What produces the torque on the shaft of a turbomachine?

Change in the fluid's angular momentum through dynamic action on blades

Static pressure acting on a fixed wall

Change of volume of a trapped fluid

Reciprocating motion of a piston

In an impulse turbine such as the Pelton wheel, where does the pressure drop occur?

Entirely in the nozzle, the rotor runs at atmospheric pressure

Which group of machines gives energy to the fluid (power-absorbing)?

Pumps, fans, blowers, compressors

Practice · 5 marks

Turbomachines: definition and classification

Short answer

A turbomachine transfers energy continuously between a rotating element and a fluid via dynamic blade action. Classification: by energy direction (turbines like Pelton, pumps like centrifugal), fluid type (hydraulic, thermal), action (impulse e.g. Pelton, reaction e.g. Francis), flow direction (axial, radial, mixed, tangential), number of stages, and shaft position.

Define a turbomachine. Classify turbomachines with suitable examples.

A turbomachine is a device in which energy is transferred continuously between a rotating element (rotor or runner) and a flowing fluid, through the dynamic action of the fluid on the blades. The change in the fluid's angular momentum gives the torque on the shaft.

Classification

1. By direction of energy transfer

Power-producing (turbines): fluid gives energy to the rotor. Examples: water turbine, steam turbine, gas turbine, wind turbine.
Power-absorbing (pumps, fans, blowers, compressors): the rotor gives energy to the fluid.

2. By the fluid handled

Hydraulic (incompressible fluid, mainly water): water turbines, centrifugal pumps.
Thermal (compressible fluid): steam and gas turbines, compressors, fans.

3. By the action of the fluid in the rotor

Impulse type: the whole pressure drop occurs in the nozzle; the rotor works at constant (atmospheric) pressure. Example: Pelton wheel, De Laval steam turbine.
Reaction type: pressure drops also in the rotor, so the rotor is full of fluid. Example: Francis and Kaplan turbines, Parsons turbine.

4. By the direction of flow through the rotor

Type	Flow direction	Example
Axial	Parallel to shaft	Kaplan turbine, axial pump
Radial (inward or outward)	Perpendicular to shaft	Centrifugal pump, old Francis
Mixed	Both components	Modern Francis, mixed-flow pump
Tangential	Jet along tangent to wheel	Pelton wheel

  Axial            Radial           Tangential
  ||| -> |||       -> O <-          jet
                                      \  (  )
                                       -> (Pelton)

5. By the number of stages: single-stage and multistage (e.g. multistage boiler feed pump).

6. By shaft position: horizontal, vertical, inclined.

✓ Answer checked by Claude Sonnet 5.5

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