Divergent nozzle for releasing pressurised gas

[T C]

TL;DR

I need the details of the type of divergent nozzle that is needed to release pressurised air/gas to atmospheric pressure level.

I have air/gas pressurised gas (pressure is 7 barG). I want to know what are the parameters of the divergent nozzle needed so that the pressurised gas can be released to atmospheric pressure level smoothly and necessary enthalpy conversion can be achieved i.e. the air/gas will accelerate to its limit.

 

[boneh3ad]

What do you mean by "smoothly" in this context? You can just have an abrupt orifice and let it exhaust and it will reach atmospheric pressure.

 

[russ_watters]

I want to know what are the parameters of the divergent nozzle needed so that the pressurised gas can be released to atmospheric pressure level smoothly and necessary enthalpy conversion can be achieved i.e. the air/gas will accelerate to its limit.

To say it another way; your goal is to achieve the highest velocity you can, correct?

 

[T C]

To say it another way; your goal is to achieve the highest velocity you can, correct?

Yes. Rockets of all kinds have divergent nozzle shaped outlet attached to their end. If just an orifice would be sufficient, then why that extra cost? Certainly there are some advantage is using a divergent nozzle shaped outlet in rockets.

 

[cjl]

There's an advantage if you want to maximize thrust and exit velocity, sure. The details of what that nozzle will look like depend on your constraints and on your reservoir conditions though.

 

[T C]

I have already told that reservoir condition.

 

[cjl]

And your question has already been answered for that simple case: yes, maximizing velocity will involve a divergent nozzle (though for a pressure ratio of 7:1, it won't have much of a diverging section - you're only looking at an area ratio of about 1.6:1 there). What are you actually trying to achieve though? What is your application here? Can you give us any more details?

 

[T C]

it won't have much of a diverging section - you're only looking at an area ratio of about 1.6:1 there)

Kindly tell me how you have achieved that ratio.

 

[cjl]

There's a good summary of the relations at the page here. It helps if you have some familiarity with gas equations. Again though, it would be very useful to know more details of what your situation is and what exactly you're trying to achieve here though.

 

[T C]

How to find out M here in the equation?

 

[cjl]

M is the mach number. If you look at equation 6, there's a relation between the pressure ratio P/P_t and the mach number, so you would first solve for the mach number based on your pressure ratio, then use that to find your area ratio.