You can always use a smaller motor “- New Technology

     Scania’s powertrain in Euro-6 engine with integrererad silencer and aftertreatment. Photo: Leon / Scania, Scania CV AB
     

Engine Development Engineer Hakan Sarby explains the technical challenges that Scania has been resolved.

Truck manufacturer Scania expects to build efficient and strong environmental diesels that meet environmental requirements only with finishing in the form of SCR and particulate filter.

What’s the catch with the technology?

– There are two. One is that you have to have an extra tank of the car and stock up on extra fuel. That’s almost a comfort issue. The technical snag is that the system must have an exhaust temperature of over 250 ° C to function. This applies to both the urea catalyst, oxidation catalyst and particle filter, says Håkan Sarby working to reduce fuel consumption and emissions.

Thus, the SCR the catalyst combines nitrogen oxides and ammonia into nitrogen and water. In the particulate filter trapped particles. But what makes the oxidation?

– It increases the proportion of nitrogen dioxide in the NO x as it becomes equal to that of nitric oxide. It is the ratio that allows the SCR catalyst works best. Some of nitrogen dioxide also reacts with the carbon particles in the particle filter and clean it to carbon dioxide and nitrogen.

What if the engine is cold?

– The evaporation of urea does not work well and the treatment is inferior. The particle filter are not cleaned properly, without clogging. For a truck, it is not such a big problem, because the engine temperature rises fairly quickly when driving with a heavy load. It is worse for city buses and passenger cars.

How can I quickly get up the temperature?

– There are different techniques for this, but in common is that the cost of fuel. One way is to increase the engine load by applying an exhaust brake, thus clog the exhaust. Then, the motor must fight against a resistance and becomes hot. Another way is to make an after injection of fuel that is not ignited but goes out with the exhaust gases. The oxidation catalyst captures the hydrocarbons and they react to carbon dioxide and water while developing heat.

Does it work there for everyone, including passenger cars?

– It depends on what technology you have, what type of filter and catalyst . For us, it works.

Is there any other way?

– You can always use a smaller engine. Then it may work more, the temperature goes up and purification works.

Then ask Ny Teknik how big a passenger car diesel optimized purification would be. Issues of diesel cars is too delicate for Scania after VW scandal. But if we assume that a 12-liter diesel is suitable for pulling 40 tons as clean as possible will be a 0.5-liter diesel that does the same job for an average-sized passenger car.