Active Filtration Systems (SMF-AR) for heavy duty applications
Active filtration systems are required on applications where exhaust temperatures are below the required threshold for normal regeneration to take place. Additional features are built into the filter system to ensure soot particles can be burnt off, regardless of duty cycle or operating temperature.
The SMF®-AR (Sintered Metal Filter with thermoelectric self-regeneration) system developed by HJS 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.
How does the SMF®-AR work?
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.
What does active regeneration mean?
The control unit triggers (active) regeneration by means of the heating elements that wrap around the filter. The soot that has built up in the filter is ignited by the energy radiated by the heating elements. After the initial ignition of the soot layer, the regeneration process runs automatically until completed, that is, all the soot has been burned off.
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