JP2008309694A - Flow rate measuring device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flow rate measuring device and a flow rate measuring method, capable of satisfactorily measuring a flow rate distribution of a non-steady flow generated between blades of an impeller. <P>SOLUTION: The flow rate measuring device 1 includes a plurality of laser Doppler flow meters 2 and measures a flow rate by use of laser beams emitted from measuring probes 5 of each laser Doppler flowmeter 2. The laser beams emitted from the measuring probes 5 disposed adjacently have different wavelengths. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flow velocity measuring device and a flow velocity measuring method.

  Laser light is used in a device (flow velocity measuring device) for measuring a flow velocity in a fluid machine or the like. As an example of a method for measuring the flow velocity using laser light, there is a method of simultaneously measuring the flow velocity on the same straight line by dividing the laser light by a diffraction grating. However, this method has a problem that versatility is low because the interval between the measurement points cannot be arbitrarily set.

  As another flow velocity measuring means, a laser Doppler velocimeter is known (for example, see Patent Document 1). Measurement using this laser Doppler velocimeter mixes small particles that scatter light into the fluid to be measured, guides the laser light from the laser light source to the measurement probe by an optical fiber, and measures the intersection of the laser light at the flow velocity measurement. The flow velocity at the flow velocity measurement point is measured by receiving laser light formed on the point and scattered by particles in the fluid. This laser Doppler velocimeter has excellent resolution and can measure the flow velocity with a simple configuration.

Therefore, for example, when measuring a complicated flow velocity distribution such as between impeller blades, the laser Doppler velocimeter is preferably used. In this case, the laser Doppler velocimeter obtains the flow velocity distribution between the impeller blades by moving the focal position (flow velocity measurement point) of the laser light irradiated from a predetermined position as the impeller (blade) rotates. Can do.
JP-A-6-308140

  However, since the flow velocity distribution obtained by the conventional method has a time lag at each flow velocity measurement point, the flow velocity in the unsteady flow generated between the impeller blades as described above should be measured well. Was difficult.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a flow velocity measuring apparatus and a flow velocity measuring method that can satisfactorily measure the flow velocity distribution of an unsteady flow generated between impeller blades. Is to provide.

The inventor paid attention to obtaining a two-dimensional planar flow velocity distribution by arranging a plurality of Doppler velocimeters and simultaneously measuring the flow velocity at a plurality of points.
However, since each laser Doppler velocimeter measures the flow velocity based on the scattered light as described above, when the laser Doppler velocimeters are provided in parallel, the light scattered in each measurement region interferes with each other and is accurate. As a result, it was found that reliable flow rate measurement could not be performed and the reliability of the measurement results could not be obtained.
Therefore, the present inventor has completed the present invention based on these findings.

  That is, the flow velocity measuring device of the present invention is a flow velocity measuring device that includes a plurality of laser Doppler velocimeters and measures a flow velocity using laser light emitted from a measurement probe of each of the laser Doppler velocimeters. It is characterized in that the wavelengths of the laser beams irradiated from the arranged measurement probes are different from each other.

Moreover, in the said flow velocity measuring apparatus, it is preferable to set it as the structure by which the said measurement probe is arrange | positioned regularly.
At this time, in the measurement probe, the flow velocity measurement points at which the laser light emitted from the measurement probe is focused are equally spaced in the first direction on the flow velocity measurement surface and in the second direction orthogonal to the first direction. It is more preferable to arrange them as follows.

  Moreover, in the said flow velocity measuring apparatus, it is preferable that the wavelength difference of the laser beam irradiated from the said adjacent measurement probe is 30 nm or more.

  The flow velocity measuring method of the present invention is a method of measuring a flow velocity using a flow velocity measuring device having a plurality of laser Doppler velocimeters, and among the measurement probes in the adjacent laser Doppler velocimeters, the measurement probes adjacent to each other. The flow velocity is measured by irradiating laser beams having different wavelengths.

