Insufficient jet range - HELP ASAP

Hi all,

I'm a mechanical engineering student manufacturing a laminar jumping jet as part of a project and when I connect the system to a mains water supply and also a pump I am getting a very poor range, suggesting there are huge pressure losses within my system. The range I get is about 2 feet maximum.

I am using a 4 inch diameter tube, 11 inches long with a 20mm (0.8 inch) converging nozzle. The input from the pump/ mains tap is a 10mm diameter tube.

Hopefully the images below work and you can see what I mean. The flow is perfectly laminar and has the standard scouring pads, straws set up although it has an axial input (which i doubt has any impact on the range). The mains water supply has a range of about 15 feet  yet when connected to the laminar jet it deteriorates massively.

I dont have any air release valves attached as the instruction video and a few others ive seen didnt include these.

Does anybody know why this is, or what I can try to resolve this? Any help would be greatly appreciated as my deadline is soon approaching.

https://i.servimg.com/u/f55/18/80/99/64/img_3911.jpg

https://i.servimg.com/u/f55/18/80/99/64/img_3710.jpg

https://i.servimg.com/u/f55/18/80/99/64/img_3711.jpg

Thanks in advance,

Nick

Did you get it sorted in time?  I haven't logged on since last summer but just started working on my jet again for this summer.  From what you have said it sound like your exit nozzle is too large compared to the inlet tubing, on my unit the exit nozzle is around 12mm and the water feed is 20mm tubing from a pump.

Okay thanks,

I still have a week to submit and will be modifying the nozzle once i can get back into the uni labs tomorrow.

Is it a general rule that the flow inlet diameter must be larger than the flow outlet diameter (nozzle)?

Or if it was proportional would that still be okay? For example if I had a 10mm diameter inlet and a 10mm diameter outlet

I am no expert, but as I understand it, any reduction in the size of the exit nozzle compared to the inlet flow pipe size will cause the amount of water flowing to reduce but at the same time increase the pressure making the water go a further distance, for example if you had the open end of the inlet pipe in your hand and covered part of it with your finger the water will go further but the amount of water flowing will reduce.

Hope this helps
Paul

Looking at your pics, your inlet is definitely too small for much more flow. Small tubes restrict flow and cause back pressure that many pumps are not made to handle. A good rule of thumb is always to oversize your inlet and to some degree your pump and then restrict the flow via the pumps own mechanisms. A laminar stream can carry a LOT of water since there is not air spacing in the middle taking up volume.

What is the flow rating of your pump?