A system for improving fuel-air mixing inside an injection system of a turbomachine combustion chamber. An air intake ring has an annular deflection wall, or venturi, having an internal profile provided with a discontinuity inducing an increase in the radius (φ) of the internal profile downstream of the discontinuity. A method of atomizing fuel includes separating fuel trickling over the internal profile of the annular deflection wall from the internal profile at the level of the discontinuity so as to form droplets within a flow of air coming from an upstream air circulation space of the air intake ring.