JPH07103877B2 - Axial compressor - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an axial flow compressor, and more particularly to an axial flow compressor characterized by the shape of its moving blades and stationary blades.

[Technical background of the invention and its problems]

Generally, in an axial compressor, as shown in FIG.
One section is formed by the moving blades 2 planted in the rotor 1 and the stationary blades 4 fixed to the casing 3, and an axial flow compressor is configured by combining a plurality of these sections in the axial direction.
An annular passage 7 through which a working fluid flows is formed between a rotor-side inner wall (hereinafter referred to as an inner wall) 5 and a casing-side outer wall (hereinafter referred to as an outer wall) 6 of this axial flow compressor. In such an axial flow compressor, the working fluid flowing from the suction pipe 8 through the inlet guide vane 9 into the first stage moving blade 2a is given a swirling force by the first stage moving blade 2a rotating with the rotor 1 and is accelerated. The pressure increases due to the deceleration by the first stage stationary blade 4a. Further, since the working fluid flowing into the next paragraph repeats the same operation, its pressure is gradually increased while flowing in the annular passage 7 in the axial direction, and finally the working fluid is discharged through the outlet guide vanes 10. Discharged to pipe 11.

However, when the working fluid passes through the annular passage 7, due to the viscosity of the working fluid, a low-velocity environment layer is generated on the surfaces of the inner wall and the outer wall, and this environment layer grows as it goes downstream. FIG. 7 shows the distribution in the height direction of the axial flow velocity component of the working fluid from the inner wall to the outer wall. A speed reduction part δ is seen near the inner wall and the outer wall. This deceleration part δ is the boundary layer,
Velocity component CXA at the first stage inlet and velocity component C at the final stage outlet
Comparing with XB, the boundary layer δ is such that δHB and δCB at the outlet are larger than δHA and δCA at the inlet, and as shown in Fig. 8, gradually increase from the first stage inlet to the last stage outlet. It was measured to grow. Then, due to the growth of the boundary layer, the inflow angle of the working fluid into the moving blades 2 or the stationary blades 4 deviates from the design value, and the deviation of the inflow angle causes the deterioration of the paragraph performance.

FIG. 9 shows the outflow angle α1 of the working fluid from the preceding stage vane 4 ′, the inflow angle β1 into the stage moving blade 2, the outflow angle β2 from the stage moving blade 2 and the inflow angle α2 into the stage stationary blade 4. It shows the relationship of. As shown by the dotted line in the figure, the working fluid flowing out from the preceding stationary vane 4'at the speed C1A and the angle α1A has a relative speed W1A because the corresponding stage moving blade 2 is rotating at the speed U.
It is designed to optimally flow into the blade 2 with a relative inflow angle β1A. However, since the axial velocity component decelerates from CX to CX 'in the boundary layer near the wall surface, the vane outflow velocity is decelerated from C1A to C1B as shown by the solid line in the figure, and actually flows into the blade 2. The working fluid has a relative velocity W1B and a relative inflow angle β1B, and flows into the blade 2 from a direction away from the design value. The same applies to the stage vane 4, and the working fluid flowing out from the stage vane 2 at the speed W2A and the angle β2A is designed to optimally flow into the stage vane 4 at the relative velocity C2A and the relative inflow angle α2A. However, in the boundary layer, the relative velocity C2B and the relative inflow angle α2B flow into the stationary blade 4, causing a deviation from the design value.

When the inflow angle of the working fluid deviates from the optimum inflow angle in this way, the flows are separated at the back surfaces of the moving blades 2 and the stationary blades 4, causing a large blade row loss. The loss due to this boundary layer occupies a particularly large proportion of the internal loss of the compressor, and an effective measure for it has been demanded from the viewpoint of effective use of energy. Further, since the separated flow is an unstable flow, there is a risk that the entire compressor enters a surge, and there is a demand to prevent the separated flow from the viewpoint of operating the compressor safely.

Conventionally, as a means for solving the above-mentioned demands, there has been proposed a technique of deforming a blade end portion of a moving blade or a stationary blade operating in a boundary layer so as to perform a constant work in a height direction (Japanese Patent Laid-Open No. 2000-242242). (See Japanese Patent Publication No. 59-99096). According to this technology, the inflow angle of the working fluid to the moving blade or the stationary blade can be optimized for the relevant paragraph, but the pressure rise in the paragraph is not constant in the height direction of the blade and is affected by the boundary layer. There is a problem that the pressure rise at the blade tip becomes larger than that of other blade portions, and the volumetric flow rate of the working fluid passing through the blade tip decreases. Therefore, in the vicinity of the inner wall or outer wall of the compressor, in addition to the deceleration of the flow due to the boundary layer, the deceleration due to the decrease of the volumetric flow rate is added,
There is a problem that the flow of the working fluid to the next paragraph is remarkably deformed and causes a large loss.In particular, in the case of the other stage compressor, there is a problem that it is difficult to properly design the downstream paragraph due to the cumulative effect. It was

[Object of the Invention]

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional technology, reduce blade row loss due to the boundary layer formed in the annular passage of the axial compressor, and a rotor blade that exhibits excellent paragraph performance. It provides the shape of a vane.

