JP2003322097A - Flow rate control method for fluid machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow rate control method capable of easily securing a wide flow rate control range. <P>SOLUTION: In this flow rate control method for a fluid machine 1, flow rate of fluid sucked into the fluid machine 1 is regulated by controlling the opening of a variable inlet guide vane. In this method, suction volume flow rate FI of fluid sucked into the fluid machine 1 is measured, an isoentropy head of the fluid machine 1 obtained by compressing fluid by the fluid machine 1 is calculated, whether or not the measured suction volume flow rate FI and the calculated isoentropy head H exceed a rotational speed change boundary value set in advance from the relation of the suction volume flow rate and the isoentropy head according to the fluid machine 1 is decided, and rotational speed SI of a driven shaft 17 of the fluid machine 1 is selectively changed based on the decision result. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a flow rate of a fluid machine such as a blower and a compressor for sending a fluid under pressure.

[0002]

2. Description of the Related Art Conventionally, an operation control method for controlling the operation of a fluid machine by controlling the opening of a variable inlet guide vane provided at the inlet of a fluid machine that pumps fluid and the rotational speed of a driven shaft of the fluid machine. Have been proposed.

For example, in Japanese Patent Laid-Open No. 56-66490, which is a conventional technique of this kind, a variable inlet guide vane provided at the inlet of a fluid machine is optimized so that the operating efficiency corresponding to the operating state of the fluid machine is optimized. And the rotational speed of the driven shaft of the fluid machine are calculated, and the opening degree of the variable inlet guide vanes and the rotational speed of the driven shaft of the fluid machine are controlled based on the calculation result.

Further, in Japanese Unexamined Patent Publication No. 9-133093, a fluid is provided so that fluctuations in operating conditions such as surging that occur at a flow rate smaller than the design flow rate of a fluid machine can be detected quickly and accurately for stable operation. The opening of the variable inlet guide vanes of the machine and the rotation speed of the driven shaft of the fluid machine are controlled.

[0005]

The above operation control methods for fluid machines are all focused only on the efficiency or stability of operation of the fluid machine, and to widen the flow control range of the fluid machine. Not considered. However, in a plant having a constant pressure characteristic such as an aeration facility in which the above fluid machine is used, there is a demand not only for efficiency and stability of operation of the fluid machine but also for securing a wider flow control range. Especially, when the flow rate of the fluid sucked into the fluid machine is low or when the suction temperature of the fluid sucked into the fluid machine rises, the discharge pressure of the fluid pumped from the fluid machine must be maintained at the pressure necessary for the plant. is important.

Further, when the rotational speed of the driven shaft of the fluid machine is constantly controlled as in the conventional flow rate control method of the fluid machine, the rotational speed of the driven shaft changes frequently, so the blades of the fluid machine are changed. Fatigue may also occur in the vehicle or the driven shaft connected to it.

The present invention has been made in view of the above demands, and a wide flow rate control range can be easily provided by selectively changing the rotational speed of the driven shaft according to the operating state of the fluid machine. An object of the present invention is to provide a flow rate control method for a fluid machine that can be secured.

[0008]

In order to solve the above problems, the present invention adjusts the flow rate of fluid sucked into a fluid machine by controlling the opening of a variable inlet guide vane provided in the fluid machine. In the flow rate control method of the fluid machine, the suction volume flow rate of the fluid sucked into the fluid machine is measured, the isentropic head of the fluid machine obtained by compressing the fluid by the fluid machine is calculated, and the measured suction volume flow rate is calculated. The isentropic head calculated as follows determines whether or not the rotational speed change boundary value set in advance from the relationship between the suction volume flow rate and the isentropic head is exceeded according to the fluid machine, and based on the determination result. It is characterized in that the rotational speed of the driven shaft of the fluid machine is selectively changed. Here, the isentropic head is the minimum work amount per unit weight of the fluid added in the process of isentropic compression of the fluid sucked into the fluid machine.

