Labyrinth seal for fan assembly

1. A transport refrigeration unit for use with a transport trailer comprising:

a structural framework mountable to a wall of the transport trailer;

a condenser heat exchanger unit mounted to the structural framework;

an evaporator housing separated from the condenser heat exchanger by a distance; and

at least one condenser fan assembly positioned aft of the condenser heat exchanger unit and forward of the evaporator housing, the at least one condenser fan assembly including:

a fan casing having a plurality of guide vanes connected thereto, the fan casing having a trench formed therein, a first and second end surface of the trench being beveled;

a fan rotor arranged upstream from the plurality of guide vanes relative to a flow through the condenser fan assembly, the fan rotor being rotatable relative to the fan casing about an axis, the fan rotor having:

a plurality of fan blades; and

a shroud coupled to a radially outer end of the plurality of fan blades, the shroud including an axially oriented protrusion extending from a distal end of the shroud towards the fan casing, wherein the protrusion is aligned with a central portion of the trench and includes a first beveled edge and a second beveled edge, the first beveled edge being positioned adjacent to the first beveled surface and the second beveled edge being located adjacent to the second beveled surface; and

a clearance formed between the protrusion and the casing defining a convoluted flow path that wraps around both the first beveled edge and the second beveled edge of the protrusion.

2. The transport refrigeration unit according to claim 1 , wherein the convoluted flow path forms a labyrinth seal including a plurality of abrupt turns.

3. The transport refrigeration unit according to claim 2 , wherein the plurality of abrupt turns includes at least one 180 degree turn.

4. The transport refrigeration unit according to claim 3 , wherein the at least one 180 degree turn of the convoluted flow path directs an air flow parallel to the axis.

5. The transport refrigeration unit according to claim 3 , wherein the at least one 180 degree turn includes a first 180 degree turn and a second 180 degree turn.

6. The transport refrigeration unit according to claim 1 , wherein the shroud radially overlaps a portion of the casing.

7. The transport refrigeration unit according to claim 6 , wherein the shroud has a bellmouth curve.

8. The transport refrigeration unit according to claim 6 , wherein the protrusion extends from a portion of the shroud in overlapping arrangement with the casing.

9. The transport refrigeration unit according to claim 1 , wherein a contour of the trench is complementary in shape to the protrusion.

10. The transport refrigeration unit according to claim 1 , wherein the casing includes a lip, and the trench is at least partially defined by the lip.

11. The transport refrigeration unit according to claim 10 , wherein a surface of the lip has an angle between about 0 degrees and 90 degrees relative to horizontal.

12. The transport refrigeration unit according to claim 1 , wherein the convoluted flow path fluidly couples an interior of the fan assembly to an inlet end of the fan assembly.

13. The transport refrigeration unit according to claim 12 , wherein the convoluted flow path restricts a flow of air from a high pressure area towards a low pressure area.