JPH06167299A - Surging detection device - Google Patents

Abstract

PURPOSE:To obtain a surging detection device at low cost which does not require a pressure difference detector for detecting minute pressure difference two pressure detectors requiring careful zero correction. CONSTITUTION:A pressure detector 8 detects an inlet pressure of a diffuser 5. A motor current detector 9 detects current of a motor 4 which drives an impeller 3. A controller 10 computes output signals of the detectors 8, 9, and outputs a surging signal when a fluctuation ration DA of the current in the specified time and a fluctuation DP of a pressure in the same time are larger than ratio preset reference values PS, AS. Generation of surging can be detected when both the pressure fluctuation ratio (pressure waveform) and current fluctuation ratio (current waveform) exceed the respective reference values. Surging detection can be carried out at low cost with high precision without an expensive pressure difference detector which detects minute pressure difference or two pressure detectors which require zero correction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a surging detection device,
Specifically, the present invention relates to a surging detection device in a turbo compressor including an impeller and a diffuser.

[0002]

2. Description of the Related Art Conventionally, as a surging detecting device for a turbo compressor, for example, one disclosed in Japanese Patent Laid-Open No. 3-199700 has been already known.

As shown schematically in FIG. 4, the surging detecting device of this publication has a hub side conduit B and a shroud side for guiding a hub side pressure to a diffuser A having a hub side inlet part and a shroud side inlet part. A shroud-side conduit C for guiding the pressure is provided, and a pressure sensor is provided on each of these conduits B, C. A differential pressure detector D is connected to these pressure sensors, and a hub side for detection by the differential pressure detector D is provided. When the differential pressure between the pressure and the pressure on the shroud side reaches a set differential pressure that is lower than the differential pressure when surging occurs, a surging signal is output. Incidentally, E is an output unit, and has a comparator F which compares the measured differential pressure detected by the differential pressure detector D with the set differential pressure as a reference value.

[0004]

However, since the pressure difference between the hub-side pressure and the shroud-side pressure is small, for example, a minute pressure difference of about 0.04 to 0.1 kg / cm ² , the above-mentioned difference. The pressure detector D is required to have high precision, two high precision pressure sensors are required, and it is necessary to carefully perform zero correction of these pressure sensors, so that the whole detection device becomes expensive. there were.

An object of the present invention is to pay attention to the fact that when surging occurs, the current waveform of the motor driving the impeller and the pressure at the inlet of the diffuser, for example, the pressure waveform of the pressure on the shroud side, change at the same time. It is an object of the present invention to provide a surging detection device that can detect surging with high accuracy at low cost while using an inexpensive pressure detector without using two expensive pressure sensors or differential pressure detectors that detect

[0006]

In order to achieve the above object, in the present invention, in a surging detecting device in a turbo compressor having an impeller 3 and a diffuser 5, the pressure near the inlet of the diffuser 5 is detected. A pressure detector 8 and a motor current detector 9 for detecting the current of the motor 4 for driving the impeller 3 are provided, while the output signals of the detectors 8 and 9 are calculated to change the current in a predetermined time. The controller 10 is provided which outputs a surging signal when both the rate and the rate of change in pressure at the same time are larger than a preset reference value.

[0007]

Based on the output signals of one of the pressure detector 8 and the motor current detector 9, the rate of pressure change at the inlet of the diffuser 5, that is, the pressure waveform and the current change of the motor 4 at the same time. Rate, that is, the current waveform, and when both the pressure change rate and the current change rate are higher than the respective reference values, the occurrence of surging can be detected. Without using an expensive differential pressure detector that detects the differential pressure with the side pressure or two pressure detectors that require careful zero correction, it is possible to accurately perform surging while using an inexpensive pressure detector. It can be detected.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a turbo compressor 1 used for a refrigerating machine, for example.
An impeller 3 having a hub 3a is rotatably supported and is driven by a motor 4 provided on one side of the housing 2 via a gear mount assembly 11.

The outlet 3b of the impeller 3 is faced with a diffuser 5 having a hub-side inlet and a shroud-side inlet, while a guide vane connected to an operating motor 6 is provided on the inlet 3c side of the impeller 3. 7, the air volume can be adjusted by changing the opening of the guide vane 7. In FIG. 1, 12 is a ring gear coupling and 13 is a discharge pipe.

However, in this embodiment, as shown in FIGS. 1 and 2, a pressure introducing pipe 81 to which a pressure detector 8 is connected is provided at the shroud side inlet of the diffuser 5, and the pressure detector 8 is used. The pressure of the inlet of the diffuser 5 introduced from the pressure introducing pipe 81 can be detected, and a motor current detector 9 is provided in the motor 4 so that an input current to the motor 4 can be detected.

Further, for example, a controller 10 composed of a microcomputer is provided, and the detectors 8 and 9 are connected to the input side of the controller 10 for a predetermined time based on the output signals from the detectors 8 and 9. (1 second or less, for example, 0.2
Current change rate DA and pressure change rate DP for up to 0.5 seconds) are calculated in parallel, and current change rate D at the same time is calculated.
The current waveform and the pressure waveform are obtained by A and the pressure change rate DP, and the operation motor 6 of the guide vane 7 and the central monitoring board 20 are connected to the output side of the controller 10 so that the same time can be obtained. Reference values AS and P preset by both the current change rate DA and the pressure change rate DP
When it is larger than S, the opening of the guide vane 7 is controlled, and a surging signal is output to the central monitoring board 20 to display an alarm.

