JP2005320863A - Operation control method of axial flow or mixed flow pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation control method of a pump always operated in a proper pump operation characteristic state in an area of a wide range over a low head area from a high head area in the axial flow or mixed flow pump without mechanically complicating a structure in the vicinity of a suction port. <P>SOLUTION: This operation control method of the axial flow or mixed flow pump, selects a rotating speed on the basis of an input signal by inputting its detecting signal to a control device of a pump motor by detecting a suction side water level by a water level sensor when starting the pump; and performs operation for a high head and a small flow rate by selecting shaft output setting control when actual operation output of the pump is equal to preset output and an actual rotating speed is a preset rotating speed or less with a pump operation point as a boundary when the actual operation output of the pump is equal to the preset output and the actual rotating speed of the pump is equal to the preset rotating speed; and performs operation for a low head and a large flow rate by selecting rotating speed setting control when the actual operation output of the pump is the preset output or less and the actual rotating speed is equal to the preset rotating speed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an operation control method for an axial flow or mixed flow pump.

  As is well known, the operating characteristics of an axial flow or mixed flow pump are such that the shaft power increases as it approaches the cutoff on the small flow rate side of the high head, and conversely, the shaft power decreases on the large flow rate side of the low head. It is generally used in a large flow area with a low head. However, as a measure for use in a small water volume region with a high head where the shaft power is large, conventionally, for example, a throttle blade with a variable blade angle is pivotally attached to the rotating shaft by lever operation on the inner circumference of the suction pipe in front of the impeller. During operation near the pump cutoff or partial load operation, the throttle blade is rotated in the closing direction to narrow the suction pipe flow path, thereby reducing the axial power. By rotating it to widen the flow path of the suction pipe, the efficiency and suction performance of the pump can be exhibited to the original performance (for example, see Patent Document 1). Further, as another known example, when the impeller blade is pivotally attached to the peripheral surface of the impeller boss by a blade shaft to have a variable impeller structure, the discharge amount is adjusted by opening and closing the discharge valve. There is also one in which the blade angle of the impeller blade is changed by a fluid force corresponding to the adjusted discharge amount (see, for example, Patent Document 2).

However, as described above, in order to optimize the operating characteristics of the pump, the pivoting angle of the diaphragm blades and the impeller blades can be made variable, which not only increases the manufacturing and equipment costs but also increases the complexity and structure. It cannot be reduced in weight and size, and maintenance and inspection will require a great deal of time due to entanglement of foreign matter.
JP-A-8-2263979 (FIG. 1) JP-A-9-4597 (Fig. 1-3)

  The problem to be solved is that, in a wide range of operation from the high head region to the low head region of an axial flow or mixed flow pump, a conventional throttle blade or a variable blade angle type impeller is provided around the pump suction port. It eliminates the need for a large and complicated structure with an operating mechanism, enables light weight and downsizing, and allows for drainage in full operation with pump operation output equivalent to the set output when the head is high. If the suction level is low and the suction water level is low, excessive pump drainage can be constrained, vortex generation and cavitation are suppressed, and proper pump operation is always possible over a wide range from a high flow rate to a low flow rate range. It is to provide an operation control method of an axial flow or mixed flow pump operated in a characteristic state.

  In the present invention, the suction-side water level at the time of starting the pump is detected by the water level sensor, and the detection signal is input to the control device of the pump motor, the rotation speed is selected based on the input signal, and the actual operation output of the pump is the set output. Axis output setting control when the actual pump output is equal to the set output and the actual engine speed is less than or equal to the set output at the pump operating point where the actual pump speed is equivalent to the set engine speed. Is selected and operation for high head and small flow rate is performed, and when the actual operation output of the pump is equal to or less than the set output and the actual rotation speed is equal to the set rotation speed, the rotation speed setting control is selected and low. The most important feature is that operation for the lift and large flow is performed.

  According to the control method of the present invention, in a wide range of operation from a high head area to a low head area of an axial flow or mixed flow pump, drainage in a full operation state with a pump operation output equivalent to a set output when the lift is high. If the head is low and the suction water level is low, excessive pump drainage can be constrained, vortex generation and cavitation are suppressed, and it is always in a wide range from a small flow range with a high head to a large flow region with a low head. This produces an effect of operating in an appropriate pump operation characteristic state. In addition, in order to produce such an effect, a large-scale and complicated structure of providing a conventional diaphragm blade and a variable blade angle impeller around the pump suction port and an operation mechanism thereof is unnecessary, and it is lightweight. Since the size can be reduced, the manufacturing cost and the equipment cost of the axial flow or mixed flow pump are reduced, and the foreign matter is not entangled, which is advantageous in terms of maintenance.

  The suction-side water level at the start of the pump is detected by the water level sensor, and the detection signal is input to the pump motor control device, the rotation speed is selected based on the input signal, the actual operation output of the pump is equal to the set output, and the pump The shaft output setting control is selected when the actual operation output of the pump is equal to the set output and the actual number of rotations is less than or equal to the set output at the pump operating point where the actual number of rotations is equal to the set number of rotations. When operation for high head and small flow rate is performed, and the actual operation output of the pump is less than the set output and the actual rotation speed is equal to the set rotation speed, the rotation speed setting control is selected and the low lift and large flow volume are selected. Driving for is performed. Further, as the suction side water level approaches the predetermined pump stop water level, the control is switched step by step to the predetermined rotational speed setting control to reduce the discharge amount.

