Pneumatic Flow Rate Source

Ideal compressor with constant mass flow rate


Pneumatic Sources


The Pneumatic Flow Rate Source block represents an ideal compressor that maintains a specified mass flow rate regardless of the pressure difference. Use this block when delivery of an actual device is practically independent of the source pressure, for example, in positive displacement compressors. The compressor adds no heat. Block connections A and B correspond to the pneumatic inlet and outlet ports, respectively.

The block positive direction is from port A to port B. This means that the flow rate is positive if it flows from A to B. The pressure differential is determined as p = pA – pB and is negative if pressure at the source outlet is greater than pressure at its inlet. The power generated by the source is negative if the source adds energy to the flow.

    Warning   Be careful when driving an orifice directly from a flow rate source. The choked flow condition limits the flow that is possible through an orifice as a function of upstream pressure and temperature. Hence the flow rate value produced by the flow rate source must be compatible with upstream pressure and temperature. Specifying a flow rate that is too high will result in an unsolvable set of equations.

Dialog Box and Parameters

Mass flow rate

Specify the mass flow rate of the source. The default value is 0.001 kg/s.


The block has the following ports:


Pneumatic conserving port associated with the source inlet.


Pneumatic conserving port associated with the source outlet.

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