Science questions not worth a thread I: I'm a moron!
- Thread starter The Imp
- Start date
- Status
Lohrenswald
世界的 bottom ranked physicist
That was kinda what I was thinking about. Like I would imagine a centre of mass for everything in existence would have been stationary. Though I do of course see this is a pretty iffy question, for the reasons uppi explained.
The centre of mass isn't an object, though, but a calculation based off the position of all objects, which have positions that can be measured relative to each other.
hobbsyoyo
Deity
- Joined
- Jul 13, 2012
- Messages
- 26,575
Lets say that you have a stream of hot gas and mixed in with this gas is some small portion of soot (carbon by-products from an upstream reaction process that happened in the gas). The presence of soot is detrimental to the system and I wish to find a way to remove it. I have an idea of using a centrifuge to push the solid soot particles to the outside walls of the centrifuge while allowing the gas (and only the gas) to flow through the middle of the centrifuge and on through more piping.
How might I go about calculating how fast the centrifuge needs to spin or what size it needs to be to remove a given amount of soot from the gas stream? Are there better ways to do this?
Thanks
How might I go about calculating how fast the centrifuge needs to spin or what size it needs to be to remove a given amount of soot from the gas stream? Are there better ways to do this?
Thanks
Your turbine cannot just be a rotating tube, it will need internal leaves. Once the soot hits a leaf, then centrifugal effects will take place.
And then it matters how much friction the leaf has towards the soot, and that will help determine how fast the leaves need to be moving in order to eject soot towards the perimeter.
And then it matters how much friction the leaf has towards the soot, and that will help determine how fast the leaves need to be moving in order to eject soot towards the perimeter.
hobbsyoyo
Deity
- Joined
- Jul 13, 2012
- Messages
- 26,575
By leaves, do you mean like baffles?
I had planned on including blades inside the centrifuge to use the stream of gas itself to spin it up. If I picked a material of sufficient friction for the blades would that work?
Where can I find equations that relate some of these things?
I had planned on including blades inside the centrifuge to use the stream of gas itself to spin it up. If I picked a material of sufficient friction for the blades would that work?
Where can I find equations that relate some of these things?
Is there a particular reason you cannot just use a filter?
I don't have resources hobbs. I'm sorry. Ostensibly, you will need a minimum level of centrifugal force exerted on the flakes.
It strikes me that this won't clog filters as quickly.
It strikes me that this won't clog filters as quickly.
I guess so, but at one point the centrifuge might also be full, and cleaning that might be much more difficult than changing a filter. I have no idea, what would be more efficient in the end.
But if he really wants a centrifuge:
Actually, I do not think friction is important here. The leafs can just make ballistic collisions with the soot particles. And if there would be too much friction, the soot would just stick to the leafs and not travel outwards.
What you want to know is the velocity distribution of the particles. There will always be particles that have just the right velocity vector to scatter into the exit. The faster your leafs move, the smaller that fraction of particles will be. I think what you want is that the relative velocity of your leafs is fast against the mean velocity of your particles. And that would make a centrifuge powered by the gas itself to be quite inefficient, because you would want your centrifuge to rotate against the direction of the gas flow.
Unfortunately, I do not think that is an easy problem to calculate, especially because the velocity distribution will likely be non-thermal.
hobbsyoyo
Deity
- Joined
- Jul 13, 2012
- Messages
- 26,575
Filters would clog and cause a pressure drop that would be unacceptable for the gas flow. But the centrifuge would likely cause the same problem if it was powered by the gas as well.
For this and other reasons, we've dropped the centrifuge idea. But I don't know how else to remove soot from the flow given the problem with filters.
Also, I wasn't able to find a lot of information on high speed centrifuge design. :-(
For this and other reasons, we've dropped the centrifuge idea. But I don't know how else to remove soot from the flow given the problem with filters.
Also, I wasn't able to find a lot of information on high speed centrifuge design. :-(
I know nothing about this, but it sounds a little like something else I heard of. I am sorry I cannot remember the context, but I think they gave the particulates a charge using an electron source and then used an electomagnet to attract them and pull them out of the main flow. I do not know if you could use something similar.
After thinking a bit more I may have been thinking about mass spectrometry, not a clearing technology. May well not be in the slightest bit relevant.
What's the velocity of your gas flow? And is there gravity, or are you in space? I'm thinking of some sort of trap, where the gas flows in and kind of circulates around, and the lightest part escapes through the top, the gas, and the soot settles to the bottom.
Do radio waves become corrupt in space? If some species on a different planet has broadcast radio programs, are we sure to recognize it when the waves reach us?
Well, removing soot from a gas sort of is mass spectroscopy, so your idea might work. The problem is getting all those particles charged. As far as I know, the bad efficiency of this kind of mass spectrometers is caused by inefficient ionization, as you cannot get high intensities with an electron beam because of Coulomb repulsion.
Anything that involves settling probably requires a reduction in pressure.
I can think of three effects that could be a problem:
1) Redshift: As space is expanding, the signal will be shifted to lower frequencies. A lower carrier frequency has less bandwidth, so a densely coded signal might lose information.
2) Attenuation: At large distances, any signal will decrease in intensity with one over the square of the distance. At interstellar distances, you would have to start out with a huge signal so that you can recover a tiny amount of it.
3) Dispersion: Although space is mostly empty, it still has some matter that amounts to a tiny amount of dispersion. If the signal travels long enough through a dispersive medium, it will lose information.
So no, a signal emitted by aliens is not guaranteed to be recognizable when it reaches us. How much a signal is degraded and by what effect is probably specific to the signal and the exact nature of the space in between, so I do not think there is a general answer.
Does attenuation happen even when there are no air particles in the way? If so, how?
The signal just spreads and covers a larger area. How much it spreads is governed by Maxwell's equations - there is not much you can do about that. So if you have an antenna of fixed size, you receive less signal. You could increase the signal again, by using a much larger antenna, so maybe attenuation is not the best word to describe the effect.
If you have additional attenuation by particles, the problem gets much worse: That scales exponentially with distance, so even a tiny amount of that attenuation will kill your signal quite soon.
- Status
