Mailing List Archive Mailing List Archive
>I have noticed that venturi effect in the TX20 becomes "weaker" >as pressure drops in the bottle. I am talking about noticeable >changes between, say, 200 bar and 100 bar. > Venturi effect is depending on dynamical pressure of fluid flow (meaning with density of inhaled gas and square potential of velocity - breathing intensity). So what is changing with different pressure in bottle and the same depth of diving, same rate of breathing (there are some other but not so important)? Cracking pressure and IP - little but obviously you can notice it. Secret of regulator producers. The one of the most important think in understanding of this anomalies is that there are no just balanced and nonbalanced I and II stages. Most of balanced I and II stages are in reality partially balanced. For example: most of all II Apeks stages (20,40,50) are balanced about 60% (as I remember of my last time Apeks balance piston measurement). 40% of shutting force is caring by spring (adjustment of cracking force). This meaning when you inhale only pressure difference you have to overdo is the force of the spring (40%). Balanced part of force (60%)is released almost momentarily (with little time delay - important because of regulator fluttering possibility). Now Venturi (if it is adjusted) is activating because of dynamical process of breathing and making uderpressure on membrane and by this it correcting the cracking pressure (this 40% force of the spring). Again not to much because it is possible for regulator to became unstable - fluttering. (If you look at inhale test of some regulator, just look at the inhale graph and find some oscillations in pressure - this is acceptance design mistake - for me unacceptable example are tests of extreme balanced Poseidon regulators). With depth viscosity of gas is increasing dumping also and fluttering usually stops. (this is also typical experience of divers which use Poseidon). By my opinion (between other reasons - and them are a lot) is much better to switch on He mictures to decrease viscosity of gas and regulator will work excellent also extremly deep. This is right way no extreeme balance unstable regulators. So it is looking that it is Venturi but in real that is because of partial balancing. Now you can imagine how many problems engineers have to solve to make regulator working properly (right diameter of balanced tube - proper damping etc.). Sometimes they have luck with excellent design. Sometimes not. The real problem is to make regulator robust, compact and time constant - reliable and on the other side low breathing effort. This Britt's (Apeks) are definitely succeed in compromise of all of this demands and (by my opinion) are one of the best in world. So, you mentioned some remodeling of regulator? Fine. B.r. Viktor Sajn Laboratory of fluid mechanics and aerodynamics Faculty of Mechanical Engineering University of Ljubljana Slovenia (ps. be aware of extremely high balanced regulators - extreemly sensitive and danger) -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]