Which of the following is NOT a typical compression ratio for screw, rotary vane, or high-speed reciprocating compressors?

Which of the following is NOT a typical compression ratio for screw, rotary vane, or high-speed reciprocating compressors?

• A. 20:1
• B. 4:1
• C. 8:1
• D. 6:1

Answer: (D)

Compression ratio for screw, rotary vane, or high‑speed reciprocating compressors is typically in the range of 4:1 to 8:1. This keeps the discharge temperature and mechanical stresses manageable while delivering the needed pressure rise. When higher overall pressure is required, designers use multiple stages with intercooling, rather than pushing a single stage to a very high ratio. So a very high ratio like twenty to one is not typical for these single‑stage machine types. The options within the normal range—4:1, 8:1, and 6:1—fit typical practice, while twenty to one does not.

Compression ratio for screw, rotary vane, or high‑speed reciprocating compressors is typically in the range of 4:1 to 8:1. This keeps the discharge temperature and mechanical stresses manageable while delivering the needed pressure rise. When higher overall pressure is required, designers use multiple stages with intercooling, rather than pushing a single stage to a very high ratio. So a very high ratio like twenty to one is not typical for these single‑stage machine types. The options within the normal range—4:1, 8:1, and 6:1—fit typical practice, while twenty to one does not.