JPH04301200A - Control method of surging of fluid machinery - Google Patents

Abstract

PURPOSE:To carry out highly precise detection of surging generation limit by making the limit whereat surging prevention control is started under a specified condition in a fluid machine wherein a premonitory phenomenon of surging generation is detected to control flow and pressure and prevent generation of surging. CONSTITUTION:When necessary gas glow of a supply destination 8 whereto compressed gas is supplied from a blower 1 is less than the flow of surging generation limit of the blower 1, the generation of surging 1 is prevented by opening a blow-off valve 6 and increasing the flow of passing gas of the blower 1. In this case, a microphone 2 that measures the sound that the blower 1 produces is provided, and the measured sound signal is spectrally analyzed by a frequency analyzer 5. And, the state wherein the spectral height of both the component of the product of the number of blades of the impeller of the obtained frequency spectrum and the rotation speed of the impeller and its integral multiple or one of them exceeded a critical value is constituted as the limit whereat surging prevention control is started, and the blow-off valve 6 is opened by a valve driving system 5 when it reached the surging generation limit.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surging control method for a fluid machine such as a turbo blower or compressor.

0002

[Prior Art] In a turbo blower or compressor, when the flow rate decreases below a limit value, or when the pressure rise before and after the turbo blower or compressor exceeds a limit value, a so-called surging phenomenon occurs, resulting in characteristic periodic sounds, intense vibrations, or noise. occurs. The severe vibration or noise that accompanies this surging phenomenon can cause equipment damage or failure in large-capacity models. Such prevention of surging is described, for example, in ``Turbo Blower and Compressor'' by Ikui and Inoue, Corona Publishing, 1983-8, pages 598 to 600.

0003

[Problem to be solved by the invention] For this reason, the operating flow rate and pressure rise are constantly monitored, and if these amounts exceed the limits, the flow rate is increased by bypass control, etc., and the equipment is stopped, etc., to prevent the occurrence of the surging phenomenon. . However, the flow rate and pressure rise at the threshold for surging change depending on the suction temperature of the turbo blower or compressor, fluctuations in rotational speed, and dirt on the impeller. For this reason, normally, operating operations to prevent surging must be performed before the operating state reaches the actual surging generation limit, which increases energy loss due to bypass control or the like, or makes it difficult to reduce the number of times the equipment stops.

0004

[Means for Solving the Problems] The present invention analyzes the frequency spectrum of the measured pressure, sound, or vibration by installing a pressure sensor, a microphone, or an acceleration sensor for measuring the vibration of the wall surface of the fluid machine inside or outside the fluid machine. means for determining the analyzed frequency spectrum distribution; and (1) means for variably controlling one or both of the movable and variable impeller blades and/or the stationary structure. (2) Means for controlling rotation speed control. (3) Means for controlling the pressure difference between the suction and discharge sides of the turbo blower or compressor. (4) Means for controlling flow rate. It consists of means for controlling both or one of the flow rate and pressure rise of a fluid machine by one or a combination of two or more types.

[0005]

[Operation] In a fluid machine such as a turbo blower or a compressor, impeller or diffuser rotating stall generally occurs when operating conditions approach the surging generation limit. Since a rotating stall generates clear pressure fluctuations with a frequency of about a fraction of the impeller rotation speed, it is effective to detect this pressure fluctuation to detect the limit of surging occurrence. During this phase, rotating stalls occur intermittently and for extremely short periods of time. In this state, pressure fluctuations caused by rotating stall only last for a very short time and are difficult to observe. However, components of the product of the number of impeller blades and the number of rotations of the impeller and its integral multiples in the frequency spectrum of the pressure, sound, or vibration of the turbo blower or compressor wall measured inside or outside the turbo blower or compressor continue for an extremely short time. The spectral height, spectral width, or both increase also in response to pressure fluctuations during a rotating stall. By detecting this spectrum change, the surging generation limit is detected with high precision and is set as the limit at which surging prevention control is started. (1) Variable control of one or both of the impeller blades configured to be movable and/or the stationary structure. (2) Rotation speed control. (3) Controlling the pressure difference between the suction and discharge sides of a turbo blower or compressor. (4) Flow rate control. By controlling both or one of the flow rate and pressure rise of the turbo blower or compressor using one or a combination of two or more of the following, the operating state is prevented from approaching a surging state from the state where the limit for starting surging prevention control is reached. control.

