Love the systematic approach here. The insight about using a bundle of straws to prevent coalescence is elegent, and the self-recovery mechanism with holes is really clever for handling overflow states. I've ben tinkering with low-energy water systems at a small scale and the tension between efficiency and maintenace-free operation is exactly the tradeoff nobody talks about. That manifold design for controlled bubble nucleation could probably apply way beyond just pumps.
No mechanism to entrain air bubbles is needed in the trompe. What actually happens in a 4 inch or 6 inch diameter pulser pump is that the water has a half meter or more of free fall. What does it do in a half meter? It accelerates. But water is incompressible, if water is moving faster in the pipe than the water that is going to the pipe, there is extra space, and that space is taken up by air. Eventually you can get a more or less steady state, where the water finds its speed and air bubbles are leaving at the bottom at about the same rate as they are being replaced by air coming in at the top. The straws idea might work. I have suggested it too, the issue is, how do you direct the right amount of air to each straw? In real life, when I had 2 airlift pumps working from the one trompe (with the airlift part and the trompe part separated), I had to have a tiny bead in the line before each one. (Otherwise, the tendency was for most of the air to go to whichever airlift pump was slightly lower). I use tiny airlift pumps connected to an aquarium air pump to water my garden. I usually have about 10 connected to the pump. You need a little adjustable air tap before each airlift pump, otherwise, all the air will go to the airlift pump with the lowest submergence, you tweak them all at the start, to get everything going, and then all should be good. (Taps are like variable resistors in an electrical circuit). Another thing to note is you do NOT want a whirlpool going into the trompe. Any time I had one, there was less air going down. What I did with my last trompe the 6 inch diameter one, was I got about a 6 inch long piece of pipe, cut it in half and screwed them together so they are like 2 C's back to back, then I put them over top of the pipe, and cut 4 notches in them so that the sat at the right heigh on the pipe. Then I put a plastic can over top. I had a hole in the top of the can to let in air. No more whirlpool with that. I think I had a 1/2 inch pipe going down to the entrance to the 6 inch pipe, but I don't remember. The 6 inch trompe was too big for the stream. It needed 500 or 600 liters per minute, but the stream usually topped out at about 350 liters per minute. This worked well for a 4 inch trompe. My stream had 45 to 55 cm of head. Thanks for being interested. People need to make trompes with 10 cm, 15 cm, and 20 cm and 4 inch 6 inch and 8 in diameter pipes. Trompes with half meter head, 3/4 meter, and 1 meter head, and going down 1, 1.5, 2 and 2.5 meters below the exit water level. That will finally tell people how efficient they are. I tried to guide students doing experiments with small models. They tend to be willful. One left out the taps, because he didn't understand the "why" and he got really low efficiency as a result. It was very annoying because the results were posted. My results for compressing air, with a half meter head and going to 2.5 meters down, was around and just over the 30% efficiency rate, while pumping water to 3.5 or 4 meters was about 6% efficient. And the thing that matters is cost, not efficiency. Think about it, the stream I used could have a half meter head pulser pump every 50 meters, so in 200 meters of stream length, you can have 5 pulser pumps pumping 4 liters of water per minute to 3.5 meters. That's 20 liters per minute gone from your 350 liter per minute stream flow in a very short distance. (or a whole lot more if you are pumping to 2 meters high). Much airlift pump calculations and experiments have been done, but very little work has been done on low pressure trompes. That is the part that needs experiments. It beats me why no plastic pipe company has done this work. They could sell a lot of pipes and a lot of fittings, if people started using pulser pumps. My greenhouses and some of my garden planters use circulating water, and this is supplied by a little aquarium air pump. But if I lived near a small river or a stream, I could easily supply way more than enough air with a pulser pump. A one meter deep trompe would be enough to supply my type of airlift pumps in a garden. I hope that helps, Brian
Love the systematic approach here. The insight about using a bundle of straws to prevent coalescence is elegent, and the self-recovery mechanism with holes is really clever for handling overflow states. I've ben tinkering with low-energy water systems at a small scale and the tension between efficiency and maintenace-free operation is exactly the tradeoff nobody talks about. That manifold design for controlled bubble nucleation could probably apply way beyond just pumps.
Feel free to do any experimentation with these ideas you want. I claim no IP over them!
No mechanism to entrain air bubbles is needed in the trompe. What actually happens in a 4 inch or 6 inch diameter pulser pump is that the water has a half meter or more of free fall. What does it do in a half meter? It accelerates. But water is incompressible, if water is moving faster in the pipe than the water that is going to the pipe, there is extra space, and that space is taken up by air. Eventually you can get a more or less steady state, where the water finds its speed and air bubbles are leaving at the bottom at about the same rate as they are being replaced by air coming in at the top. The straws idea might work. I have suggested it too, the issue is, how do you direct the right amount of air to each straw? In real life, when I had 2 airlift pumps working from the one trompe (with the airlift part and the trompe part separated), I had to have a tiny bead in the line before each one. (Otherwise, the tendency was for most of the air to go to whichever airlift pump was slightly lower). I use tiny airlift pumps connected to an aquarium air pump to water my garden. I usually have about 10 connected to the pump. You need a little adjustable air tap before each airlift pump, otherwise, all the air will go to the airlift pump with the lowest submergence, you tweak them all at the start, to get everything going, and then all should be good. (Taps are like variable resistors in an electrical circuit). Another thing to note is you do NOT want a whirlpool going into the trompe. Any time I had one, there was less air going down. What I did with my last trompe the 6 inch diameter one, was I got about a 6 inch long piece of pipe, cut it in half and screwed them together so they are like 2 C's back to back, then I put them over top of the pipe, and cut 4 notches in them so that the sat at the right heigh on the pipe. Then I put a plastic can over top. I had a hole in the top of the can to let in air. No more whirlpool with that. I think I had a 1/2 inch pipe going down to the entrance to the 6 inch pipe, but I don't remember. The 6 inch trompe was too big for the stream. It needed 500 or 600 liters per minute, but the stream usually topped out at about 350 liters per minute. This worked well for a 4 inch trompe. My stream had 45 to 55 cm of head. Thanks for being interested. People need to make trompes with 10 cm, 15 cm, and 20 cm and 4 inch 6 inch and 8 in diameter pipes. Trompes with half meter head, 3/4 meter, and 1 meter head, and going down 1, 1.5, 2 and 2.5 meters below the exit water level. That will finally tell people how efficient they are. I tried to guide students doing experiments with small models. They tend to be willful. One left out the taps, because he didn't understand the "why" and he got really low efficiency as a result. It was very annoying because the results were posted. My results for compressing air, with a half meter head and going to 2.5 meters down, was around and just over the 30% efficiency rate, while pumping water to 3.5 or 4 meters was about 6% efficient. And the thing that matters is cost, not efficiency. Think about it, the stream I used could have a half meter head pulser pump every 50 meters, so in 200 meters of stream length, you can have 5 pulser pumps pumping 4 liters of water per minute to 3.5 meters. That's 20 liters per minute gone from your 350 liter per minute stream flow in a very short distance. (or a whole lot more if you are pumping to 2 meters high). Much airlift pump calculations and experiments have been done, but very little work has been done on low pressure trompes. That is the part that needs experiments. It beats me why no plastic pipe company has done this work. They could sell a lot of pipes and a lot of fittings, if people started using pulser pumps. My greenhouses and some of my garden planters use circulating water, and this is supplied by a little aquarium air pump. But if I lived near a small river or a stream, I could easily supply way more than enough air with a pulser pump. A one meter deep trompe would be enough to supply my type of airlift pumps in a garden. I hope that helps, Brian