Mechanism of Void Formation during Brazing of Ni Paste Brazing Filler Metal

Automobiles are equipped with EGR (Exhaust Gas Recirculation) coolers to improve fuel economy and exhaust gas suppression performance. Inside the EGR cooler, the moisture in the gas is condensed by cooling the hot exhaust gas. This condensed water is highly corrosive because sulfur oxides dissolve. Therefore, stainless steel and Ni-based brazing metal having excellent corrosion resistance are used for the EGR cooler.Until now, stainless steel has been brazed under a vacuum atmosphere. However, there are increasing opportunities to braze stainless steel in an inert atmosphere gas at atmosphere for cost reduction and mass production. In this case, a paste-type brazing filler metal consisted of a powder brazing filler metal and a binder is used. As is well known, a debinding process that volatilizes the binder is needed. From previous research in this laboratory, it is clarified that the binder causes voids. In addition, it is said that the size and location of voids generated at the brazed joint affect the product performance. On the other hand, the detailed investigation about the influence which the installation position of a paste type brazing filler metal on the void formation process has not yet been made. Therefore, in this study, the arrangement method and influence on heating rate and debinder temperature on void formation were investigated by X-ray CT.

Experimental and Numerical Delving Of Full Spiral Shell and Tube EGR Cooler

Exhaust gas recirculation (EGR) coolers can profoundly reduce hazardous NOx emissions from Diesel engines. In this project flow and heat transfer characteristics of Full spiral shell and tube EGR cooler is investigated experimentally and numerically using CFD (ANSYS FLUENT V16.4) software. Geometrical parameters of modification of spiral corrugated tubes include diameters (inside and outside), effective length, thickness, Pitch, number of revolutions were made by constructing 5 models of EGR coolers with A-7 tubes, B-9 tubes, C-11 tubes, D-13 tubes and E-15 tubes using ANSYS FLUENT. Model D with 13 tubes is found to be efficient and economical. Using spiral corrugated tubes shown improvement in Heat transfer effectiveness and heat transfer coefficient experimentally and numerically for 13 tubes EGR Cooler. Also almost 22% increase in effectiveness is observed using spiral corrugated tubes instead of plain tubes. Both experimental and numerical results are obtained and are compared. BS-VI is a significant advancements with regard to NOx limits having 0.06 gm/km. EGR cooler with spiral corrugated tubes can help in reducing NOx limits to great extent.