Diffuser for rotating detonation engine

1. A diffuser, comprising:

a radially inner wall including an arc angle, wherein the arc angle increases as the radially inner wall extends axially;

a radially outer wall disposed radially outward from the radially inner wall;

a first side wall disposed between the radially inner wall and the radially outer wall; and

a second side wall disposed between the radially inner wall and the radially outer wall, the second side wall disposed opposite the first side wall, wherein:

the radially inner wall, the radially outer wall, the first side wall and the second side wall define a duct therebetween, and

the first side wall and the second side wall merge at an outlet of the duct.

2. The diffuser of claim 1 , wherein the radially inner wall, the radially outer wall, the first side wall, and the second side wall define a cross-sectional area of the duct, and wherein the cross-sectional area increases as the diffuser extends axially.

3. The diffuser of claim 1 , further comprising an inlet, wherein the arc angle is between 20 degrees and 120 degrees.

4. The diffuser of claim 3 , further comprising an outlet, wherein the outlet comprises an annular ring shape.

5. The diffuser of claim 4 , wherein the arc angle increases through a transition portion of the diffuser, the transition portion disposed between the inlet and the outlet.

6. The diffuser of claim 4 , wherein the first side and the second side wall merge proximate the outlet forming the annular ring shape.

7. A diffuser, comprising:

an inlet comprising a chin portion defining a duct, the inlet defined by a first side wall, a second side wall, a radially inner wall and a radially outer wall;

an outlet disposed axially opposite the inlet, the outlet defining an annular ring shape, the outlet defined radially between the radially inner wall and the radially outer wall of the diffuser; and

a transition portion disposed between the inlet and the outlet, wherein the transition portion transitions from the chin portion at the inlet to the annular ring shape at the outlet wherein the first side wall and the second side wall merge at the outlet of the duct.

8. The diffuser of claim 7 , wherein an arc angle of the radially inner wall increases as the diffuser extends axially through the transition portion from the inlet to the outlet.

9. The diffuser of claim 7 , wherein the inlet defines an axial cross-sectional area, wherein the axial cross-sectional area increases as the diffuser extends axially through the transition portion from the inlet to the outlet.

10. The diffuser of claim 8 , wherein the arc angle of the radially inner wall is between 20 degrees and 120 degrees.

11. The diffuser of claim 10 , wherein the arc angle increases as the diffuser extends axially through the transition portion from the inlet to the outlet.

12. The diffuser of claim 7 , further comprising the radially outer wall disposed radially outward from the radially inner wall, the first side wall disposed between the radially inner wall and the radially outer wall, the second side wall disposed between the radially inner wall and the radially outer wall opposite the first side wall.

13. The diffuser of claim 12 , wherein the first side wall and the second side wall merge proximate the outlet.

14. A vehicle assembly, comprising:

an airframe;

a rotating detonation engine disposed within the airframe at an aft end; and

a diffuser disposed in the airframe, the diffuser comprising:

a radially inner wall and a radially outer wall disposed radially outward from the radially inner wall, the radially inner wall and the radially outer wall partially defining a duct therebetween;

an inlet having an arc angle of the radially inner wall and the radially outer wall between 20 degrees and 120 degrees, the inlet defined by the radially inner wall, the radially outer wall, a first side wall, and a second side wall; and

an outlet disposed proximate the rotating detonation engine, wherein the first side wall and the second side wall merge at the outlet.

15. The vehicle assembly of claim 14 , further comprising a transition portion disposed between the inlet and the outlet, wherein an arc length of the radially inner wall increases gradually as the diffuser extends from the inlet axially through the transition portion to the outlet.

16. The vehicle assembly of claim 15 , wherein the arc angle of the radially inner wall increases as the diffuser extends from the inlet axially through the transition portion to the outlet.

17. The vehicle assembly of claim 15 , wherein the outlet includes an annular shape.

18. The vehicle assembly of claim 15 , wherein the first side wall is disposed between the radially inner wall and the radially outer wall at a first arc end, and wherein the second side wall is disposed between the radially inner wall and the radially outer wall at a second arc end, wherein the second arc end is opposite the first arc end.

19. The vehicle assembly of claim 18 , wherein the first side wall, the second side wall, the radially inner wall and the radially outer wall define the duct and a cross-sectional area of the duct, and wherein the cross-sectional area increases as the diffuser extends from the inlet axially through the transition portion to the outlet.