Device for guiding a main air flow for an aircraft turbine engine

A device for guiding a main air flow for an aircraft turbine engine, this device comprising:

• a first pipe for the flow of a main air flow, this first pipe having a main axis,
• a plurality of ejectors of a secondary air flow located inside the first pipe and configured to eject a secondary air flow and force the flow of the main air flow in this first pipe, said ejectors being distributed around said main axis on a tubular wall of one end of the first pipe, and
• a second exhaust pipe located at outlets of the ejectors and comprising an end which is connected to the end of the first pipe and which directly receives said secondary flow to force the flow of the main air flow from the first pipe to the second pipe,
• wherein the end of the second pipe is engaged in the end of the first pipe, and a peripheral edge of the end of the first pipe is located downstream of a peripheral edge of the end of the second pipe,
• wherein the second pipe comprises a constriction which is at least partly located in said end of the first pipe,
• wherein the peripheral edge of the end of the second pipe extends in a plane perpendicular to said main axis, said plane passing upstream of said outlets and said peripheral edge comprising notches configured to each receive a base of one of said ejectors, and
• wherein a maximum cross-section of the second pipe at the peripheral edge of the second pipe is greater than a maximum cross-section of the second pipe at the peripheral edge of the end of the first pipe,
• wherein said constriction comprises:
• an intermediate section comprising a passage cross-section Smin,
• an upstream section located between the intermediate section and the ejectors, this upstream section comprising at an upstream end a passage cross-section Smax or Smax1 substantially identical to a passage cross-section of the first pipe, and at a downstream end a passage cross-section Smin which is smaller than Smax, and
• a downstream section located between the intermediate section and the rest of the second pipe, this downstream section comprising, at an upstream end, a passage cross-section Smin and, at a downstream end, a passage cross-section Smax substantially identical to the passage cross-section of the first pipe or a passage cross-section Smax2 between Smin and Smax1,
• and wherein the upstream section has a length L1 or axial dimension less than or equal to a length L2 or axial dimension of the downstream section, the length L2 being defined by L2=K.L1 with K between 3 and 5.