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Rotary compressor unit and method of controlling operation thereof

a compressor unit and rotary technology, applied in the direction of machines/engines, liquid fuel engines, positive displacement liquid engines, etc., can solve the problems of reducing the compression efficiency the compressor unit is not always operated to produce the rated discharge pressure of the unit, and so as to improve the durability of the compressor unit

Inactive Publication Date: 2008-10-02
ANEST IWATA CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention relates to a rotary compressor unit comprised of a low pressure stage compressor and a high pressure stage compressor connected in series, and a method for controlling the rotation speed of each compressor independently. The invention allows for optimal load balancing of the compressors, resulting in optimal efficiency and durability of the compressor unit. The invention can be applied to a compressor unit with intermediate pressure stage compressors connected in series to the low and high pressure stage compressors, and load balancing of the compressors can be achieved.

Problems solved by technology

However, the compressor unit is not always operated to produce the rated discharge pressure of the unit.
Therefore, unbalance in load occurs between the low pressure stage compressor and the high pressure stage compressor, and temperature rise in the low pressure stage compressor becomes larger than that in the high pressure stage compressor, compression efficiency of the low pressure stage compressor decreases leading to decreased compression efficiency of the compressor unit, and in addition deleterious effect is caused on the durability of the compressor unit.
To achieve proper load balancing of the low pressure stage and high pressure stage compressors, it is needed to decrease the rotation speed of the low pressure stage compressor and increase the rotation speed of the high pressure stage compressor, which is however not possible with the conventional drive system of the compressor unit.
In a case the compressor unit is operated to produce a discharge pressure higher than the rated discharge pressure of the unit as shown by the lateral line z, the load of the high pressure stage compressor becomes relatively larger as compared to the load of the low pressure stage compressor and unbalance in load occurs in the two compressors.
Therefore, temperature rise in the high pressure stage compressor becomes larger than that in the low pressure stage compressor causing decrease in compression efficiency of the high pressure stage compressor.
Consequently, compression efficiency of the compressor unit is decreased and in addition deleterious effect is caused on the durability of the compressor unit.
To achieve load balancing of the low pressure stage and high pressure stage compressors, it is needed to increase the rotation speed of the low pressure stage compressor and decrease the rotation speed of the high pressure stage compressor, which is however not possible with the conventional drive system of the compressor unit.

Method used

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  • Rotary compressor unit and method of controlling operation thereof
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  • Rotary compressor unit and method of controlling operation thereof

Examples

Experimental program
Comparison scheme
Effect test

first embodiment

The First Embodiment

[0044]A first embodiment of the invention will be explained referring to FIG. 1. FIG. 1 is a schematic overall configuration of a rotary compressor unit having a low pressure stage compressor and a high pressure compressor of tooth type for example. Referring to FIG. 1, the rotary compressor unit comprises a low pressure stage compressor(hereafter referred to as LP compressor) 11, a high pressure stage compressor (hereafter referred to as HP compressor) 12, a LP compressor driving electric motor(hereafter referred to as LP motor) 13 connected directly to the LP compressor 11, and a HP compressor driving electric motor(hereafter referred to as HP motor) 14 connected directly to the HP compressor 12. Further, a LP motor controlling inverter circuit (hereafter referred to as LP inverter circuit) 15 for varying rotation speed of the LP motor 13 by varying frequency of power supply to LP motor 13 and a HP motor controlling inverter circuit (hereafter referred to as HP...

second embodiment

The Second Embodiment

[0052]Next, a second embodiment of the invention will be explained referring to FIG. 2. In FIG. 2, constituents same as those of FIG. 1 are denoted by the same reference numerals and explanation of them is omitted. Different point of the second embodiment of FIG. 2 from the first embodiment of FIG. 1 is that an intermediate pressure sensor 31 is provided to the discharge flow path 17 to detect discharge pressure of the LP compressor 11. Otherwise is the same as the first embodiment of FIG. 1. The pressure value detected by the intermediate pressure sensor 31 is inputted to the controller 22 in addition to the pressure value detected by the pressure sensor 21, and rotation speed of the LP and HP compressors 11, 12 are controlled via the LP and HP inverter circuits 15, 16 base on both the detected pressure values.

[0053]With this configuration of the second embodiment, not only the discharge pressure of the HP compressor 12 is detected in the discharge flow path 19...

third embodiment

The Third Embodiment

[0054]Next, a third embodiment of the invention will be explained referring to FIG. 3. In FIG. 3, constituents the same as those of FIG. 2 are denoted by the same reference numerals and explanation of them is omitted. Difference of the third embodiment of FIG. 3 from the second embodiment of FIG. 2 is that a single electric motor 41 is employed to drive the compressor unit, a variable speed gear (hereafter referred to as LP transmission) 43 is provided for varying the rotation speed of the LP compressor 11, a variable speed gear (hereafter referred to as HP transmission) 44 is provided for varying the rotation speed of the HP compressor 12, and a gear box 42 is connected to the electric motor 41, whereby the LP compressor 11 and HP compressor 12 are driven via the LP transmission 43 and HP transmission 44 respectively. Otherwise is the same as the second embodiment of FIG. 2.

[0055]With the compressor unit of the third embodiment, rotation of the electric motor 41...

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PUM

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Abstract

The compressor unit having at least two compressors, for example a low pressure stage compressor 11 and a high pressure stage compressor 12 connected in series, of which the low pressure sage compressor 11 and high pressure stage compressor 12 are driven by driving devices 13 and 14 respectively separately or driven by a single driving device 41 via variable speed gears 43 and 44 respectively connected to each of the compressors, and rotation speed of the low pressure stage compressor 11 and that of the high pressure stage compressor 12 are controlled independently in accordance with various operating conditions of the compressor unit so that optimal load balancing of the compressors 11 and 12 is always achieved.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a rotary compressor unit composed of a lower pressure stage compressor and a higher pressure stage compressor connected in series, and a method of controlling operation thereof, the unit being made possible to be operated with proper load balance of each of the compressors, thereby achieving efficient operation of the unit.[0003]2. Description of the Related Art[0004]Generally, a tooth type rotary compressor consists of two rotors, a male rotor and a female rotor, each having claw-like teeth, or lobes. They turn in opposite directions without contact to each other to compress gas trapped in the compression pockets formed between the lobes and inner surface of a compressor casing as the rotors rotate. As the rotors do not contact with each other and with the inner surface of the compressor casing, the rotors do not wear and have a long life. Further, lubrication of the rotors is not neede...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): F04C14/08F04C28/08
CPCF04C18/123F04C23/001F04C28/02F04C28/08F04C2270/051F04C2270/0525F04C2270/18
Inventor KIMURA, HIDEYUKI
Owner ANEST IWATA CORP