JPS6394098A - Surging detecting device for compressor - Google Patents

Abstract

PURPOSE:To detect surging certainly by providing two circuits in parallel between a pressure signal transmitter and a receiver, one makes sampling short period and the other makes sampling in long period having the least common multiple period of in large value. CONSTITUTION:Signals from a pressure difference transmitter 5 on the suction side of a compressor 2 are given to a receiver 6 in form of two systems of signal different in sampling period such as A system sampling 7 and a B system sampling 8. The sampling periods of A system and B system are chosen in such manner that the least common multiple of those periods becomes as large as possible. Therefore, both systems seldom coincide with each other in their surging periods for eliminating any oversight of a surging and delay in detection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surging detection device applied to a centrifugal or axial flow compressor.

[Conventional technology]

In the compressor, as shown in the 4th diagram, the rotation speed r
When the flow rate is decreased in the direction of the arrow with Ll constant, and it reaches point A, the fluid stalls, the wind pressure and air volume vibrate, and noise is generated, causing the rotating machine to vibrate and become inoperable. This results in the so-called surging phenomenon.

Therefore, it is necessary to operate the compressor while avoiding the occurrence of the surging phenomenon. Conventionally, the surging detection device is installed on the suction side of the compressor 2 driven by the driver 1, as shown in the system diagram in Figure 5. To attach the flow rate measuring orifice 4 to the piping 3, the differential pressure between α and b before and after the orifice is oscillated by the differential pressure oscillator 5, the output signal is received by the receiver 6, and the differential pressure is compared with the signal from one second ago, for example. If there is a fluctuation of 1° or more, it is determined that surging has occurred, and an appropriate surging prevention device is activated.

This type of surging detection means is based on the flow rate Q and the differential pressure Pα-pb.
It uses the following relationship between

Q=αεAJ2f(Pα−Pb]/γ.

A is the cross-sectional area of the niorifice, α is the flow rate coefficient, i is the acceleration of gravity, γα is the specific weight of the fluid immediately before the niorifice, and ε is the correction coefficient due to the expansion of the fluid.

[Problem that the invention seeks to solve]

However, such a surging detection means has the following problems.

In other words, in the differential pressure fluctuation waveform during surging shown in Fig. 6, if the sampling period S seconds matches the surging period S' seconds, even if surging occurs, it will not be able to be detected and will not be completely detected. Even if they do not match, if they are nearby, there will be a time delay in detection.

On the other hand, although it is possible to theoretically determine the surging limit, the frequency varies depending on the type of plate gas and the piping system even in the same compressor, so it is only possible to determine the surging limit based on actual results and actual machine tests. This is the current state of the industry.

The present invention was proposed in view of the above circumstances, and an object of the present invention is to provide a highly reliable surging detection device that can quickly and reliably detect surging.

[Means for solving problems]

To this end, the present invention provides a compressor surging detection device in which a flow rate measuring orifice is inserted into the suction side piping of the compressor, and the pressure at this orifice is detected via a pressure transmitter, a sampling circuit, and a receiver. , a first series sampling circuit that is connected in parallel between the pressure transmitter and the receiver and performs sampling in a relatively short period, and a sampling circuit that performs sampling in a long period having a relatively large least common multiple with respect to the short period. A second series of sampling circuits are provided.

[For production]

With this configuration, there are two systems of sampling circuits, and the least common multiple of the sampling periods of both sampling circuits is selected to have a large value, so it is possible to detect surging differential pressure by matching the sampling period with the surging period. It is possible to prevent it from falling.

〔Example〕

To explain one embodiment of the present invention with reference to the drawings, Fig. 1 is a system diagram thereof, Fig. 2 is a line diagram showing the sampling procedure in Fig. 1, and Fig. 3 is a line diagram showing the sampling procedure not adopted in Fig. 1. It is a diagram.

First, in FIGS. 1 and 2, the same symbols as in FIGS. 5 and 6 indicate the same members as in FIGS. 5 and 6, respectively. In FIG. ,
In the B-system sampling 8, two systems of signals with different sampling periods are given to the receiver 6.

At this time, if the sampling period of both systems A and B is a simple multiple such as 2 or 3, it is not preferable because both systems may coincide with the surging period.

For example, as shown in FIG. 3, when the sampling period of system B is twice the sampling period of system A, the surging phenomenon may be overlooked.

Therefore, in the present invention, as shown in the sampling period shown in FIG. 2, the A system and the B system are selected so that the least common multiple is as large as possible, such as 7=22.

Although the differential pressure before and after the orifice was detected using the flow rate as a means of surging detection, depending on the situation, only the front pressure or back pressure of the orifice may be detected.

〔Effect of the invention〕

According to such a device, the following effects could be achieved.

(1) There is no oversight of compressor surging or delay in detection, and an accurate surging occurrence signal can be quickly sent to the surging prevention mechanism.

(2) Therefore, compression troubles due to surging are eliminated, and reliability can be improved.

In short, according to the present invention, a surging detection device for a compressor is configured such that a flow rate measuring orifice is inserted into the suction side piping of the compressor, and the pressure at this orifice is detected via a pressure transmitter, a sampling circuit, and a receiver. , a first series sampling circuit that is connected in parallel between the pressure transmitter and the receiver and performs sampling in a relatively short period; and a sampling circuit that performs sampling in a relatively short period with a long period having a relatively large least common multiple with respect to the short period. The present invention is industrially extremely useful because it provides a highly reliable surging detection device that can quickly and reliably detect surging by providing a second series of sampling circuits that perform this.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the present invention, and Fig. 2 is a system diagram showing an embodiment of the present invention.
A diagram showing the sampling procedure in Figure 3, Figure 1
FIG. 3 is a diagram showing a sampling procedure not adopted in the figure. FIG. 4 is a diagram showing surging in a known compressor, FIG. 5 is a system diagram showing a known compressor surging detection device, and FIG. 6 is a diagram showing an example of the sampling period in FIG. . 1. Drive machine, 2. Compressor, 3. Suction side piping, 4.
- Orifice, 5... Differential pressure oscillator, 6... Receiver, 7,
8...Period and differential pressure fluctuation value discriminator sub-agent Patent attorney Masa Tsukamoto Figure 1 Figure 4 0, KoniQ

Claims (1)

[Claims] A surging detection device for a compressor in which a flow rate measuring orifice is inserted into the suction side piping of the compressor, and the pressure in this orifice is detected via a pressure transmitter, a sampling circuit, and a receiver. , a first series sampling circuit that is connected in parallel between the pressure transmitter and the receiver and performs sampling in a relatively short period, and a sampling circuit that performs sampling in a long period having a relatively large least common multiple with respect to the short period. A surging detection device for a compressor, comprising a second series of sampling circuits for detecting surging.