olddragger

iTrader: (3)

I know a lot of you have read about Ford experimenting with substituting lasers for conventional sparkplugs. I got to thinking about/if this would be of benefit on a rotary engine. Course the first thing I thought of was how the spark could actually be placed "IN" the comcustion chamber instead of on the edge/recessed as it now is. That would be an advantage. But, then I got to thinking more:
with lasers the leading sparkplug HOLE would not be needed---thats a biggee!
With laser--heat ranges would not exist --so FI spark would be a non issue etc.
With lasers there is nothing to collect deposits
With lasers there is more of a complete burn (because spark placement is optimal)
with lasers --you would never have to replace a sparkplug
with lasers there would be more laternal room available in the engine compartment
with lasers a feedback system would be available in real time so a more precise a/f ratio could be dialed in? this is important from rotor to rotor, face to face monitoring.
And you could disconnect one and drive your dog/cat crazy while they try to catch the dot
Hmmmmm---food for thought

Spinning Sushi

iTrader: (21)

Nah, I doubt that it's practical to play with your dog/cat with it... maybe you burn a hole through them though.

reddozen

iTrader: (1)

with ford developing it, there's potential for mazda to use it.

JinDesu

iTrader: (2)

I'd imagine it's a short range pulse laser, so you're not gonna do much to your cat/dogs =p

Spinning Sushi

iTrader: (21)

^ Damn, where's the fun in that?

dillsrotary

With lasers you can choose where to ignite instead of a fixed position that is "optimal", plus you can control the power going into the pulse.

There will still be deposits, only way to remove them is to change your fuel.

rxat2012

iTrader: (1)

i dunno about all that... our spark plugs are expensive enough..... can you imagine haveing to pay to replace a laser........ F$$K that... im pretty sure the stealership will love them tho.. lol

JinDesu

iTrader: (2)

I think he meant the deposits on the plugs. By having the ignition point away from the plug, the majority of the deposits will be generated at the spark point, not on the plug.

Yeah, but I can't imagine you needing to replace a laser plug unless something seriously went wrong lol

rafaga

iTrader: (1)

How would we de-flood the engine without spark plug holes ?? lol

Gripen

iTrader: (2)

Regarding deposits as dillsrotary brought up, how would you keep the laser emitter's optics clean unless you were required to periodically remove the emitter for cleaning? even if the combustion was very clean, over time there would be some sort of buildup.

I would imagine this technology would be great for a hydrogen-fueled engine as the only emission would pretty much be water.

ZeroHP

I've done a lot of research into this topic for some time now. Laser ignition would be easier to implement in a rotary than a piston engine. The placement options for a laser window are far greater than for a spark plug.

In a rotary, you could easily place it around the 1:30 to 2 o' clock position, and because of the beam focusing characteristics of the optical window, have the actual ignition take place wherever you wanted along a line of sight from the window, where the beam is most focused. By the time the flamefront would reach the window, the apex seal has traversed it, preventing the flame from getting to it. Just one example of many.

Ford, by the way, is pursuing this for emissions purposes, not fuel economy or power, which are both very possible with laser ignition, but not likely with the Ford system. Different requirements and all.

jasonrxeight

you can adjust timing on a sparkplug system too, its called variable timing.
even distributer cap age had variable timing.

elysium19

iTrader: (1)

That is really REALLY cool. I think everyone needs to re read that to understand exactly what he's describing....

I have a feeling this is still too expensive/impractical/etc to actually work anytime soon ( < 5-10 years) but it's still sounds pretty slick!

elysium19

iTrader: (1)

I think you're missing the point - in theory you could not only decide WHEN in the cycle the ignition occurs (as with conventional technology), but WHERE as well. The ignition could start (and propagate from) a site in the center of the chamber many inches AWAY FROM the laser. The same way that one could pass your finger in front of a surgical laser without harm if it is not near the focal point.

NotAPreppie

Two main problems that I see.
The light photons have to be emitted from somewhere. Whatever this aperture is it is likely to get fouled with carbon unless we are talking about a several-watt (or hundreds or thousands of watts) laser.

Most lasers powerful enough to ignite even volatile substances are fairly fragile, especially the DPSS variety. I've had several 5-20 mW 532nm lasers (green, all DPSS) fail on me despite extremely careful handling and usage.

