Deposit removal in EGR cooler and effectiveness improvement by non-thermal plasma reactor with different gas sources

An experimental study of deposit removal and effectiveness improvement of EGR cooler was conducted by a non-thermal plasma reactor with different gas mixtures (80-20, 60-40, 40-60, 20-80 and 0-100 of N2 and O2). Generating mechanism of active substance in NTP reactor was firstly implemented by OES and concentration analysis. Comparison of removal mass, axial temperature distribution as well as effectiveness improvement was analyzed. Besides, deposits before and after NTP treatment was analyzed by TGA. The results shows that the second positive band of N2 (C3Πu → B3Πg) could be clearly observed and its emission intensity decreased with increasing O2 concentration, and O3 and NO2 were the main active substances whose concentrations grew with a higher O2 concentration. The total removal mass as well as effectiveness improvement and decrease in LMTD peaked when the O2 concentration was 80%. The overall axial temperature growth increased when O2 concentration grew, and peak temperatures at each point occurred one after another in chronological order. TGA shows that NTP had a positive effect on improvement of deposit reactivity. Consequently, a NTP reactor with oxygen-enriched gas source is more beneficial to deposit removal and effectiveness improvement of EGR cooler.