- #1

Hello!

We are 3 students working on a bachelor thesis rigth now, with the purpose to determine the efficiency for different nozzle designs. We have done several practical tests, where we have logged the water pressure and the flow out from the nozzle, and calculated the nozzle efficiency based on the following equation:

Three of the nozzles we have tested is as following, all with nozzle diameter 1 mm:

Nozzle 1:

Nozzle 2:

Nozzle 3:

The tests gave us surprisingly results. All three nozzles is tested is tested with 200 bar water pressure, and the measured average speed is about 120 m/s. That gave us the following efficiencies:

Nozzle 1: 37 %

Nozzle 2: 47 %

Nozzle 3: 63 %

That will say, the voumetric flow rate would increase as the nozzle leangth increase.

We thougth that the nozzle efficiency would decrease as the nozzle length increase. But as you can see, that did not happen, the results says the opposite. We have also done the same tests with 2 and 3 mm nozzle diameter, and found that this effect would decrease as the nozzle diameter increase. For the 3 mm nozzle, the efficiency is decreasing as the nozzle length increase, which is opposite to the result from nozzle 1.

We are currently a bit stuck on this. Is there anyone out there who have a explanation or a theory around this phenomenom?

Thank you in advance for all replies, we appreciate all inputs!

Andreas Gjestvang

NTNU Gjovik

We are 3 students working on a bachelor thesis rigth now, with the purpose to determine the efficiency for different nozzle designs. We have done several practical tests, where we have logged the water pressure and the flow out from the nozzle, and calculated the nozzle efficiency based on the following equation:

Three of the nozzles we have tested is as following, all with nozzle diameter 1 mm:

Nozzle 1:

Nozzle 2:

Nozzle 3:

The tests gave us surprisingly results. All three nozzles is tested is tested with 200 bar water pressure, and the measured average speed is about 120 m/s. That gave us the following efficiencies:

Nozzle 1: 37 %

Nozzle 2: 47 %

Nozzle 3: 63 %

That will say, the voumetric flow rate would increase as the nozzle leangth increase.

We thougth that the nozzle efficiency would decrease as the nozzle length increase. But as you can see, that did not happen, the results says the opposite. We have also done the same tests with 2 and 3 mm nozzle diameter, and found that this effect would decrease as the nozzle diameter increase. For the 3 mm nozzle, the efficiency is decreasing as the nozzle length increase, which is opposite to the result from nozzle 1.

We are currently a bit stuck on this. Is there anyone out there who have a explanation or a theory around this phenomenom?

Thank you in advance for all replies, we appreciate all inputs!

Andreas Gjestvang

NTNU Gjovik

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