According to the present invention, the following effects can be obtained.
Since a plurality of laser Doppler velocimeters are provided, a plurality of flow velocity measurements can be performed simultaneously. Therefore, since the flow velocity can be measured in a two-dimensional plane, the flow velocity can be accurately measured even in an unsteady flow such as between the impeller blades of the compressor. And since the laser beams of different wavelengths are irradiated from the adjacent measurement probes, it is possible to prevent the light interference between the adjacent measurement probes, and the measurement probes can be arranged in close proximity. A product with high resolution can be provided.

  Hereinafter, embodiments of a flow velocity measuring device and a flow velocity measuring method of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of a flow velocity measuring apparatus according to the present embodiment, and FIG. 2 is a diagram showing a flow velocity measuring surface in the flow velocity measuring apparatus, which corresponds to the XY plane in FIG. In the drawing, the X, Y, and Z directions indicate the XYZ orthogonal coordinate system, and the XY plane corresponds to the flow velocity measurement surface in the flow velocity measuring device.

  As shown in FIG. 1, the flow velocity measuring device 1 includes a plurality of laser Doppler velocimeters 2. Although not shown, it is assumed that a plurality of laser Doppler velocimeters 2 are similarly provided in the X-axis direction in FIG.

  The laser Doppler velocimeter 2 can optically measure the fluid velocity using the Doppler effect caused by the scattered light from the particles (tracer) contained in the fluid. The laser Doppler velocimeter 2 includes a laser oscillation device 3 that generates laser light such as an Ar ion laser, a measurement probe 5 that transmits the laser light generated by the laser oscillation device 3 through an optical fiber 4, and A photomultiplier tube 7 coupled to the measurement probe 5 via an optical fiber 6 and a signal processing device 9 connected to the output side of the photomultiplier tube 7 by a signal cable 8 are configured. Of the laser Doppler velocimeters 2, members other than the measurement probe 5 are accommodated in a housing of the flow velocity measuring device 1 (not shown).

  The measurement probe 5 is arranged such that its laser light emission surface faces the flow velocity measurement surface (XY plane) (see FIG. 2), and is transmitted through the optical fiber 4 as shown in FIG. Laser light is irradiated from the measurement probe 5. Specifically, the laser beam generated by the laser oscillation device 3 is branched into two inside the measurement probe 5 and then focused on the flow velocity measurement plane (XY plane). The position where the laser beam is focused in this way is the flow velocity measurement point P.

  As shown in FIG. 2, the measurement probes 5 are regularly arranged. Specifically, the measurement probe 5 has a flow velocity measurement point P at which the laser light emitted from the measurement probe 5 is focused on the Y-axis direction (first direction) on the flow velocity measurement surface (XY plane) and the Y-axis direction. Are arranged at equal intervals in the X-axis direction (second direction) orthogonal to each other. That is, the flow velocity measurement points P on which the laser beams emitted from the measurement probes 5 are focused are arranged in a matrix on the flow velocity measurement surface (XY plane).

Each laser Doppler velocimeter 2 guides laser light diffused by particles (tracer) flowing in the fluid corresponding to each flow velocity measurement point P from the optical fiber 6 to the photomultiplier tube 7 and converts it into an electrical signal. This electric signal is sent from the signal cable 8 to the signal processing device 9 to calculate the fluid flow velocity at the flow velocity measurement point P.
Therefore, the flow velocity measuring apparatus 1 including a plurality of laser Doppler velocimeters 2 can simultaneously measure the flow velocity at each flow velocity measurement point P. Each flow velocity measurement point P can be arbitrarily adjusted by appropriately changing the position where the measurement probe 5 is disposed.

  By the way, the resolution of the flow velocity measuring device 1 is improved as the interval at which the measurement probes 5 are arranged becomes smaller. In the present embodiment, the interval between the flow velocity measurement points P shown in FIG. 2 is 1 mm.

  Further, each laser Doppler velocimeter 2 is configured to receive the scattered light by irradiating each flow velocity measurement point P with laser light from the measurement probe 5 as described above. However, when the measurement probes 5 are arranged close to each other as described above, the scattered light corresponding to the adjacent measurement probes 5 may interfere with each other, so that there is a possibility that the flow velocity measurement cannot be performed satisfactorily.

