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."

Keeping the emitter clean...

[dlingman]

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?

I drive a diesel

[MyNicknameSucks]

I drive a diesel, you insensitive clods.

But, seriously, diesels work on compression alone and don't need spark plugs.

Or...

[jensend]

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...

Re:I can't wait for the hacks

[rednip]

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.

From tfa:

The laser is not strong enough to light the leanest fuel mixtures with a single pulse. By using several 800-picosecond-long pulses, however, they can inject enough energy to ignite the mixture completely.

A commercial automotive engine will require 60 Hz (or pulse trains per second), Taira says. He has already tested the new dual-beam laser at 100 Hz. The team is also at work on a three-beam laser that will enable even faster and more uniform combustion.

Re:NASCAR? Not likely this century

[Trecares]

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.