Two types of dynamic compressors are in use today—they are the axial compressor and the centrifugal compressor. The axial compressor is used primarily for medium and high horsepower applications, while the centrifugal compressor is utilized in low horsepower applications.

Both the axial and centrifugal compressors are limited in their range of operation by what is commonly called stall (or surge) and stone wall. The stall phenomena occurs at certain conditions of flow, pressure ratio, and speed (rpm), which result in the individual compressor airfoils going into stall similar to that experienced by an airplane wing at a high angle of attack. The stall margin is the area between the steady state operating line and the compressor stall line. Surge or stall will be discussed in detail later in this chapter. Stone wall occurs at high flows and low pressure. While it is difficult to detect. Stone wall is manifested by increasing gas temperature.