Internal combustion engine, vehicle, marine vessel, and secondary air supply method for internal combustion engine

Abstract

An internal combustion engine capable of efficiently supplying air to an exhaust path even in a high load state. The internal combustion engine includes a convergent section, a divergent section, and a branch section. The branch section branches a shock wave, propagating in a downstream direction at a higher velocity than exhaust gas flowing into an exhaust path from a combustion chamber when an exhaust valve is opened, from a portion of the exhaust path which is upstream with respect to the divergent section, and propagates the shock wave back to the exhaust path. The exhaust gas is caused to pass the convergent section and to collide against the shock wave between the branch section and the divergent section so as to increase the pressure of the exhaust gas in the convergent section. Such exhaust gas is caused to pass the divergent section to generate a new shock wave. A secondary air supply system includes a supply section arranged to supply air to a portion of the exhaust path which is upstream with respect to the divergent section, using a negative pressure generated by the newly generated shock wave.