Patent ID: 8312723

Claim:
A system for injecting a mixture of air and fuel into a turbomachine combustion chamber, comprising: a fuel injector and a Venturi positioned downstream of the injector, coaxial therewith, the Venturi comprising an interior surface delimiting a premixing chamber in which fuel is mixed with a stream of air taken from an external space and passing through a primary swirler positioned upstream of the Venturi, wherein the Venturi comprises an internal annular air-flow cavity, the cavity being connected by air inlet ducts to the external space and by air outlet ducts to the premixing chamber, the air outlet ducts opening onto the interior surface of the Venturi so as to prevent the deposition of soot and the formation of coke on the surface, wherein the Venturi comprises, at its upstream end, an annular rim extending radially outwards and separating the primary swirler from a secondary swirler for the passage of a second stream of air, the annular cavity extending as far as the rim of the Venturi, wherein the Venturi is formed of two annular components of substantially L-shaped cross section which are fitted coaxially one inside the other and are joined together by brazing or by welding, the first and second components between them delimiting the annular airflow cavity, wherein the first component extends upstream of and inside the second component, the first component having a substantially radial upstream annular wall which is connected at its internal periphery to a substantially cylindrical downstream wall in which the air outlet ducts are formed, wherein the second component comprises a substantially radial upstream annular wall which is connected at its internal periphery to a substantially cylindrical downstream wall, the radial wall being fixed at its external periphery to an external periphery of the radial wall of the first component, and its cylindrical wall being fixed at its downstream end to a downstream end of the cylindrical wall of the first component, and wherein at least part of the air inlet ducts run substantially radially with respect to an axis of the injector and are formed at the external periphery of the radial wall of one or each component and/or run substantially parallel to the axis of the injector and are formed through the vanes of the secondary swirler and the radial wall of the second component.