An Integrated Diesel Engine ART-EGR System for Particulate/NOx Control Using Engine Sensory Inputs 970477
New developments for optimized control of Aerodynamically Regenerated Traps (ART) - Exhaust Gas Recirculation (EGR) integrated systems for diesel engines are presented herein. Such systems employ high-efficiency ceramic monolith filters to retain 99% of the emitted particulates. Regeneration is achieved periodically by short pulses of compressed air, flowing in the opposite direction to the exhaust. The soot is collected in a chamber, outside of the monolith, where it is oxidized with an electric burner. A fraction of the filtered exhaust is returned to the engine and this reduces NOx emissions, typically, by more than 50% at 18% EGR. However, since the amount of EGR, the frequency of regeneration and the frequency and duration of burning have a bearing on the fuel consumption of the engine, their optimization is imperative. Thus, provisions were made to collect intelligent information, leading to continuous assessment of the engine performance and fuel economy. Sensory inputs are recorded from the alternator, to assess the engine speed, from flow meters, to measure the air and fuel intake of the engine, from a specially-developed torque meter, to measure the torque at the drive shaft and, finally, from several pressure transducers and thermocouples. Such data was coupled with on-line readings of NO, CO and O2 emissions. Computer algorithms were then derived to optimize the EGR flow and the operation of the trap. One such algorithm implemented 18% EGR at low to medium loads (equivalence ratios up to 0.4), while it curtailed EGR to 0% at very high loads. NO was reduced by 30% while CO emissions were increased by 40%. The specific emissions of NO and CO were maintained well within the 1998 US EPA standards throughout the test. The operation of the ART-EGR-incineration system also reduced the particulate emissions by 96-99%, those of unburned hydrocarbons by 65% but increased the specific fuel consumption by 15%. The last value was unusually high and may be partially attributed to a recently experienced loss of engine power, which prevented the completion of the optimization. Final results will be obtained in the near future. Finally, this paper reports on the construction and evaluation of two new designs of effective post-filter soot burners.