Variable geometry turbomachine

A variable geometry turbomachine uses movable vanes to optimize its efficiency at different operating conditions. This article refers to movable vanes as used in liquid pumps and turbocharger turbines. It does not cover the widespread use of movable vanes in gas turbine compressors.

If all fluid velocities at corresponding points within the turbomachine are in the same direction and proportional to the blade speed, then the operating condition of a turbomachine at two different rotational speeds will be dynamically similar. If two points, each on dissimilar head-flow characteristics curve, represent similar dynamic operation of the turbo machine, then the non-dimensional variables (ignoring Reynolds number effects) will have same values.

Head coefficient

Efficiency

Power coefficient

Where,

${\displaystyle N}$ is speed of rotation.

${\displaystyle Q}$ is flow rate.