Laser Ignition

jackssmirkingrevenge · Tue Apr 26, 2011 4:34 am

Interesting ideas, though it looks like it will be a while before they have practical spudgun application.

al-xg · Tue Apr 26, 2011 6:21 am

Wow that is weird, I was just thinking about that. I should be revising, so obviously my brain was trying to think of alternate methods of ignition...

CpTn_lAw · Tue Apr 26, 2011 6:29 am

al-xg wrote:Wow that is weird, I was just thinking about that. I should be revising, so obviously my brain was trying to think of alternate methods of ignition...

Haha !!

Also in Over-brain-boost right now lol Electromagnetics have this tendancy to make me sail in the worlds of unexplored high-energy plasma ignitions lol

@JSR , very nice find!

POLAND_SPUD · Tue Apr 26, 2011 7:19 am

hey what about laser sharks ?

Doctore · Tue Apr 26, 2011 10:41 am

How much they cost,and is it possible to modify a normal spark ignitor for a combustion or hybrid cannon???

saefroch · Tue Apr 26, 2011 11:41 am

What they're doing is really nothing too surprising... the article makes their efforts seem much more grand than they are. I can't be totally sure why they mention attaching two segments, but they're really just employing a standard infared Nd:YAG solid-state laser, which is the most commonly used solid-state gain medium by far. Almost every solid-state laser in existence uses a Nd:YAG gain medium. What I'd be far more interested in is how they're pumping the laser, and what electronics are being used to control the pumping to produce 800 picosecond pulses.

Skywalker · Tue Apr 26, 2011 11:54 am

Sounds to me like a diode-pumped system to me -- maybe with a Q-switch or a Pockell's cell to create the short pulse width. No way any flash-lamp system is going to survive in an automobile.

And I'm right: http://www.kigre.com/files/nd41.pdf. Looks like they might be heading away from Nd:YAG, though... interesting!

For my research this summer I'm going to be working with a multi-Joule, rapid pulsed Nd:YAG laser. That'd be a bit of overkill for igniting an ICE.

saefroch · Tue Apr 26, 2011 1:06 pm

Er:Glass is moving away from the classic Nd:YAG, yay! I've honestly never heard of the issues with the pumping band changing with temperature, which betrays my noobishness I'm afraid.

And there's the sapphire windows again... I'd like to see some Magnesium spinel windows in there, it has better optical properties (cubic structure) for mass production.

I wonder if there are any practical uses for the laser-ablation effect that occurs (other than the neat self-cleaning), or if it will interfere with engine lubrication...

Hotwired · Tue Apr 26, 2011 2:35 pm

Does this remind anyone else of the research into making tank guns more powerful by plasma ignition of the propellant for an improved burn.

The pulsed plugs referred to further to the bottom of the article seem pretty simple.

Normal spark plugs are just a couple of terminals but the variation seems to be one which has a little circuit for a briefer, hotter spark.

I'd speculate it charged a small HV capacitor with the energy being delivered from the ignition coil and only discharged that to the spark plug terminals once it reached X voltage.

Simplest thing about it is you can just use the spark gap already on the spark plug to switch the capacitor. Voltage rises high enough and it jumps across.

Fnord · Tue Apr 26, 2011 6:35 pm

If I remember correctly that small laser pistol that was posted on here displayed a similar useful effect. The guy at one point focused the beam tightly so as to heat the air in the focal region to candescence.

Such a system might have an advantage in a high mix hybrid. The system wouldn't even have to be inside the chamber, so long as the beam wavelength could pass easily through say, polycarbonate.

Hotwired · Tue Apr 26, 2011 7:07 pm

Thing is that bugger was pretty big and didn't seem to be remotely cheap.

These plugs are supposed to be spark plug size.

Technician1002 · Tue Apr 26, 2011 7:27 pm

Most high energy lasers focused in air do less heating to incandescence than a more simple ionization of the air due to the high flux. This ionization overcomes the bond of O2, in the air and bonds of the fuel hydrocarbons which recombine into an oxidized state. This initial reaction is exothermic and is the original ignition source.

This is what the focused spot of ionized air looks like.

saefroch · Tue Apr 26, 2011 8:48 pm

Hotwired wrote:Does this remind anyone else of the research into making tank guns more powerful by plasma ignition of the propellant for an improved burn.

That is actually mentioned in one of the articles linked in this thread.

Are you saying that the formation of O from O<sub>2</sub> is exothermic? I don't have my SRP right now to check, but I bet it's actually endothermic (which means the reverse reaction is exothermic). I think the glowing spot of ionized air is actually the nitrogen and oxygen fluorescing, you're seeing a composite emission spectrum of nitrogen and oxygen plasma.

If the Er:Glass lasers are mass-produced at near the price of Nd:YAG lasers, they should be cheap enough to be a viable upgrade.

Technician1002 · Tue Apr 26, 2011 9:28 pm

No. The resuting combination of the free Oxygen with the free components of the fuel is exothermic.

saefroch · Tue Apr 26, 2011 9:40 pm

Ahhhh. Of course that'd be correct. Ambiguous wording I guess...
Or not?

Laser Ignition

Donating Members