JP2003097214A - Ceramic rotor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic rotor device capable of unfailingly preventing its blades from being damaged by collision of foreign substance. SOLUTION: A ceramic rotor 3 having a plurality of blades 9 formed on an outer periphery of a hub 7 is provided within a passage through which gas flows. Also, a protective net 5 for preventing the entering of foreign substance is provided on the windward side of the ceramic rotor 3 in the passage. In this device, when the number of revolutions of the ceramic rotor 3 in the steady operation is represented as W, the maximum diameter of meshes of the protective net 5 is D, ϕ=0.0026×D<2> -0.0017×D, the radius of the ceramic rotor defined by a distance from a center of the hub 7 to an end of the blade 9 is R0 , and the average strength of ceramics of which the ceramic rotor 3 is made is σf , the thickness (t) of the blade 9 with an arbitrary radius R from the center of the hub 7 satisfies a formula represented as t>C×R/R0 (wherein, C=πϕWR0 /60σf ).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic rotor device, and in particular, in a passage through which gas flows,
The present invention relates to a ceramic rotor device in which a ceramic rotor having a plurality of blades formed on the outer periphery of a hub portion is provided, and a protective net for preventing foreign matter from entering is provided in a passage on the windward side of the ceramic rotor.

[0002]

2. Description of the Related Art In recent years, a rotating body of various industrial machinery used in a high temperature atmosphere has characteristics of ceramics which are excellent in mechanical strength, heat resistance and wear resistance and can be reduced in weight due to its small specific gravity. To utilize silicon nitride (Si ₃
Various rotors using ceramic sintered bodies such as N ₄ ), sialon and silicon carbide (SiC), in particular, ceramic rotors made of silicon nitride sintered bodies have been developed and proposed.

Conventionally, in order to achieve high thermal efficiency, a ceramic rotor of this type has been introduced by introducing combustion gas of higher temperature and high pressure to increase the number of revolutions. However, such a ceramic rotor is required to increase the number of revolutions. The more it increases, the greater the centrifugal force generated, and therefore the stress generated in the ceramic rotor itself including the blade portion and the hub portion where the blade portion is formed also increases,
The possibility of destruction is extremely high. In order to avoid this, a design method is widely used in which the thickness of the blade is reduced to reduce centrifugal stress.

However, although it is possible to reduce the centrifugal stress acting on the root of the blade by forming the blade portion of the ceramic rotor thin, generally, a ceramic material has a toughness as compared with a metal material. Since it is a low brittle material, it is weak against impact force, and when foreign matter such as metal mixed from the air suction hole collides with the tip of the blade on the gas inlet side, there is a problem that the tip of the blade is damaged. .

In order to solve such a problem, conventionally, it has been proposed to set the wall thickness of the blade tip portion from the fracture toughness value of the ceramic constituting the ceramic rotor.

[0006]

However, since the impact stress generated in the ceramic rotor at the time of foreign matter collision depends on the peripheral speed at the foreign matter collision position and the size of the foreign matter, the ceramic rotor is designed so as not to suffer impact damage. In this case, not only a single parameter such as the strength and fracture toughness value of the ceramic but also a design standard taking these into consideration was necessary.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a ceramic rotor device which can surely prevent blade damage due to foreign matter collision.

[0008]

In the ceramic rotor device of the present invention, a ceramic rotor having a plurality of blades formed on the outer circumference of a hub is provided in a passage through which gas flows, and the wind is higher than that of the ceramic rotor. A ceramic rotor device having a protective net for preventing foreign matter from entering the upper passage, wherein the rotational speed of the ceramic rotor during normal operation is W,
The maximum mesh diameter of the protective net is D, φ = 0.0026 ×
D ² -0.0017 × D, where R _{0 is} the radius of the ceramic rotor defined by the distance from the center of the hub portion to the blade tip, and σ _f is the average strength of the ceramics forming the ceramic rotor. , The thickness t of the blade portion at an arbitrary radius R from the center of the hub portion satisfies the relational expression represented by t> C × R / R ₀ (where C = πφWR ₀ / 60σ _f ). is there.