According to this structure, the rotational speed of the driven shaft of the fluid machine is determined based on the rotational speed change boundary value of the fluid machine which is set in advance from the relationship between the suction volume flow rate and the isentropic head according to the fluid machine. Since the change is selectively made, the flow rate control range of the fluid machine can be expanded by changing the rotational speed of the driven shaft of the fluid machine with few changes.

Specifically, first, a rotation speed change boundary value for the isentropic head is calculated from the measured suction volume flow rate and a preset "relationship between the suction volume flow rate of the fluid machine and the isentropic head". , And compares the rotational speed change boundary value with the calculated isentropic head. Alternatively, instead of this, the rotation speed change boundary value for the suction volume flow rate is calculated from the calculated isentropic head and the preset "relationship between the suction volume flow rate of the fluid machine and the isentropy head", and the rotation is calculated. It is also possible to compare the speed change boundary value with the measured suction volume flow rate. Here, the preset "relationship between the suction volume flow rate of the fluid machine and the isentropic head" is peculiar to the fluid machine, and its characteristics are the suction temperature and suction of the fluid sucked into the fluid machine under a constant rotation speed. It has a certain relationship that is not affected by pressure or the like (suction state). Further, the suction volume flow rate of the fluid machine is approximately proportional to the rotational speed ratio of the driven shaft of the fluid machine, and the isentropic head of the fluid machine is
It is approximately proportional to the square of the rotation speed ratio of the driven shaft of the fluid machine.
From the above, even when the suction state of the fluid machine changes, it is possible to easily determine the change in the rotation speed of the non-driving shaft of the fluid machine. The relationship between the suction volume flow rate and the isentropic head is created in advance by a performance test of the fluid machine and stored in a controller that controls the fluid machine.

As a result of the above comparison, when the calculated isentropic head is in a region exceeding the rotation speed changing boundary value, the operation of the fluid machine becomes unstable. The rotation speed of the drive shaft is increased to a predetermined rotation speed. When the operating condition of the fluid machine is changed and the calculated isentropic head is in a region below the rotational speed change boundary value, the rotational speed of the driven shaft of the fluid machine is returned to the rotational speed before the change. In this way, by selectively changing the rotational speed of the driven shaft of the fluid machine, the flow rate control method of the fluid machine is simplified compared to the case where the rotational speed of the driven shaft of the fluid machine is controlled steplessly. can do. Further, compared to the case where the rotational speed of the driven shaft of the fluid machine is always controlled, the rotational speed of the driven shaft of the fluid machine is changed less frequently, so the impeller of the fluid machine or the driven shaft connected thereto is changed. It is also possible to prevent fatigue from occurring.

In the present invention, the rotational speed of the driven shaft of the fluid machine can be selectively changed from the rated rotational speed and the increased rotational speed increased or decelerated from the rated rotational speed. it can. Here, the "rated rotation speed" is the rotation speed (100%) at the time of designing the fluid machine.
On the other hand, the “accelerated rotation speed” is a rotation speed (105%) obtained by increasing the rated rotation speed by, for example, about 5%. Further, the “decelerated rotation speed” is, for example, a rotation speed (95%) reduced by about 5%. Note that these rotation speeds are appropriately set depending on the characteristics of the fluid machine and the characteristics of the plant to which the fluid machine is applied.

As described above, since the rotational speed of the driven shaft of the fluid machine can be selectively increased or decreased, the flow control range of the fluid machine can be expanded.
As a result, in a plant to which the fluid machine is applied, for example, in a plant having constant pressure characteristics such as aeration equipment, even when the required flow rate required by the plant is significantly changed, The flow rate control method can be sufficiently adapted.

Further, according to the present invention, the suction temperature of the fluid sucked into the fluid machine may be measured, and the rotational speed of the driven shaft of the fluid machine may be corrected by the suction temperature.

According to this structure, since the rotational speed of the driven shaft of the fluid machine is corrected by the suction temperature of the fluid sucked into the fluid machine, the flow rate of the fluid sucked into the fluid machine can be accurately controlled. .

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the attached drawings.

