Internal combustion engines used to drive gas compression machinery burning natural gas typically operate on which cycle?

• A. Rotary
• B. Variable Heat
• C. Brayton
• D. Two-Stroke or Four-Stroke

Answer: (D)

The main idea here is that the motors used to drive gas compression machinery are reciprocating internal combustion engines, which run on the standard piston engine cycles—either two-stroke or four-stroke.

In a two-stroke cycle, the power cycle is completed in two piston movements (one up, one down), with intake and exhaust processes typically occurring alongside compression and combustion. In a four-stroke cycle, the cycle spans four movements (intake, compression, power, exhaust), with each function occupying its own stroke. Both configurations are common for stationary natural‑gas engines used to drive large compressors, depending on the design and service demands.

The other options point to different technologies: Brayton is the cycle for gas turbines, not reciprocating engines; rotary refers to a different engine type (like a Wankel) that isn’t the standard piston cycle for these applications; variable heat isn’t a defined engine cycle. So the best answer is that these engines operate on either two-stroke or four-stroke cycles.