In the ceramic rotor device of the present invention, the steady rotation speed of the ceramic rotor and the radius of the ceramic rotor,
Average strength of ceramics and maximum mesh size of protective mesh,
That is, since the thickness t at an arbitrary position of the blade is set from the maximum diameter of the foreign matter which may be mixed in the combustion gas and fly to damage the blade, the thickness of the blade can be made more realistic. It is possible to reliably prevent damage to the blade portion due to foreign matter, and to minimize the centrifugal stress that occurs by setting the thickness of any portion of the blade portion to the minimum thickness that can prevent damage due to foreign matter.

Further, in the present invention, it is desirable that the maximum mesh diameter of the protective net is 0.4 mm or less. As a result, the impact stress is further alleviated.

Furthermore, it is desirable that the ceramics forming the ceramic rotor have an average strength σ _f of 600 MPa or more. This makes it possible to obtain a ceramic rotor that is less likely to suffer impact damage.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The ceramic rotor device of the present invention will be described below in detail with reference to FIG. FIG. 1 shows a ceramic rotor device of the present invention, in which a ceramic rotor 3 is housed in a housing 1,
The inside is a passage through which gas flows.

In the housing 1 on the windward side of the ceramic rotor 3 in this passage, a protective net 5 for preventing foreign matter from entering is provided.
Is provided. As the protective net 5, a metal wire woven or a metal plate having a through hole is used, and the maximum diameter of the opening (mesh) is D. The maximum mesh diameter is the diameter of the opening hole when it is circular, but it means the length of the diagonal line when it is rectangular. Therefore, the maximum diameter of the foreign matter that collides with the ceramic rotor 3 is the maximum mesh diameter of the protective net 5.

The maximum mesh diameter D of the protective net 5 is 0.4 mm.
The following is desirable from the viewpoint of reducing impact stress.

The ceramic rotor 3 is preferably made of a silicon nitride sintered body and has an average strength σ _f of 600 MPa or more. As a result, it is possible to obtain a ceramic rotor that is less susceptible to impact damage.

FIG. 2 is a view of the ceramic rotor 3 as seen from the direction of the rotation center axis. The ceramic rotor 3 is formed by forming a plurality of blades 9 on the outer periphery of the hub portion 7, and the rotation center thereof. The distance from the center of the shaft 15, that is, the hub portion 7 to the tip of the blade portion (radius of the ceramic rotor) is R ₀ (mm).

In such a ceramic rotor, when the rotation speed is W (rpm), the peripheral speed V (m / sec) from the rotation center shaft 15 to the arbitrary radius R position is expressed by the following equation.

[0018] _{V = Wπ (R / R 0} ) R 0/60 (1) On the other hand, the stress σ is typically generated when a foreign object collides,
It is known to be proportional to the collision speed and the size of foreign matter, and inversely proportional to the blade thickness. Further, the moving speed of the foreign matter contained in the combustion gas (gas) is equal to the flow speed of the combustion gas, but in most ceramic rotors, the flow speed of the combustion gas is negligibly smaller than the rotor peripheral speed V. Therefore, the collision speed of the foreign matter can be considered to be substantially equivalent to the peripheral speed V of the ceramic rotor. Therefore, considering that the stress σ when the foreign matter collides is proportional to the peripheral speed V and inversely proportional to the thickness t, it is expressed as σ∝V / t. Here, it is assumed that the above equation (1) is expressed as σ = φ × V / t (2) with φ being a constant. Further, it is assumed that the condition that the impact fracture does not occur is that the impact stress σ shown in the equation (2) does not exceed the average strength σ _{f of the} ceramics. That is, σ / σ _f = φ × V / σ _f t <1 (3) is a condition that does not cause impact fracture. Therefore, the standard formula for calculating the blade thickness that does not cause impact fracture from the formulas (3) and (1) is: t> C × R / R ₀ (4) (where C = πφWR ₀ / 60σ _f ) Therefore, since the radius R _{0 of the} ceramic rotor, the rotational speed W of steady operation, and the average strength σ _{f of the} ceramics are known, the blade thickness t at an arbitrary radius R position can be designed if φ is known.

