Hello,
First of all, i have to mention that the capacity (more specifically, the mass flow rate)
delivered by a reciprocating compressor cylinder depends on the following parameters and
conditions:
- cylinder volume and piston action type;
- cylinder volumetric efficiency (depends on suction valve, cylinder geometry and Variable Volume
Pocket);
- speed;
- gas mass density (inlet gas T, P and MW)
In the attached snapshot is the HYSYS PFD for the following situation:
Two cylinders with double acting pistons have the same geometry, clearance etc specified at
Settings in Design tab after Reciprocating Compressor radio button is checked.
An ADJ block (ADJ1) is used to set the 2nd stage speed equal to the 1st stage speed (condition
which has to be fulfilled because pistons share the same shaft with no gearbox in between) by
adjusting the interstage pressure. Naturally, for a steady state there is an unique pressure
which satisfy the equality: mass_flow_out_stage1 = mass_flow_in_stage2.
The same flowsheet configuration can be applied for cylinders with different geometry and clearances.
To summarize the main variables type:
- speed is dependent;
- interstage pressure is dependent;
- inlet T, P and outlet P are independent.
@ Bobby:
Also this is a solution, but for a different scenario (clearance adjusted, interstage pressure
specified by user - which is not natural).
Two Stage Recip Compressor.PNG 114.5KB
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