  Therefore, the flow velocity measuring apparatus 1 according to the present embodiment is configured to irradiate laser beams having different wavelengths from the adjacent measurement probes 5 in order to prevent such a problem from occurring. As a result, the scattered light is prevented from interfering between the adjacent measurement probes 5, so that the flow velocity at each flow velocity measurement point P can be measured satisfactorily.

  In addition, it is preferable to set each wavelength difference between adjacent measurement probes 5 to 30 nm or more. In this way, the interval between the measurement probes 5 can be made smaller than the above 1 mm (see FIG. 2), and the flow velocity can be measured even when the measurement positions in the adjacent measurement probes 5 are substantially overlapped. . Therefore, since each flow velocity measurement point P can be brought close, the resolution of the flow velocity measuring device 1 can be improved.

Next, an operation method of the flow velocity measuring device 1 will be described.
First, small particles that scatter light are mixed in the fluid to be measured, and moved together with the fluid. Then, the flow velocity measuring device 1 is operated to irradiate the fluid with laser light.
Specifically, the laser beam generated by the laser oscillation device 3 is guided to the measurement probe 5 and irradiated to each of the flow velocity measurement points P.

  Then, the laser light emitted from the measurement probe 5 is scattered by particles in the fluid. At this time, the scattered light has a very slight change in frequency according to the moving speed of the fluid (the moving speed of the particles) due to the Doppler effect.

The scattered laser light is guided to the photomultiplier tube 7 through the optical fiber 6 to be converted into an electric signal. This electrical signal is sent to the signal processing device 9 via the signal cable 8 to undergo processing such as Fourier transform, and the fluid flow velocity at each flow velocity measurement point P is calculated from the frequency of the Doppler signal. The above processing is performed in each laser Doppler velocimeter 2, and flow velocity information at each flow velocity measurement point P is sent to a calculation unit (not shown) of the flow velocity measurement device 1.
Therefore, the flow velocity measuring device 1 can obtain a two-dimensional planar flow velocity distribution on the flow velocity measurement surface (XY plane).

As described above, according to the flow velocity measuring apparatus 1 according to the present embodiment, a plurality of laser Doppler velocimeters 2 are provided, so that a plurality of flow velocity measurements can be performed simultaneously. In addition, since a two-dimensional planar flow velocity measurement is possible, an unsteady flow can be measured with higher accuracy than when a flow velocity measurement is performed using a single laser Doppler velocimeter. Further, since the laser beams having different wavelengths are irradiated from the adjacent measurement probes 5, it is possible to prevent light interference between the adjacent measurement probes 5, and the measurement probes 5 can be arranged close to each other. Resolution can be obtained.
Furthermore, since the flow velocity measurement device 1 has the flow velocity measurement points P evenly arranged on the flow velocity measurement surface (XY plane), the flow velocity measurement device 1 can well measure the flow velocity of a complex flow such as an unsteady flow.

  Next, as an embodiment of the flow velocity measuring method of the present invention, a case where the flow velocity distribution between blades constituting the impeller of the compressor is measured using the flow velocity measuring device 1 will be described as an example.

  FIG. 3 is a diagram illustrating a schematic configuration of the compressor 100. The compressor 100 includes an impeller 20 and a housing 24 provided so as to surround the impeller 20. The impeller 20 includes a rotating shaft 21 provided to be rotatable around a predetermined axis O, and a plurality of blades 23 arranged radially with respect to the rotating shaft 21 (axis O). A plurality of blades 23 are provided at equal intervals around the axis O (rotary shaft 21). The impeller 20 is connected to a turbine impeller (not shown) via a shaft, and rotates via the shaft when the turbine impeller is rotated by exhaust gas from an engine or the like. As the impeller 20 rotates, intake air from a suction port (not shown) is compressed and drawn into the engine. As described above, the flow velocity distribution between the blades 23 of the impeller 20 accompanied by the rotational motion is an unsteady flow, and the flow velocity measuring device 1 can be suitably employed when measuring the flow velocity distribution.

