greater diffusion in the channel generates an increase in performance on the first stage with a better acceleration in the distributor thin lines d in fig1 show the contours of such an optimized profile however a steep slope at the entrance to the low pressure turbine creates risks of detachments of the boundary layer along the external wall of the main flow originating from the high pressure turbine these detachments greatly harm the performance of the bp turbine in the proposed solution a significant gas flow is injected at the exit from the high pressure turbine at the wall in order to keep it at the wall this injection of air is commonly called blowing fig2 shows the technological integration of the blowing that is the subject of the invention in an engine environment example the figure shows a portion in axial section of the transition channel 10 this channel 10 is situated between the hp turbine 12 of which a portion of blade can be seen and the distributor 14 at the entrance to the bp turbine section of which a portion of blade is also seen the blading of the hp turbine 12 can move inside an annular channel defined externally relative to the axis of the engine by a sealing ring 121 this ring is attached in an internal casing element 123 called the hp turbine casing this casing.