JPH0442556B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a multi-stage fluid machine, mainly a multi-stage centrifugal compressor each having a vane whose opening can be adjusted on the suction side of each stage, and an axial-flow compression stage and a centrifugal compression stage. The present invention relates to a capacity adjustment device used in a composite compressor, etc.

[Prior art]

There is a conventional multi-stage fluid machine having a capacity adjustment device disclosed in Japanese Patent Application Laid-Open No. 123394/1982. For example, in a four-stage centrifugal compressor, each of compressors 1 to 4 is Coolers 5 to 7 are provided between the stages, and vanes 8 to 11 driven via vane drive devices 12 to 15 are provided on the suction side of each compressor 1 to 4, respectively. The vane driving devices 12 to 15 function to convert the vane opening command signal 22 from the controller 29 into mechanical force for driving each vane 8 to 11.

On the other hand, the flow rate discharged from the final stage compressor 4 is
It is measured by the differential pressure of the orifice 16 provided on the discharge side, and the discharge temperature and pressure by a detector (not shown) provided on the upstream side of the orifice 16. These measured values are each converted into electrical signals by the converters 19 to 17, and then input to the calculator 20, where they are converted into a discharge flow rate signal. A flow rate signal 23 output from the calculator 20 is fed back to the controller 29. Since the target flow rate signal 21 of the compressor is input to this controller 29, only the deviation between this target flow rate signal 21 and the flow rate signal 23 is used as the vane opening command signal 22 for each vane driving device 12 to 15, the capacity of the compressor can be adjusted.

Compressor performance is usually designed so that the fluid flow best corresponds to the internal shape of the compressor so that optimal efficiency is achieved near the flow rate when the vanes are fully open. However, when the compressor flow rate decreases due to a decrease in the required amount of the plant, the flow angle of the handled fluid inside the compressor changes from the designed state, and losses increase, resulting in a decrease in efficiency.

Compressor capacity adjustment methods include rotation speed control, suction throttle, discharge throttle, vane controller, etc. Among these, rotation speed control is optimal for minimizing the above-mentioned efficiency drop. However, since this method causes a large drop in discharge pressure, it is not effective for general plants where the discharge pressure is nearly constant.
On the other hand, vane controllers are widely used because there is little drop in discharge pressure and the drop in efficiency when reducing the amount of fuel can be controlled by rotational speed.

In recent years, from the perspective of global resource conservation and energy conservation, it has become extremely important to improve not only design point efficiency but also partial load efficiency. There are many plants that do this. Furthermore, in air separation plants and the like, the compressor accounts for about 60% of the plant power, so improving the efficiency of the compressor is very important. Therefore,
Even when adjusting capacity using a vane controller,
A more efficient method was needed.

It is easy to provide vanes in multiple stages, and automatic control by an operator or an automatic controller is also possible, but it is better to use only one adjustment signal. To explain the reason with reference to Figure 2, the compressor conditions required by the plant are the flow rate Q and pressure pd.
This is because for one point A expressed by , there are countless combinations of vane openings that satisfy this condition.
Note that 27 and 28 in the figure indicate the compressor characteristic curve and the plant resistance line. Therefore, even if there are multiple stages of vanes, they are not controlled independently, but the relative motion relationship is fixed and the vanes are moved using a single command signal.

Therefore, with conventional capacity adjustment by adjusting the vane opening, it is impossible to change the optimal relative relationship of the vane opening caused by state changes such as changes in compressor inlet temperature and cooling water temperature. The drawback was that it could not meet the need for improved efficiency.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a capacity adjustment device for a multistage fluid machine that can always operate near the maximum efficiency even if the compressor inlet temperature (initial stage suction temperature) changes.

[Summary of the invention]

In order to achieve the above object, the present invention provides a multi-stage fluid machine in which each stage has vanes whose opening degree can be adjusted on the suction side. A plurality of vane drive devices are each connected to a vane controller, and a proportional setting device is provided on any input line of the vane drive devices,
This proportional setting device adjusts the magnitude of the opening command signal from the vane controller in accordance with the suction temperature on the first stage suction side, and supplies the same to the vane drive device.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. Among the symbols shown in FIG. 3, the same symbols as those shown in FIG. 1 indicate the same parts.

FIG. 3 is a system diagram of a four-stage centrifugal compressor equipped with the capacity adjustment device of this embodiment, in which the vanes 8 to 11 provided on the suction side of each stage are The vanes of both groups, that is, the vanes 8 of the front group are driven by the front vane drive device 12, and the vanes 9 to 11 of the rear group are driven by the rear single vane drive device 24. These vane drives 1
2 and 24 act to convert the vane opening command signal 22 into mechanical force for driving the vane.
The front vane drive device 12 is directly connected to a vane controller 29, while the rear vane drive device 24 is connected to the vane controller 29 via a proportional setting device 26. The proportional setting device 26 is connected to a temperature detector 25 connected to the suction side of the first stage compressor 1. The rest of the structure is the same as the conventional example shown in FIG. 1, so the explanation will be omitted.

Next, the operation of this embodiment configured as described above will be explained.

