Methods and Systems for Injecting Liquid Into a Screw Compressor for Noise Suppression
A screw compressor for use in a chiller assembly includes cooperating screw rotors configured to increase the pressure of a vaporized refrigerant flowing through the compressor, a venturi tube arranged in a flow path of the refrigerant in the compressor downstream of the rotors, and an inlet port in fluid communication with a throat of the venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the flow path of the refrigerant in the compressor. The venturi tube is configured to cause a pressure drop in the refrigerant in the compressor. The liquid refrigerant delivered from the condenser reduces pulsations in the pressure of the refrigerant discharged from the compressor.
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The present invention relates to suppressing noise generated in mechanical systems. In particular, the present invention relates to noise suppression in screw compressors used in commercial and industrial air conditioning and refrigeration systems.
The use of compression type water-cooled chillers is the most common method of cooling air in medium or large commercial, industrial and institutional buildings. Compression type water-cooled chillers are usually electrically driven, but may also be driven by a combustion engine or other power source. There are several types of compressors employed in water-cooled chillers. One common compressor is a screw compressor, which uses a rotary type positive displacement mechanism to compress a working fluid, such as a refrigerant.
Water cooled chillers used in air conditioning and refrigeration systems are required to meet stringent noise level requirements, such as those prescribed by the Occupational Safety and Health Association (OSHA). However, screw chillers have a tendency to generate significant noise during operation. The primary source of noise generated in these types of chillers is pressure pulsations originating from the compressor, which generates noise, as well as vibration of adjoining components. In addition to the screw compressor, there is a multitude of secondary sources of noise, such as the evaporator, the condenser, and the economizer.
Prior screw compressor designs have employed various devices and methods to suppress the noise generated by the compressor, such as mufflers and baffle plates arranged in the discharge chamber. Additionally, prior chillers have injected liquid refrigerant from the condenser into the gas refrigerant flow discharged from the compressor to suppress noise generated from pressure pulsations. However, under many operating conditions, these prior chiller designs have required a pressure application device, such as a pump, to compensate for a negative pressure differential between the condenser and the compressor. The addition of a pump, or other device, increases the cost and complexity of the system.
SUMMARYA screw compressor for use in a chiller assembly includes cooperating screw rotors configured to increase the pressure of a vaporized refrigerant flowing through the compressor, a venturi tube arranged in a flow path of the refrigerant in the compressor downstream of the rotors, and an inlet port in fluid communication with a throat of the venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the flow path of the refrigerant in the compressor. The venturi tube is configured to cause a pressure drop in the refrigerant in the compressor. The liquid refrigerant delivered from the condenser reduces pulsations in the pressure of the refrigerant discharged from the compressor.
Chiller assembly 10 may commonly be located in relatively close proximity to people and as such may be designed to suppress noise production and radiation as much as possible. Screw compressor 12 is a significant contributor to noise generation, because of pressure pulsations created when the refrigerant is compressed. Pressure pulsations in compressor 12 result from unsteady mass flux caused by the refrigerant compression process performed within compressor 12. The pressure pulsations in compressor 12 produce undesirable noise, which noise in turn is radiated from chiller assembly 10. Additionally, the pressure pulsations may generate mechanical vibrations in components of chiller assembly 10 such as piping, heat exchangers, or compressor housing 20 itself. Mechanical vibrations propagating through chiller assembly 10 may themselves result in further noise generation and radiation.
In order to suppress noise generated from the pressure pulsations in compressor 12, chiller assembly 10 includes liquid refrigerant conduit 46 shown in
In order to deliver the liquid refrigerant from condenser 16 to the superheated gas refrigerant flow in compressor 12, the pressure in the condenser 16 must be greater than in the compressor 12. However, downstream of compression chambers 36 the superheated gas refrigerant often has a higher pressure than the pressure of the liquid refrigerant in condenser 16. Embodiments of the present invention therefore provide methods of and systems for inducing a pressure drop in the superheated gas refrigerant flow in compressor 12 sufficient to reduce the pressure in compressor 12 below the pressure in condenser 16 without the addition of work to the system.
As refrigerant flow 52 passes through venturi tubes 50, the velocity of flow 52 increases while the pressure of flow 52 decreases. The throat of venturi tubes 50 defines not only the location of minimum cross-sectional area, but also the location of minimum pressure of refrigerant flow 52. Venturi tubes 50 thereby induce a pressure drop in refrigerant flow 52 being discharged from compressor 12 through bearing housing 28 and discharge chamber 32 to condenser 16. In embodiments of the present invention, venturi tube 50 is configured to induce a pressure drop in refrigerant flow 52 sufficient to reduce the pressure of flow 52 at the throat of venturi tube 50 below the pressure of liquid refrigerant directed through conduit 46 from condenser 16. Therefore the liquid refrigerant from condenser 16 used to suppress noise in compressor 12 may freely flow from condenser 16 to compressor 12 without adding work to the system, e.g., without the use of a pressure applicator like a pump.
