Abstract

The research aims to verify the feasibility of an on-the-road prototype of a power train for a hybrid-powered vehicle. The current propulsion systems are built to increase the power of internal combustion engines as much as possible. The aim is to achieve this by keeping the size of the engine contained, but the complexity is such that to increase the power of a powertrain, maintaining its original dimensions and geometries unchanged, therefore its displacement, it is necessary to increase its maximum speed of rotation (rpm) or to increase the thermal and volumetric efficiency of the engine itself. It has been seen that the increase in power can be achieved through supercharging, i.e. through the introduction of a greater amount of air inside the cylinder, improving, through this device, the filling coefficient and therefore the volumetric efficiency. In addition, the research status is focused on ensuring lower fuel consumption, with cleaner and more efficient engines, in line with stringent anti-pollution regulations. This need has generated technical solutions such as downsizing and down speeding, for which it has been possible to reduce the number of cylinders, displacements, and rotational regimes in favor of efficiency. It should not be forgotten in this context the efforts made to ensure the reduction of the phenomenon of turbo-lag, together with the need to improve the operation of the engine in transients, especially at low speeds where greater torque is required. In detail, the study focuses on decoupling the overfeeding group. The preliminary proposal is to mechanically disconnect the compressor/turbine complex, supporting the rotation of compressor C with a dedicated electric motor and creating a turbine T connected to a generator. Mechanical decoupling C/T allows both machines to be designed so that they operate near the maximum efficiency point for most of the expected real operating range. Thus, the turbine will presumably have a slightly lower rotational speed than the original group and will therefore be slightly larger. Since the turbine is now disconnected from the compressor, the surplus is recovered at the high speeds that are usually discharged through the waste-gate valve, providing further turbine expansion. The subsequent generation of additional electrical power, can, after being cut from that required by the electric motor + compressor complex, be used where required (for example to power auxiliaries or recharge batteries in hybrid configuration). The study concludes, at the moment, with the evaluation of mechanical and thermal stresses (through a FEM analysis) to evaluate the coupling with the high-speed electric generator.

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