The role of the engine brake is to convert a power-producing engine into a power-absorbing retarding mechanism. Modern heavy-duty vehicles are usually equipped with a compression braking mechanism that augments their braking capability and reduces the wear of the conventional friction brakes. This work presents an engine brake mechanism modeling and design based on decompression effect, obtained by exhaust valve opening during the end of the intake cycle. Besides that, during the system operation the emissions are drastically reduced, even eliminated, since there is no fuelling, contributing to pollution level reductions. In this sense, this work describes a development of such engine brake system for a 4 and a 6 cylinder diesel engines.
The engine brake performance was predicted by the development of 1D engine models. The 1D engine models are able to simulate the valve train, including the valves operation, brake flap actuation, hydraulic actuator behavior, and also the major engine breathing characteristics: gas flow rate, turbocharger efficiency, temperatures and pressures along the intake/exhaust system, etc. The gas distribution along the exhaust system can be predicted and its effects on the brake system performance evaluated. With these first assumptions, the first prototype is constructed and the simulation results are compared to the test bench acquired data.
