Parsons Reaction Turbines and Velocity Diagram Triangles

Parsons reaction turbines are a type of steam turbine where the steam flows through a series of stationary and rotating blades. The blades are designed to gradually increase the velocity of the steam, which in turn drives the rotation of the turbine.

Velocity diagram triangles are used to visualize the flow of steam through the turbine. There are two velocity diagram triangles, one at the inlet and one at the outlet. These triangles show the velocity components of the steam at different points in the turbine.

Congruent Velocity Diagram Triangles

The correct answer is option D, or that the velocity diagram triangles at the inlet and outlet are congruent. This means that the two triangles are identical in shape and size.

Congruent velocity diagram triangles indicate that the steam flow through the turbine is uniform and efficient. This is desirable because it means that the turbine is operating at maximum efficiency and producing the most power possible.

Other Types of Velocity Diagram Triangles

While congruent velocity diagram triangles are desirable, there are other types of triangles that can occur in Parsons reaction turbines. These include:

- Asymmetrical triangles: These occur when the steam flow through the turbine is uneven, such as when there is a blockage in the steam path.
- Isosceles triangles: These occur when the steam flow through the turbine is partially blocked, such as when there is a partial blockage in the steam path.
- Right-angled triangles: These occur when the steam flow through the turbine is perpendicular to the blade surfaces, such as when the steam is not properly aligned with the blades.

In conclusion, congruent velocity diagram triangles indicate that a Parsons reaction turbine is operating at maximum efficiency, while other types of triangles can indicate problems with the steam flow through the turbine.