Eberspächer makes diesel engines suitable for Euro 7 . standards

Hot tunnel mixer for urea injection
Eberspächer makes diesel engines suitable for Euro 7 . standards

Eberspächer has developed a new Adblue technology to improve diesel emissions. This effectively reduces nitrogen oxides even when the engine is cold.

Even if the European Union has been working with great enthusiasm to blow up the diesel engine, compression ignition engines will still be with us for a while. For the next and more stringent Euro 7 emissions standard, which is currently on the calendar for 2025, the industry is still preoccupied with developments to make diesel exhaust even cleaner than it already is.

Urea against nitrogen oxides

An important aspect here is the NOx in the exhaust gas, which is now very well controlled with current technology with urea injection and SCR catalysts. For this purpose, another catalytic converter is installed in the exhaust system after the oxidation catalytic converter and the particulate filter, the SCR (Selective Catalytic Reduction) catalytic converter. In order for this to be able to convert nitrogen oxides (NOX) into components of water and nitrogen, another tool is needed, namely urea. This urea solution, known by the brand name Adblue, is injected into the exhaust gas stream prior to the SCR catalytic converter and evaporates.


Emission control for diesel cars in schematic representation.

This is where the so-called tunnel mixer comes into operation, which is responsible for the optimal evaporation of the urea solution. Eberspächer subsidiary Purem has been offering such a tunnel mixer for a long time. But it gives the best results, especially in optimal operating conditions with a warm diesel engine and sufficient engine load. If the equipment has just started cold or is operating without a high load, the urea solution cannot be vaporized in the exhaust gas flow sufficiently and the SCR catalytic converter does not operate optimally.

Optimum emission control even when the engine is cold

With the “Heated Tunnel Mixer”, the Eberspächer Purem exhaust department wants to eliminate this problem. In this solution, the tunnel mixer, which is a relatively inconspicuous portion of the pressed sheet metal, is also heated electrically. Due to the evaporation energy needed, Adblue dosing in conventional SCR systems only starts after the exhaust gas temperature in the mixing section area reaches about 190-200°C. However, at this temperature level, only relatively small amounts of HWL (HWL = urea-water solution) can be evaporated or processed due to the evaporation energy required. This is where Purem from Eberspächer’s Heated Tunnel Mixer comes in.

Purem video image by Eberspächer

The primary goal is optimal HWL handling even at very low exhaust gas temperatures. By heating the areas relevant to the preparation, the atomizer impingement surface of the mixer, into which AdBlue is injected, is brought to the optimum temperature level for evaporation immediately after the engine is started. As a result, very good evaporation rates have already been achieved at exhaust gas temperatures of 160 °C. This means that the Adblue mixture can be started earlier than the non-heated system. In addition, significantly higher dose rates can be achieved much earlier thanks to efficient evaporation. As a result, the ammonia store of the SCR catalytic converter can be filled earlier and faster. Another positive effect is a slight increase in the temperature of the exhaust gas due to the electric power supplied. Together, all the advantages mean that the conversion of NOx in the SCR catalytic converter starts earlier on the one hand and achieves significantly higher efficiency earlier on the other.

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Eberspächer subsidiary Purem has developed a new mixing system that can effectively reduce nitrogen oxides (NOX) in exhaust gas by electric heating immediately after the diesel engine’s cold start. In this way, the SCR catalytic converter can also operate under operating conditions in which effective NOx conversion was not previously possible. Eberspächer sees this technology as a building block on the way to meeting the Euro 7 emissions standard for diesel engines.

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