How to use electrode space optimally to increase force at fixed voltage and distance collector/wire

Triangular Lifter configuration has been used for a while now. With known advantages it has also some obvious problems. For example, there is a large unused space in the center of triangle. If we want to make Lifter electrode array as compact as possible, we should find a way to obtain maximal force from minimal area covered by lifter.

At the other hand, to reduce weight it would make sense to minimize amount of armature wich does not provide lift by itself, e.g. to have more electrodes at the same holder.

For example we have provided by our holder area S. How many lines of wire/collector can we squeeze into this area? The simplified "sqare-lifter" configuration for which below considerations is valid is shown below:

Answer is not quite obvious, because if you look at eqn. 1 for lifter force (parameter explanation is same as in above chapters)

Length L is related to width of collector simply as S/W. Therefore you can see that collector width W at one side decreases thrust linearly, but at the other side (in f_geo2) increases it in a more subtle way.

So which one is more important? To answer this I made calculations for fixed area S = 100mm x 100mm for different W ranging from 100 mm and down to 5 mm (which is about the limit after which corona-wires will be so near that corona onset voltage will start to deviate from Peek’s equation). Calculations are made for usual parameters of Lifter 1, except more popular lately distance d=70mm.

Here is the resulting thrust

This picture speaks for itself. We can get out of 100 square millimeters arrangement whooping thrust of 5 g, if we use wire-spacing 5 mm. The less, the better. But what about efficiency?

Efficiency is here:

Wonderful, it does not change with collector width, so we have all our thrust increase “for free”.

Conclusion and suggestions:

It makes all the sense to use mesh-like electrode arrangement which squeezes as much collector/corona wires together as possible.

- Corona wire is light, but collector is heavy, so we will reduce weight by reducing W.

- We reduce size of arrangement, so we need in average fewer armatures so all becomes lighter. In fact if we use mesh sheets for both corona and collector we might not need any armature at all! We will need something which keeps them from sticking together, a spacer. Something like that?

The whole electrode-arrangement would look like two nets with ultra-thin plastic caps in between. The whole thing is ultra-light and flexible. It only needs to be fixed by ropes at the corners. When electric field is applied, it will press both shits together by electrostatic attraction and structure will become rigid.

- We win thrust/area without sacrificing efficiency

What limits the squeezing:

- Minimum inter-wire distance required for corona formation (3-10mm)

- Collector area should have enough holes in so it will not pose too much aerodynamic resistance to outgoing air. So I would arrange it not as a wide plate but rather as a mesh made of rather thick conducting tubes (which might be soft for easy processing, like foil wrapped around a rope). They should be just thick enough to prevent corona formation on each one.

- Btw. same logic can be applied to AC/DC 3 electrode lifter, which hopefully will provide even more thrust/area.