JPS6312802A - Ceramic blade construction - Google Patents

Abstract

PURPOSE:To allow friction to occur on the contact surface of each divided piece so as to provide structural damping and raise logarithmic attenuation for reducing resonance stress by dividing a blade mode of ceramics in the direction of thickness into a plural number of pieces, with each divided piece adjoined in contact. CONSTITUTION:A blade 3 made of ceramics used for a fan and the like forms a root 3a at its base, and the root 3a is so constructed, e.g., as to be fit in the circumference of a disc connected to a rotary shaft. In this case, the blade 3 is divided in the direction of thickness into a plural number of pieces and is formed of each piece being adjoined in contact. Further, the blade 3 is provided with a contact face 4, which is designed, e.g., for the contact between flat surfaces. Therefore, the structural damping provided by friction occurring on the contact face 4 permits greater logarithmic attenuation to achieve significant reduction in resonance stress.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to the structure of ceramic blades of fans, blowers, pumps, etc., and is devised to have structural damping.

<Prior art> In fans, blowers, pumps, etc., for example, 1000℃
When using high-temperature fluids, strong corrosive fluids, or strong magnetic fields, it is difficult or impossible to use metal as the material.
Ceramic materials are mainly used.

Figures 2 (al and bl) show an example of a conventional ceramic blade. As shown in both figures, the root of the blade (g) 03 ( An opening 02a corresponding to the shape of blade root 03a is formed in the thickness direction (axial direction), and a root 03a of the blade 03 is fitted into this opening 02a.The cross-sectional shape of this root 03a is circular. However, there are various other shapes, and there are various fitting directions of the blade 03 other than the axial direction as in this example.
The shape of 3 is the longitudinal cross-sectional shape, presence or absence of skew,
Although various shapes can be considered depending on the cross-sectional shape, here, a tapered flat blade is used. In such a structure, when the rotating shaft 01 is rotated, a function as a fluid mechanism occurs, and there are various types such as axial flow, diagonal flow, and centrifugal flow.
Regarding the positioning of blade 2 and blade 03, consider cases where they are located between the bearings, or where they are shifted to the overhang part.

<Problems to be Solved by the Invention> When a fluid machine using ceramic blades as described above is operated, the following problems arise when considering the vibration resistance of the blades.

Human In the case of a single blade, the natural frequency (bending, torsion) f
becomes low, and as shown at f1 in Fig. 3, the operating range (N
1. ~NN), resonance occurs with the low-order harmonic component H of the rotational speed (H = rotational speed Xi; i=1.2.3), and the vibration stress level increases (here, low-order is one step higher). (i < 5 to 8)B Ceramics have small material damping, but structural damping cannot be expected due to the fixation of the root joint of a general blade due to centrifugal force, so the logarithmic damping rate δ of the elastic vibration of the blade itself is δ ku0001~
It becomes very small at 0.0 O5.

Therefore, the blade resonance stress becomes a large value even if the external force level is small.

Further, when variable speed operation is performed in the operating range as shown in FIG. 3, it is impossible to avoid resonance throughout the entire range. Furthermore, as a result of this, the limit for the occurrence of flutter and the like is lowered, and there is a fear of premature failure in the event of surging, turning stall, etc. occurring. Furthermore, due to the reason B mentioned above, the stress level also increases due to resonance when the working fluid itself contains pulsations. As described above, in conventional ceramic blades, a dangerous phenomenon that directly leads to fatigue failure is likely to occur.

In view of these circumstances, an object of the present invention is to provide a ceramic blade structure that has both material damping and structural damping, thereby significantly increasing the logarithmic damping rate.

Means for Solving the Problems> The structure of the present invention that achieves the above object is that a ceramic blade is manufactured by dividing into a plurality of pieces in the thickness direction, and a part or all of these pieces are brought together in contact with each other. It is characterized by being done.

<Function> In the above configuration, structural damping is applied due to friction on the contact surfaces that are brought into contact, and the logarithm or λ back wheel becomes large.

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 (n1 to +f) shows a ceramic blade structure according to an embodiment of the present invention. The attachment of these blades to the disc is the same as in the prior art, as shown in FIG. 2, and will not be described here. In addition, Fig. 1 (11) to (
C1 is a side view of the ceramic blade, Figure 1 (dl~f
fl is a cross-sectional view.

As shown in these drawings, all the blades 3 are manufactured by being divided into two pieces in the thickness direction, and these are brought together in contact and embedded in the disk as one blade 3. The blade 3 has a contact surface 4 and is partially colored. Here, (U) is an example of contact between planes, (b
When manufacturing l, curved surfaces are provided on both sides, and when combined, the contact surface 4
tc) shows an example in which the contact surface 4 is a broken line. Other examples include those in which the contact surface 4 is curved, and those in which the contact surface 4 is stepped in the longitudinal direction. Also,
Although the contact surface 4 may be partially provided in the longitudinal direction, it is preferable that the route 3a is in a joined state even in this case. On the other hand, the shape of the contact surface 4 in the width direction may be divided entirely as shown in (d) or partially as shown in (e) or (f). Further, the contact direction 4 in the width direction may also have an arbitrary curved shape. Further, in FIG. 1 tar to ffl, only an example in which the film is divided into two in the thickness direction is shown, but the invention is of course not limited to this, and there is no problem even if the film is divided into three or more.

In such a ceramic blade structure, friction occurs at the contact surface 4, which provides structural damping. For example, in a conventional ceramic blade, if the logarithmic damping rate δ is 0.005, the resonance magnification Q is about 630, but if structural damping is applied as described above, δ-0,
Since it becomes 1, it becomes Q-30. In this way, with the ceramic blade structure of the present invention, the vibration stress level can be reduced to about 1/2.
0, and the vibration resistance can be significantly improved.

<Effects of the Invention> As specifically explained above in conjunction with the examples, with the ceramic blade structure according to the present invention, friction occurs on the contact surface and structural damping is imparted, so that the logarithmic damping rate δ of the blade increases. δ≧0.1, and the resonance force is significantly reduced.

[Brief explanation of the drawing]

Fig. 1 (al to ffl are explanatory diagrams showing a ceramic blade structure according to an embodiment of the present invention, Fig. 2 (a); (bl is an explanatory diagram showing a fluid machine using a ceramic blade according to the prior art; Fig. 3 is a graph showing the relationship between rotational speed and vibration frequency in a fluid machine using ceramic blades according to the prior art. In Fig. 3, 3 is the blade, 3a is the root, and 4 is the contact surface. be.

Claims (1)

[Claims] A ceramic blade structure characterized in that the ceramic blade is manufactured by being divided into a plurality of pieces in the thickness direction, and some or all of these pieces are brought together in contact with each other.