Now, the φ introduced in the equation (2) is a constant determined by the peripheral speed, the blade thickness, the size of the foreign matter, etc., and cannot be determined by experiments such as the foreign matter collision test. Then φ
Was obtained from the numerical simulation, and the results are shown below.

First, the impact stress was calculated by changing the maximum particle diameter, the collision speed, and the plate thickness by simulation.
A summary of the results is shown in FIG. The horizontal axis shows the ratio V / t of the collision speed V and the plate thickness t, and the vertical axis shows the maximum value of the impact stress generated by the collision. As assumed by the above equation (2), it is confirmed by simulation that the impact stress increases as V / t increases. From this figure, it can be seen that the impact stress drops sharply when the maximum diameter of the foreign matter is 0.4 mm or less.

Although the maximum diameter of the foreign matter is changed to five types, the larger the maximum diameter of the foreign matter, the greater the impact stress. V
By linearly approximating the calculation results of / t and σ, the slope of the straight line can be obtained for each maximum particle diameter. This becomes φ in equation (2). φ
The relationship between the maximum particle diameter D and the foreign matter is shown in FIG. The slope φ between V / t and σ obtained from the simulation depends on the maximum particle diameter D, and the relationship between the two is φ = φ = 0.0026 × D ² −0.0017 × D from the approximation by the quadratic curve. It is expressed as (5).

Since φ is expressed as a function of the maximum diameter of the foreign matter in the equation (5), the blade portion thickness t of the ceramic rotor is calculated from the equation (4) as to the rotational speed, the rotor radius, the average strength of the ceramics, and the foreign matter. It can be calculated considering the maximum diameter.

Next, the thickness of the blade tip of the ceramic rotor that does not cause impact damage is proposed below. The tip of the blade of the ceramic rotor has the highest peripheral speed, and is the place where foreign matter impact destruction is most likely to occur. Therefore, the thickness design of this portion is an important point in the design of the ceramic rotor.

The minimum blade tip thickness tmin can be calculated from tmin> πR ₀ (W × φ) / 60σ _f (6) with R / R ₀ = 1 in the equation (4).

The blade tip minimum thickness tmin depends on the mesh maximum diameter (maximum foreign particle diameter) D, the rotation speed W, the rotor radius R ₀ , and the average strength σ _{f of the} ceramics. However,
In the ceramic rotor device, a protective net is provided in the housing in order to prevent large foreign matter from entering, and the maximum mesh diameter D of the protective net is the maximum foreign matter diameter D. Therefore, the blade tip thickness of the ceramic rotor can be designed if two simple items, namely, the number of revolutions during steady operation and the maximum mesh size of the foreign matter-containing protective net are known from the specifications of the ceramic rotor device incorporating the ceramic rotor. Specifically, since W × φ in the equation (6) is determined by the specifications of the ceramic rotor, the rotor radius R ₀ and the blade tip minimum thickness tmi are based on this.
The relationship of n is determined by the average strength σ _f of ceramics.

Ceramics used for engine parts such as gas turbines are required to withstand not only impact damage but also stress generated by centrifugal stress without damage. From the experience so far, it is necessary that the average strength of ceramics that can withstand centrifugal stress be at least 600 MPa or more. Therefore, the average strength of the ceramic rotor according to the present invention is also 60.
More preferably, it is 0 MPa or more.

The design values of the blade tip minimum thickness tmin of the ceramic rotor for each W × φ range are summarized below.

