Researchers at Lund University working in collaboration with Swedish Biomimetics 3000 have developed a new technique that more efficiently removes harmful oxides of nitrogen, NOx, from the exhaust of diesel engines. The new technology applies a more efficient injector into existing emission control systems currently installed in class Euro 6/VI vehicles and it is expected to be in production within the next two years.
The injector is inspired by an unusual insect: the bombardier beetle. Nature has equipped the small beetle with a built-in chemical reactor that fires a warm, toxic, liquid spray from its abdomen when it feels threatened. The construction of the beetle’s defence mechanism is a natural phenomenon, and has fascinated and inspired researchers and engineers alike.
Whilst diesel engines are energy efficient, their exhaust fumes contain harmful oxides of nitrogen that have a negative impact on people’s health as well as the environment. As a result there has been much talk recently, in the press and at a global governmental level, of an end to all combustion engines in the near future, with the prediction of a corresponding rapid rise in the use of electric vehicles.
However, according to combustion engine researchers this is an exaggeration and something that is not practical or possible in the projected time scales. What is most likely is that most electric vehicles will be hybrids using combustion engines to augment their power requirements.
“Ultimately, it will be a long time before most electricity production is green. Therefore, the end goal is not electric cars per se, but rather ensuring that we accelerate the production of green energy from wind power, hydropower and biomass, and that we use it where it is best needed”, argues Per Tunestål, professor of combustion engines at Lund University.
The new injector has been applied to an existing NOx reduction technique called Selective Catalytic Reduction (SCR). SCR systems inject aqueous Urea solution into the reduction catalyst of Diesel engines which then converts NOx into harmless nitrogen and water vapour. The process is currently used in Diesel vehicles classed as Euro 6/VI but is currently inefficient especially under cold engine running conditions.
The tests performed in the Lund University engine laboratories using the new injector show that it is able to reduce the NOx content of the exhaust to a significantly lower level than the currently available technology.
“Our tests show that not only is the NOx content significantly reduced, it also reduces harmful ammonia emissions that are usually formed when NOx emissions are detoxified in this manner”, says Per Tunestål.
The explanation? There are several, but the key factor is the phenomenon of the beetle-inspired spray.
“We have created a spray with many small warm droplets which are injected at much higher speed than today’s systems. This facilitates the mixing with the exhaust fumes and makes for better distribution across the catalytic converter’s surface”, says Per Tunestål.
About the project:
The project was partly financed by the Swedish Energy Agency and is a collaboration with Swedish Biomimetics 3000. There are currently other development projects, using different techniques, that aim to reduce the NOx content from diesel engines.
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