[Outline of Invention]

In order to achieve the above object, the present invention provides, in an axial flow compressor including a moving blade and a stationary blade, a blade root portion and a blade tip portion of the moving blade and the stationary blade operating in a viscous boundary layer, It is formed so that the pressure rise in the paragraph consisting of blades and stators is constant in the passage height direction.By preventing separation flow at the back of the rotor blades and stator blades, the performance of the axial compressor is improved. It has been achieved.

Example of Invention

An embodiment of an axial compressor according to the present invention will be described below with reference to FIGS. 1 to 5. Since the overall structure of the axial compressor is the same as that of the conventional compressor shown in FIG. 6, its explanation is omitted.

FIG. 1 is a height direction distribution diagram from the inner wall to the outer wall of a stagger λR showing the shape of a moving blade of an axial flow compressor. The stagger distribution λRB of the moving blade according to the present invention is shown by a solid line, and the stagger distribution of the conventional moving blade is shown. λRA is shown by a broken line. Here, stagger refers to the angle between the axial velocity direction of the compressor and the chord line of the blade. The conventional blade stagger λRA gradually increases from the inner wall to the outer wall in response to the increase in the rotating peripheral speed due to the increase in radius, and the blade is formed so that the torsion increases from the root to the tip. ing. On the other hand, the stagger λ RB of the moving blade according to the present invention increases from the central portion of the blade toward the end portion on the inner wall side and the outer wall side, and the blade heads toward the root portion from a position above the root portion by a predetermined height δH. The twist is continuously increased in accordance with the above, and the twist is continuously increased from a position lower than the tip portion by a predetermined height δC toward the tip portion. Further, as in the conventional case, the central portion is formed so that the torsion increases from the root portion toward the tip portion. Here, the predetermined heights δH and δC
Is the boundary layer thickness at the inner and outer walls, and is shown in FIG.
As shown in the figure, it can be determined by an actually measured value or a logically calculated value.

FIG. 2 is a height direction distribution diagram of the stagger λS showing the shape of the vane of the axial compressor, in which the stagger distribution λSB according to the present invention is shown by a solid line and the conventional stagger distribution λSA is shown by a broken line. The stagger λSA of the conventional vane is almost constant in the height direction of the blade, and the twist of the blade is almost constant in the height direction. On the other hand, the vane stagger λ SB according to the present invention is
Similar to the case of the moving blade, the blades are formed so that the inner wall side and the outer wall side increase from the central portion of the blade toward the end portion, and the blade is formed so that the torsion increases continuously at the root portion and the tip portion. Here, δH and δC in the figure indicate boundary layer thicknesses on the inner wall and the outer wall, and are determined in the same manner as in the case of the moving blade.

As described above, in the moving blade and the stationary blade according to the present invention, the stagger of the blade located in the boundary layer region of the inner wall and the outer wall is formed larger than the stagger of the central portion of the blade. Hereinafter, a method for determining the increase amount of the stagger will be described with reference to FIG. FIG. 3 shows velocity triangles of the working fluid at the inlet and outlet of the blade according to the present invention, the solid line is the actual velocity triangle in the boundary layer with flow deceleration, and the dotted line is the flow velocity due to the boundary layer. The speed triangle is shown without deceleration. When there is no flow deceleration due to the boundary layer, the relative velocity W
The working fluid flowing from the preceding stage stationary blade into the relevant stage stationary blade at 1A flows out from the relevant stage stationary blade to the relevant stage stationary blade at a relative speed W2A because the moving blade rotates at the peripheral speed U. Here, the circumferential direction components of the relative velocities W1A and W2A at this time are respectively W1yA and W2.
If yA, the difference can be expressed as ΔWA = (W1yA−W2yA).

However, in the actual boundary layer, the axial velocity component is
Since we slow down from CX to CX ', we must transform the velocity triangle accordingly. Therefore, the rotor blade according to the present invention is
The circumferential components of the actual relative inflow velocity W1B to the stage rotor blade and the actual relative outflow velocity W2B from the stage rotor blade are W1yB and W2yB, respectively, and the difference βΔWB = (W1yB−W2yB) is the design value ΔWA. Transform the velocity triangle to be the same as
Determine the blade stagger λ RB in the boundary layer region. here,
The blade stagger λRB in the boundary layer region is almost equal to the average value of the relative inflow angle β1B and the relative outflow angle β2B, and can be approximately calculated by λRB = 0.5 (β1B + β2B). In addition, the pressure rise ΔPB per unit height in the boundary layer basin is
Since PB = ρUΔWB (ρ: average density), the pressure increase in the paragraph can be made constant in the height direction of the moving blade by determining the stagger λRB so that ΔWB = ΔWA as described above.

