Basic Principles and Energy Transfer in Centrifugal Compressor Part - I

Summary

This video script provides a detailed explanation of centrifugal compressors, focusing on their operation and key components such as the impeller, diffuser, and casing. The impeller draws in air axially and accelerates it radially, increasing its velocity and pressure. The diffuser slows the air to convert kinetic energy into static pressure, boosting overall efficiency. The script also covers the principles of centrifugal force, velocity triangles, and energy transfer equations, offering a thorough understanding of how centrifugal compressors function in applications like gas turbines and turbojets.

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Q & A

What are the primary fluid machines discussed in the course?

The primary fluid machines discussed include Pelton turbine, Francis turbine, Kaplan turbine, centrifugal pump, and reciprocating pumps. These machines primarily use water as the working fluid.

What differentiates compressible flow machines from hydraulic machines?

Compressible flow machines differ from hydraulic machines because they use compressible fluids like air, steam, or gases, which change in density with pressure and temperature. In contrast, hydraulic machines use incompressible liquids like water.

What are the key components of a centrifugal compressor?

A centrifugal compressor consists of three main components: the casing, the impeller (rotating part), and the diffuser (static part). The impeller imparts energy to the fluid, while the diffuser converts kinetic energy into static pressure.

How does a centrifugal compressor increase the pressure of air?

A centrifugal compressor increases air pressure by imparting velocity to the fluid through the rotating impeller. The fluid then passes through the diffuser, where its velocity decreases, and pressure increases.

What is the function of the diffuser in a centrifugal compressor?

The diffuser slows down the air, converting the fluid’s kinetic energy (velocity) into static pressure. This process helps increase the air pressure while reducing the velocity.

What is the difference between a centrifugal pump and a centrifugal compressor?

The main difference is that a centrifugal pump uses water as the working fluid and is designed to handle liquids, while a centrifugal compressor uses air or other gases and is designed for compressible fluids.

What is the significance of the impeller's rotation in a centrifugal compressor?

The impeller's rotation imparts energy to the fluid, increasing both its pressure and velocity. This energy transfer is crucial for the functioning of the compressor, which aims to raise the static pressure of the air.

How does the centrifugal force affect the air inside the compressor?

As the air moves radially outward through the impeller, the centrifugal force generated by the rotation causes the pressure to rise. This force creates a pressure gradient, pushing the air outward and increasing its static pressure.

Why is the flow through a centrifugal compressor described as radially outward?

The flow is described as radially outward because the impeller draws in air axially (along the center) and then pushes it outwards along a radial path through the impeller blades. The air flows in a radial direction after entering the impeller eye.

What role do the vanes in the diffuser play in the compression process?

The vanes in the diffuser help decelerate the airflow. As the air slows down, its velocity decreases and static pressure increases. This transformation of kinetic energy into pressure is essential for achieving the desired high-pressure air at the compressor outlet.