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pneumatic chamber

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Tomas Iesmantas
Tomas Iesmantas 2011년 4월 8일
Hello, I'm creating new pneumatic chamber with inlet and outlet. for such a chamber mass continuity equation would be like this:
mas accumulation rate within chamber = inlet mass flow rate - outlet mass flow rate
as I understand, expression for mass accumulation rate in chamber is the same as in constant volume pneumatic chamber already created in simscape foundation library. I modified the code of constant volume penumatic chamber:
component chamber1
nodes
A = foundation.pneumatic.pneumatic; % A:top
B = foundation.pneumatic.pneumatic; % B:top
end
variables
gas_flow = { 0, 'kg/s' };
heat_flow = { 0, 'J/s' };
pressure = { 0, 'Pa' };
temperature = { 0 , 'K' };
end
parameters
Volume = { 1e-3, 'm^3' }; % Chamber volume
p0 = { 101325, 'Pa' }; % Initial pressure
T0 = { 293.15, 'K' }; % Initial temperature
end
function setup
through( gas_flow, A.G, B.G );
through( heat_flow, A.Q, B.Q);
across( pressure, A.p, B.p );
across( temperature, A.T, B.T );
% Initial conditions
pressure = p0;
temperature = T0;
end
equations
gas_flow == Volume/A.R/temperature * (pressure.der - ...
pressure* temperature.der/temperature);
heat_flow == A.c_v * Volume / A.R * pressure.der;
end
end
it works when I conect pressure source, new chamber, orifice and atmospheric reference, but I have doubts about the results. And it won't work when I connect pneumatic pump made of rotational pneumatic converter (this pump works when I don't use my new chamber). maybe I missunderstood something, and that somebody will help me with this.
P.S. if my question is unclear, please wright to me and i will clarify it.

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Arnaud Miege
Arnaud Miege 2011년 4월 8일
I don't think it's as simple as this. You need the concept of orifices for the inlet and oulet of the chamber. A better way would be to use the Constant Volume Pneumatic Chamber block from the Foundation Library as a building block for a 2-port pneumatic chamber. A simple way to do this is to use 2 Constant Area Pneumatic Orifice blocks with their B ports connected to the Constant Volume Pneumatic Chamber block.
HTH,
Arnaud
  댓글 수: 2
Tomas Iesmantas
Tomas Iesmantas 2011년 4월 8일
could you please clarify: what is the role of reversed orifice? since if I connect two orifices with both B ports at the chamber one orifice models negative flow rate, or mybe I'm wrong at this?
thanks in advance for your always fast responses.
Arnaud Miege
Arnaud Miege 2011년 4월 8일
One orifice would represent the inlet orifice, while the second orifice would represent the outlet orifice. I think they need to be connected back to to back so that the same convention for the flow rate is used, but I could be wrong. I'd suggest trying with the orifices back-to-back and also in the same direction to see the impact on the simulation results. It should be clear which one is incorrect.

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