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Lasers To Replace Sparkplugs In Engines?
An anonymous reader writes "For more than 150 years, spark plugs have powered internal combustion engines. Automakers are now getting close to being able to replace this long-standing technology with laser igniters, which should enable cleaner, more efficient, and more economical vehicles. Price and size have been issues holding up such an advance, but a Japanese team is set to announce they've overcome those hurdles."
Seriously, just think of the potential hacking uses of a pencil sized high powered laser! Cutting and drilling through hardened steel. Remote ignition of fires or detonation of explosives. Actual blinding weapons in a flashlight case.
I'm afraid they'll be too cool to be let out in public.
John
Um - I've looked at spark plugs. They start out nice and shiny, but get gummed up rather quickly. Are the lasers going to need to be strong enough to burn through the carbon buildup as well as igniting diesel/gasoline?
It expands the distance from stoichiometric that you can go (on the lean side, at least) while still being able to get it to catch on fire correctly while having a good lifespan of your igniter.
So it's not that the laser "needs" leaner mixtures; it's saying they enable leaner mixtures than current (mass-market) spark plug technology. And for steady-state cruising, that could be a great way to cut down on NOx emissions. (Not sure if it will reduce fuel consumption.) Of course, I thought the catalytic converters were already digesting all the NOx, so, I'm not sure why this is super-awesome...
TFA talks about that.
The shape of the flame makes a difference in how well the fuel burns, and in how efficiently the piston transduces the pressure curve into mechanical motion. Same reason for differing piston and head shapes.
You don't really want fuel to explode, you want it to burn quickly and in the right shape. Apparently, starting the flamefront from a single point is not super-efficient even if you have control of the shape of the cylinder.
At least in part at "Japan’s National Institutes of Natural Sciences," according to a string of letters and spaces in TFA.
Catalytic converters are expensive and relatively heavy. Take them out and you get a cheaper, lighter car. Cheaper is always good, and lighter translates to better handling and better fuel economy. Probably nothing major, but every little bit helps.
'Sensible' is a curse word.
According to the article, one of the main reasons spark plugs get gummed up is the electrical sparks they are putting out. Electric arcs tend to corrode their endpoints. With a laser, this isn't a problem. Also, the lasers aren't going to try to ignite combustion right in front of them: It's more efficient to ignite it away from them, in the center of the cylinder. Spark plugs can't do that at all.
Plus, of course, any laser capable of igniting a fuel-air mixture reliably in a few nanoseconds can burn through a bit of soot on the way.
If the air fuel mixture is correct, the plugs on a healthy engine won't get gummed at all. If it is too rich or burning oil, it won't matter where the plug or spark originates as the build up occurs everywhere in the combustion chamber (although the rings scrape the wall clean). One only has to pull the heads off an engine to look at the carbon buildup that is no where near the spark gap.
But the article talks about it being cheaper (okay, more economical). Sparkplugs cost around $3 to $6 each. It seems that a laser strong enough to get through the carbon build up is going to cost more than that. Since plugs now last well over 36,000 miles in new vehicles, it seems trying to improve on an inexpensive technology with a high tech solution is anything but economical.
you could just go diesel and skip this business entirely. More than half of the vehicles sold in Europe are diesel; it just makes more sense fuel-economy wise. We need to get with the program on this side of the pond.
I'm still waiting for my VW XL1...
I bought a diesel. My 2001 VW Jetta TDI gets about 45mph highway. No spark plugs, no lasers, no problem. *shrug*
Shark injectors, obviously.
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Cutting and drilling through hardened steel.
Doubtful for a laser designed for use *inside* an engine. :-)
The reason why this is so novel is not the power of the laser, but it's size, timing and durability. It'll be interesting to see if NASCAR allows it, as efficiency is a big part of winning that closely regulated league.
Ummm... The mass-market car manufacturers abandoned carburetors for fuel injection back in 1987, yet NASCAR is still just thinking about using fuel injection maybe in 2012.
I think you can safely forget about laser ignition systems in NASCAR for a good long time after they're available in regular production cars. While NASCAR cars have been refined over the decades, they are still not using very much technology that would have been unfamiliar to a regular car mechanic in the late 1970s.
Now, if you'd said Formula 1, then that would make sense.
Putting moderation advice in your
One of the benefits and drawbacks of running lean is the mixture burns hotter. This produces more NOx, not less. I'm not sure what the article is going on about.
Believe it or not, carburetors are better at atomizing the fuel mixture at full throttle conditions compared to injectors.
Since airflow through a engine at wide open throttle is fairly well known, and easy to meter for, the carb can be adjusted to precisely match that and get the desired air-fuel ratios.
Injectors can have trouble delivering large quantities of fuel at wide open throttle. When the duty cycle of the injector exceeds about 85-90%, it starts to have problems metering fuel correctly, and the coil starts to overheat. So the typical solution is to drop in larger injectors so a shorter duty cycle can be used.
The other part of the issue with injectors is the short amount of time they have to deliver and atomize the fuel. The fuel is sprayed against the closed intake valves moments before the intake valves opens. The heat from the valves helps to vaporize the fuel. Since there's only so much heat, and only so much air in the intake port, not all of the fuel may be completely vaporized. The incoming air then has only a bit of time to attempt and vaporize what is left before the valves closes and combustion occurs.
So why do we use fuel injectors? Because they excel at the thing carbs suck at, part throttle atomization. Injectors can easily meter out a precise amount of fuel determined by the amount of air entering the engine according to it's sensors. A carb has to deal with what it sees across the venturi which isn't as sensitive at part throttle conditions. Toss in the complicated dynamics of the air inside the plenum and it's hard for carbs to precisely meter out fuel.
It may just about be possible for racing, but normal owners would not want to have to readjust the carburetor every time the barometric pressure or temperature changed. And then you have the little problem that a carb will always change the mixture slightly when cornering. It is just not possible to adjust automatically for lateral, rotational and acceleration forces on a pot of gasoline which is being used as the input to a metered jet. Anybody familiar with racing carbs knows that they are a complete pain to set up and keep adjusted.
Your second point is nonsense. You're just saying "The injector has to be the correct size for the application".
Third, this is a gross oversimplification. You do not want the fuel completely vaporised. That will cause explosion. Enough fuel has to be vaporised for the ignition to work, but otherwise it has to be atomised - i.e. present as very small droplets - which can then burn at a controlled rate, preventing uncontrollable pressure rise with the risk of gaskets blowing and bearings failing. This problem is common to carburetors and injectors alike. (Diesels do not need any vaporisation at all because they do not have spark ignition.)
Only your last paragraph is correct. Injectors can do a better job, not only of metering fuel, but also of timing it, stratifying the charge, and ensuring that the mixture around the plugs is ignitable. A carb is basically a crude analog solution to a complex fluidics problem. (Incidentally you contradict yourself - you correctly refer to "atomisation" in that para, whereas you refer to "vaporized" above.)
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