Air-oil heat exchanger

A heat exchanger comprising:

• a plurality of fins arranged as a network and delimiting corridors;
• an envelope comprising:
• an internal wall and an external wall, the internal and external walls delimiting between them a channel for a flow of a first fluid in a main direction, the channel being, in the main direction, divergent and then convergent;
• and
• at least one passage for a flow of a second fluid being embedded in at least one of the internal and external walls;
• wherein the network of fins is arranged in the channel and connected to the internal and external walls;
• wherein the internal and external walls are arched, seen in a plane perpendicular to the main direction;
• wherein the envelope has a radial height between the internal wall and the external wall, the radial height defining a radial direction perpendicular to the main direction, the radial height of the envelope being variable along the main direction;
• and
• wherein the envelope as two side walls connecting the internal wall to the external wall and the envelope has a circumferential width between the side walls defining a circumferential direction perpendicular to the radial direction and to the main direction, the circumferential width being variable along the main direction.