Reaction Turbine Characteristics

A reaction turbine operates under a pressure drop across the runner. The fluid's pressure and velocity change as it flows through the runner, converting potential energy (enthalpy) and some kinetic energy into mechanical work.

Analyzing Turbine Operation Principles

Let's evaluate each option based on the operation of a reaction turbine:

• Option 1:
  kinetic energy is appreciable as the fluid leaves the runner and enters draft tube

  Correct. In a reaction turbine, the pressure decreases significantly across the runner. While work is extracted, the fluid still possesses considerable kinetic energy upon exiting the runner. The draft tube is specifically designed to recover some of this kinetic energy, indicating its significance.

• Option 2:
  the vanes are partly filled

  Incorrect. This describes an impulse turbine, where the jet strikes only a portion of the runner's circumference, and the vanes are only partly filled.

• Option 3:
  total energy of fluid is converted to kinetic energy in the runner

  Incorrect. In a reaction turbine, the total energy (pressure energy + kinetic energy) decreases, but it's converted into mechanical work. Only a part of the energy conversion involves a change in kinetic energy; a significant portion is from the pressure drop (potential energy conversion).

• Option 4:
  it is not exposed to atmosphere

  Incorrect. While reaction turbines often operate in sealed casings (like Francis turbines), this is not a defining characteristic specific only to reaction types. Also, some reaction turbines like Kaplan turbines can have parts exposed or operate under varying atmospheric pressure conditions.

Therefore, the most accurate description highlighting a key aspect of reaction turbine operation is the significant kinetic energy at the runner exit and its interaction with the draft tube.