FIG. 1 is a longitudinal sectional view of a fluid machine to which the flow rate control method according to the present invention is applied. A turbo single-stage blower will be described here as an example of a blower that is a fluid machine, but it may be applied to other fluid machines.

The fluid machine 1 includes a spiral casing 11
The casing 11 accommodates an impeller 12 that has a plurality of blades radially outward and that pressurizes the inflowing fluid by rotating. Casing 1
An inflow passage 13 through which a fluid flows is connected to a substantially central portion of 1. A plurality of inlet guide vanes 14 (variable inlet guide vanes) that form a substantially fan shape in the middle and adjust the inflow direction of the fluid flowing into the impeller 12 and the opening area of the inflow passage 13 are provided in the circumferential direction of the inflow passage 13. It is arranged. Further, a plurality of outlet guide vanes 1 are provided radially outward of the impeller 12 along the direction in which the fluid pressurized by the impeller 12 smoothly flows out.
5 are installed around. Between the outlet guide vanes 15, a smooth enlarged flow path is formed radially outward. An outflow passage 16 through which the fluid flows out is attached to the casing 11.

According to this structure, the fluid sucked by the rotation of the impeller 12 of the fluid machine 1 is
After entering the inflow passage 13 as indicated by the arrow GIN in FIG. 1, it is introduced into the inlet guide vane 14. The entrance guide vane 1
By opening and closing 4 with respect to the inflow direction of the fluid, the direction in which the fluid flows into the impeller 12 downstream of the inlet guide vane 14 is adjusted. As a result, efficient flow rate control of the fluid machine 1 can be performed. Then, the fluid flowing into the impeller 12 is pressurized outward in the radial direction and flows into the outlet guide blade 15. The fluid flowing out from the outlet guide vanes 15 flows into the outflow passage 16 and then outflows from the outflow passage 16 to a passage (not shown) connected downstream from the outflow passage 16 as indicated by an arrow GOUT in FIG. 1.

FIG. 2 shows the configuration of the control system of the fluid machine 1. The inflow passage 13 of the fluid machine 1 is provided with a flow rate measuring device 30, a pressure measuring device 31, and a temperature measuring device 32, and the outflow passage 16 is provided with a pressure measuring device 33. The impeller 12 has a drive shaft 1 via a driven shaft 17.
8 is attached, and the driven shaft 17 is provided with a tachometer 34. These measuring instruments 30 to 34
Are connected to the controller 50 via lines 51 to 55, respectively, and signals from the respective measuring instruments are input to the controller 50. The controller 50 is connected to the actuator 22 via a line 58, and the actuator 22 is connected to the controller 50.
The inlet guide vane 14 is transmitted based on a signal from the transmission mechanism 21.
Open and close via. Further, the controller 50 is connected to the driving machine 18 via the line 56, and controls the rotation speed of the driven shaft 17 connected to the driving machine 18 based on a signal from the controller 50.

A method of controlling the flow rate of the fluid machine 1 configured as described above will be described below with reference to FIGS. 2 and 3.

FIG. 3 is a flow chart of the flow rate control method according to the present invention. First, in step S1, the suction flow rate Q in the reference state of the fluid sucked into the fluid machine 1 is set. The “reference state” refers to a case where the temperature and pressure of the fluid sucked into the fluid machine 1 are predetermined temperatures and pressures such as 0 ° C. and 1 atm. Here, “reference temperature” is used as the reference state for simplification of description.

Next, in step S2, the flow rate measuring device 3
0, the pressure measuring device 31, and the temperature measuring device 32 are used to measure the suction volume flow rate FI, the suction pressure PI, and the suction temperature TI of the fluid sucked into the fluid machine 1. Similarly, the discharge pressure PO of the fluid pumped from the fluid machine 1 and the rotation speed SI of the driven shaft 17 of the fluid machine 1 are measured.

Thereafter, steps S3 to S6 and steps S7 to S16 are processed in parallel.

Specifically, in step S3, the set intake volume flow rate Qt is calculated by correcting the intake flow rate Q set in step S1 with the intake temperature TI based on [Equation 1].

