Still smoking

Engine companies have been up against their toughest challenge to date as new regulations come in to force.
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Engines have been much in the news recently, as a number of deaths have been attributed to smoky old generators pressed into service during the Sharjah power cuts. This brings to the fore the ongoing debate around the world about engines, and inparticular the need for diesel engine makers to clean up their act.

For an engineer, however the diesel motor is something of a paradox – on one hand it follows the same principals as the man from whom it takes its name. On the other, ever more demanding emissions rules from legislators, and efficiency needs form users mean that the blueprints grow more technical each year.

However, engine companies have been up against their toughest challenge to date, as a new standard referred to as ‘Tier IV/Stage 3b’ comes in to force.

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This standard means that the amount of unburnt hydrocarbons, more commonly known as soot, must be brought down to the sort of level that is going to make the exhaust almost cleaner going out, than the air being drawn in. Ironically, as we will see, some of Rudolf Diesel’s original design elements are being reintroduced as the drive for more pressure, more power – and literally more ‘bang for your buck’ continues.

Diesel
Modern diesel fuel will burn relatively cleanly in the right engines. The problem is that most of the diesel available in the region is far from modern.

Old refining methods mean that local juice is likely to have a much higher sulphur content as well as containing a mix of toxic heavy metals, notably palladium, but also a variety of other nasties.

Selective
‘Selective catalytic reduction’ or SCR is a very technical way of getting a catalytic converter to work effectively.

To put what is a complex process into layman’s terms, a regular catalytic converter, such as what you might find on a car, works by introducing a ‘catalyst’, usually platinum, to a chemical reaction, which renders the end product (in this case the exhaust gas) relatively harmless.

SCR differs by using a liquid ‘reducing agent’ actually a fluid which is sprayed onto the catalyst. At one time the chemical used was ammonia, to kill the nitrous oxide (NOx) by converting the output of industrial boilers into harmless diatomic nitrogen or water.

These days, a number of manufacturers have adapted this technology for use in roadgoing diesel engines, but by using an injection of a chemical based on the substance found in animal urine known as urea, the NOx is knocked down by up to 95% with no other toxic by products.

There are a variety of different systems on the market at the moment, though as using urea injection is not mandated in the Middle East, few users take advantage.

One notable exception is the RTA in Dubai, which is using the stuff across its fleet.