System and method for mixing gas / liquid in an exhaust aftertreatment system

An exhaust gas treatment system for an internal combustion engine having an improved mixing of the injected fluid, comprising an exhaust pipe, which is configured to receive an exhaust gas from an internal combustion engine, and supplies the exhaust gas to the exhaust gas treatment system. A fluid injection means in fluid communication with the exhaust conduit is configured for delivering a fluid into the exhaust gas, and an evaporation volume downstream in the exhaust pipe is disposed, the fluid injection means is configured to slow the flow velocity of the fluid and exhaust gas mixture, whereby the residence time of the exhaust gas mixture therein is increased. An exhaust gas treatment system is configured to receive the fluid and exhaust gas mixture.