1) When the average strength of ceramics in a ceramic rotor having a radius R ₀ (mm) supplied to a ceramic rotor device satisfying 80 <W × φ is σ _f ,
The minimum thickness tmin (mm) of the blade tip is tmin> 4.1
It is desirable to satisfy 89R ₀ / σ _f .

[0029] 2) 70 <W × supplied to the ceramic rotor device as a phi ≦ 80, when the average intensity of the ceramic in the ceramic rotor having a radius R ₀ (mm) and sigma _f, the wing tip minimum thickness tmin ( mm) is tmin>
It is desirable to satisfy 3.665R ₀ / σ _f .

[0030] 3) 60 <W × supplied to the ceramic rotor device as a phi ≦ 70, when the average intensity of the ceramic in the ceramic rotor having a radius R ₀ (mm) and sigma _f, the wing tip minimum thickness tmin ( mm) is tmin>
It is desirable to satisfy 3.142R ₀ / σ _f .

4) In a ceramic rotor having a radius R ₀ (mm) supplied to a ceramic rotor device satisfying 50 <W × φ ≦ 60, when the average strength of the ceramics is σ _f , the blade tip minimum thickness tmin ( mm) is tmin>
It is desirable to satisfy 2.618R ₀ / σ _f .

5) In a ceramic rotor having a radius R ₀ (mm) supplied to a ceramic rotor device satisfying 40 <W × φ ≦ 50, when the average strength of the ceramics is σ _f , the blade tip minimum thickness tmin ( mm) is tmin>
It is desirable to satisfy 2.094R ₀ / σ _f .

[0033] 6) 30 <W × supplied to the ceramic rotor device as a phi ≦ 40, when the average intensity of the ceramic in the ceramic rotor having a radius R ₀ (mm) and sigma _f, the wing tip minimum thickness tmin ( mm) is tmin>
It is desirable to satisfy 1.571R ₀ / σ _f .

[0034] 7) 20 <W × supplied to the ceramic rotor device as a phi ≦ 30, when the average intensity of the ceramic in the ceramic rotor having a radius R ₀ (mm) and sigma _f, the wing tip minimum thickness tmin ( mm) is tmin>
It is desirable to satisfy 1.047R ₀ / σ _f .

8) When the average strength of the ceramics in a ceramic rotor having a radius R ₀ (mm) supplied to a ceramic rotor device satisfying W × φ ≦ 20 is σ _f ,
Minimum blade tip thickness tmin (mm) is tmin> 0.5
It is desirable to satisfy 24R ₀ / σ _f .

[0036]

Example 1 A ceramic rotor (average strength of 700 MPa) made of a silicon nitride sintered body containing silicon nitride (Si ₃ N ₄ ) as a main component and yttria (Y ₂ O ₃ ) as a sintering aid. 25) were prepared as evaluation samples. Radius R of this rotor
₀ was 50 mm, and the minimum blade thickness tmin at the blade tip was 1.0 mm.

This sample for evaluation was mounted on a rotary tester, and a metal pipe for mixing foreign matter was introduced at a position 1.5 mm from the tip of the blade on the gas inlet side, which is the outermost peripheral portion of the blade, to the side of the central axis. The equipment was improved so that foreign matter of arbitrary diameter could be mixed in from the outside of the rotation tester. The blade thickness t at the foreign matter collision position was 1.2 mm.

The foreign matter has a diameter of 0.5 mm, 0.8 mm,
Steel balls of 1.0 mm, 1.3 mm and 1.5 mm were used.
The rotation speed W of the evaluation sample was set to 20,000 rotations, 40,000 rotations, 60,000 rotations, 80,000 rotations, 100,000 rotations, and the above-mentioned foreign matter was introduced while maintaining the respective rotation speeds to carry out a foreign matter collision test. Carried out.

The number of foreign matter charged was one for each rotor, and after the foreign matter was charged, the evaluation sample was taken out regardless of the presence or absence of collision damage. After the foreign matter collision test, the evaluation sample was visually inspected with a stereoscopic microscope for defects, and the fluorescent penetration flaw detection method was used to confirm the presence or absence of damage.

