Patent Application
20210033112
This application relates to a compressor for an air machine.
Air machines include a turbine and a compressor. Partially compressed air is delivered to the compressor, and the compressor is driven to further compress this air. A motor drives the compressor. This compressed air is passed downstream to drive a turbine, with the turbine in turn helping to drive the compressor as the air expands across the turbine. This expanded air is then utilized for a downstream use, such as cabin air for an aircraft.
Air machines have a shaft which connects the compressor and the turbine. Bearings facilitate rotation of the shaft. Heat accumulates in the copressor as the air machine operates, and in particular, at the bearings and motor.
A compressor according to an exemplary embodiment of this disclosure, among other possible things includes, a rotor driven by a shaft and configured to compress air. A motor is drives the shaft. First and second journal bearings facilitate rotation of the shaft. The first journal bearing is located upstream from the motor, and the second journal bearing is located downstream from the motor. A thrust bearing also facilitates rotation of the shaft. The thrust bearing is downstream from the second journal bearing. A tie rod connects the shaft to a motor rotor shaft adjacent the first journal bearing. The tie rod includes an opening which is configured to communicate cooling air from the motor to the rotor.
In a further example of the foregoing, the compressor includes a transfer tube. The transfer tube is configured to provide cooling air from a bearing cooling air inlet to the second journal bearing.
In a further example of any of the foregoing, the cooling air travels in the same direction as a direction of airflow through the compressor.
In a further example of any of the foregoing, the compressor includes a seal upstream from the first journal bearing which is configured to direct cooling air from the transfer tube to the first journal bearing.
In a further example of any of the foregoing, a bearing cooling air inlet is in fluid communication with the thrust bearing.
In a further example of any of the foregoing, the thrust bearing includes a thrust shaft and a thrust plate. The thrust shaft includes first and second orifices. The first and second orifices are in fluid communication with a bearing cooling air inlet.
In a further example of any of the foregoing, the second journal bearing is in fluid communication with the second orifice and the thrust bearing is in fluid communication with the first orifice.
In a further example of any of the foregoing, the compressor includes a passage between the motor and the shaft. The passage is in fluid communication with the bearing cooling air inlet via the first and second orifices.
In a further example of any of the foregoing, the bearing cooling stream includes first and second bearing cooling streams. The first bearing cooling stream passes through the second journal bearing and the second bearing cooling stream does not pass through the second journal bearing.
In a further example of any of the foregoing, the compressor includes a seal immediately upstream from the second journal bearing and is configured to direct the first bearing cooling stream to the motor.
In a further example of any of the foregoing, the rotor includes an opening that is configured to communicate the cooling air from the tie rod to an inlet of the compressor.
In a further example of any of the foregoing, a heat shield is located upstream from the motor from the opening in the tie rod and downstream from the rotor.
A method for cooling a compressor according to an exemplary embodiment of this disclosure, among other possible things includes providing a cooling air stream to a thrust bearing and a first journal bearing. The thrust bearing and first journal bearings are configured to facilitate rotation of a shaft in a compressor. A cooling air stream is provided to a rotor of a motor which is configured to rotate the shaft. The cooling air stream is communicated to a rotor of the compressor via an opening in a tie rod connecting the shaft to a motor rotor shaft.
In a further example of the foregoing, a second cooling air stream is provided to a second journal bearing such that that cooling air provided to the second journal bearing does not pass through the first journal bearing.
In a further example of any of the foregoing, the second cooling air stream is provided to the second journal bearing from a bearing cooling air inlet via a transfer tube.
In a further example of any of the foregoing, the second cooling air stream flows through the second journal bearing in the same direction as a direction of airflow through the compressor.
In a further example of any of the foregoing, the method includes communicating the cooling air stream through an opening in a rotor of the compressor.
A thrust bearing 33 and a journal bearings 34a, 34b facilitate rotation of the driveshaft 30. The thrust bearing 33 includes a thrust bearing disk 36 which is associated with a thrust shaft 38. The thrust shaft 38 connects to the motor rotor shaft 39. The thrust bearing disk 36 has thrust bearing surfaces 40.
The motor 28, the thrust bearing 33, and the journal bearings 34a, 34b are cooled with cooling air.
A motor cooling stream MC is drawn from the compressor inlet 20 at 42 and provided to a motor cooling inlet 44. The motor cooling stream MC ultimately exits the compressor 20 via a cooing air outlet 48. In one example, the outlet 48 ducts to ram (e.g., ambient) air. A bearing cooling stream BC is drawn from downstream of the compressor outlet 26 and provided to a bearing cooling inlet 50. In one example, a heat exchanger (not shown) is upstream from the bearing cooling inlet 50 and downstream from the compressor outlet 26, and cools air in the bearing cooling stream BC.
The bearing cooling stream BC cools both the thrust bearing 33 and the journal bearings 34a, 34b, and provides cooling to the motor 28, which will be explained in more detail below.
