Passenger Car Serial Application of a Particulate Filter System on a Common Rail Direct Injection Diesel Engine 2000-01-0473
Although combustion system improvements allow extremely low level of particulate (EURO 4 particulate level is already achieved) the particulate filter appears to be the only solution to reduce solid particulate emission by two to three order of magnitude over the whole size range starting from 10 nm. This is the reason why an active particulate filter system has been developed.
The major issue was to fill in the gap between particulate regeneration temperature (550°C) and the naturally low exhaust gas temperature of modern DI diesel engine (150°C to 200°C in city driving conditions). This low exhaust gas temperature is the result of overall efficiency improvement to reduce fuel consumption. The active system created is based on three main groups of elements: first a specific software dedicated for regeneration control and system diagnosis, second a filtration medium made of porous Silicon Carbide (SiC) located downstream an oxidation catalyst plus a differential pressure sensor and two temperature sensors and finally a fuel additive in a specific tank and a dosing system in the main fuel tank.
The active system continuously monitors the mass of soot in the filter from the filter pressure loss to start or stop the regeneration process. This process begins with an in-cylinder gas temperature increase by specific management of multiple injection and air boost pressure to keep the torque at the same level for driveability. As soon as the oxidation catalyst in front of the filter has lit off the amount of hydrocarbon in the exhaust gas is increased by multiple injection tuning to create catalytic post combustion. The temperature rise generated by these two actions (+300°C) completed by the effect of the additive in the particulate insures the rapid and complete regeneration of the filter.
This paper presents the features and the performances of the first active particulate filter system available on a serial passenger car. This system developed in just eighteen months and whose operating modes are unnoticeable to the driver makes the most of the flexibility and the performance of the Common Rail fuel injection system. It also illustrates the continuously growing potential of modern direct injection diesel engines.