JPH0788829B2 - Capacity control device for flow machine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacity adjusting device for a fluid machine, and more particularly to a capacity adjusting device suitable for an electric motor driven centrifugal compressor.

[Conventional technology]

A conventional capacity adjusting device for a fluid machine will be described with reference to FIG. 3 by taking a centrifugal air compressor as an example. FIG. 3 is a system diagram of the capacity adjusting device of the centrifugal compressor 1 having the guide vane 2 at the inlet. The guide vane at the inlet is opened and closed by the drive device 3. The vane drive device 3 converts a vane opening command signal from the adjusting device 10 into a mechanical force for rotating the vane. The handling gas is regulated by the inlet guide vanes 2 and discharged through the compressor 1.
The flow rate of the compressor 1 is measured by the orifice flow meter 4 on the discharge line. The pressure difference before and after the orifice plate, the total pressure and the total temperature of the flow upstream of the orifice plate are converted into electric signals by the converters 5 to 7, respectively, and converted into a flow rate signal by the calculator 8. This flow signal 9 is fed back to the adjusting device 10.

The target flow rate signal 11 of the compressor is instructed to the adjusting device 10, and the vane opening command signal 12 is instructed from the adjusting device 10 to the vane drive device 3 in accordance with the deviation from the flow rate with the feedback signal.

The capacity of the compressor is adjusted as described above.

Note that Japanese Patent Publication No. 56-50119 is related to this type of device.

[Problems to be Solved by the Invention]

By the way, it is very important to improve the partial load operation efficiency as well as the design point efficiency of fluid machinery due to the recent global resource saving and energy saving. From the viewpoint as described above, the above-mentioned conventional example also does not sufficiently consider the following points.

FIG. 4 shows the relationship between the guide vane angle and the compressor flow rate. The guide vane angle and the flow rate are not in a linear relationship, and the flow rate change is large in the range where the vane angle is small, and the flow rate change is small in the range where the vane angle is large. Also, this relationship changes due to the influence of the compressor inlet temperature. In the conventional example, since such a flow rate characteristic was not taken into consideration, the flow rate control region caused variations in control speed and accuracy, which in turn affected the partial load operating efficiency.

Further, in the oxygen separation plant, a rapid flow rate change is not preferable due to the ability of the plant to follow, but in the conventional method, since this control is difficult, the target flow rate must be manually changed in small steps.

It is an object of the present invention to provide a capacity adjusting device for a fluid machine that adjusts the capacity by adjusting the vane opening degree and that can obtain highly accurate adjustment accuracy even if the flow rate range changes.

[Means for Solving the Problems]

In order to achieve the above object, it has a flow rate detecting device and a variable guide vane arranged on the inlet side of the compressor, and outputs an operation command to this variable guide vane if the deviation with respect to the target flow rate is equal to or more than an allowable value. In a fluid machine having an adjusting device provided with an indicating means, the adjusting device is provided with a storage means for storing the relationship between the guide vane angle and the flow rate, and the fluid machine stores the relationship between the guide vane angle and the flow rate stored in the storing means. A correction calculation is performed based on the inlet temperature of, and in the large flow rate range, the slope of the flow rate change with respect to the guide vane angle,
In the small flow rate range, a calculating means for calculating the inclination of the change in the guide vane angle with respect to the flow rate is provided, and the instructing means gives an operation instruction of the guide vane corresponding to the target flow rate deviation based on the output of this calculating means. is there.

[Action]

The present invention was made by paying attention to the fact that the relationship between the vane angle and the flow rate is roughly classified into two when the vane angle is small and when the vane angle is large. That is, when the vane angle is small, the flow rate changes greatly with a slight change in the vane angle, whereas when the vane angle is large, the flow rate does not change even if the vane angle changes greatly. Conversely, focusing on the flow rate, the vane angle changes little when the flow rate is low, and the vane angle changes significantly when the flow rate is high.

Therefore, in the fluid machine that changes the guide vane angle to optimize the flow rate when the flow rate deviation from the target flow rate exceeds a predetermined range, the rate of change of the guide vane angle with respect to the flow rate is calculated on the low flow rate side. On the other hand, on the large flow rate side, the rate of change of the flow rate with respect to the guide vane angle is calculated. Since these change rates are not very small values, no digit cancellation occurs in the calculation, and the calculation can be easily performed with high accuracy. The relationship between the vane angle and the flow rate is stored in the storage means provided in the adjusting device, and is used after being corrected by the inlet fluid temperature of the fluid machine in the calculation of the rotation amount of the vane angle. Therefore, even if the specific gravity of the gas changes due to the inlet temperature that changes seasonally, the vane angle can be determined precisely corresponding to the flow rate of the gas flowing through the fluid machine such as the compressor, so that the control accuracy is improved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a system diagram of a centrifugal compressor having a guide vane at the inlet, and is a diagram showing details of a capacity adjusting device that adjusts the capacity by adjusting an angle. The inlet guide vane 2 is driven by the drive device 3. The drive device 3 converts the opening degree designation signal 12 into a mechanical force for rotating the vane. The method of detecting the flow rate of the compressor is the same as the conventional method, but the inlet vane angle is detected by the detector 13 and the inlet temperature is detected by the detector 15, and the result is taken into the adjusting device 10.

