HYDRODYNAMICS AND HYDROSTATICS

HYDRAULIC POWER TRANSMISSION IS THE POWER TRANSFER BY MEANS LIQUID.

Hydrodynamic power transmission:

• Turbo pump and turbine.

• Power transmission by kinetic energy of the fluid.

• The relative spatial positions of the prime mover and actuator and system components are fixed

• Compact units 

 Hydrostatic power transmission:

• Positive displacement pump

• Creates high pressure and through a transmission line and control elements this pressure drives an actuator (linear or rotational)

• The relative spatial position is arbitrary but should not be very large because of losses (< 50 m)

• A continuously variable transmission is possible.

 

Roughly speaking:

Power = pressure difference * flow or (discharge) or (Q)

Large Q, small pressure difference @ hydrodynamic transmission

Large pressure difference, small Q @  hydrostatic transmission.

But there is no general rule, depends on the task.

 

Generally larger than 300 kW power hydrodynamic is more favorable.

But for soft operation (starting of large masses) hydrodynamic is used for smaller powers either.

 

Linear movement against large forces: hydrostatic is favorable.

Linear movement and stopping in exact position: also hydrostatic is favorable.

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