Also, what does this even mean?
Are you talking about propagation delay? I'm guessing that the delay of a charge through the coil, wire and plug isn't going to be any better or worse than that of laser.

heyarnold69

iTrader: (1)

I think this could work .. however there are several factors to consider ... I think the only true way would be to use a trinary beam to not only control the power, but also the exact position of the ignition point. There is also a heat issue .. perhaps basalt crystals may work .. most likely a synthetic crystal would have to be used.

I agree -- most likely a fuel change would be required .. I think diesel may be a choice.

I have to say ... this isn't a new concept.. few patents are help by the Russian version of bnl .. however there are several doe projects that are looking into several alternative uses for laser tech.

ZeroHP

This is why the Ford system won't revolutionize ignition systems. Still based on the age old idea of shoving energy into fuel, making it pyrolize to facilitate combustion.

There are better alternatives for laser ignition, but no prototypes currently exist. By far the most interesting to me is the selective excitation of triplet oxygen to produce singlet oxygen. Instant (and nearly instantaneous) complete combustion without pyrolysis of fuel. I wish Ford et al would have gone that route.

olddragger

iTrader: (3)

excellant thoughts all.
The laser "lens" if you would, have been found to be self cleaning--so no carbon accumilation issues.
Flame propergation would/could be greatly influenced and thermal efficentcy would increase.
A 3 point laser ingnition system(think 3 sparkplugs per rotor) could possibily make the engine carb complience without a cat and could substancially increase gas milage.
Its a shame tech is available or soon will be, but it will not be used since the present tech has not been max capitilized.
Would you believe I saw home lcd tv's in the mid 90's.?

heyarnold69

iTrader: (1)

Perhaps an after market conversion kit could be developed.

Voltage wise .. I'm pretty sure only 1.2 amps would be needed for a laser based ign system. what is the current amp draw ... that combined with an led conversion would drastically cut the power/ amperage requirement. Also -- No more ... igniter, coils, plugs, wires, etc ...


technically speaking the light could be transmitted by some special single mode fiber lines and the unit could be removed in order to be maintenance .. if needed ... easily.

NotAPreppie

This is sort of a fallacy.
You'll still have a laser module to emit the beam. The laser module WILL fail so it'll have to be separate from the block/head/whatever. The laser will still need to be near the combustion chamber unless you want to trust some greaseball Jiffy Lube tech with glass fiber optical cable (plastic is unlikely to be good enough for high-powered applications like this).

If you want multiple lasers per combustion chamber then you'll either need multiple modules or a higher-output module with a prism (or similar optics) to split the beam. Either way, you're looking at increasing costs due to more parts or more powerful parts.

I'm skeptical about how the aperture that the photons pass through could be self-cleaning well enough to not attenuate the beam significantly after 10k miles of use. If it doesn't get cleaned well enough then the aperture itself could be damaged by the superheated carbon (the energy that doesn't make it through the dirt will go into heating up the dirt).

ZeroHP

All correct suppositions, NotAPreppie. Laser modules are also physically larger than ignition coils and drivers, and also require cooling. Their service life is very dependent upon service conditions. Hot engine bays are a harsh environment for a power laser. It is not a perfect solution, but the rewards are immense.

As for laser delivery, I personally would use a terminal junction very similar to a spark plug, with the optical window at its tip. This way the entry angle can be standardized, and designed to be adjustable if necessary.

Dirty window after 10k miles? Remove your laser plugs and clean them; then reinstall and adjust if necessary. Sounds easy? It probably would be. Sounds easy to design? Very likely wouldn't be. Just an idea, though.

The waste heat of the laser, like any other heat generating energy converting system, is dependent upon total power flux, and total energy conversion efficiency. You're not too likely to see any new major revolutions in laser efficiency soon; and if we do, the aerospace guys will keep it for themselves for some years. Lowering the waste heat is only (realistically) possible by reducing the power flux (reducing the power output of the laser).

The good news is that this is a very viable solution, as the laser only facilitates combustion by supplying activation energy for a chemical reaction (just like a spark plug). Where it can differ from spark plugs is in the choice of the reaction. Modern ignition operates on the mechanism of introducing an immensely high temperature in a small volume. The fuel in this volume, being hydrocarbons, pyrolyzes into much simpler smaller hydrocarbon and hydrogen radicals, which combine with the available oxygen to initiate combustion. At this point you have ignition. From this point on, combustion is facilitated by propagation of a flamefront, or a wave of high temperature sufficient to ignite the material next to it via the same mechanism.