[0006]

Embodiments In the embodiments described below, a fluid machine such as a turbo blower or a compressor will be simply referred to as a blower for the sake of simplicity. An embodiment will be described with reference to FIGS. 1 to 4. FIG. 1 shows a case in which the surging generation limit is detected with high accuracy based on sound measured outside the blower and is set as the limit at which surging prevention control is started. The blower 1 supplies compressed gas to a supply destination 8 . If the required gas flow rate of the supply destination 8 is less than the surging generation limit flow rate of the blower 1, the blower valve 6 is opened and the compressed gas flows out to the blower pipe 7 to increase the gas flow rate passing through the blower 1, thereby causing surging. This is a configuration that prevents this. A microphone 2 is installed outside the blower 1 to measure the sound generated by the blower 1 in order to determine the surging generation limit. The acoustic signal measured by the microphone 2 is subjected to spectrum analysis by the frequency analyzer 3. The controller 4 determines whether the operating state of the blower 1 has reached the surging generation limit based on the spectrum obtained by the frequency analyzer 3, and if the operating state of the blower 1 has reached the surging generation limit, the valve driver 5
The blower valve 6 is opened to prevent the blower 1 from surging. The operation of determining the surging occurrence limit may be continuous or intermittent. Details of the discrimination method and air release valve 6 are shown below.
Describe the operation.

FIG. 2 is a diagram showing the characteristics of the blower 1. When the relationship between the flow rate and pressure rise at the blower operating point is in region a, the blower is in a normal state. FIG. 3 shows the spectral distribution in this state. Product of impeller blade number and impeller rotation speed ωr
and a high spectrum appears at an integer multiple of that. A spectrum with a high integral multiple of ωr clearly appears when a stationary blade is provided immediately downstream of the impeller. When the operating point is in region b, a rotating stall occurs in the impeller or diffuser. The rotating stall generates clear pressure fluctuations with a frequency of about a fraction of the impeller rotation speed, but the spectrum of ωr and its integral multiples also changes. FIG. 4 shows a spectrum when the operating point is in region b. When a rotating stall occurs, fluctuations other than the rotating stall frequency also increase due to a significant increase in blower internal flow turbulence. Therefore, the overall spectral height increases, but in the spectrum of ωr and its integral multiples, the height increases not only significantly, but also the spectral width increases. Furthermore, the increase in spectral width is large on the low frequency side. Therefore, depending on whether or not the height or width of the spectrum of ωr and its integral multiple, or both values exceed the state of region a, which is the reference state, the occurrence of a turning stall can be determined.
Therefore, it becomes possible to determine whether the operating point is in region a or region b.

There are several methods of operating the blowoff valve 6. In the case of a model in which the blower 1 compresses high-pressure gas or rotates at high speed, long-term operation is undesirable because rotating stall itself generates severe vibration or noise in many cases. In such a case, after determining that the operating point has entered region b, the blowoff valve 6 is immediately opened until the operating point is in region a, and the operating point is moved, for example, to the position of point M in FIG. 2.

If the increase in vibration or noise due to rotating stall is small, it is not necessary to immediately change the operating point to the state of the blower in region a, so after determining that the operating point has entered region b, the blower valve 6 is slightly turned off. Open to. Thereafter, if the operating point is still in region b, the blowoff valve 6 is further opened slightly using the method described above. By repeating these operations, the blowoff valve 6 is opened until the operating point reaches the boundary R between area a and area b.

[0010] Furthermore, after determining that the operating point has entered region b, there is also a method in which an alarm is issued along with the above operations, or an alarm is issued but a control system provided separately is used to operate the blow-off valve.

