1000psi), and regulated down to whatever pressure you need?

RE: Working models

(OP)
I've done the bottle thing when I need small volumes of high control. This application is large volumes of zero control. Wells give me 6 MSCF/d for a few seconds, then 60 MSCF/d for 3 minutes, followed by another number for a different time. That variation in gas is with a reasonably constant liquid flow (about 80-90%% liquid by mass). With the eductor idea as long as I have enough suction flow to prevent cavitation in the throat and get enough air flow that the top valve has to operate occasionally I'm golden.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

RE: Working models

(OP)
The patent was published yesterday. It is Patent No. 8,439,999. Thanks for the kind words Raven.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

RE: Working models

WhDo you need a specific pump working principle to demonstrate a particular feature of the technology, or just something hidden behind a screen to feed your eductor?

HPLC pumps are good for low flow rates, and have all the head you could possibly want. You could even have some a preprogrammed flow rate ramps to cover a range of different operatibng conditions, or for customer-pleasing prettiness.

Matthew

RE: Working models

(OP)
Looks interesting, I'd never looked at HPLC pumps before. I hope to get back to my Similitude analysis next week and develop flow rates and pressures. I'm thinking that I'll need more flow and less pressure than I can get from the HPLC, but I haven't done the math yet.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

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