As the internal-combustion engine has received more and more improvements in the past two decades—and more are coming—from direct injection and variable valve timing to advanced turbocharging and stop-start systems, one engine feature has remained the same: the spark plug. Every gas-fed engine uses them, but their design hasn’t varied much since the internal-combustion engine first hit the scene. But in the quest for greater fuel efficiency and output maximization, the status quo simply won’t do. And that’s why Federal-Mogul, Champion’s parent company, is working on a new type of ignition device that uses controlled ionization to ignite the fuel mixture.
It sounds fancy, but the basic thrust behind the idea is fairly simple: Conventional spark plugs create a single, tiny (about 1 mm) arc of electricity for a fixed duration. That single arc leaves a lot of room in the combustion chamber without adequate ignition, and the arc’s controllability is fairly binary—it’s either on or off. Federal-Mogul’s Advanced Corona Ignition System (ACIS) promises more controllability with potentially variable power output, ignition duration, and ignition area. The “Corona” portion of the name refers to the web of ion streams (plasma) the system produces in the combustion chamber; the word means “crown” in Latin. Federal-Mogul says the streams can stretch up to 25 mm in length, vastly longer than a spark plug’s arc, and there are multiple streams.
ACIS ignitor tip vs. traditional spark plug.
The hardware consists of a two-piece igniter that fits in roughly the same area and mounting location as a traditional spark plug. An inductor sits above a four-electrode firing tip, which emits an electric field that “excites” the air/fuel mixture in the combustion chamber until it creates a plasma (charged ions). As a technical paper released by Fedral Mogul states, “when the electron density reaches a sufficient level, multiple long streams of ionized gas extend into the combustion chamber and ignite the charge.” Just as direct injection has enabled the more-controlled distribution of the fuel mixture to the combustion chamber, Advanced Corona Ignition could bring a similar level of precision to the ignition of the fuel mixture. Ignition could be varied and optimized for different fuel mixtures, and the added precision, combined with the increased ignition area, theoretically could take better advantage of the increased levels of fuel vaporization afforded by direct injection, leading to a more thorough and powerful combustion.
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Federal-Mogul also claims its system’s enhanced level of control makes it HCCI-compatible (that’s Homogeneous Charge Compression Ignition). HCCI engines can operate similar to a spark-ignited gas engine under high load or as a compression-ignition mill for lighter-load scenarios; the key difference between HCCI motors and diesels is the fuel and air are mixed before being injected into the combustion chamber. Presumably, Advanced Corona Ignition could ensure a more-thorough burn of this fuel mixture when the HCCI engine is operating with electronic ignition, as well as a smoother transition between that mode and compression ignition.
The company estimates the technology could return a fuel-economy boost and CO2 emissions reduction of greater than 10 percent when employed as a “screw-in” option. If ACIS is fully adapted—meaning the engine and its computer are tuned to work with the system—Federal Mogul says efficiency could increase 30 percent. A big caveat is that the plugs need their own computer, but either way, automaker adoption of the new plug design would require equally new development and tuning work. That’s a big commitment, and the tech’s long-term durability and effectiveness is essentially unproven. Cost is another issue, given the plugs’ added complexity, but Federal Mogul’s researchers claim the ignitor’s low current and heat discharge, electrical erosion isn’t a problem and the plugs could be “developed to serve as a lifetime component.” Ever-tightening fuel-economy regulations don’t look like they’ll get any less “ever-tightening” anytime soon, however, so don’t count ACIS out yet.
Source: CarAndDriver
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