Valve Wagging Prediction Methodology for Engine Brake Application

Eaton's decompression engine braking technology for medium and heavy-duty diesel engines delivers high braking power and provides several advantages to the commercial truck owner. Eaton offers rocker arm-based 1 stroke, 1.5 stroke, and 2 stroke systems for overhead cam and cam in block engine architectures. The Compression Release (CR) engine brake avoids overheating and fading of primary friction brake. It reduces or eliminates the need for a driveline retarder.One of the failure modes for Engine Brake (EB) system is excessive lateral displacement of the exhaust valve, caused by non-uniform pressure distribution across the valve during Brake Gas Recirculation (BGR) and Compression Release modes. This excessive deformation is referred to as Valve Wagging. Valve wagging significantly affects the structural stability of the engine brake mechanism. Analyzing its behavior is essential to minimize excessive wear on valve guide and Valve Seat Insert in new designs. Since evaluating the valve wagging phenomenon through prototype testing is both costly and time-consuming, a validated analytical approach was developed.A coupled CFD and structural dynamics analysis approach was developed to predict valve wagging phenomena. This approach includes simulating transient valve motion using a dynamic mesh technique, capturing the influence of valve motion on surrounding flow-field, and assessing the impact of flow field on valve structural displacement. The developed methodology was validated by comparing simulated valve lateral displacement with experimental results, showing good agreement between the two.