[0026]

[Formula 1] Qt = QxTI / reference temperature In step S4, the set suction volume flow rate Qt calculated in step S3 is compared with the measured suction volume flow rate FI. If the former is larger than the latter, step S5 is executed. As shown, the inlet guide vane 14 is opened, and if the former is smaller than the latter, as shown in step S6, the inlet guide vane 1
Close 4. Then, the process returns to step S2, and steps S3 to S6 are similarly repeated.

In parallel with the above steps, step S7
Then, the isentropic head H is calculated from the measured suction temperature TI, suction pressure PI, and discharge pressure PO based on [Equation 2].

[0028]

[Equation 2]

Here, g is gravitational acceleration, n is isentropic volume index, and R is gas constant.

In step S8, in order to determine whether to change the rotational speed SI of the driven shaft 17 of the fluid machine 1 from the isentropic head H, the limit value Q1 (rotational speed of the suction volumetric flow rate of the fluid machine 1 is determined. Change boundary value) is calculated. The limit value Q1 of the suction volume flow rate is calculated from the relationship between the isentropic head and the suction volume flow rate, which are created in advance by the performance test of the fluid machine 1. The characteristic curve L showing the relationship can be shown as shown in FIG. 4, for example. As shown in the figure, the above limit value Q1 of the suction volume flow rate is calculated as a value corresponding to the isentropic head H on the characteristic curve L. The relationship between the isentropic head of the fluid machine 1 and the suction volume flow rate is stored in the controller 50 in advance as a functional expression or data.

In step S9, the set suction volume flow rate Qt calculated in step S3 is compared with the suction volume flow rate limit value Q1 calculated in step S8.
If the former is smaller than the latter, the selected rotation speed N2 is selected as the target rotation speed of the driven shaft 17 of the fluid machine 1 as shown in step S10. When the former is larger than the latter, the selected rotation speed N1 is selected as the target rotation speed of the driven shaft 17 of the fluid machine 1 as shown in step S12. That is, as shown in FIG. 4, when the set suction volume flow rate Qt of the fluid machine 1 is in the region on the left side of the characteristic curve L (selected rotation speed N2 region) with respect to the isentropic head H, the target of the fluid machine 1 is reduced. The selected rotation speed N2 is selected as the target rotation speed of the drive shaft 17. On the other hand, when the set suction volume flow rate Qt of the fluid machine 1 is in the region on the right side of the characteristic curve L (selected rotation speed N1 region), the driven shaft 17 of the fluid machine 1 is
The selected rotation speed N1 is selected as the target rotation speed. In this embodiment, the rated rotation speed of the drive machine 18 that drives the fluid machine 1 is selected as the selected rotation speed N1, and the increased rotation speed obtained by increasing the rated rotation speed by about 5% is selected as the selected rotation speed N2. You have selected. It should be noted that here, a case is shown in which the rotational speed of the driven shaft 17 of the fluid machine 1 is increased. However, when the boosting capacity of the fluid pumped from the fluid machine 1 is higher than the required discharge pressure, Machine 17
The rotational speed of may be reduced. In that case, as in the case of increasing the rotation speed of the driven shaft 17 of the fluid machine 1, a selected rotation speed (not shown) for deceleration is set in advance.
Specifically, the selected rotation speed is selected by reducing the rated rotation speed of the drive machine 18 that drives the fluid machine 1 by about 5%. However, these numerical values are set according to the characteristics of the fluid machine 1 and the characteristics of the plant (not shown) to which the fluid machine 1 is applied, and are not limited to the above numerical values. .

Further, here, the limit value Q1 of the suction volume flow rate is calculated from the isentropic head H measured in steps S8 and S9, and this value is compared with the set suction volume flow rate Qt of the fluid machine 1. However, instead of this, the limit value of the isentropic head may be calculated from the set suction volume flow rate Qt of the fluid machine 1 and compared with the isentropic head H calculated in step S7.

