JPS6296798A - Adjusting device for displacement of fluid machine - Google Patents

Abstract

PURPOSE:To control a change of flow amount to a fixed value over the whole flow amount regions, by changing the method, which calculates a vane angle change amount corresponding to a deviation of flow amount from the target flow amount, in a large flow amount region to be different from that in a small flow amount region. CONSTITUTION:An adjusting device 10 stores in memory a relation of a vane angle to a flow amount and a critical angle thetac in an optional temperature T. The relation between the vane angle and the flow amount is corrected by an inlet temperature To fetched by a detector 15. An inlet guide vane 2, being driven by a driving gear 3, is controlled in accordance with a turning amount of the vane. Consequently, a change of flow amount can be controlled to almost a fixed value over the whole region of the flow amount by enabling a change rate of the vane angle to the flow amount, corresponding to an operative condition, to be accurately calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a capacity adjustment device for a fluid machine, and particularly provides a capacity adjustment device suitable for an electric motor-driven centrifugal compressor.

[Background of the invention]

A conventional capacity adjustment device for a fluid machine will be described using a centrifugal air compressor as an example with reference to FIG. FIG. 3 shows a system diagram of a capacity adjustment device for a centrifugal compressor 1 having a guide vane 2 at the inlet. The guide vanes at the entrance are opened and closed by a drive device 3. The vane drive device 3 converts a vane opening command signal from the adjustment device 10 into mechanical force for rotating the vane. The treated gas is regulated by an inlet guide vane 2 and discharged through a compressor 1. The flow rate of the compressor 1 is measured by an orifice flow meter 8 in the discharge line. The orifice differential pressure, orifice total pressure, and gold salt are each converted into electrical signals by converters 5 to 7, and converted into flow signals by a computing unit 8. This flow rate signal 9 is fed back to the regulator [10].

A compressor target flow rate signal 11 is instructed to the regulator, and a vane opening command signal 12 is sent from the regulator 10 to the vane driving device 3 in response to the deviation between the feedback signal and the flow rate.
be instructed.

The capacity of the compressor is adjusted as described above.

By the way, in recent years, with global resource and energy conservation, etc., not only the design point efficiency of fluid machinery but also the improvement of partial load operation efficiency has become very important. When viewed from this perspective, the above-mentioned conventional example also has the following drawbacks.

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; 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. Moreover, this relationship changes depending on the influence of the compressor inlet concentration. In the conventional example, such flow rate characteristics were not taken into account, so the control speed was backed up depending on the flow rate adjustment range, resulting in poor accuracy and, in turn, affecting part-load operation efficiency.

Further, in an oxygen separation plant, it is not desirable to rapidly increase the flow rate due to the plant's follow-up ability, but in the conventional system, this control is difficult, so the target flow rate has to be changed manually in small increments.

In addition, related to this type of equipment is the Special Publication No. 56-501.
There is No. 19.

[Purpose of the invention]

An object of the present invention is to provide an adjustment device that can provide the same adjustment speed and accuracy even if the flow rate range changes when adjusting the capacity of a fluid machine by adjusting the vane opening.

[Summary of the invention]

The present invention focuses on the fact that the relationship between vane angle and flow rate is roughly divided, and the flow characteristics are different when the vane angle is small and large. The relationship between the guide vane angle and flow rate is stored in the adjustment device, and the slope of the flow rate change with respect to the guide vane angle is determined in the high flow rate area, and the slope of the flow rate change with respect to the guide vane angle is determined in the low flow rate area. The slope of the change is used to instruct the guide vane operation corresponding to the target flow rate deviation.

[Embodiments of the invention]

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

FIG. 1 shows a system diagram of a capacity adjustment device by angular adjustment of a centrifugal compression zone having a guide vane at the inlet according to the invention. The inlet guide vane 2 is driven by a drive device 3. The drive device 3 converts the opening command signal 12 into mechanical force for rotating the vane. The compressor flow rate detection method is the same as the conventional method, but the inlet vane angle is detected by the detector 13.
Accordingly, the inlet temperature is detected by the detector 15 and taken into the regulating device 10.