In general, region b is limited to the vicinity of the surging occurrence limit S and is significantly narrower than region a. Therefore, the surging occurrence limit must be detected with high precision to prevent the occurrence of surging, resulting in an increase in energy loss or an increase in equipment loss. The number of stops can be reduced.

In the embodiment, the blower operating point is controlled by air discharge control, but the same effect can be obtained by using other control methods. FIG. 5 shows an embodiment suitable for the case where the gas compressed by the blower cannot be discharged to the outside of the equipment. That is, the suction side and the discharge side of the blower are connected by a return pipe 9, and a return valve 10 is installed in the middle.
will be established. When the return valve 10 is opened, the pressure difference between the suction side and the discharge side decreases, and the flow rate passing through the blower increases. Therefore, return valve 1
The control method of 0 is exactly the same as the blowoff valve of the embodiment shown in FIG.

FIG. 6 shows an embodiment suitable for a large-capacity model, and when the flow rate passing through the blower decreases and reaches the surging generation limit, surging generation is avoided by a combination of the following methods. (1) The electric motor 12 that drives the blower has a variable speed, and when the flow rate passing through the blower decreases and reaches the surging generation limit, the rotation speed controller 11 lowers the rotation speed. (2) Inlet stationary blade 13
is rotatably supported by a stator blade drive machine 15,
When the flow rate passing through the blower decreases and reaches the surging generation limit, the inlet stationary blade is rotated in a direction away from the rotation axis of the impeller. (3) Moving blade 14 attached to the impeller
is rotatably supported by a rotor blade drive machine 16,
When the flow rate passing through the blower decreases and reaches the surging generation limit, a control signal generated by the controller 4 is transmitted to the rotor blade driver 16 via the slip ring 17 to move the rotor blade 14 in the direction of the rotation axis of the impeller. Rotate it in the direction away from the In this embodiment, since the flow rate passing through the blower is reduced, the power required to boost the pressure of the passing gas is also reduced, resulting in good energy efficiency.

[0014] The detection of the operating state is not limited to sound; similar effects can be obtained by using internal or external pressure fluctuations or vibrations of the blower wall surface. The blower 1 is not limited to one blower having one impeller, but may be a blower having many impellers or a large number of blowers.

[0015]

According to the present invention, it is possible to detect the limit of surging occurrence with high accuracy, and by reducing the number of driving operations to prevent surging occurrence, the energy loss for preventing surging occurrence is increased. Alternatively, it becomes possible to reduce the number of times the equipment is stopped.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between blower flow rate and pressure rise.

FIG. 3 is a diagram showing the acoustic spectrum of the blower under normal operating conditions.

FIG. 4 is a diagram showing an acoustic spectrum of the blower in the operating state at the generation limit.

FIG. 5 is a configuration diagram showing another embodiment of the present invention.

FIG. 6 is a configuration diagram showing still another embodiment of the present invention.

[Explanation of symbols]

1...Blower, 2...Microphone, 3...Frequency analyzer, 4
... Controller, 5 ... Valve drive machine, 6 ... Air discharge valve, 7 ... Air discharge pipe, 8 ... Supply destination, 9 ... Return pipe, 10 ... Return valve, 11 ... Rotation speed controller, 12 ... Electric motor, 13 ... Inlet static wings, 1
4... Moving blade, 15... Stator blade drive machine, 16... Moving blade drive machine, 17
...Slip ring.

Claims (1)

[Claims] Claim 1: Means for measuring the pressure of a fluid machine and acoustic wall vibration, means for analyzing the frequency spectrum of the measured pressure and acoustic vibration, and detecting a precursor phenomenon of surging based on the analyzed frequency spectrum distribution. In turbo blowers and compressors that control the flow rate and pressure rise of the turbo blower or compressor to prevent the occurrence of surging, both the component of the product of the number of impeller blades and the impeller rotation speed of the analyzed frequency spectrum and the integral multiple thereof, or A surging control method for a fluid machine, characterized in that a state in which one spectrum height exceeds a critical value is set as a limit for starting surging prevention control.