Abstract: A compact muffler (40) for an engine exhaust system, which is particularly applicable for use with small, reciprocating piston two-stroke engines of the type used on unmanned aerial vehicles (UAVs). The compact muffler (40) comprises an exhaust gas flow path (67) between an inlet (61) and an outlet (63). The exhaust gas flow path (67) comprises a plurality of adjacent flow passages (65), wherein at least two of the adjacent flow passages (65) are fluidly connected in series to enable the flow of exhaust gas from one to the other along the flow path (67). The adjacent flow passages (65) are configured for fluid flow therealong in opposed directions. A bypass passage (70) is provided between the two adjacent flow passages (65) for further communication between the two flow passages and to promote an equalisation of fluid pressure within the two adjacent passages (65). A UAV having an internal combustion engine (31) fitted with an exhaust system comprising the compact muffler (40) is also disclosed.

Abstract: A compact muffler (40) for an engine exhaust system, which is particularly applicable for use with small, reciprocating piston two-stroke engines of the type used on unmanned aerial vehicles (UAVs). The compact muffler (40) comprises an exhaust gas flow path (67) between an inlet (61) and an outlet (63). The exhaust gas flow path (67) comprises a plurality of adjacent flow passages (65), wherein at least two of the adjacent flow passages (65) are fluidly connected in series to enable the flow of exhaust gas from one to the other along the flow path (67). The adjacent flow passages (65) are configured for fluid flow therealong in opposed directions. A bypass passage (70) is provided between the two adjacent flow passages (65) for further communication between the two flow passages and to promote an equalisation of fluid pressure within the two adjacent passages (65). A UAV having an internal combustion engine (31) fitted with an exhaust system comprising the compact muffler (40) is also disclosed.

Abstract: Disclosed is an internal combustion engine comprising at least one cylinder with a reciprocating piston to provide said engine with at least one combustion chamber, said combustion chamber further comprising a delivery injector for injecting fuel directly into said combustion chamber, said engine further comprising at least one valved inlet air duct for delivering combustion air into said combustion chamber, wherein at least said inlet air duct and/or its valve is arranged to provide a low tumble inlet port to said at least one combustion chamber, said combustion chamber, in use, having low in-cylinder tumble gas motion of said combustion air and wherein said low in-cylinder tumble gas motion of said combustion air reduces over-enleanment of fuel in end gas regions of said combustion chamber.

Abstract: Disclosed is an Internal combustion engine comprising at least one cylinder with a reciprocating piston to provide said engine with at least one combustion chamber, said combustion chamber further comprising a delivery injector for injecting fuel directly into said combustion chamber, said engine further comprising at least one valved inlet air duct for delivering combustion air into said combustion chamber, wherein at least said inlet air duct and/or its valve is arranged to provide a low tumble inlet port to said at least one combustion chamber, said combustion chamber, in use, having low in-cylinder tumble gas motion of said combustion air and wherein said low in-cylinder tumble gas motion of said combustion air reduces over-enleanment of fuel in end gas regions of said combustion chamber.