JPH11148885A - Rotation strength testing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To separate influence by a vibration from that by a thermal expansion by detecting by two optical position detectors a position change in a radial direction of a concentric light-shade pattern of an outer circumferential part of a sample impeller, obtaining a difference of the position changes and measuring the temperature in a noncontact manner. SOLUTION: A concentric light-shade pattern is plotted on a surface of a core plate of a sample impeller 7, and the change in a boundary position between the light and shade is detected by optical detectors 4, 5 set symmetrically with respect to the center of a rotary shaft. A difference of detected amounts by the optical detectors 4, 5 becomes a change amount of a diameter from which influences of a vibration are offset. A temperature change ΔT of the sample impeller 7 is measured by a noncontact thermometer 6, and a change amount ΔT×α×d because of the temperature change is calculated with the use of a diameter (d) of the boundary position of the light and shade and a coefficient of linear expansion α, so that the change amount is offset. Accordingly the change in an outer shape of the sample impeller 7 can be measured in real time during a rotation test, and a rotational frequency when a plastic deformation is brought about can be easily detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention aims at improving the accuracy and efficiency of a rotational strength tester for an impeller used in a turbomachine or the like. It can also be applied to general strength tests of structures that have been tested.

[0002]

2. Description of the Related Art In the prior art, the shaft vibration during the rotation test was large (compared to the deformation of the impeller itself) and could not be measured by a normal vibrometer. Therefore, the measurement of elastic deformation is usually performed indirectly using a strain gauge. In addition, in the test for detecting the limit of the occurrence of plastic deformation, the number of revolutions of the test impeller was increased to a certain point, deceleration was stopped once, and the dimensions and shape of the impeller were measured in the stopped state, and compared with the initial state. It was usual to calculate the amount of change by doing.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to measure the deformation of an impeller during a rotation test directly from vibration and thermal deformation, which cannot be achieved by the above-mentioned prior art.

[0004]

A concentric pattern consisting of a light portion and a dark portion is drawn on the outer periphery of a core plate or a side plate of a test impeller, and a change in a radial position of the boundary portion is determined by a rotation axis. With the center as the center, non-contact measurement is performed by two optical position detectors arranged at symmetrical positions, and the difference due to vibration is calculated by calculating the difference between the two detection amounts to cancel the detection due to vibration,
Only the deformation of the impeller can be detected. Further, by measuring the temperature of the impeller in a non-contact manner, it is possible to separate the true deformation from the thermal expansion.

[0005] That is, as the impeller is mounted on the rotation test device and the rotation speed is increased, the outer diameter of the impeller becomes 2 as shown in FIG. 2 within the range where the impeller is elastically deformed. It increases in proportion to the power and returns to the original state when the rotation is stopped. Above a certain rotational speed, plastic deformation occurs, above which the linear relationship is lost and greater deformation occurs. When the rotation is stopped, residual deformation remains.

In a rotational strength tester, it is important to detect the rotational speed at which the plastic deformation occurs.

[0007] During the rotation test, the test impeller vibrates. Therefore, in one optical position detector, a change due to deformation of the impeller itself, a change due to vibration, and a change due to temperature are superimposed.

In order to identify this, two optical position detectors are arranged at symmetrical positions with respect to the rotation axis, and the difference between the two detection amounts is calculated to cancel the amount due to vibration. Can be. Further, the temperature of the test impeller is measured by a non-contact thermometer, and a change due to thermal expansion can be canceled from the linear expansion coefficient.

As a result, it is possible to measure a change in the outer diameter of the test impeller while it is rotating.

[0010]

3 and 4 show one embodiment of the present invention. In FIG. 3, the test impeller 1 has a concentric pattern drawn on the surface of its core plate. The optical non-contact position detectors 2 and 3 detect a change in the boundary position between the bright and dark portions of the concentric pattern.

Both changes are as shown in FIG. 4 as δ ₁ and δ ₂ , and δ ₁ −δ ₂ is the amount of change in diameter. On the other hand, FIG.
Temperature change Δ of the test impeller by the non-contact thermometer 4 shown in
T is measured, and assuming that the diameter at the boundary between the light and dark portions of the concentric pattern is d and the linear expansion coefficient is α, ΔT × α × d is canceled as a change due to a temperature change.

[0012]

According to the present invention, the change in the outer diameter of the test impeller during the rotation test can be measured in real time, and the rotational speed at which plastic deformation occurs can be easily detected.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an entire rotational strength test apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing changes in the rotation speed and the outer diameter of an impeller.

FIG. 3 is a conceptual diagram illustrating the principle of measuring the outer diameter of an impeller of the present invention.

FIG. 4 is a diagram showing a waveform detected by the position detection device shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Drive turbine, 2 ... Vacuum tank, 3 ... Protective wall, 4, 5
... Optical length measuring device, 6. Non-contact thermometer, 7.

Claims (1)

[Claims] 1. An impeller rotational strength test apparatus comprising a driving turbine, a vacuum chamber, a protective wall, an optical length measuring device, a non-contact thermometer, and a test impeller, which are arranged at symmetrical positions with respect to the rotation axis. By using the two non-contact optical position detectors, a pattern consisting of the boundary between the light and dark areas distributed concentrically around the rotation axis is drawn around the outer circumference of the test impeller, By detecting this, and comparing this with the boundary position at the time of stop, the change in the outer diameter of the test impeller is measured in real time during the rotation test, and the temperature of the test impeller is measured in a non-contact manner, and the position detector detects A rotational strength test apparatus characterized in that it is possible to detect the presence or absence of plastic deformation of a test impeller during rotation by correcting the measured value for temperature.