The results of the foreign matter collision test are shown in FIG. O marks indicate that the tip of the blade was not chipped or damaged, and ● marks indicate that chipping or damage was found. The horizontal axis represents the rotational speed W of the ceramic rotor, and the vertical axis represents the diameter D of the introduced foreign matter. Further, the curve is calculated by the equation (4) with the left side = the right side. Since the collision position of the foreign matter is 1.5 mm from the tip of the blade on the central axis side, R / R ₀
= 48.5 / 50 = 0.97 and the blade thickness t = 1.2 at the collision position were calculated by substituting them into the equation (4).
From the idea of the equation (4), the area on the upper right of this line is the area where impact damage occurs.

From FIG. 5 to the reference line of the impact breakage of the equation (4), there are two types, one that is damaged by foreign matter collision and the other that is not damaged by the collision, and when t> C × R / R ₀ is satisfied. It turns out that no damage occurs.

Example 2 Using the ceramic rotor of Example 1 above, the foreign matter was made to collide with the tip of the blade portion, and the rotation speed and the foreign matter diameter were changed.
The theoretical value of πR ₀ (W × φ) / 60σ _f representing the blade tip thickness tmin was calculated, and the minimum blade thickness tmin (1.0 m at the blade tip of the actually used ceramic rotor was calculated.
m). The results are shown in Table 1.

[0043]

[Table 1]

From Table 1, the actual blade tip thickness is πR.
It can be seen that no damage occurs when the value is larger than the theoretical value of ₀ (W × φ) / 60σ _f .

[0045]

As described above in detail, in the ceramic rotor device of the present invention, the steady rotational speed of the ceramic rotor, the radius of the ceramic rotor, the average strength of the ceramics, and the maximum mesh diameter of the protective net, that is, in the combustion gas, Since the thickness t at an arbitrary position of the wing is set from the maximum diameter of the foreign matter that may mix and fly and damage the wing, the wing thickness can be made more in line with the actual state, and the wing can be made The damage can be reliably prevented, and the centrifugal stress that occurs can be suppressed to a minimum by setting the thickness of an arbitrary portion of the blade portion to the minimum thickness that can prevent the damage due to foreign matter.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a ceramic rotor device according to the present invention.

FIG. 2 is a sectional view of a ceramic rotor.

FIG. 3 is a graph showing the relationship between speed / plate thickness and stress.

FIG. 4 is a graph showing a relationship between a constant φ and a foreign matter diameter D.

FIG. 5 is a graph showing the relationship between the foreign matter diameter and the rotor rotation speed in the foreign matter collision test.

[Explanation of symbols]

3 ... Ceramic rotor 5 ... Protection network 7 ... Hub 9 ... Wing

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Claims (3)

[Claims] Claim: What is claimed is: 1. A ceramic rotor having a plurality of blades formed on an outer periphery of a hub is provided in a passage through which gas flows, and a foreign matter is prevented from entering a passage on a windward side of the ceramic rotor. A ceramic rotor device provided with a mesh, wherein the number of revolutions of the ceramic rotor during steady operation is W, the maximum mesh diameter of the protective mesh is D, and φ = 0.002.
6 × D ² −0.0017 × D, the radius of the ceramic rotor defined by the distance from the center of the hub portion to the blade tip is R ₀ , and the average strength of the ceramics forming the ceramic rotor is σ _f Then, the thickness t of the blade portion at an arbitrary radius R from the center of the hub portion satisfies the relational expression represented by t> C × R / R ₀ (where C = πφWR ₀ / 60σ _f ). A ceramic rotor device characterized by the above. 2. The ceramic rotor device according to claim 1, wherein the maximum mesh diameter of the protective net is 0.4 mm or less. 3. The ceramic rotor device according to claim 1 or 2, wherein the ceramic forming the ceramic rotor has an average strength σ _f of 600 MPa or more.