In some applications, space constraints in compressor 12 may not permit venturi tubes 50 to be disposed in bearing housing 28. In an alternative embodiment (
Embodiments of the present invention provide methods of and systems for inducing a pressure drop in the superheated gas refrigerant flow in a screw compressor of a chiller assembly sufficient to reduce the pressure in the compressor below the pressure in a condenser without the addition of work to the system. Inducing a pressure drop in the compressor refrigerant flow enables liquid refrigerant from the condenser to freely flow to the compressor without the use of a pressure application device, such as a pump. Embodiments of the present invention thereby suppress noise generated from pressure pulsations in the screw compressor by injecting liquid from the condenser into the gas refrigerant flow in the compressor without significantly increasing the cost and complexity of the chiller assembly.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
Claims
1. A screw compressor for use in a chiller assembly, the compressor comprising:
- a plurality of cooperating screw rotors configured to increase the pressure of a vaporized refrigerant flowing through the compressor;
- a first venturi tube arranged in a first flow path of the refrigerant in the compressor downstream of the rotors for causing a pressure drop in the refrigerant; and
- a first inlet port in fluid communication with a throat of the first venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the flow path of the refrigerant in the compressor for reducing pulsations in the pressure of the refrigerant discharged from the compressor.
2. The compressor of claim 1, wherein the first venturi tube is located in a bearing housing of the compressor.
3. The compressor of claim 1, wherein the first venturi tube is located in a discharge housing of the compressor.
4. The compressor of claim 1 further comprising:
- a second venturi tube arranged in a second flow path of the refrigerant in the compressor; and
- a second inlet port in fluid communication with a throat of the second venturi tube and configured to deliver liquid refrigerant from the condenser to the second flow path of the refrigerant in the compressor.
5. The compressor of claim 1, wherein the first venturi tube reduces the pressure of the refrigerant in the compressor below a pressure of the refrigerant in the condenser.
6. A chiller assembly comprising:
- a screw compressor;
- a condenser coupled to the screw compressor;
- a first venturi tube arranged in a first flow path of a refrigerant passing through the compressor, wherein the first venturi tube comprises a convergent portion connected to a divergent portion at a throat; and
- a first conduit coupled between the throat of the first venturi tube and the condenser and configured to deliver liquid refrigerant from the condenser to the first flow path of the refrigerant in the compressor for reducing pulsations in the compressed refrigerant exiting the compressor.
7. The assembly of claim 6, wherein the screw compressor comprises:
- a plurality of cooperating screw rotors configured to increase a pressure of the refrigerant flowing through the compressor, wherein the first venturi tube is arranged downstream of the screw rotors.
8. The assembly of claim 7, wherein the first venturi tube is located in a bearing housing of the compressor.
9. The assembly of claim 7, wherein the first venturi tube of the discharge chamber is located in a discharge housing of the compressor.
10. The assembly of claim 6 further comprising:
- a second venturi tube arranged in a second flow path of the refrigerant in the compressor, wherein the second venturi tube comprises a convergent portion connected to a divergent portion at a throat; and
- a second conduit coupled between the throat of the second venturi tube and the condenser is configured to deliver liquid refrigerant from the condenser to the second flow path of the refrigerant in the compressor.
11. The assembly of claim 6, wherein the first venturi tube reduces a pressure of the refrigerant in the compressor below a pressure of the refrigerant in the condenser.
12. A screw compressor for use in a chiller assembly, the compressor comprising:
- a screw rotor bearing housing;
- a first venturi tube disposed in the bearing housing and arranged in a first flow path of a refrigerant carried through the bearing housing for decreasing the pressure of the refrigerant; and
- a first inlet port in fluid communication with a throat of the first venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the first flow path of the refrigerant in the bearing housing.
13. The compressor of claim 12 further comprising:
- a second venturi tube disposed in the bearing housing and arranged in a second flow path of the refrigerant carried through the bearing housing; and
- a second inlet port in fluid communication with a throat of the second venturi tube and configured to deliver liquid refrigerant from the condenser to the second flow path of the refrigerant in the bearing housing.
14. The compressor of claim 12, wherein the venturi tube reduces a pressure of the refrigerant in the bearing housing below a pressure of the refrigerant in the condenser.
15. A screw compressor for use in a chiller assembly, the compressor comprising:
- a discharge housing;
- a first venturi tube disposed in the discharge housing and arranged in a first flow path of the refrigerant carried through the discharge housing for decreasing the pressure of the refrigerant; and
- a first inlet port in fluid communication with the throat of the venturi tube and configured to deliver liquid refrigerant from a condenser of the chiller assembly to the first flow path of the refrigerant in the discharge housing.
16. The compressor of claim 15 further comprising:
- a second venturi tube disposed in the discharge housing and arranged in a second flow path of the refrigerant carried through the discharge housing; and
- a second inlet port in fluid communication with a throat of the second venturi tube and configured to deliver liquid refrigerant from the condenser to the second flow path of the refrigerant in the discharge housing.
17. The compressor of claim 15, wherein the first venturi tube reduces a pressure of the refrigerant in the discharge housing below a pressure of the refrigerant in the condenser.
18. A method of suppressing noise in a screw compressor of a chiller assembly, the method comprising:
- introducing a liquid refrigerant from a condenser of the chiller assembly into a compressed gas refrigerant flowing through the screw compressor to reduce pulsations in the refrigerant; and
- reducing, without adding work, a pressure of the gas refrigerant in the compressor below a pressure of the liquid refrigerant in the condenser to facilitate introduction of the liquid refrigerant into the gas refrigerant.
19. The method of claim 18, wherein the pressure of the gas refrigerant is reduced by passing the gas refrigerant through one or more venturi tubes.
20. The method of claim 18, wherein the pressure of the gas refrigerant is reduced in one of a bearing housing or a discharge housing of the compressor.
Type: Application
Filed: May 19, 2009
Publication Date: Jan 27, 2011
Applicant: CARRIER CORPORATION (Farmington, CT)
Inventor: Vishnu M. Sishtla (Manlius, NY)
Application Number: 12/933,729
International Classification: F25B 1/00 (20060101); F01C 1/16 (20060101);