How could laser ignition change this? By changing the mechanism of ignition from pyrolysis of fuel and dumping heat into the mix to raise its temp to selectively (or nonselevtively, who cares I guess) changing oxygen from its normal triplet state to its extremely reactive singlet state by selectively exciting a miniscule quantity of special dye added to the fuel. The laser-excited dye reacts with tO2 to form sO2, and combustion is facilitated by contact of the O2 with fuel (via hydrogen abstraction).

It is *much* faster, much lower power, has the potential to be able to ignite up to the whole chamber simultaneously, and the quantity of dye required is barely measurable, and it burns during the combustion, as it is just a hydrocarbon. Sure, it would need to be blended in the fuel, and people could whine about that, but additives in gasoline, while contributing only around ~2-12% of the mass, account for over 50% of the chemical makeup. There are sometimes dozens of additives in gasoline blends. What's one more?

I hope Ford does well with their system, and hopefully it is just a prelude to something even better. I just fear it won't be.

ZeroHP

Also, forgot to mention that the single greatest benefit to this system is the ability to completely decouple the relationship of AFR and load. Let me explain, as this is very exciting.

In modern engines, the need to facilitate combustion with a flamefront necessitates staying within defined AFRs that accomplish this. Because of this one small fact, load is invariably tied to AFR. If we want to burn less fuel, we must admit less air to the cycle to maintain proper AFR. This problem creates many of the *major* efficiency problems we face today. Doing away with it does away with them as well.

With laser ignition, you open the possibility of combusting obscenely lean ratios of, oh I don't know, 100,000:1 or whatever ridiculous number you want. Basically you could inject such a small quantity of fuel as to be unreliably metered with tiny injectors, and then ensure it combusted. You wouldn't release much energy, but this is an extreme.

This already eliminates the need for air throttling, reducing pumping losses, a la diesel. But it goes so much further. With super lean ratios, the total heat energy released is the same as with richer ratios to stoic because it is based on the fuel combusted, but the temperature drops rapidly. In fact, this is one of the two reasons lean ratios won't facilitate combustion: the temperature of reaction falls below a critical point, and the chain reaction cannot be maintained.

Because the same heat energy is dispersed amongst more working fluid, the temperature of the working fluid is correspondingly lower. PV=nRT right? Heat transfer to the cooling medium is mediated by convection assisted conduction, with radiation heating making up a small fraction due to the time available at the proper intensity. Simplified conductive heat transfer is a function of temperature gradient and thermal resistance of the pathway. By dramatically reducing the temperature gradient, we correspondingly reduce the heat transfer to the cooling medium, instead retaining it in the working fluid.

Laser ignition could be the engine technology that turns the tables on efficiency, but only if it is done right.

NotAPreppie

That's an interesting idea. Use a substance that is reactive to certain wavelengths of light (like dental cement and UV light). This would definitely reduce the power requirement of the laser itself. With lower power requirements, you could easily use lower cost light transmission material (more durable plastic fiber optics) and move the laser module(s) to a location that is more hospitable.

Hell, if we are just talking about certain wavelengths, you don't even need a laser. If you can get manufacturing process that can reliably produce a 5W LED within a very narrow and specific wavelength then that can be used for light generation (probably already can). I wonder if the on/off cycle of LED technology is rapid enough for use as an ignition source. The spark pulse of a Renesis at redline would be what? 50hz?

ZeroHP

All your ideas would work because this isn't theory, this is how singlet oxygen is made in a laboratory all the time. Lasers just provide a good delivery medium; better than noncoherent dispersed light.

The dyes don't need to be discovered/designed/experimented with, as they have existed for decades.

As far as I know, most of the dyes are not sensitive to a particular wavelength, but a decent narrow-to-medium spectrum such that often times a full spectrum flash lamp is used in labs. But lasers are far neater, aren't they?

Nubo

9000/60 = 150Hz, on a per-chamber basis. 300Hz if you want the same source to energize both chambers. This is assuming the need for "trailing" ignition is eliminated.