Bright sparks ignite new plug innovation

A NEW attempt to improve on the traditional spark-ignition method for petrol engines has been revealed in the shape of a high-intensity plasma burst – otherwise known as a corona – which utilises electrical energy in a more controlled way than is possible with a spark.

Michigan-based international automotive supplier Federal-Mogul is behind the technology, which it says has brought fuel efficiency gains of up to 10 per cent in testing compared with conventional spark plugs.

The Advanced Corona Ignition System (ACIS) – which was unveiled at the recent Frankfurt motor show – is claimed to produce a faster, larger ignition source that is spread throughout the combustion chamber, so a more thorough burn of the air-fuel mixture is possible, allowing engines to run leaner, with higher compression ratios and increased amounts of exhaust gas recirculation (EGR).

In addition, ignition timing can be more accurately managed to make the most of precise direct-injection fuel systems, while enabling a quicker burn that ensures more of the energy contained in fuel is converted to mechanical motion.



Left: Laser spark plug.

This also has the side benefit of potentially reducing engine cooling requirements – which can save weight, for example through the use of smaller radiators.

Federal-Mogul president and CEO Jose Maria Alapont said the company’s testing – and that of its customers – has demonstrated fuel economy and emissions improvements “at levels unachievable with spark ignition”.

The company has “optimised” ACIS to be easily implemented in high-volume applications for “both current and future powertrain architectures” by designing it to fit in the space occupied by a conventional ignition setup, enabling engine manufacturers to build the technology into their products “with no adverse impact on engine design or assembly”.

Another claimed advantage over conventional spark plugs is that ACIS does not suffer from electrode erosion, resulting in greater reliability and potentially longer service intervals.

In addition, Federal-Mogul also claims the materials used in ACIS are “already proven in automotive applications to ensure durability throughout the designed service life”.

Federal-Mogul powertrain energy director for ACIS Kristapher Mixell described the technology as game-changing and one that presents possibilities for further improving existing internal combustion technology.

“We have already recorded fuel consumption improvements of up to 10 per cent on a 1.6-litre turbocharged gasoline direct-injection engine, and there is potential for further improvements,” he said.

“The technology enables powertrain engineers to more efficiently develop combustion strategies, such as stratified charge, lean burn and high levels of EGR, to reduce fuel consumption and exhaust emissions.”Engineers are beginning to see the humble spark plug –which has been around since 1860 and was first made commercially viable by Robert Bosch in 1898 – as one of the weakest links in the race to squeeze more efficiency out of the petrol engine.

ACIS is not the only spark plug alternative in development. A Japan-based team of researchers – as well as separate attempts by Colorado State University in the US and Liverpool University in the UK – have been investigating the use of lasers for initiating internal combustion.

The Colorado team patented a special type of optical fibre that could withstand the high levels of energy required to create a spark in an internal combustion engine, but the British team said it struggled to deliver a strong enough laser beam into the combustion chamber without directly focussing the beam – generated by a large laser unit that would not fit under a car bonnet – through a lens placed in a hollowed-out conventional spark plug.

However, the team in Japan – backed by the Japan Science and Technical Agency with support from Toyota-owned component manufacturer Denso – overcame the challenges by using ceramics to make a powerful composite laser just 9mm wide by 11mm long that generated two beams able to simultaneously start combustion in separate areas of the combustion chamber.

Another school of thought being pursued by General Motors is to use compression ignition for petrol engines – like a diesel engine, using the heat generated by compression to ignite the fuel/air mixture.

Mr Alapont said Federal-Mogul will continue developing spark plug technology alongside ACIS, given there are expected to be more than 1.2 billion cars on the road worldwide by 2015 – ensuring a continued high level of demand for conventional spark ignition systems.