Small Diameter Nozzle Testing

Todays testing was to ensure the smaller diameter discs would not crack or break when high pressure water passed through them. We setup a vertical test stand with a 1.5L bottle and a standard water volume of 600ml.

We first tested the bottle with the 6mm diameter disc inside the nozzle at both 80psi and 140psi
The 6mm disc was then removed and tested again at 80psi and 140psi.

The disc survived the testing without any signs of cracking or stretching

It was obvious even in real time that the 6mm diameter disc slowed the water coming out quite significantly. So we slowed the videos down in VirtualDub (video processing software) and recorded the exact time it took to empty the water from the bottles. The results were

Nozzle Diameter  (mm) Pressure  (psi) Time to Empty Bottle (seconds)
6 80 1.243
6 140 1.000
9 80 0.533
9 140 0.433

Here is a video of the testing

The 6mm nozzle disc has a 44 percent smaller area than the 9mm nozzle.The water took 2.3 times longer to be pushed out of the bottle or 43% slower than the 9mm at the same pressures.

Looks like the size of the nozzle discs we make will slow the water down in proportion to the surface area of the hole. This will provide a longer thrust phase with lower magnitude thrust which is what we need to control our thrust steering problem.

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