Patent Application
20230151818
Compressors have various uses including, for example, refrigerant circuits useful for refrigeration or air conditioning. A variety of compressor designs are available. One type of compressor includes magnetic bearings to facilitate rotation of the rotating components of the compressor, such as the motor shaft. Magnetic bearings can contribute to longer compressor life and less maintenance because they provide a contactless support of the rotating components.
One shortcoming of magnetic bearings is a limited ability to withstand certain aerodynamic forces. For example, during a surge or an uncontrolled shutdown, unsteady aerodynamic forces acting on the compressor components can cause the magnetic bearings to effectively lose control over the position of the motor shaft resulting contact with a touchdown bearing. When that occurs, bearing life is reduced. Additionally, when motor shaft control is lost, a bearing alarm is tripped requiring a manual reset.
An illustrative example embodiment of a compressor assembly includes a compressor housing having a suction inlet and a discharge outlet. A flow restricting valve allows unrestricted fluid flow in a first direction into the housing through the suction inlet and out of the discharge outlet during a first operating condition. The flow restricting valve allows a restricted fluid flow in a second, opposite direction into the housing through the discharge outlet in a second operating condition.
In addition to one or more of the features described above, or as an alternative, the flow restricting valve includes a fluid passage and a blocking member configured to be in a first position during the first operating condition and in a second position during the second operating condition; the fluid blocking member allows the unrestricted flow through the fluid passage in the first position; and the fluid blocking member partially blocks the passage in the second position to allow the restricted fluid flow through the passage during the second operating condition.
In addition to one or more of the features described above, or as an alternative, the fluid blocking member includes at least one hole through which some fluid may flow past the blocking member and through the passage when the fluid blocking member is in the second position.
In addition to one or more of the features described above, or as an alternative, the fluid blocking member comprises a flap.
In addition to one or more of the features described above, or as an alternative, the flap comprises a disk; the disk is supported by an arm adjacent the disk; and the at least one hole is aligned with the arm such that at least some fluid flowing through the at least one hole encounters the arm before continuing through the passage in the second direction.
In addition to one or more of the features described above, or as an alternative, the passage includes a surface that the fluid blocking member is at least partially received against in the second position; and at least one of the surface or the fluid blocking member includes a feature that prevents a complete seal from being established between the surface and the fluid blocking member in the second position.
In addition to one or more of the features described above, or as an alternative, the restricted fluid flow is between 5% and 15% of the unrestricted fluid flow.
In addition to one or more of the features described above, or as an alternative, the restricted fluid flow is between 5% and 10% of the unrestricted fluid flow.
In addition to one or more of the features described above, or as an alternative, the restricted fluid flow is about 12.5% of the unrestricted fluid flow.
In addition to one or more of the features described above, or as an alternative, the restricted fluid flow is less than 10% of the unrestricted fluid flow.
In addition to one or more of the features described above, or as an alternative, the compressor assembly includes at least one rotating component within the housing; and at least one magnetic bearing that supports the at least one rotating component in a manner that facilitates rotation of the at least one rotating component.
An illustrative example embodiment of a method of controlling fluid flow through a compressor housing having a suction inlet and a discharge outlet includes: allowing unrestricted fluid flow in a first direction into the housing through the suction inlet and out of the discharge outlet during a first operating condition; and allowing a restricted fluid flow in a second, opposite direction into the housing through the discharge outlet in a second operating condition.
In addition to one or more of the features described above, or as an alternative, the compressor housing contains rotating compressor components and a magnetic bearing that facilitates rotation of the rotating compressor components.
In addition to one or more of the features described above, or as an alternative, the method includes placing a flow restricting valve in a position to control fluid flow through the discharge outlet; opening the flow restricting valve during the first operating condition; and at least partially closing the flow restricting valve during the second condition.
In addition to one or more of the features described above, or as an alternative, the restricted fluid flow is between 5% and 10% of the unrestricted fluid flow.
The various features and advantages of at least one disclosed example embodiment will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.
The refrigeration circuit 20 includes a condenser 22, an expansion valve 34 and a cooler 36. The compressor 22, condenser 32, expansion valve 34, and cooler 36 each operate in a generally known manner.
A flow restricting valve 40 is configured to allow unrestricted fluid flow in a first direction into the housing of the compressor 22 through the suction inlet 24 and out of the discharge outlet 26 in a first operating condition, which corresponds to normal or desired operation of the refrigeration circuit 20. In other words, the flow restricting valve 40 does not hinder the flow of fluid, such as refrigerant, within the circuit 20 in a first operating condition. The flow restricting valve is also configured to allow restricted flow in second, opposite direction into the compressor 22 through the discharge outlet 26 in a second, different operating condition.
