Owing to greatly differing application profiles with exhaust-gas temperatures that are frequently too low, mobile machinery and stationary applications are usually fitted with active systems, such as the SMF®-AR (Sintered Metal Filter with thermoelectric self-regeneration) system developed by HJS. With this system, the particulate filter can be regenerated at almost any engine operating point, irrespective of exhaust-gas temperature. The heat necessary to burn off the particulate matter is generated by the SMF®-AR system itself. Thanks to the compact and modular design of the SMF®-AR system, it can be put to use in many different applications. Pipes and brackets can be modified as required to match the different machines and vehicles.
The SMF®-AR system filters the exhaust gases until an optimum quantity of soot for regeneration has been collected in the filter. The system makes use of the positive active properties of a fuel additive that on the one hand lowers the soot's ignition temperature and on the other hand increases its burn-off speed.
The soot trapped in the filter can, therefore, be burned off automatically in a regeneration process when the exhaust-gas has a temperature of around 400°C. If, however, the necessary temperature is not reached – which is frequently the case in the low-load range – the system's active, thermoelectric regeneration function cuts in.
This occurs at regular intervals. However, the control unit not only triggers ignition of the soot, but also doses the optimum amount of additive, monitors the filter load and, with the help of sensors, calculates the best timing for regeneration.
In addition, a self-learning driving-cycle recognition functionality generally ensures that a regeneration cycle that has already started is not interrupted when the engine is switched off. Thanks to the high soot holding capacity of the SMF®-AR system, there isn't just one single ideal moment for regeneration, rather regeneration takes place within a wide time slot. Terminating regeneration by switching off the engine therefore poses absolutely no problem to reliable, safe operation of the SMF®-AR system. A further advantage of the SMF® is its high ash holding capacity, which allows for long servicing and cleaning intervals.