Chamber pre-combustion is the ultimate expression of the petrol internal combustion engine and Mercedes understands this. Thanks to the expulsion of high-temperature burning gases from the primary chamber, ignition and combustion in the main chamber is greatly accelerated, which reduces heat losses to the walls and ultimately increases overall efficiency. The most popular system for cost reasons is The passive typeas the pre-chamber does not contain a dedicated fuel injector and therefore the mixture reaches it from the main chamber.
Passive port limits
Unfortunately, passive primary combustion is limited to a narrow range of conditions. Indeed, when the engine is at low loads and speeds, the exchange of air inside the primary chamber is not sufficient to adequately clean it from burning gases. The result is Unstable combustion with frequent malfunctions, where the lack of ignition of the pre-chamber affects the absence of combustion in the main chamber. So far, designers have come up with some tricks to get around the problem. The Maserati Nettuno engine adopts dual combustion technology, for example, in which the pre-chamber combustion is deactivated at low loads and speeds, or in any case always supported by a second spark plug capable of starting combustion independently in the main chamber. On the other hand, the rapid combustion system developed by Italtecnica envisages only one spark plug per cylinder, but these are strategically placed inside the primary chamber in line with the contact holes of the main chamber. In fact, in this area it has been found that the concentration of residual gases is lower, which always ensures that the initial chamber is well ventilated under all conditions.
Mercedes and the troubled introductory room
However, the solutions proposed so far have not succeeded in removing the problem of residual gas concentration in the pre-chamber. Instead, Mercedes patented the United States Patent and Trademark Office A system that ensures adequate washing of the initial chamber even at low loads and speeds. The German brand has carried out elaborate CFD fluid dynamics studies, perfecting the turbulent motions of air in the cylinders in order to Cleaning the room before the combustion gases. Mercedes in particular exploited tumbling action, the circular movement of air from top to bottom in the combustion chamber. The idea is that at the top air flows with sufficient energy into the primary chamber, whose contact holes are designed in such a way that they create another turbulent motion within the primary chamber itself, this time with an inverted direction of rotation.
Thus Mercedes exploits the high energy of airflow turbulence to clean the initial chamber, and push the remaining gases out through the washing process. The result is a primary chamber free of burning gases, which is capable of It works perfectly even at low loads and rates. At the moment, there is no official news or statements on whether the patent will be applied to mass production. However, its mere presence betrays how Mercedes does not yet seem ready to abandon the internal combustion engine altogether.
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