Intebrake 3-D CFD Transient Simulation Studies for Predicting Flow Performance

This paper presents transient, complex, moving mesh, three-dimensional CFD analysis of Intebrake lubrication oil circuit for predicting flow performance. Intebrake is a method of improving braking performance during overspeeding conditions by briefly opening the exhaust valve at the end of compression stroke with a small valve lift and releasing the compressed gases. There is no fueling and hence, no combustion during the Intebrake operation. During intebrake operation, opening of exhaust valve is achieved by using a complex lube oil circuit inside the exhaust rocker lever. The intebrake lube oil circuit consists of various spring-operated valves with micron sized clearances, high oil pressure generation up to ~ 250 bar, three-dimensional movement of the parts, and transient operation. The three-dimensional motion consists of simultaneous rotation and translatory motion with some dynamic motions due to net force balance between spring and fluid forces. All these factors make simulation an absolute need as testing is very costly and difficult due to tight space. However, these factors make it a challenge to simulate this system at 3D CFD level. In the current work, 3D CFD simulation approach using Simerics-MP+ is developed which can model the Intebrake operation by modeling dynamic mesh, small clearances, and oil compressibility effects. The predicted Intebrake lube system oil pressure is compared with transient crank angle based test data and the results are found to be in good correlation. This approach has helped in better understanding the Intebrake responses to variation in different design parameters and has helped in resolving field failures. The dynamic CFD model which can consider Intebrake ON and OFF operations automatically makes dynamic mesh motion even more complex. After a single cylinder Intebrake model validation, it has been extended for modeling 6-cylinders and integrated with engine 3D CFD lube system as well.