Design Enhancement of EGR System for Improved Vibration Performance on Truck Diesel Engine

In the diesel engine Exhaust Gas Recirculation (EGR) components, valve and connecting pipes are the critical components and often fail during new engine development. These components are important for meeting NOx emission norms. Thus design of these components should remain robust. The compact packaging of complete EGR components on the engine, however, is counted as a designing challenge in which the consequent vibration-related failure plays a major role. Normally in pneumatic EGR valve, shaft spring stiffness is considered important for shaft opening and closing. But during emission testing in this layout, shaft is self-opened without feedback signal from sensor; this is due to resonance where the problem is solved by increasing the spring stiffness. The next key components are the EGR pipes; the flexible bellows on these pipes are useful for thermal expansion during hot conditions. In this case the bellow crack failure is observed due to vibration. Therefore, design improvements due to proper design of bellow geometry and bracket support for these pipes facilitated prevention of EGR pipe failure. This paper also describes the methodology of conducting proper failure investigation to identify the root cause for vibration-related failures of EGR system during new product development.