  As shown in FIG. 3, a flow velocity measurement window 25 is provided at a position corresponding to the blade 23 in the housing 24. The flow velocity measurement window 25 is made of a transparent material such as glass. Yes. Specifically, the flow velocity between the blades 23 of the impeller 20 rotating in the housing 101 by irradiating a plurality of laser beams from each measurement probe 5 of the flow velocity measuring device 1 into the flow velocity measuring window 25. Distribution can be measured.

  FIG. 4 shows a plan view of the impeller 20 at the time of flow velocity measurement. As shown in FIG. 4, the light emitted from each measurement probe 5 constitutes a flow velocity measurement surface in which a plurality of flow velocity measurement points P are uniformly arranged between the blades 23 of the impeller 20. Therefore, a two-dimensional planar flow velocity distribution can be obtained between the blades 23 by simultaneously measuring the flow velocity at each flow velocity measurement point P.

  By the way, when the flow velocity distribution between the blades 23 in the impeller 20 is measured using the single laser Doppler velocimeter 2 as in the prior art, the flow velocity measurement point P of the measurement probe 5 sequentially moves as the impeller 20 rotates. A flow velocity distribution between the blades 23 is obtained. In this case, the flow velocities in the plots of the respective flow velocity measurement points constituting the flow velocity distribution are not measured at the same time, but are measured with a slight time difference.

  However, since the flow generated between the blades 23 of the impeller 20 is unsteady, there is a possibility that the flow velocity at each flow velocity measurement point may change even during this short period of time. That is, it is difficult to say that the flow velocity distribution obtained by using a single laser Doppler velocimeter 2 as in the past has sufficient reliability.

  FIG. 5 is a diagram showing a flow velocity distribution between the blades 23 of the impeller 20 measured by using the flow velocity measuring device 1 of the present invention. FIG. 5 is a diagram showing the flow velocity distribution from the suction surface side to the pressure surface side between the blades 23 of the impeller 23 corresponding to the plurality of flow velocity measurement points P arranged in the region indicated by the dotted line in FIG. .

  According to the flow velocity measuring method of the present invention, the flow velocity is measured using the flow velocity measuring apparatus 1 including a plurality of laser Doppler velocimeters 2 as described above. Can be measured simultaneously without being measured by Therefore, even if the flow velocity distribution of the unsteady flow such as between the blades 23 in the impeller 20 is obtained, a good measurement result as shown in FIG. 5 can be obtained.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of invention. For example, although the flow velocity measurement points P are arranged in a matrix in the above embodiment, they may be arranged regularly like a zigzag pattern, or the flow velocity measurement points P need not be on a two-dimensional plane.

It is a figure which shows schematic structure of a flow velocity measuring apparatus. It is a figure which shows the flow velocity measurement surface in a flow velocity measuring apparatus. It is a figure which shows schematic structure of the impeller which comprises a compressor. The top view of the impeller at the time of the flow velocity measurement is shown. It is a figure which shows the speed distribution between the blade | wings of the impeller measured with the flow velocity measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Flow velocity measuring apparatus, 2 ... Laser Doppler velocimeter, 5 ... Measuring probe

Claims (5)

A flow velocity measuring device comprising a plurality of laser Doppler velocimeters and measuring a flow velocity using laser light emitted from a measurement probe of each laser Doppler velocimeter,
A flow velocity measuring device, wherein the wavelengths of laser beams irradiated from the measurement probes arranged adjacent to each other are made different from each other.   The flow velocity measuring device according to claim 1, wherein the measurement probes are regularly arranged.   The measurement probe is arranged so that the flow velocity measurement points on which the laser light emitted from the measurement probe is focused are equally spaced in the first direction on the flow velocity measurement surface and in the second direction orthogonal to the first direction. The flow velocity measuring device according to claim 2, wherein   The flow velocity measuring device according to any one of claims 1 to 3, wherein a wavelength difference between laser beams irradiated from adjacent measurement probes is 30 nm or more. A method of measuring a flow velocity using a flow velocity measuring device including a plurality of laser Doppler velocimeters,
A flow velocity measurement method, wherein flow velocity measurement is performed by irradiating laser beams having different wavelengths from measurement probes adjacent to each other among measurement probes in adjacent laser Doppler velocimeters.

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