Flow characteristics in turbines – typical speed levels In steam or gas turbines operating under design conditions, the working fluid undergoes continuous steady flow with a speed of flow that is generally:

Introduction / Context:
Turbines are energy-conversion devices that accelerate fluids through nozzles and blade passages to extract mechanical work. Recognizing the typical magnitude of flow speeds helps set expectations for Reynolds number, Mach number, and loss mechanisms.

Given Data / Assumptions:

• Well-designed axial or radial turbines with correctly matched pressures.
• Continuous steady flow, not intermittent like in reciprocating machines.
• Compressible effects relevant in many stages (especially gas turbines and high-pressure steam).

Concept / Approach:
Turbines convert pressure/enthalpy drop into kinetic energy and then into rotor work. Consequently, blade-relative and absolute velocities are generally high (tens to hundreds of metres per second in steam turbines; even higher in gas turbines). “Very high” might suggest extreme supersonic conditions everywhere, which is not generally true across entire stages, while “low” or “very low” contradicts the acceleration purpose of nozzling.

Step-by-Step Solution:
Recognize nozzle role → accelerates fluid to large velocities.Rotor extracts work via change in whirl component → still requires high-through-flow speeds.Therefore, typical turbine flow speeds are high.

Verification / Alternative check:
Design data show nozzle exit velocities often 150–400 m/s in steam stages and 300–600 m/s (or higher locally) in gas turbines, confirming “high.”

Why Other Options Are Wrong:

• “Very low/low” mischaracterize turbine operation.
• “Very high” suggests an overgeneralization; not all passages are supersonic or at extreme speeds.
• “Approximately static” is incorrect for flowing turbomachinery.

Common Pitfalls:
Equating “high” with “always supersonic”; many efficient stages remain subsonic or transonic outside special nozzles.

Final Answer:
high