# Hydrocarbon Compression

## DYNAMIC COMPRESSORS – AXIAL COMPRESSORS

Motion along the axis of a shaft is called axial motion. This takes place in a straight line. A compressor in which the gas moves parallel to the axis of its shaft is called an axial compressor. An axial compressor has stator and rotor blades, as shown below.

The rotor blades are attached to the shaft and rotate with the rotary motion of the shaft. The stator blades are attached to the casing, as shown in the above figure.

The arrangement of the blades is such that there is a set of stator blades between each two sets of rotor blades, as shown in the figure below.

The rotor blades behave in the same manner as the blades of a fan. As they rotate, they force the gas to move. The rotor blades impart both pressure and velocity to the gas.

As the gas is thrust into the stator blades, the openings between the blades act as diffusers and reduce the velocity of the gas. With the decrease in the velocity, the pressure of the gas increases. The stator blades guide the gas into the next set of rotor blades. The gas entering the second set of rotor blades has a slightly higher pressure. Thus, each set of stator and rotor blades increases the gas pressure.

In axial compressor, the pressure increase of a gas is achieved by using many sets of stator and rotor blades. The blades in an axial compressor are not of the same size. The blades get gradually smaller toward the discharge end of the compressor, as shown below.

As the gas flows through an axial compressor, it occupies less volume successively in its flow path. Thus, the gas pressure increases. The flow of gas in an axial compressor is somewhat linear and in the direction
of its axis.

Two forms of gas energy are pressure and velocity. Energy cannot be created or destroyed, but it is convertible from one form to another. By doing work on a gas, the compressor adds energy to the gas. The total energy of a flowing gas is a function of its pressure, velocity, and temperature. Where the gas velocity reduces, pressure increases (Bernoulli’s Theorem).

Written by Jack

October 1st, 2021 at 2:42 am

Posted in Fundamental