Supercharged internal combustion engines

DETAILED DESCRIPTION According to the invention, there is provided a power unit comprising: an internal combustion engine having variable volume combustion chambers; a turbocompressor supercharging unit having a compressor and a turbine, the inlet of said turbine being connected to receive the exhaust gas of said engine; continuously open bypass conduit means having an inlet and an outlet connected to flow the air delivered by said compressor and not drawn by the engine to the inlet of said turbine with a pressure loss which, if appreciable, is substantially independent of the ratio of the flow rate traversing said bypass conduit means to the air flow delivered by the compressor; an auxiliary combustion chamber connected to the outlet of said bypass conduit means and to the exhaust of said engine and having an output connected to the inlet of said turbine; ejector-diffuser means having a driving gas inlet connected to the outlet of said compressor to receive the total air flow from said compressor, a driven gas inlet and an outlet connected to the intake of said engine and to the inlet of said bypass conduit means; branch pipe means connected between the outlet of said auxiliary combustion chamber and said driven gas inlet of said ejector-diffuser means; and means for adjusting the ratio between a cross-sectional area on the driving gas flow path and a cross-sectional area in said branch pipe means.
The ejector produces a local pressure decrease in the pipe supplying air to the engine and to the bypass.
That decrease is determined for the pressure to be lower than the pressure at the inlet of the branch pipe, so that transfer of a proportion of the hot gases from the combustion chamber need not pumping means.
The diffuser then raises again the pressure of the mixture of air from the compressor and hot recycled gases, to a value greater than the pressure at the engine exhaust.
The invention may be used in power units whose bypass does not produce an appreciable pressure drop as well as when a throttle means is disposed in the bypass so that there is a considerable pressure difference between the engine intake and exhaust, so as to provide good scavenging which is essential for two-stroke engines and is also useful for four-stroke engines, inter alia high-power four-stroke engines