Next, the operation of the present invention will be described. FIG. 2 shows the relationship between the inlet vane angle and the flow rate. The flow rate characteristic is divided into a large flow rate range and a small flow rate range by an arbitrary angle θ _c .

Now, the deviation flow rate from the target flow rate is ΔQ, and the vane rotation amount corresponding to it is Δθ. The flow rate before rotation and the state quantity of the vane angle are Q ₀ and θ ₀ , respectively. A device for adjusting the relationship between the vane angle and the flow rate at _a certain arbitrary temperature T _a and the limit angle θ _c
Remember in 10. Θ ₀ taken from the detector 13 is compared with θ _c, and in an operating state where θ ₀ > θ _c is established, the flow rate change rate with respect to the vane angle at the point corresponding to the vane angle θ ₀ corresponds to the deviation flow rate ΔQ. The amount of vane rotation Δθ is obtained.

Therefore, the target vane angle θ ₁ is given by the following equation.

_{θ 1 = θ 0 + Δθ ...} (2) comparing the theta ₀ and theta _c captured from the detector 13, theta ₀ is theta
If it is smaller than _c, the vane rotation amount Δθ corresponding to the deviation flow amount ΔQ is obtained from the change rate of the vane angle with respect to the flow amount at the point corresponding to the flow amount Q ₀ .

Further, the relationship between the vane angle and the flow rate stored in the adjusting device 10 is corrected by the inlet temperature T ₀ taken in from the detector 15 before the above-described rotation amount calculation. For example, if the vane angle is fixed and the flow rate is corrected, the flow rate is corrected by the equation (4).
Corrected flow rate Q _a corresponding to arbitrary angle θ _a , and corrected flow rate
Q _a1 is obtained.

Here, Q _a1; flow rate after correction corresponding to an arbitrary angle θ _a Q _a; before correction corresponding to an arbitrary angle theta _a flow T _a; store and Q _a, theta relationship temperature of _a T _0; Inlet detection temperature when adjusting capacity By performing this correction, it is possible to always determine the vane rotation amount using the characteristics of the vane angle and flow rate that are close to the actual values.
The control accuracy can be improved and the control speed can be easily adjusted.

〔The invention's effect〕

According to the present invention, the rate of change of the flow rate with respect to the vane angle corresponding to the operating state at an arbitrary point and the opposite rate of change can be calculated accurately and easily, and therefore the capacity can be adjusted with high accuracy. In addition, since the change in the flow rate can be controlled with high accuracy over the entire range of the flow rate, the capacity can be adjusted with high reliability.

[Brief description of drawings]

FIG. 1 is a system diagram showing a capacity adjusting system of a fluid machine according to an embodiment of the present invention, FIG. 2 is a diagram showing a relationship between a vane angle and a flow rate, which is a diagram for explaining the operation of the present invention, and FIG. Fig. 4 shows the capacity control system of a conventional fluid machine, and Fig. 4 shows the inlet vane angle and flow rate characteristics of a centrifugal compressor. 1 ... Centrifugal compressor, 2 ... Inlet vane, 3 ... Vane drive device, 4 ... Orifice, 5 ... Orifice differential pressure, 6
...... Orifice total pressure, 7 …… Orifice total temperature, 8 …… Flow meter, 9 …… Flow signal, 10 …… Adjuster, 11 …… Target flow rate, 12 …… Vane angle command signal, 13 …… Vane angle Detector, 14 …… Vane angle signal, 15 …… Inlet temperature detector, 16
…… Inlet temperature signal.

Claims (1)

[Claims] 1. A flow rate detecting device and a variable guide vane disposed on the inlet side of the compressor, and an instruction means for outputting an operation command to the variable guide vane if the deviation from the target flow rate is not less than an allowable value. In a fluid machine having an adjusting device provided therein, storage means for storing the relationship between the guide vane angle and the flow rate is provided in the adjusting device, and the relationship between the guide vane angle and the flow rate stored in the storage means is stored in the inlet of the fluid machine. Compensation calculation is performed based on the temperature, and a calculating means is provided for calculating the inclination of the flow rate change with respect to the guide vane angle in the large flow rate region and the inclination of the guide vane angle change with respect to the flow rate in the small flow rate region. A capacity control device for a fluid machine, characterized in that an operation instruction of a guide vane corresponding to a target flow rate deviation is given based on an output.