When the axially moving fluid hits the side of the stationary turbine blade it gets turned in a spiral motion and the fluid emerges from the turbine with a tangential velocity component. The reaction of this fluid on each turbine blade is a tangential force producing torque to turn the turbine in the opposite direction of the deflected flow.

For a given fuel flow the turbine will accelerate until it reaches such a rotational speed as to cause the fluid to meet the turbine blade point on. Under this condition, the fluid will cease to accelerate the turbine which will maintain a constant speed.

For a certain turbine the blade angle sets proportionality between axial flow velocity (flow) and tangential blade velocity (rotational speed) at which the turbine rotation will stabilize.

With the magnetic pick-up assembly detecting the turbine blade motion a pulse output at a frequency proportional to turbine speed will be produced.
Thus the pulse frequency produced by the turbine flow transducer is proportional to the flow rate. It is then used with electronic devices to calculate and display flow rates as well as flow volume over a period of time.

Effect of Friction:

The most significant friction effect is due to liquid viscosity. Both bearing friction and pick-up magnetic drag are comparatively small and are covered by calibration test runs.

Viscous friction tends to lower the rotational speed and hence the flow K-Factor, especially at low flow and high viscosity conditions.

The frequency of pulse rates generated at different flows ideally follows a straight line. Viscous friction causes deviation at low flow as shown.

The flow K-Factor plotted against the output pulse frequency divided by the kinematic viscosity (i.e. H/) gives the viscous performance curve, which will be fixed for a specific turbine regardless of what liquid was used.

The viscous performance curve is divided into three regions:

Material Selection:

All the body components, including the flow straighteners and ball bearings, are made out of 303 stainless steel which has no magnetic properties but is ideal as far as the yield stress, high melting point and resistance to corrosion.

The turbine is made of a magnetic stainless material (14 pH) with a medium permeability number to facilitate disturbing the magnetic field.

The electronics body is made of carbon steel to act as a shield from any external magnetic field generated by the aircraft electrical systems.