In FIG. 2, 21 is a switch provided in the power supply circuit 22 of the motor 4, and 23 is a fuse.

In the above structure, for example,
When the turbo compressor 1 is used in a refrigeration system that cools a condenser by a cooling water pipe connected to a cooling tower, the high pressure of the compressor 1 decreases when the temperature of the cooling water in the condenser decreases, and At the time of starting the compressor 1, since a large starting current flows in the motor 4, that is, only one of the current and the pressure may change, but as described above, the current change at the same time. By calculating the rate DA and the pressure change rate DP,
Even if only one of the current and pressure changes, the surging signal is not output.

Next, the operation of the refrigerating apparatus configured as described above will be described with reference to the flow chart shown in FIG.

First, the current reference value AS and the pressure reference value PS are set in the controller 10 and the operation is started. After the start, in step 1, the current value A1 output by the current detector 9 and the shroud pressure value P1 output by the pressure detector 8 are detected and stored. Then, the elapsed time is counted by the timer in step 2, and the current value A2 and the pressure value P2 are detected again in step 3 after the elapse of a certain time, for example, 0.5 seconds (Δt), and in step 4, 0.5 seconds. The current change rate DA and the pressure change rate DP during (Δt) are calculated at the same time.

Therefore, in step 5, the current change rate DA is compared with the current reference value AS, and the pressure change rate DP is compared with the pressure reference value PS, and the current change rate DA is the current. Above the reference value AS, and
It is determined whether or not the pressure change rate DP is equal to or higher than the pressure reference value PS, and if YES in step 5, that is, when both the pressure change rate DP and the current change rate DA are equal to or higher than the reference values PS and AS. Then, it is judged that surging has occurred, and in step 6, the guide vanes 7 are controlled to be opened, and in step 7, an alarm is displayed.

If the answer in step 5 is NO, it is determined that surging has not occurred, the process returns to step 1, and the current value A1 and the shroud pressure value P1 are detected again as described above.

Therefore, in the embodiment shown in FIGS. 1 and 2, the pressure introducing pipe 81 is provided only on the shroud side at the inlet of the diffuser 5, and the pressure change rate at the inlet of the diffuser 5 is provided by the pressure detector 8. D
P, that is, the pressure waveform is detected, and at the same time when the pressure change rate DP is detected, the current change rate DA of the motor 4, that is, the current waveform is detected, and the pressure change rate D is detected.
When both A and the current change rate DA are higher than the respective reference values PS and AS, the occurrence of surging can be detected, so that the differential pressure between the shroud side pressure and the hub side pressure, which is a minute difference as in the conventional case, is detected. It is possible to detect surging with high accuracy while using an inexpensive pressure detector, without using an expensive differential pressure detector or two expensive pressure detectors that require careful zero correction. It is possible to obtain a surging detection device having high performance and low cost.

In the embodiment shown in FIGS. 1 and 2, the pressure introducing pipe 81 is provided on the shroud side of the diffuser 5 and the pressure on the shroud side at the inlet of the diffuser 5 is detected. The pipe 81 may be provided on the hub side of the diffuser 5.

[0020]

As described above, according to the present invention, in the surging detecting device in the turbo compressor provided with the impeller 3 and the diffuser 5, the diffuser 5 is used.
A pressure detector 8 for detecting the pressure near the inlet of the motor, and a motor current detector 9 for detecting the current of the motor 4 for driving the impeller 3, while each of the detectors 8,
When the output signal of 9 is calculated and the rate of change of the current at a predetermined time and the rate of change of the pressure at the same time are both larger than a preset reference value, a controller 10 is provided for outputting a surging signal. Based on the output signals of the detector 8 and the motor current detector 9, the pressure change rate at the inlet of the diffuser 5, that is, the pressure waveform, and the current change rate of the motor 4, that is, the current waveform, are calculated at the same time. If both the pressure change rate and the current change rate are higher than the respective reference values, the occurrence of surging can be detected. Therefore, an expensive differential pressure detector that detects the pressure difference between the shroud side pressure and the hub side pressure, which is a minute difference as in the past, and two expensive pressure detectors that require careful zero correction are used. It is possible to obtain a low-cost surging detecting device that can detect surging with high accuracy without using an inexpensive pressure detector.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a turbo compressor to which a surging detection device of the present invention is applied.

FIG. 2 is a block diagram of a controller.

FIG. 3 is a flowchart showing an example of the operation of the controller.

FIG. 4 is a schematic diagram illustrating a conventional example.

[Explanation of symbols]

 3 Impeller 4 Motor 5 Diffuser 8 Pressure detector 9 Motor current detector 10 Controller

Claims (1)

[Claims] 1. A surging detection device in a turbo compressor comprising an impeller 3 and a diffuser 5, comprising:
A pressure detector 8 that detects the pressure near the inlet of the diffuser 5 is provided, and a motor current detector 9 that detects the current of the motor 4 that drives the impeller 3 is provided, while the outputs of the detectors 8 and 9 are provided. A surging detection device characterized in that a controller 10 is provided for calculating a signal and outputting a surging signal when both the rate of change of current at a predetermined time and the rate of change of pressure at the same time are larger than a preset reference value. .