Stagnation Pressure Rise in a Centrifugal Compressor Stage

The stagnation pressure rise in a centrifugal compressor stage takes place in both the diffuser and the impeller. Let's discuss each component in detail.

1. Impeller:
The impeller is the rotating component of the centrifugal compressor. It consists of curved blades or vanes that accelerate the incoming gas radially outward. As the gas flows through the impeller, it gains kinetic energy due to the high rotational speed of the impeller. This kinetic energy is converted into potential energy in the form of pressure rise.

2. Diffuser:
After leaving the impeller, the gas enters the diffuser section. The diffuser is a stationary component that converts the high-velocity, low-pressure gas exiting the impeller into low-velocity, high-pressure gas. It works by slowing down the gas and converting its kinetic energy into static pressure. This process is achieved by gradually expanding the cross-sectional area of the diffuser, allowing the gas to decelerate and increase in pressure.

Stagnation Pressure:
Stagnation pressure refers to the pressure of a fluid when it is brought to rest or slowed down to zero velocity. In a centrifugal compressor stage, the stagnation pressure rise occurs as the gas passes through both the impeller and the diffuser.

When the gas enters the impeller, it experiences an increase in velocity and a decrease in pressure due to the acceleration imparted by the rotating blades. However, the stagnation pressure remains constant during this process.

As the gas leaves the impeller and enters the diffuser, it undergoes a gradual deceleration and expansion, which results in an increase in pressure. The diffuser converts the kinetic energy gained in the impeller into potential energy in the form of higher pressure. Therefore, the diffuser plays a crucial role in further increasing the stagnation pressure of the gas.

Conclusion:
In a centrifugal compressor stage, the stagnation pressure rise occurs in both the diffuser and the impeller. The impeller imparts kinetic energy to the gas, while the diffuser converts this kinetic energy into potential energy in the form of higher pressure. Both components work together to achieve the desired pressure rise in the compressor stage.