Next, the operation of the present invention will be explained. FIG. 1 shows the relationship between the inlet vane angle and the flow rate, and the flow characteristics are divided into a large flow rate region and a small flow rate region according to a certain arbitrary angle Oc.

Now, let Δθ be the deviation flow rate from the target flow rate, and let Δθ be the corresponding amount of vane angle rotation. The flow rate and vane angle state ffjA amount before rotation are each θ0. θ. shall be. Relationship between vane angle and flow rate and limit angle θ at a certain arbitrary temperature T
. is stored in the regulating device 10.

θ0 taken from the detector 13 is compared with θC, and θ0>θ
In the operating state where C holds true, the vane rotation amount Δθ corresponding to the deviation flow rate Δθ is obtained from the vane angle at the point corresponding to θ0 and the rate of change of the flow rate.

Therefore, the target vane angle is θ'=00+Δθ (2) Compare θ0 and θC taken from the detector 13.

When θ0 is smaller than θC, the vane rotation amount Δθ corresponding to the deviation flow rate Δθ is obtained from the flow rate at the point corresponding to θ0 and the rate of change of the vane angle.

Furthermore, the relationship between the vane angle and the flow rate stored in the adjustment device 1-◯ is corrected using the inlet temperature To taken in from the detector 15 at the stage before the rotation amount calculation described above. For example, when correcting the flow rate by fixing the vane angle, the correction is performed using equation (4). Flow rate θ corresponding to flow rate θ− corresponding to arbitrary angle θ umbrella
Umbrella correction.

O Here, θ'; the corrected flow rate θ corresponding to the arbitrary angle θ; the flow rate before correction T; the memorized relational temperature condition of θ・, θ・ To +, perform the capacity adjustment. By performing this correction, the amount of vane rotation can be determined using the characteristics of the vane angle and flow rate that are close to the actual values.
Control accuracy can be improved and control speed can be easily adjusted.

〔Effect of the invention〕

According to the present invention, the degree ratio between the vane angle and the flow rate corresponding to the operating condition at any point can be calculated accurately and easily, so that the change in flow rate is accurate and almost constant over the entire flow rate. This allows highly reliable capacity adjustment.

[Brief explanation of drawings]

FIG. 1 is an example of the capacity adjustment system of the fluid machine of the present invention, and FIG.
The figure is an explanatory diagram of the operation of the present invention, Figure 3 is an example of a capacity adjustment system of a conventional fluid machine, and Figure 4 is an inlet vane angle and flow rate characteristics of a centrifugal compressor. DESCRIPTION OF SYMBOLS 1... Centrifugal compressor, 2... Inlet vane, 3... Vane drive device, 4... Orifice, 5-7... Orifice differential pressure, total pressure, gold salt, 8... Flow rate Meter, 9...Flow rate signal, 10...Adjusting device, 11...Target flow rate, 1
2... Vane angle command signal, 13, 14... Vane angle detector, signal, 15-16... Inlet temperature detector,
signal.

Claims (1)

[Claims] 1. A fluid machine that has a variable guide vane and a flow rate detection device at its inlet, and has an adjustment device that outputs an operation command to the variable guide vane if the deviation from the target flow rate is greater than or equal to an allowable value, The relationship between the guide vane angle and flow rate is stored in the adjustment device, and the target flow deviation can be adjusted by using the slope of the flow rate change with respect to the guide vane angle in large flow areas and the slope of the guide vane angle change with respect to flow rate in small flow areas. A capacity adjustment device characterized by instructing a guide vane operation. 2. A capacity adjustment device in a fluid machine having the adjustment device according to claim 1, wherein the relationship between the guide vane angle and the flow rate is corrected based on the inlet temperature ratio of the fluid machine. 3. A capacity adjustment device for correcting the guide vane angle in a fluid machine having the adjustment device according to claim 2.