Emissions reduction in diesel engines


Tackling the cause of the problem

The subject of emissions is about air quality. It makes sense that in countries and areas of the world that are heavily populated and industrialised it should matter.

“In terms of technology, the drive is to lessen the volume and harmfulness of emissions that are actually the fruits of combustion before they leave the exhaust.” Payne adds. “Treating emissions afterwards (referred to as after-treatment) is expensive and should only be used where the rewards are greatest: high load and high hours operation. For emergency standby use it makes sense to minimise there production in the first place: in the cylinder”.

Through in-cylinder design improvements and precision control of the combustion process, Cummins has developed technologies that reduce primary pollutants in the diesel generator set exhaust by around 80 per cent (since 1996 when USA emissions regulations for non-road diesel engines first went into effect).

Using a tier system to bring emissions under control

The USA and EU are leading the way in terms of setting standards and regulation. In the USA, the EPA has established a tier system (Tiers 1 – 4) for introducing regulations for non-road and stationary diesel engines. This establishes uniform federal standards for emissions for mobile and stationary generator sets. The EU has implemented a similar scheme comprising stages I-IIIA for mobile generators. In both schemes, each Tier (or stage) specifies lesser amounts of four specific pollutants: NOx (nitrogen oxide), HC (hydrocarbons), CO (carbon monoxide) and PM (particulate matter).

As of January 1st, 2007, requirements for stationary generator applications (including standby generators) came into line with prevailing non-road regulations in the USA, taking account of the fact that it does not make sense to apply after-treatment to emergency standby generator sets. The target is for NOx and PM levels to have dropped by 98% below unregulated levels by 2014. Tier levels are applicable to the power rating of the engine but only apply to new engines.

Other countries too (Germany, France and China) have their own versions. In Germany, TA Luft sets the standard for NOx and PM reductions, while in France, Directive 2910 controls emissions of NOx, CO, SOx (sulphur dioxide), NMOC (non methane organic compounds) and PM.

Payne explains: “Development of low emissions technology is expensive and requires a big market to pay for it. The USA and EU are highly populated and interested in controlling air quality because it gives a better quality of life and saves on health care.”

Alain Charles Publishing, University House, 11-13 Lower Grosvenor Place, London, SW1W 0EX, UK
T: +44 20 7834 7676, F: +44 20 7973 0076, W: www.alaincharles.com

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