Making A Better Pulser Pump

Some engineering flights of fancy

This video caught my fancy so here are my thoughts on improving the design. There seems to be a lot of things which can be done which should make big improvements but consider everything in this post speculative spitballing. Anyone who wants to improve on this mechanism is free to try my ideas.

Technically it’s a bit wrong to say this mechanism has ‘no moving parts’. It does have moving parts, they’re just air bubbles which are being captured on the fly and hence aren’t subject to wear. The problem is that air bubbles don’t like behaving.

Starting with where the water comes in:

The mechanism in the above video is cheating a bit because the pump getting the water into the top is aerating it. A proper mechanism should have a way of getting air into the water when it’s coming in slowly and steadily. In particular it should have a mechanism for being able to recover if the mechanism as a whole ever gets overflowed so it isn’t stuck with no bubbles in it forever. The simplest mechanism for this is to have a section of the pipe going down which has holes in the sides. As long as water is flowing fast it will pull air bubbles in through the holes. If it gets backlogged water will escape through the holes and can be directed to the exit, making room for air to be let in. The ideal size and spacing of the holes is unclear. If the mechanism were big enough it would probably improve things a lot to split across multiple pipes which have air intake holes to pull more bubbles in. It might also be a good idea to make a whirlpool and stick a pipe in the middle to help the air go down but that gets complicated.

Once bubbles are captured the downward pipe should be split into a bundle of straws to keep the bubbles from coalescing and forcing their way upwards. The ideal diameter of the straws is probably somewhat dependent on their length but should be small enough that surface tension makes water form plugs. The length of the downward pipe in the above model seems to be way too long. It appears to be that this is being done to make the pulsing effect happen but there’s a better way of doing that which I’ll get to.

The intake for the air bubbles should come from the bottom of the chamber where the pumping upwards happens. That should lead upwards to a manifold which is a short pipe with a horizontal cap at the top with holes in it, all kept under water. Air will then build up in the pipe and result in a steady stream of bubbles coming out of the holes. The size and depth of the holes as well as the material they’re made out of and the width of the pipe relative to the rate of air coming in all affect the nucleation of bubbles. What should happen is that bubbles of a reasonably consistent size come up at a reasonably consistent rate in a nice steady stream instead of the chaos you see above. There’s probably a range of possible sizes and rates of bubbles which are possible and that needs to be studied.

Instead of a single pipe going upwards there should be a bundle of straws. The bottoms of the straws should splay out and have tapered inlets with a one to one correlation with the holes in the manifold so the bubbles from that hole go directly into that straw and push the water upwards. The ideal number and diameter of the straws is very dependent on how far the water is being pumped, how quickly the air is coming in, and what they’re made out of. They should be thin enough that surface tension causes water in them to form a plug and makes bubbles force the water upwards. The idea is to make the water flow up slowly and steadily, with the upwards force of the bubbles just barely able to force it to the height it’s being pumped to, without wasting any energy on the momentum from those pulses. Maybe this shift in emphasis makes the whole thing technically a different mechanism.

At the top the straws should flare away from each other so the water going out of one straw doesn’t fall into its neighbors.

Hopefully these changes can improve the efficiency of the system from awful to merely bad. You’d still only use it when you care less about efficiency than low maintenance or quiet or specifically want aeration. Using all those straws will reduce how well it works on water containing particulates.