Variable Space Vacuum Tank - Pump question help

[ccc1522]

This process and mechanism is very difficult to explain via the computer and even during presentations many people simply do not grasp the concept so I am trying my best to explain it easily and ask my questions as best as I can so that you guys understand me. I really need help with these few questions as I am on the verge of completing this project.

I am creating a variable space vacuum tank and i need help.

The tank works as follows.

The tank is made of a rigid material. There are two openings on the tank.
One opening is connected to a pump
The second opening is covered by a bladder and nozzle.

(see picture at this point)Initially both the bladder and tank are at P1 and filled with air, though the bladder is collapsed so it is virtually completely empty.

The mechanism works by pumping air out of the tank which will drop the pressure in the tank.
This allows for the bladder (which is inside of the tank) to expand thus creating a vacuum.

The volume of the bladder increases as the pressure in the tank (P2) decreases because the pressure inside of the bladder (P1) remains the same.

This expansion allows the bladder to be filled with fluid as the volume must be displaced.Now my question arises

As the vacuum pump pumps air out of the tank the bladder expands.
Does this expansion of the bladder keep the volume of air (which is in the tank) dense enough to keep the pump efficiency or will the efficiency drop?

Second question:

The volume is not fixed as the bladder will expand due to vacuum and volume must be displaced within the bladder, so what do I use or how do I determine the pump efficiency during this process?
Thank you

 

[Nidum]

The actual configuration of the tank and bladder is largely irrelevant . All the pump sees is a decreasing pressure on the suction side . 'Efficiency' in the strict sense is probably not a very meaningful quantity in this situation . The effectiveness of the pump in reducing the tank pressure becomes less and less as the tank pressure drops .

This type of bladder in a tank arrangement is quite well known . More commonly used in the reversed configuration where the bladder is filled initially and gas pressure fed into the containing tank squeezes the bladder and forces the bladder contents out . Used in the aerospace industry for fuel supply systems in some specialist applications . Has the merit of working at any attitude and without need for pumps and tank scavenging systems .