One example of such a second operating condition occurs immediately after a shutdown of the compressor 22. For example, immediately after some types of compressor shutdown, a significant pressure difference exists between the cooler 36 and the condenser 32. The circuit 20 will tend toward equilibrium and the higher pressure in the condenser 32 will force fluid back toward the cooler 36, which is at a lower pressure. Since the compressor 22 is in the pathway between the condenser 32 and the cooler 36, the fluid will flow into the discharge outlet 26 and through the compressor 22. The flow restricting valve 40 controls such fluid flow and only allows a restricted amount of fluid flow into the housing of the compressor 22 through the discharge outlet 26 under such conditions. The refrigeration circuit 20 includes a hot gas bypass path 42 through which the fluid may flow as the pressures in the condenser 32 and cooler 36 equalize. A valve 43 controls whether fluid can flow through the bypass path 42. The valve 43 remains closed during normal operation of the refrigeration circuit 20. The valve 43 is opened during conditions that may result in undesired backflow through the compressor 22.
The flow restricting valve 40 remains fully open during the first operating condition to allow unrestricted fluid flow into the suction inlet 24 and out of the discharge outlet 26. The flow restricting valve 40 allows some, restricted flow into the discharge outlet 26 and through the compressor 22 during the second operating condition. Completely cutting off such fluid flow at shutdown might be desirable from one perspective, however, a valve that would do so introduces other potential complications.
The flow restricting valve 40 operates like a modified check valve. A typical check valve allows flow in only one direction. The flow restricting valve 40 allows unrestricted flow in one direction and at least some, restricted flow in an opposite direction.
If the flow restricting valve 40 were designed to completely close off or prevent flow in one of two directions through the valve, that could result in a rapid change in flow through the compressor 22 during surge, for example. Such a change is undesirable because it imparts an impulsive force within the compressor 22 that tends to cause the magnetic bearing 30 to lose control over the position of at least the shaft of the motor 28. Allowing some, restrictive flow through the flow restricting valve 40 dampens or reduces such a rapid change in fluid flow through the compressor 22.
The flow restricting valve 40, therefore, allows at least some flow in each of two directions. Controlling the amount of flow in the second direction into the discharge outlet 26 of the compressor 26 as the circuit 20 equilibrates avoids an amount of flow in the second direction that would otherwise cause reverse rotation of the rotating components of the compressor 22 at a speed that may cause the magnetic bearing 30 to lose control over the position of the shaft of the motor 28. Some fluid may flow in the second direction into the discharge outlet 26 and through the compressor, even at a level that results in reverse rotation of the rotating components in the compressor 22, provided that such flow is not enough to introduce sufficient aerodynamic forces to overcome the position control provided by the magnetic bearing 30.
The flow restricting valve 40 strikes a balance between the need to avoid impact forces within the compressor 22 under some conditions, such as surge, and the need to prevent significant backward flow through the compressor 22 under other conditions. The flow restricting valve 40 may be considered a modified or partial check valve.
As shown in
In the example of
Whether the fluid blocking member 44 includes at least one hole or is prevented from establishing a seal against flow in the second direction, the restricted fluid flow is a relatively low percentage of flow compared to that permitted through the flow restricting valve 40 in the first operating condition when the valve is fully open. A restricted flow that is up to 15% of the flow when the valve is open is useful in some example embodiments. Restricting the flow in a second operating condition, such as immediately after a shutdown, to a limit between 5% and 15% of the unrestricted fluid flow accommodates some fluid flow through the compressor 22 while avoiding reverse rotation at an undesirably high speed. In some embodiments, the restricted fluid flow is kept between 5% and 10% of the unrestricted fluid flow based on the configuration of the flow restricting valve 40. In one example embodiment, the restricted fluid flow is about 12.5% of the unrestricted fluid flow. Some embodiments include maintaining the restricted fluid flow less than 10% of the unrestricted fluid flow provided that at least some flow is allowed.
The way in which the flow restricting valve 40 allows at least some restricted flow in two, opposite directions reduces the severity of flow interruption through the valve 40 and the compressor 22 during surge as the valve 40 transitions between closed and open positions. This improves the stability of the magnetic bearing 30 during surge conditions. Moderating the rate at which refrigerant can flow backward through the compressor 22 following an unpowered shutdown, for example, reduces a maximum reverse rotation speed of rotating components of the compressor 22. Keeping reverse rotation speeds within desired limits avoids conditions that would overcome the ability of the magnetic bearing to maintain control over the position of the shaft of the motor 28.
Controlling fluid flow through the compressor in a manner consistent with that described above increases bearing life and reduces the frequency of compressor maintenance, both of which contribute to longer-lasting and more reliable compressor performance.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.
This application claims priority to U.S. Provisional Application No. 63/279,781, which was filed on Nov. 16, 2021.
| Number | Date | Country | |
|---|---|---|---|
| 63279781 | Nov 2021 | US |