Arithmetic unit 2 input to vane controller 29
Flow rate feed hack signal from 0 (compressor flow rate)
23 is larger than the target flow rate signal (target flow rate) 21 input to the vane controller 29,
The vane opening command signal 22 is the vane controller 2
9 directly to the front stage vane drive device 12, and at the same time, is outputted to the rear stage vane drive device 24 via the proportional setting device 26. The proportional setting device 26
If not, remove the front and rear group vanes 8 and 9.
The opening relationship between the openings 1 to 11 is as shown by the straight line a in FIG.

However, even if the required flow rate of the plant is the same, the environmental conditions of the compressor are not always the same. If the fluid to be handled is air, not only the intake temperature and cooling water temperature differ during the day and night, and between summer and winter, but also the humidity. Of these, the one that most strongly influences the efficiency of the compressor is the difference in the relative relationship between the first stage suction temperature and each stage suction temperature (cooler outlet temperature). This is because the temperature of the cooling water changes slowly relative to the temperature change during standby, so the cooler outlet temperature also changes slowly.

On the other hand, in the design of a multi-stage compressor, one
Since the design is such that the optimum efficiency can be obtained under the conditions of the stage suction temperature and each stage suction temperature (cooler outlet temperature), the relative relationship of the vane openings to achieve the optimal efficiency also deviates. In other words, as shown in Figure 5, the efficiency of the compressor is expressed by the combination of the front stage opening and the rear stage opening, so the efficiency for each combination under certain operating conditions is determined and contour lines are drawn as shown in Figure 5. It will look like line d, and if you connect these contour lines, it will look like line e. The contour line d changes depending on the relative change between the first stage suction temperature and the each stage cooler outlet temperature. As the iso-efficiency curve d moves, its ridge also changes from e to g (FIG. 5). When adjusting the capacity under the above operating conditions, optimal efficient operation can always be achieved by selecting a combination of the front and rear vane openings along the ridge e.

The movement of the ridge of the contour line d is largely influenced by the suction temperature of the first-stage compressor because the cooler outlet temperature is slow as described above. Therefore, by providing the rear group vane drive device with a proportional setting device 26 that adjusts the magnitude of the opening signal of the rear group according to the suction temperature of the first stage, the relative opening of the front and rear groups can be adjusted as shown in FIG. relationship, 4th
As shown in the figure, it can be changed to straight lines a to c.

As mentioned above, since the operating conditions are not constant but change, the efficiency of the combination of front and rear vane openings also changes in response to this change. That is, the contour line d
and ridge e also change, and an example of this change is shown by contour line f and ridge g. In this way, in the present invention, the combination of vane openings of the front stage and the rear stage is set as shown in FIG.
Since it can be adjusted as shown in c, it can always be operated at maximum efficiency regardless of changes in operating conditions.

In this embodiment, there is only one opening degree command signal for the rear group, but the vane opening degree can be relatively changed by adjusting the length of the arm of the vane opening/closing link mechanism.

Further, the vane drive device may be provided in multiple stages, and a proportional setting device may be provided on the upstream side of the second and subsequent stages of the vane drive device, each of which is adjusted by the first stage suction temperature.
Furthermore, although vanes were provided in all stages in this embodiment, they do not need to be provided in all stages if there are multiple stages.

The present invention is not limited to the multi-stage centrifugal compressor described above, but can also be applied to multi-stage fluid machines such as a composite compressor that includes an axial flow stage and a centrifugal stage, with a cooler provided between the stages. Of course.

〔Effect of the invention〕

As explained above, according to the present invention, a proportional setting device is provided in the input line of the vane drive device of any group of multiple vane drive devices, and the magnitude of the opening command signal from the vane controller is adjusted to the first stage. Since it is adjusted according to the suction temperature on the suction side and applied to the vane drive device of the line with the proportional setting device, even if the initial stage suction temperature of the compressor changes, the opening combination of the front and rear stage vanes at that suction temperature can be adjusted. , the efficiency of the compressor can be adjusted to always be at its highest, thus regardless of changes in the first stage suction temperature.
This has the effect that the multistage fluid machine can always be operated near its maximum efficiency.

[Brief explanation of the drawing]

1 and 2 are a system diagram and an operating state diagram of a multistage fluid machine equipped with a conventional capacity adjustment device, and FIG. 3 is a system diagram and an operating state diagram of a multistage fluid machine equipped with an embodiment of the capacity adjustment device of the present invention. 4 and 5 are explanatory diagrams of the operation of the same embodiment. 1-4... Compressor, 8-11... Vane, 1
2, 24... Vane drive device, 21... Target flow rate signal, 22... Vane opening command signal, 23... Flow rate feedback signal, 26... Proportional setting device, 2
9... Vane controller.

Claims (1)

[Claims] 1. In a multi-stage fluid machine in which each stage is provided with a vane whose opening degree can be adjusted on the suction side, each of the vanes is grouped into a plurality of groups, and a plurality of vanes connected to each group of vanes are connected to each other. The vane drive devices are each connected to a vane controller, and a proportional setter is provided on any input line of the vane drive device, and this proportional setter adjusts the magnitude of the opening command signal from the vane controller. 1. A capacity adjustment device for a multi-stage fluid machine, characterized in that the capacity adjustment device adjusts the temperature according to the suction temperature on the first stage suction side and applies the same to the vane drive device. 2. Each of the vanes is grouped into two groups, a first stage and a second stage, the vanes of both groups are connected to two vane drive devices, and the vane drive device of the latter group is provided with a proportional setting device. A capacity adjustment device for a multi-stage fluid machine according to claim 1, characterized in that: