Page 418 - Reciprocating Compressors Operation Maintenance

Reciprocating Compressor Calculations 4O3

k - I
ACFMxl44xP,
HP =
k_-_l
"ad
k
612x144x150
33000x0.206 0.80
= 1160

Referring to Table A-l, we find that 1160 HP is too large for one
throw, and a compression ratio of 6.67 is larger than the normal ratio of
3.0. Therefore, the machine is best configured as a two-stage machine.
We decide on a two-cylinder, two-stage machine with a 14-inch stroke,
327 rpm, 45,000 Ib rod load.
Using a blank Compressor Worksheet (Figure A-10A), we fill in the
following data and ultimately obtain Figure A-l OB.

Ratio per stage = (6.67)° 5
= 2.58
Interstage pressure = 150 x 2.58 = 386.0 psia
Interstage temperatures (from Figure A-l) = 172°F
Capacity of second stage:
10 6 144 632 I
Capacity = 9 x -^—- x — x — x —— = 289 ACFM
F J
1440 386 520 0.98
We are assuming a clearance of 15%.
Approximate volumetric efficiency:

3 1 J * 7 * f 1000O 16 30 JO 40 JO tO 70 tO 10 1OOOOO

FIGURE A-9. Estimated efficiency as a function of compression ratio-
centrifugal compressors.