Multi-cylinder internal combustion engine, vehicle, marine vessel, and exhausting method for multi-cylinder internal combustion engine

Abstract

A multi-cylinder internal combustion engine capable of decreasing the pressure or temperature of exhaust gas. The internal combustion engine includes at least two cylinders and an exhaust path. The exhaust path includes a convergent-divergent nozzle and an exhaust merging section provided upstream with respect to an upstream end of the divergent section arranged to connect only exhaust ports of combustion chambers for which the opening periods do not overlap. A shock wave propagating in a merging upstream section is branched at a connection section, and the branched shock wave is reflected by an exhaust valve of cylinder and collides against the exhaust gas. In accompaniment with the passage of the exhaust gas having the pressure increased by the shock wave through the convergent-divergent nozzle, a new shock wave propagating in a downstream direction in the exhaust path is generated and also an expansion wave propagating in an upstream direction in the exhaust path is generated. Thus, the temperature and pressure of the exhaust gas are significantly decreased.