injection system for a turbomachine combustion chamber comprising an annular wall has inner tapered profile

The main object of the invention is an air and fuel injection system (24) for bottom annular combustion chamber (10) for a turbomachine, comprising at least two fuel injection device including an injector central (26) and a peripheral annular injector (43) arranged around said central injector (26) and an inner annular channel (71) of air intake into which the central injector (26) to allow mixing between fuel from the central injector (26) and the air admitted into the inner annular channel (71), and at least one external annular channel (30; 30a, 30b) of air intake to allow enrichment air of this mixture and stabilization of the pilot combustion zone (P), characterized in that the inner annular channel (71) and said at least one external annular channel (30; 30a, 30b) are separated by an intermediate annular wall (70) extending around the central injector (26) and meadows entant an internal profile (70a) converge.