For Parson's reaction turbine, which of the following condition is correct? [Where $α$ = Nozzle angle, $ϕ$ = Exit angle of moving blade, $θ$ = Entrance angle of moving blade, $β$ = angle which the discharging steam makes with the tangent of the wheel at the exit of the moving blade]

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Answer 1

Explanation:

Parson’s Reaction Turbine

Parson's reaction turbine is a type of reaction turbine where the steam expansion takes place both in fixed nozzles (or guide blades) and moving blades. This turbine operates on the principle of reaction, which means the steam not only changes its direction but also expands as it flows through the blades, producing an equal and opposite reaction that drives the rotor.
In Parson's reaction turbine, the steam expands partially in the fixed nozzles (or guide blades), where it gains velocity, and then further expands in the moving blades, where a reaction force is generated. The turbine blades are designed with changing cross-sectional areas to facilitate this expansion and create a reaction force, which rotates the rotor. The velocity diagrams are critical for analyzing the forces and angles in the turbine.

The correct condition for Parson's reaction turbine is:

θ = β, ϕ = α

This condition satisfies the velocity triangle analysis for Parson's reaction turbine. The angles are defined as follows:

α (Nozzle angle): The angle at which steam enters the fixed blades (or nozzles).
ϕ (Exit angle of moving blade): The angle at which steam exits the moving blades.
θ (Entrance angle of moving blade): The angle at which steam enters the moving blades.
β (Discharge angle of moving blade): The angle which the discharging steam makes with the tangent of the wheel at the exit of the moving blade.

For Parson's reaction turbine, the following relationships hold true:

The entrance angle of the moving blade (θ) equals the discharge angle of the moving blade (β), as the steam flow is symmetrical relative to the moving blades.
The exit angle of the moving blade (ϕ) equals the nozzle angle (α), which ensures proper alignment and efficient energy transfer.

Thus, the condition θ = β and ϕ = α is correct for Parson's reaction turbine.