Browse Publications Technical Papers 2008-36-0129

Development and performance analysis of an Exhaust Valve Brake System for a Diesel engine through 1D simulation 2008-36-0129

The need for braking capacity improvement has a negative impact as it increases the loads acting on the conventional brake system, increasing wear between its components and requiring a more robust design.
Looking this scenario, an available option is to use the engine as a source of braking power. Some conventional engine brake systems consume the vehicle/engine inertia power through the exhaust system closing (total or partial). However, the braking efficiency of this version is limited by bouncing occurrence on the exhaust valves, generating stronger impact of valve and valve seat. The developed solution consists in creating an engine brake mechanism acting directly on the exhaust valve, achieving greater efficiency. The mechanism is based on a hydraulic actuator positioned between the exhaust rocker arm and the valve stem top. When bouncing occurs, the actuator, moved by an internal spring and oil pressure, shifts and locks the exhaust valve, avoiding it to return to its original position. The system keeps the valve opened during the intake cycle, generating braking power from the air system decompression.
Based on the design parameters, a 1D numerical model of the engine including the System Design brake system was built to verify its efficiency and functionability. The model allows the investigation of changes in the design without adding costs with prototyping and tests. Finally, the numerical results were compared with test data to validate the model and check its accuracy.


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