Luminaire having inner flow path

1. A luminaire comprising:

a base including a first tube part, a second tube part, a joint part connected between said first and second tube parts, a connector, and an inner flow path defined cooperatively to extend within said first tube part, said joint part, and said second tube part in a coaxial manner between opposite first and second ends, an inner diameter of said first tube part being different from that of said second tube part, said joint part being frustoconical and being coupled to said second tube part to define a Y-shaped contour such that said inner flow path is continuously enclosed along the Y-shaped contour from said first tube part to said second tube part, said connector being disposed at said first end of said inner flow path and being formed with at least one first aperture;

a light-emitting unit disposed on said outer surfaces of said second tube part and said joint part in such a manner to allow heat generated from said light-emitting unit to be transmitted onto said base and to emit light with different light emitting angles; and

a lamp cover fixed on said base for covering said light-emitting unit, said lamp cover being formed with at least one second aperture;

wherein, when a temperature of said base is increased as a result of the heat, heat exchange occurs between said base and air in said inner flow path to form hot air in said inner flow path, so that the hot air flows out of said luminaire through one of said first and second apertures, and cold air is sucked into said luminaire through the other one of said first and second apertures, thereby creating an inner airflow.

2. The luminaire as claimed in claim 1 , wherein said second tube part has an inner diameter smaller than that of said first tube part.

3. The luminaire as claimed in claim 2 , wherein a cross-sectional area ratio of said first tube part to said second tube part is greater than 2.25.

4. The luminaire as claimed in claim 1 , wherein: said base further includes a plurality of inner fins extending from an inner surface of at least one of said first tube part, said second tube part, and said joint part; and each of said first tube part, said second tube part, said joint part, and said inner fins is made of a thermally conducting material.

5. The luminaire as claimed in claim 1 , wherein: said base further includes a plurality of outer fins disposed on outer surfaces of said second tube part, said joint part, and said first tube part; and each of said first tube part, said second tube part, said joint part, and said outer fins is made of a thermally conducting material.

6. The luminaire as claimed in claim 5 , wherein said outer fins are divided into a plurality of radially arranged sets, each of which includes at least one of said outer fins.

7. The luminaire as claimed in claim 6 , wherein each of said sets includes a plurality of said outer fins that are parallel to each other.

8. The luminaire as claimed in claim 6 , wherein each of said sets includes a plurality of said outer fins that are radially arranged.

9. The luminaire as claimed in claim 1 , wherein an end of said first tube part distal from said joint part defines said first end of said inner flow path.

10. The luminaire as claimed in claim 9 , wherein said lamp cover has a distal end that is distal from a top portion of said base, and that is aligned with said second end of said inner flow path.

11. The luminaire as claimed in claim 10 , wherein said base further includes an extending part having an open end that is open toward said distal end of said lamp cover and that defines said second end of said inner flow path, said lamp cover including a cover plate for covering said open end of said extending part, said second aperture being formed through said cover plate.

12. The luminaire as claimed in claim 11 , wherein a ratio of a maximum inner diameter of said extending part to a depth of said extending part is between 1.3 and 1.9.

13. The luminaire as claimed in claim 9 , wherein said lamp cover includes a concentration member disposed on an end of said second tube part and having an open end opening toward said lamp cover, and a cover plate for covering said open end of said concentration member, said second aperture being formed through said cover plate, said second end of said inner flow path being defined by said open end of said concentration member.

14. The luminaire as claimed in claim 13 , wherein a ratio of a maximum inner diameter of said concentration member to a depth of said concentration member is between 1.3 and 1.9.

15. The luminaire as claimed in claim 1 , wherein said light-emitting unit includes a plurality of circuit boards disposed on outer surfaces of said second tube part and said joint part, and a plurality of LEDs disposed on said circuit boards.

16. The luminaire as claimed in claim 15 , wherein said base further includes an extending part connected to said second tube part and opening toward said distal end of said lamp cover, at least one of said circuit boards being disposed on an outer surface of said extending part.

17. The luminaire as claimed in claim 16 , wherein said connector is mounted removably to aid first tube part, and includes a ring plate and an annular wall, at least one of said first apertures being formed in said ring plate, said annular wall extending from an inner periphery of said ring plate in a direction away from said first tube part.

18. The luminaire as claimed in claim 17 , further comprising a lamp cap inserted into said annular wall and adapted for electrical connection with an external power supply.

19. The luminaire as claimed in claim 15 , wherein said LEDs of said light-emitting unit disposed on said outer surface of said second tube part emit light at an angle different from that of said LEDs of said light-emitting unit disposed on said outer surface of said joint part.