Results in the Absence of any Flow Constraints

For analysis of the accelerator models efficiency, in the absence of any flow contraints, several graphs were plotted:

  • Characteristic of the ratio Vt/Vc between flow velocity Vt in the  channel narrowerzone and the stream velocity Vc, as a function of the stream velocity Vc.

  • Characteristic of the introduced net head +DH by using such a stream accelerator, as a function of the stream velocity Vc, calculated on free conditions by +DH = (Vt2/2g) - (Vc2/2g).

Model C1

Model B1

 

Model C2

 

Model B2

 

Model B4

 

Model B3

 

Model A2

 

Model A1

Analysis of results in the absence of any flow constraints

The ratio Vt/Vc is in the absence of any flow constraints, almost steady for typical stream velocities. The following table states characteristic values of the ratio Vt/Vc in the absence of any flow constraints, for the several accelerator models tested.

Model

A1

A2

B1

C1

B2

C2

B3

B4

Vt/Vc %

140 %

130 %

110 %

105 %

115 %

115 %

120 %

115 %

Comparing the models efficiency values, we may conclude that:

  • The divergent zone should not be too short nor too long having an optimum length to guarantee an auxiliary rotation between inside and outside stream vortexes.

  • The channel narrower zone should not be too short, avoiding that turbulences at diverging zone affect turbine to work, nor too long that depression at outlet compensates concentration at the inlet.

  • Funneling of the inlet concentration zone should be adequate to have all incoming flow through the channel narrower zone.

  • The conduit external surface should be slightly inclined and not offering obstacles to the outside stream in order to facilitate creation of depression nearby the outlet section.

  • The accelerator model to be used on a industrial scale should have an optimized shape, being similar to Model A1 that is the more efficient model among all tested stream accelerator models. For this model, the flow velocity Vt through the channel narrower zone is in the absence of any flow constraints about 40% higher than the velocity Vc of the outside free stream, meaning that the flow loading in the channel narrower zone is about 2 times higher than the outside stream loading and the power density about 2,75 times higher than the power density of the outside stream. This corresponds to the introduction of a net head +DH of about 200 mm for a stream velocity Vc of 2 m/s (4 knots), of about 300 mm for a stream velocity Vc of 2,5 m/s (5 knots) and of of about 400 mm for a stream velocity Vc of 3 m/s (6 knots).