  In FIG. 1 of the embodiment, reference numeral 1 denotes an axial flow pump that is an object of the present invention, 2 denotes a pump motor that drives the axial flow pump 1, 3 denotes a pump casing, and 4 denotes an impeller accommodated in the casing 3. The blade wheel fixed type impeller blades 5, 5 are fixed on the peripheral surface of the impeller boss portion 4b. Reference numeral 6 denotes a suction casing, and no diaphragm blade is attached to the inner peripheral surface thereof. In FIG. 2, 7 is a water level sensor for detecting the suction side water level, 8 is a control device for the pump motor 2, and senses the device for detecting the shaft output and the rotational speed of the pump motor 2 and the signal of the water level sensor 7. And a device for adjusting the pump motor 2 so as to obtain a shaft output or a rotational speed corresponding to an input signal from the water level sensor 7. The description will proceed below with reference to FIGS.

  The suction-side water level at the time of starting the pump is detected by the water level sensor 7, and the detection signal is input to the control device 8 of the pump motor 2, the rotation speed is selected based on the input signal, and the actual operation output of the pump is equal to the set output In addition, at the pump operating point (point A in FIG. 4) at which the actual rotational speed of the pump is equivalent to the set rotational speed, the actual operational output of the pump is equivalent to the set output and the actual rotational speed in the high lift operating region. If is less than the set speed, the shaft output setting control is selected.If the actual operation output of the pump is less than the set output, the pump speed is increased and the pump is operated at the same output as the set output. When the output exceeds the set output, the pump speed is decelerated and the motor is operated at the same output as the set output. However, when attempting to operate with the set output over the entire operation range, the actual operating rotational speed of the pump is set to the set rotational speed by reducing the rotational speed set value according to the suction side water level condition (signal output of the water level sensor 7). The actual operation output of the pump is reduced and the pump discharge amount at the low head is reduced. In other words, for axial flow pumps and mixed flow pumps that have a driving characteristic with a downward-sloping power, if the operation output of the pump is constant, the rotational speed is increased in the low head range. By providing a value, the rotational speed set value acts preferentially before reaching the rotational speed that is the set output, and the system is not operated at a rotational speed that is equal to or higher than the rotational speed set value. When operated with the set axis output in the high lift operating range, the pump load is large and the engine is operated at a speed lower than the speed set value. As a result, the output must be operated near the set axis output value. become. Therefore, when the head is high, drainage in a full operation state with a pump operation output equivalent to the set shaft output becomes possible. Also, when the actual operation output of the pump is less than or equal to the set output and the actual rotation speed is equal to the set rotation speed in the low lift operation region, the rotation speed setting control is selected. The rotation speed setting value acts before output, and the engine is not operated at a higher rotation speed. In this way, since the pump is operated at an output lower than the set shaft output, it becomes possible to restrict the amount of excessive pump drainage at the time of low head, and naturally, the amount of suction of the pump is also limited to the appropriate amount of water. As a result, the momentum of the suction is reduced, and vortex generation and cavitation are suppressed.

  Assuming the control method of the first embodiment, as the suction side water level approaches the predetermined stop water level, it is gradually switched to the predetermined rotational speed setting control to reduce the discharge amount, thereby storing the intake side. Even in a small-capacity machine or a machine with rapid inflow fluctuations, the hunting phenomenon is suppressed by operating control that responds to the sudden fluctuations, and vibration, noise, and vortex generation that occur at low water levels are more effectively suppressed. Can do.

It is a principal part vertical side view of the axial flow pump used as the implementation object of this invention. It is a block diagram of the control system of this invention. It is a flowchart of the operation control of the pump by this invention. It is a diagram which shows the operation control characteristic of the pump by this invention.

Explanation of symbols

1 Pump 2 Pump Motor 7 Water Level Sensor 8 Pump Motor Control Device

Claims (2)

In the operation control method of the axial flow or mixed flow pump, the suction side water level at the start of the pump is detected by the water level sensor, the detection signal is input to the pump motor control device, and the rotation speed is selected based on the input signal. The actual operation output of the pump is equal to the set output and the actual rotation speed is the set rotation speed at the pump operation point where the actual operation output is equal to the set output and the actual rotation speed of the pump is equal to the set rotation speed. In the following cases, the shaft output setting control is selected and operation for high head and small flow rate is performed, and rotation is performed when the actual operation output of the pump is less than the set output and the actual rotation speed is equal to the set rotation speed. An operation control method for an axial flow or mixed flow pump, wherein the number setting control is selected and operation for a low head and a large flow rate is performed. The number of rotations is selected based on the input from the water level sensor, and as the suction side water level approaches the predetermined pump stop water level, the discharge amount is reduced by gradually switching to the predetermined rotation number setting control. The operation control method for an axial flow or mixed flow pump according to claim 1.

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