The bearing cooling stream BC is split into two bearing cooling streams BC1 and BC2, which pass along both sides of the thrust plate 36 at thrust surfaces 40 to cool the thrust bearing 33. The bearing cooling streams BC1 and BC2 continue along either side of the thrust shaft 38.
Orifices O1 and O2 are formed in the thrust shaft 38. The orifice O1 is oriented generally parallel to an axis A of the shaft 30 while the orifice O2 is oriented generally perpendicular to an axis A of the shaft 30. That is, the orifices O1, O2 are oriented generally perpendicular to one another. The first bearing cooling stream B1 passes through the journal bearing 34a and then through the orifice O2. The second bearing cooling stream BC2 passes through the orifice O1. The first bearing cooling stream BC1 then joins the second bearing cooling stream BC2 and both streams pass along the inside diameter of the motor 28, via a passage 45 adjacent the shaft 30, providing cooling to the motor 28 and/or shaft 30. The bearing cooling streams BC1, BC2 then pass through an opening 68 in a tie rod 70, which is adjacent the journal bearing 34b. The tie rod 70 connects the motor rotor shaft 39 to the driveshaft 30. The bearing cooling streams BC1, BC2 then pass through an opening 72 in a compressor rotor 22. The opening 72 is at an upstream end of the rotor 22, adjacent the compressor inlet 24. The bearing cooling streams BC1, BC2 then mix with air in the compressor inlet 24, increasing the amount of air in the compressor inlet 24, thereby increasing the amount of air available for being drawn for the motor cooling stream MC and bearing cooling stream BC.
A third bearing cooling stream BC3 is also provided from the bearing cooling air inlet 50 to a transfer tube 54. The transfer tube 54 communicates the bearing cooling stream BC3 to the journal bearing 34b. The transfer tube 54 is attached to a housing 56 of the motor 28 via bosses 57.
Bearing cooling stream BC3 is provided to the journal bearing 34b via an opening 35 in a bearing support 66 (discussed more below) and passes through the journal bearing 34b in the same direction as the direction of airflow through the compressor 20. The third bearing cooling stream BC3 does not pass through the thrust bearing 33 or journal bearing 34a. Accordingly, the third bearing cooling stream BC3 is relatively cool compared to the first and second bearing cooling streams BC1, BC2 at the orifice O3. Therefore, the third bearing cooling stream BC3 provides improved cooling to the journal bearing 34a as compared to a cooling stream that has passed through the thrust bearing 33 and/or journal bearing 34a. The third bearing cooling stream BC3 ultimately exits the compressor 20 via cooling air outlet 48.
A seal 59, such as a labyrinth seal (though other types of seals are contemplated), is arranged immediately upstream from the journal bearing 34a and downstream from the motor 28. The seal 59 prevents the first bearing cooling stream BC1 from entering a cavity 58 between the thrust bearing 33 and the motor 28. Thus, the first bearing cooling stream BC1 is directed into the orifice O2 and then into the motor 28 (as discussed above) by the seal 59. Air in the cavity 58 thus stays cool relative to the temperature of air in the first bearing cooling stream BC1, and provides thermal insulation for the motor 28 and other compressor 20 components from the relatively hot first bearing cooling stream BC1. Additionally, the seal 59 prevents loss of pressure in the first bearing cooling stream BC1 as it travels through journal bearing 34a. In other words, the pressure drop of the first bearing cooling stream BC1 across the journal bearing 34a is relatively low. This improves the lifetime and reliability of the journal bearing 34a.
A heat shield 60 and seal plate 62 are provided upstream from the motor 28 and adjacent the journal bearing 34b. The seal plate 62 includes a seal 64 such as a vespel seal or o-seal, though other types of seals are contemplated. In one example, seal 64 is a static o-seal. Seal 64 prevents high-pressure air in the third bearing cooling stream BC3 from leaking into the outlet 48 prior to entering the journal bearing 34b. In other words, the seal 64 helps direct bearing cooling stream BC3 into the journal bearing 34b. The seal plate 62 also includes a seal 65 such as a labyrinth seal (though other types of seals are contemplated) immediately downstream from the journal bearing 34b. As with the seal 59 adjacent the journal bearing 34a, the seals 64, 65 adjacent the journal bearing 34b maintain pressure in the journal bearing 34b to minimize pressure drop across the journal bearing 34b, which improves the lifetime and reliability of the journal bearing 34b.
The heat shield 60 and seal 64 are downstream from a bearing support 66, while the seal plate 62 and seal 65 are upstream of the bearing support 66. The bearing support in this example supports the journal bearing 34b. In some examples, the bearing support 66 includes an opening 67 through which leaked hot, high pressure air within the compressor can flow towards the outlet 48. The heat shield 60 thermally insulates the motor 28 (and in particular, the motor stator 31) and journal bearing 34b from the hot air.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