After that, step S11 and step S
In 13, the target rotational speed N is calculated by correcting the selected rotational speeds N1 and N2 selected in step S10 or step S12 based on [Equation 3] or [Equation 4] with the suction temperature TI of the fluid machine 1.

[0034]

[Equation 3]

[0035]

[Equation 4]

Here, N1, N2: the selected rotation speed selected in step S10 or step S12, T
s: Suction temperature of the fluid machine 1 at the design point. In addition, when the fluctuation of the suction temperature TI of the fluid machine 1 is small, steps S11 and S13 may be omitted.

Then, in step S14, step S
11 or the target rotation speed N calculated in step S13 and the rotation speed SI measured in step S2
Compare with. When the former is larger than the latter, the rotation speed SI of the driven shaft 17 of the fluid machine 1 is increased as shown in step S15, and when the former is smaller than the latter,
As shown in step S16, the driven shaft 17 of the fluid machine 1
The rotation speed SI of is decreased.

After that, the process returns to step S2, and steps S7 to S16 are similarly repeated.

As described above, by performing the feedback control in which steps S2 to S16 are repeated,
The measured suction volume flow rate FI is controlled so as to become the suction flow rate Q set in step S1.

Next, the effect of the flow rate control method according to the present invention will be described with reference to FIG. The flow rate (%) on the horizontal axis of FIG. 5 indicates the ratio between the suction volume flow rate of the fluid sucked into the fluid machine 1 and the suction volume flow rate actually sucked into the fluid machine 1 at the design point. The vertical axis represents the discharge pressure PO of the fluid machine 1.

In FIG. 5, the inlet guide vanes 14 of the fluid machine 1 are shown.
A characteristic curve in the case of controlling the flow rate of the fluid machine 1 using only the opening degree as the control parameter is indicated by a broken line. The characteristic curve corresponds to the case where the target rotation speed of the driven shaft 17 of the fluid machine 1 is the selected rotation speed N1 (for example, 100% of the rated rotation speed). The characteristic curve includes a characteristic curve CV1 on the right side of the figure, a characteristic curve CV3 on the left side thereof, and a surge prevention line SL1 connecting the upper ends of these characteristic curves CV1 and CV3. These characteristic curves (CV1, CV
3, the fluid machine 1 can be stably operated in the portion surrounded by SL1). Here, the characteristic curve CV1 corresponds to a case where the opening of the inlet guide vane 14 is, for example, 100%, and the characteristic curve CV3 corresponds to a case where the opening of the inlet guide vane 14 is 0%. Correspond. The surge prevention line SL1 is a line set with a certain margin with respect to the limit at which the fluid machine 1 causes surging. When the fluid machine 1 is operated at the discharge pressure P1, section A
The flow rate of the fluid sucked into the fluid machine 1 is controlled between 2 (intersection with the characteristic curve CV1) and A3 (intersection with the surge prevention line SL1). Specifically, sections A2 to A3
Corresponds to, for example, a flow rate (%) of 60 to 100%.

On the other hand, the characteristic curve corresponding to the flow rate control method according to the present invention is shown by a solid line. The characteristic curve corresponds to the case where the target rotation speed of the driven shaft of the fluid machine is N2 (for example, 105% of the rated rotation speed, N2> N1). As shown in FIG. 5, by increasing the rotational speed SI of the driven shaft 17 of the fluid machine 1 from N1 to N2, the characteristic curves (CV1, CV3, SL of the fluid machine 1 shown by the broken lines are shown.
1) is changed to a characteristic curve shown by a solid line. The characteristic curves CV2, CV4 and the surge prevention line SL2 are
It corresponds to the above-mentioned characteristic curves CV1 and CV3 and the surge prevention line SL1, respectively. In the characteristic curve indicated by the solid line, the flow rate (%) and the discharge pressure of the fluid machine 1 are generally increased as compared with the characteristic curve indicated by the broken line as shown in FIG. As a result, the flow rate control range corresponding to the discharge pressure P1 of the fluid machine 1 changes from the section A2 to A3 to the section A1 to A4.
Extended to. Specifically, for example, the flow rate (%) of the fluid machine 1 is expanded from 60 to 100% to 50 to 115%. Therefore, the flow rate control range that is normally used is 60 to
At 100%, the rotational speed S of the driven shaft 17 of the fluid machine 1
I is operated at N1 (rated rotation speed), the flow rate of the fluid machine 1 is stably controlled only by the opening of the inlet guide vanes 14 of the fluid machine 1, and only when the range is out of the range, the driven shaft of the fluid machine 1 is controlled. The operation is performed such that the rotation speed SI of 17 is increased to N2 and the required discharge pressure P1 of the fluid machine 1 is obtained. Thus, by using the flow rate control method according to the present invention, the flow rate control range of the fluid machine 1 can be easily expanded.

