Lasers to replace spark plugs in gasoline engines | Hacker News Reader

Lasers to replace spark plugs in gasoline engines

scienceblog.com

93 pointsiwwr43 comments

Wow - 9x11mm YAG laser as a spark plug to reduce emissions and increase performance - sounds cool, but I can't help but think that this is like building a carbon fiber stagecoach: cool improvement to what should be a dying technology. We can't produce a damn fuel cell cheaply, but mini YAG lasers are possible? What are you doing science?!?

Until we have electric aircraft this sounds like a very good idea

I agree, but on the other hand, it sure seems like low-hanging fruit. If this could be applied to nearly all existing combustion engines simply by changing out a sparkplug, then it might not require all of us to go out and buy a new car just to meet emissions guidlines or achieve much better mileage.

Whether the car companies like the idea is a whole other question.

Yea, I'm all for low hanging fruit, but I would've thought fuel cells using diesel (which exist now) could've been made cheaply and using existing infrastructure.

Yeah, I have always been very excited about fuel cells -- in fact I still think they could fundamentally change our notion of how energy is harvested and transferred.

As for the original article, I think I must be stuck in my midwestern mindset. Living near Kansas City (which I consider something of an homage to suburban sprawl) I have a hard time believing that people will adopt new notions of energy conversion and distribution (like fuel cells) as opposed to throwing a couple new-fangled spark plugs in their SUVs.

Or just engines using diesel, which have existed for quite some time now, and don't use sparkplugs either.

Combustion engines have over 100 years of wast R&D and real world usage behind them. We already have the infrastructure to move their fuel all over the world in wast quantities.

This means I would not be surprised if we start using solar, wind, and nuclear power to generate gasoline, and most future cars become very clean running gasoline/electric hybrids.

From Wikipedia (http://en.wikipedia.org/wiki/Hydrogen_economy): Liquefied hydrogen has lower energy density by volume than gasoline by approximately a factor of four, because of the low density of liquid hydrogen — there is actually more hydrogen in a liter of gasoline (116 grams) than there is in a liter of pure liquid hydrogen (71 grams).

They aren't sexy and few people talk about them, but if you do an engineering and economic analysis, some form of carbon-neutral liquid fuel is still very much on the table as a reasonably long-term energy transport solution. The characteristics of liquid hydrocarbon fuel are pretty good in most ways, which is why we still use them. For instance, have you ever worked the math on the amount of energy being moved when you pump ten gallons of gas in one minute and converted that back to Watts? There isn't an immediately obvious replacement for them that actually works as well. If the problems of the particular way we obtain them can be solved, then it's worth it to continue to figure out how to use them more efficiently.

And while 20 years ago you might have thought it would "just be easier" to switch away entirely to something like electric vehicles, research on that front has not proceeded as satisfactorily as would have been nice (batteries, oh batteries, why can't you just be an order of magnitude better?), and "fix the problems that liquid hydrocarbons have" has started to look less like a stupid idea.

Actually, I said fuel cell because of these reasons. H2 isn't nearly as energy dense as diesel. We've already had fuel cells that use diesel for a while:

Penn State Develops Fuel Cell for Diesel (2001):

http://www.sciencedaily.com/releases/2001/09/010905072008.ht...

Fuel cells don't seem to have quite gotten to practical yet, and large-scale usage last I knew is still problematic due to requiring more rare-earth metals than we actually have access to on planet Earth. Like pure electric, they seem stuck on "frustratingly close".

Even worse is that you need a continuing supply of them because of "poisoning" of the catalyst by contaminants in the fuel or oxidizer. Despite decades of research, they have reduced but not eliminated the problem. Also, if you use atmospheric oxygen as the oxidizer, it makes the problem worse since it is even harder to reduce its contaminants.

Someone familiar with the technology claimed to me, that in 5 years the super-capacitor batteries will be in widespread production and their prices will start dropping.

(I have no way to evaluate the accuracy of his prediction.)

What about changing out the whole battery? (You no more own a battery but you rent one from the gas station.) The infrastructure is hard to build, it's not easy to standardize in a future proof way (The same battery or at least very few different models of battery have to fit every car and they should be replaceable within minutes in some automatable way.) but I still think that the idea is very appealing.

From what I can see, it might be practical if the infrastructure already existed. The question is how we get from here to there. And it's not just the stations themselves, but the question of how we get that much electricity in there. But it at least might work; electrical recharging stations that people try to use seem impossible to me.

I suppose I should show the math, so someone could correct me if it's off. This source [1] puts the number of Joules in a gallon of gas at 130,000,000. Let's take a slow gas pump and assume five gallons in a minute. That's 4.3 megawatts [2]. For one car at a time. You can fiddle with that number if you're willing to be brutal on how far the electric car can travel or if you think people will stop every 50 miles for a 30 minute electricity topup, but no matter how you slice it you're going to need a major electrical network upgrade. I think this is a good idea anyhow, but in a country that would rather buy bread and circuses than bridges I'm not sure how it's going to happen.

[1]: http://www.evworld.com/library/energy_numbers.pdf

[2]: http://www.google.com/search?q=(1.3*10**8)+joules+per+30+sec...

> What about changing out the whole battery? (You no more own a battery but you rent one from the gas station.)

People already steal copper wires and screw up our infrastructure that way. I honestly can't imagine a world in which greedy idiots don't screw everyone over given how expensive those batteries are and that makes me sad.

If you are doing it right I can see very few scenarios for screwing the system — not more than exist now when it comes to, say, manipulating the odometer.

Such systems must already allow you to keep the battery as long as you want and to use it as often as you want (for as long as you have a contract), they must allow you to charge yourself, otherwise they wouldn't make all that much sense. The idea is that you don't have to change batteries for daily commutes or short trips (you charge at night), only for longer trips. (This is something that works much better in densely populated countries with little sprawl — the US might not be a very good candidate. I think Israel is trying out such a system in some way, its smallness makes it ideal.)

It's like a flat rate, some drive little, some drive more, but just because the battery is rented doesn't mean that driving behavior will change all that much. There is only so much you can drive and charge.

I also think that it would be somewhat involved to sell the battery on the black market. You have to at least get a replacement battery before your contract is up, so where's the advantage in selling your old battery on the black market? You might be able to profit a little, but you would also need scale, you need know how (how to manipulate the data those batteries would no doubt be collecting) and you need to be able to hide from the police. Nothing unheard of, but also no show-stopper. (People already do this with odometers and hardly anyone cares.)

This is the exact approach that Better Place is using, starting in "island" economies. The idea being that most times you can just trickle-charge, but if you need distance, you stop by a battery station and it's swapped out robotically, in about the same time it takes to fill a gas tank.

Oh, man. Now I want to build a carbon fiber stagecoach.

I'll ride shotgun, er, taser.

We can produce a damn fuel cell cheaply.

We can't due to Duponts patents on PEM :(

If engines ran leaner — burnt more air and less fuel — they would produce significantly smaller NOx emissions.

This doesn't sound right to me. I'm pretty sure engines can run lambda>1 right now, and this gives better fuel economy, but it is not allowed due to emissions requirements. lambda>1 might give less inherent NOx, but lambda=1 is required for catalytic converters to work and the decrease in NOx from higher lambda is not enough to outweigh the loss of the catalytic converter.

It's all fine and dandy till a speck of soot blocks the optics, and the engine dies.

A better solution (IMHO) would be to have multiple spark plugs.

You should file a patent. I'm sure the automotive industry has not thought of using multiple spark plugs.

http://en.wikipedia.org/wiki/TwinSpark

Relatively common on motorcycles too (well, not exactly unheard of: my '86 Honda XLV750 has it, as do various recent Ducatis and BMWs.)

Yeah that seems like an obvious problem to anyone who's looked inside a combustion chamber. I wish they'd mentioned something about how they think this is not a problem.

It seems to me like that kind of concentrated power would be capable of vaporizing any small particles (or even turning them into plasma briefly) in the way.

Maybe, but they say that it's focused in the center of the chamber because that's where you want ignition to start. In that case, you might not have that high flux at the entry aperture (you might not want this for other material reasons, too). In any case, I don't think you want to start combustion at the edge because that's the least efficient place to do it.

Maybe the beam is wide enough before it is focused so that the soot wouldn't block enough of it to be a problem before the soot is blown out of the chamber.

... before the soot is blown out of the chamber.

You've never looked inside an old engine, have you?

No. But I only intended to address the point that if the beam is focused in the center then it would take more than a speck of soot to block the wider, lower flux, defocused beam where it enters the cylinder.

Carbon has a very high melting point, never mind boiling point. If you would heat it up that much you would melt the optical port.

However, you can simply heat the carbon (all that energy has to go somewhere). Once it's hot enough it can burn in the chamber - and it would probably be hot enough to ignite the fuel as well.

That said, I don't think soot is that common anyway. Normally you run lean which prevents soot. It does need to be able to self clean, but occasional poor efficiency from soot should not be common enough to hurt.

I was wondering about that too. Perhaps the laser is powerful enough to be "self-cleaning" and blast through the soot.

Depends on whether or not the soot is transparent on the part of the spectrum the laser operates at.

Soot is one of the blackest materials known. It absorbs light in a very wide range.

I had an eye operation using a YAG laser. Whatever is not transparent gets heated up and destroyed fast. The blacker the better.

An even better solution for efficiency is no spark plugs. http://en.wikipedia.org/wiki/Diesel_engine

Been done. Imagine my surprise when I went to tune up my 4-cyl nissan pickup and had to replace 8 plugs.

http://en.wikipedia.org/wiki/Nissan_Z_engine#Z24

On the plus side, the truck still runs clean (300,000 miles later) and gets great mileage.

To be fair, if your engine is running rich, soot will prevent spark plugs from being able to spark.

I possibly overlooked it, but I didn't see how much leaner the fuel mix could be for the same power output. Seems like a pretty important consideration.

I have to wonder how much further electric vehicles (battery technology in particular) would be if we half as much resources on EV that is spent trying to improve the internal combustion engine?

I wonder if its as much trying to improve internal combustion as someone made an advancement in lasers, and is applying it to a practical purpose?

I wonder how much worse our internal combustion engines would be if we'd spent half the money that we spent on improving them on batteries instead.

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