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Diesel future: balancing act between efficiency and emissions

Do diesel engines have a future?
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Patent pending 122 years ago

1 22 years after the diesel engine was patented, the compression-ignition engine still offers enormous development potential. Its activation is worthwhile in view of the consumption advantage compared to its petrol brother, diesel experts are certain.

And that even today's diesel engine promises further improvements in consumption of around 15 percent, Rolf Bulander, Managing Director Drive Technology at Bosch, is convinced .

The future fleet consumption targets in the EU, he is certain, simply cannot be achieved without diesel. Even if the EU has put the time horizon for introducing binding consumption targets back on the back burner thanks to the intervention of the federal government, they remain a fixed target for the technicians.

Set targets achievable

The margin of just 95 grams per kilometer originally planned for 2020 would correspond to a consumption reduction of around 35% since the decision year 2009. And even a reduction of around 50% to 70 grams of CO2 /km for an average new vehicle was originally envisaged by the EU Commission.

But the Bosch engineers are sending out a clear message: with a technical measure -Package from further engine optimization to partial hybridization, the 95 gram target is no longer a distant illusion. These are ambitious goals that seem to represent a less difficult hurdle for the diesel engine than for gasoline engines.

Diesel is mutating into a clean man

The trigger for a real diesel boom down to the compact class was the mid-1970s with high-speed diesel engines à la VW Golf Diesel, which finally did away with the diesel dynamics that had been lacking until then.

Technical milestones of diesel development

Technical milestones such as distributor injection pumps, turbocharging with variable turbine geometry, direct injection including the gradual increase in injection pressure to 1,000 and now even up to 2,500 bar, common rail storage injection systems that enable up to eight multiple injections to control the combustion process very largely, mark the development path of the diesel until today.

The compression-ignition engine has always owed its low consumption values ​​to its combustion principle.

Diesel as a lame polluter?

For this, he was underestimated as a lame sucker for decades. While in the 1970s people turned up their noses above all at the clouds of soot escaping from the exhaust, with growing environmental awareness, nitrogen oxides also came into the focus of regulatory legislation.

The exhaust gas limit values ​​that have been in effect since January 1, 1993 The EU, including its gradual tightening, set a very beneficial technical development in motion, through which the diesel has long since left its former image behind.

Increasingly higher technical effort for exhaust gas cleaning

This then - parallel to the increasing emission limits - also required considerable technical effort. In addition to the 'internal engine measures', this applies above all to the other side of the coin, exhaust gas aftertreatment.

After the oxidation catalytic converter to convert unburned hydrocarbons (HC) and carbon monoxide (CO) into non-toxic carbon dioxide (CO2) and water A filter to limit unburned and harmful particles was soon unavoidable.

Diesel particle filters and their regeneration

Since it is of course not enough to retain the particles in the filter, complex controls are required for its regeneration as soon as the filter load reaches a certain limit.

At Bosch, this control is called Departronic. To regenerate particle filters, it relies on a metering system that injects precisely metered diesel fuel into the exhaust gas flow upstream of the oxidation catalytic converter. Burning the fuel raises the exhaust gas temperature to around 600 degrees Celsius and burns off the accumulated soot.

But that alone still does not allow the diesel engine to get a clean slate, which is due to its nitrogen oxide emissions . As of mid-2014, the European Union will require a drastic reduction in nitrogen oxide emissions in new cars and light commercial vehicles.

With SCR nitrogen oxide by 95 % reduce

The technical problem solution at Bosch is Denoxtronic, graduated for all vehicle classes, with which nitrogen oxides can be reduced by up to 95 percent. Primarily for commercial vehicles, SUVs and larger cars, the supplier relies on selective catalytic reduction (SCR), in which the liquid AdBlue, a harmless urea solution, is injected, which reacts with the exhaust gases and converts nitrogen oxides into harmless water vapor and nitrogen.

The Bosch strategists cannot and do not want to deny that such a system naturally burdens the diesel engine with additional costs,but they point out that the Denoxtronic can even reduce fuel consumption by up to five percent and that the system pays for itself to a large extent.

Euro 6 feasible through internal engine measures

However, there are already cars in the subcompact class that meet the NOx emission limit of 80 grams per kilometer of the Euro 6 standard specified by the EU Commission - and that solely through internal engine measures, as development manager Jürgen Gerhardt assures. Injection technology has developed enormously in recent years. And in the future, sensor-controlled combustion control promises even more potential.

However, exhaust gas recirculation is still the most effective means of reducing nitrogen oxide emissions, especially in the compact and mid-range.

Every 2nd new car a diesel

At Bosch, in any case, they are firmly convinced of the future viability of diesel. No wonder that every second new car in Germany is now a diesel engine. In the meantime, it is not only economical and clean, with its typical beefy torque and at the same time cultivated running, it also conveys the long-missed driving pleasure.

At least for the next few decades it will remain indispensable for automobility - including as Part of a hybrid drive such as the Peugeot 3008 HYbrid4 or the Volvo V60.

Huge growth opportunities in China and India

In emerging markets such as China and India in particular, the market experts predict enormous growth opportunities for diesel-powered cars. And even in the resilient US diesel market, where the share of new car registrations is currently stagnating at around 2.7%, Bosch Strategists from a market share of 10% by 2018 thanks to a significantly increasing range of light vehicles. Whether this will really happen in the face of the groundbreaking VW diesel scandal in the USA is completely open.

It should look even more difficult in diesel-abstinent Japan, where the modern diesel car does not even have a share in the registration achieved by one percent. But in the dense traffic of urban centers, the diesel hybrid could open the door to a technology that was previously reserved for commercial vehicles.


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