Volkswagen is currently investigating how they will manage to adapt the 11 million cars to be recalled. Just over 224 000 of these are in Sweden.
Diesel engineers’ challenge now is to show that it is possible to make environmental diesels without cheating. To succeed you have to use different cleaning techniques that are balanced against each other to hold the NO x , particles and fuel consumption. And to prevent the vehicle becomes dull.
truck manufacturers Scania and Volvo has gone before in this process. After a scandal (like today’s VW-gate) with accusations of “cycle beating” in the late 1990s tightened the regulations, and the opportunity to cheat and find loopholes were removed for heavy vehicles. Since then, the trucks passed tougher emissions requirements, while still holding down consumption.
For passenger cars, the situation has been different. The European acquis Euro 6 has included opportunities for “flexibility” in practice allowed cheating, and financially pressured manufacturers felt compelled to use. There’s also the difference between the certified emission values and the values have been measured in reality occurred. This applies both nitrogen oxide emissions.
The EPA 10 have similar limits Euro 6 but less flexibility. However is there a possibility of self-certification for manufacturers, where they can carry out the tests itself and ensure that the car maintains the correct values in the test. So did the Volkswagen cars, and only when they were tested by an outside organization could cheat revealed.
Now, engine engineers up to the evidence. Regulations and controls will be tightened even on the passenger side. In the United States waiting for checks and surveillance tests and in Europe are waiting tougher test rules. From 2017, new cars really clear what they purport.
Here’s engine engineers tool box:
A high injection pressure and an early fuel injection (the motorcycle) gives a better combustion with higher temperatures in the engine. It reduces the amount of particulate matter in the exhaust, the engine becomes more alert and efficient, but NO x rising. Do injection later in the cycle reduces NO x , but the particles and fuel consumption increases. The engineers try to keep both NO x , particles and fuel consumption simultaneously by injecting the fuel in several short pulses instead of all at once
More air in the combustion chamber (type turbocharger) gives approximately the same effect. Temperature increases, particles and consumption is decreasing, the engine becomes more alert, but emit more NO x .
EGR, exhaust gas recirculation, is used to reduce the NO x . Exhaust gases are led back to the combustion chamber to lower the temperature and reduce the percentage of oxygen. Both parameters have a direct impact on the NO x . EGR works best at low to medium load on the engine. Increasing the proportion of exhaust gases in the combustion chamber motor becomes too tired, thirsty and emit more particles.
SCR , Selective Catalytic Reduction , is the most effective way to remove NO x from the exhaust. Injecting urea SCR catalyst in which it reduces NO x to nitrogen and water vapor. SCR can remove as much as 95 per cent of NO x in the exhaust gases, but the catalyst has to be hot, over 180 ° C, to function properly.
Det means that the manufacturer who just want to pass the driving cycle Euro 6 (of low and medium load on the engine) has not been so great joy of the SCR. The system also requires an additional tank for the urea, or Ad Blue as the substance is also called, and it must be replenished. The great advantage of SCR is that you move out NO x ‘problem out of the combustion chamber and the engine which can be optimized to be spirited and stingy.
Lean NOx Trap, or LNT , is the second technique used to remove NO x from the exhaust. LNT called NO x trap. It works a bit like a sponge that absorbs water, but must be squeezed out at regular intervals in order to continue functioning. When the engine is running normally binds the catalyst NO x until it is saturated. It may be a few minutes during normal driving.
Since the catalyst must be emptied. It can be done by driving on a richer mixture that passes unburned hydrocarbons which reduces NO x , or injecting the gas directly into the catalyst.
A special particulate filter is needed to remove soot and other particles from the exhaust. Even if the combustion chamber is calibrated to reduce the particles remaining harmful nanoparticles are removed in this first filter.
In order to be effective need to filter be of a U-type regenerated with nitrogen or burned off when it becomes full.
Hybridization often mentioned as a way to reduce fuel consumption and thus carbon dioxide emissions. Can you combine this with the internal combustion engine may work in the cargo area where it emits the least particles and soot would have a clean and ultra-efficient diesel.
The problem here is that the diesel engine has the best efficiency in the work area where the largest emitters of nitrous oxide, so you have to choose if you want to optimize hybrid of meanness or purity.
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