The compression ratio of an axial-flow compressor depends primarily on what factor?

The compression ratio of an axial-flow compressor is fundamentally influenced by the number of compressor stages. Each stage of an axial-flow compressor contributes to a certain amount of pressure increase, with multiple stages working in tandem to achieve a higher overall compression ratio. As the airflow passes through these stages, the pressure and temperature of the air are incrementally raised, resulting in a significant increase in compression as the air progresses through the compressor.

While the diameter of the compressor can impact airflow capacity and efficiency, it does not directly determine the compression ratio. Similarly, the type of fuel used is more relevant to combustion processes rather than affecting the mechanics of compression within the engine. Operating altitude can influence overall performance due to changes in air density, but it doesn't directly dictate the compression ratio itself, which is more closely tied to the design and configuration of the compressor stages. Therefore, the number of compressor stages is the primary factor that defines the compression ratio in an axial-flow compressor.