Further, steps S11 and S1 shown in FIG.
3, the target rotation speed N of the fluid machine 1 is changed to the suction temperature TI
By adding the step of correcting using the fluid machine 1,
It is possible to accurately control the flow rate of the fluid sucked into.

[0044]

According to the flow rate control method of the present invention, the suction volume flow rate of the fluid sucked into the fluid machine and the isentropic head of the fluid machine obtained by compressing the fluid by the fluid machine are changed by these rotational speeds. The rotation speed of the driven shaft of the fluid machine can be selectively changed depending on whether or not the boundary value is exceeded. As a result, a wide flow control range can be easily secured.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a fluid machine to which a flow rate control method according to the present invention is applied.

FIG. 2 is a system diagram of a control system of a fluid machine to which the flow rate control method according to the present invention is applied.

FIG. 3 is a flowchart of a flow rate control method according to the present invention.

FIG. 4 is a diagram showing a relationship between an isentropic head of the fluid machine 1 and a suction volume flow rate.

FIG. 5 is a diagram showing characteristics of a fluid machine when the flow rate control method according to the present invention is used.

[Explanation of symbols]

1 fluid machinery 12 impeller 14 Entrance guide vanes 15 Exit guide vanes 17 Driven shaft 18 Drive 22 Actuator 30 flow meter 31 Pressure measuring instrument 32 Temperature measuring instrument 33 Pressure measuring instrument 34 tachometer 50 controller Q Suction flow rate Qt set suction volume flow rate Q1 Limit value of suction volume flow rate H isentropic head N target rotation speed N1, N2 selection speed

Continued front page    F term (reference) 3H021 AA01 BA06 BA20 CA01 CA02                       CA03 CA04 CA06 DA04 DA11                       DA29 EA03 EA10                 3H045 AA06 AA09 AA12 AA25 BA12                       BA19 BA28 CA02 CA03 CA06                       CA09 CA19 DA04 DA13 DA42                       EA04 EA36

Claims (3)

[Claims] 1. A flow rate control method for a fluid machine, wherein the flow rate of fluid sucked into a fluid machine is adjusted by controlling the opening of a variable inlet guide vane provided in the fluid machine. Measuring the suction volumetric flow rate, calculating the isentropic head of the fluid machine obtained by the fluid machine compressing the fluid, and the isentropic head calculated as the measured suction volumetric flow rate, Based on the relationship between the suction volume flow rate and the isentropic head, it is determined in advance whether or not the rotational speed change boundary value set is exceeded, and based on the determination result, the rotation of the driven shaft of the fluid machine is rotated. A flow control method for a fluid machine, characterized by selectively changing a speed. 2. The flow rate control method for a fluid machine according to claim 1, wherein the rotational speed of the driven shaft of the fluid machine is a rated rotational speed and an increased rotational speed or a decelerated rotational speed that is higher than the rated rotational speed. A method for controlling a flow rate of a fluid machine, characterized by selectively changing from a decelerated rotation speed. 3. The flow rate control method for a fluid machine according to claim 1, wherein a suction temperature of the fluid sucked into the fluid machine is measured, and a rotation speed of a driven shaft of the fluid machine is measured by the suction temperature. A method for controlling a flow rate of a fluid machine, which is characterized by modifying.