On the other hand, the same applies to the stationary blade as that of the moving blade. The stagger λSB of the stationary blade is determined by the velocity triangle described above, and is approximately calculated by λSB = 0.5 (α2B + α3B).

Since the axial flow velocity component CX 'is zero on the inner wall surface and outer wall surface, the stagger obtained by applying the above method strictly becomes 90 °, and the twisting of the blade tips of the rotor blade and the stator blade is significantly large. It becomes a thing. However, since such a blade is difficult to manufacture as a practical matter, as shown in FIGS. 1 and 2, a range εH in the immediate vicinity of the inner wall surface and the outer wall surface,
εC is determined by extrapolation from the value of the stagger of the inner blade portion without determining the stagger by the above method. Here, the above ranges εH and εC are about 10 to 20% of the boundary layer thicknesses δH and δC, respectively.

By defining the stagger of the blades and vanes to increase gradually toward the inner and outer walls, the working fluid can flow into the blades and vanes from the proper direction at any position in the boundary layer. And no separation flow occurs. Therefore, blade loss due to separated flow can be reduced, and excellent paragraph performance can be maintained. Also,
Since the pressure rise in the paragraph becomes constant in the height direction of the blade, the volumetric flow rate of the working fluid becomes constant in the height direction, and there is no adverse effect on the next paragraph.

FIG. 4 shows another embodiment of the axial flow compressor according to the present invention. The rotor blade according to this embodiment has inner and outer wall sides from the central portion of the blade as shown by the solid line in the figure. The camber θ RB is formed so as to increase toward the end. Here, the camber means the external angle formed by the tangent line at the blade inlet end and the tangent line at the blade outlet end of the camber curve connecting the centers of the inscribed circles of the blade cross section. As is apparent from the figure, in the rotor blade according to the present embodiment, the camber increases continuously from the position above the predetermined height δH above the root toward the root, and the predetermined value from the tip as in the above embodiments. The camber is formed such that the camber increases continuously from the position where the height is δC lower to the tip. The dotted line in the figure indicates the camber distribution θRA of the conventional moving blade.

FIG. 5 shows a velocity triangle that determines the increase amount of the camber, the solid line shows the actual velocity triangle in the boundary layer with flow deceleration, and the dotted line shows the velocity triangle without flow deceleration by the boundary layer. Shows. Also in this case, as in the above-described embodiment, the difference ΔWB between the circumferential components of the relative inflow velocity W1B to the moving blade and the relative outflow velocity W2B from the moving blade in the boundary layer is the designed difference ΔWA of the circumferential component. The camber θRB is determined by deforming the velocity triangle so that it becomes the same. The camber θRB is almost equal to the difference between the relative inflow angle and the relative outflow angle, and can be approximately calculated by θRB = (β1B−β2B).

〔The invention's effect〕

As is clear from the above description, the present invention is characterized in that the blade root portion and the blade tip stagger or camber of the moving blade and the stationary blade are formed larger than the stagger or camber of the blade central portion. Separation flow on the back surface of the vane can be prevented, and excellent paragraph performance can be maintained. Further, the pressure increase in the paragraph can be made constant in the height direction of the blade, and the deformation of the flow to the next paragraph due to the decrease in the volumetric flow rate of the working fluid can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram showing a stagger distribution of a moving blade of an axial flow compressor according to the present invention, FIG. 2 is a diagram showing a stagger distribution of a stationary blade of an axial flow compressor according to the present invention, and FIG. The figure which shows the velocity triangle of the working fluid in an inlet part and an outlet part, FIG. 4 is a figure which shows the camber distribution of the moving blade by the other Example of the axial flow compressor by this invention, FIG. 5 is the said other Example. Showing a velocity triangle of the working fluid at the inlet and outlet of the rotor blade of Fig. 6, Fig. 6 is a longitudinal sectional view showing the outline of the axial compressor, and Figs. 7 and 8 are annular passages of the axial compressor. FIG. 9 is a diagram for explaining the boundary layer formed in FIG. 9, and FIG. 9 is a diagram showing a velocity triangle of a conventional working fluid. 1 ... Rotor, 2 ... Moving blade, 4 ... Stationary blade, 5 ... Rotor-side inner wall, 6 ... Casing-side outer wall, 7 ... Annular passage, δ
...... Boundary layer thickness, CX, CX ′ …… Axial flow velocity component, λR, λS
…… Stagger, θR …… Camber.

Claims (3)

[Claims] 1. An axial flow compressor having a moving blade and a stationary blade, wherein the moving blade and the stationary blade of the axial flow compressor are operated in a viscous boundary layer formed near an inner wall or an outer wall of a fluid passage portion of the axial flow compressor. Axial flow compression characterized in that at least one end portion of the blade root portion and the blade tip portion is formed so that the pressure increase in the paragraph consisting of the moving blade and the stationary blade becomes constant in the height direction of the fluid passage portion. Machine. 2. The stagger of the moving blades and the stationary blades increases continuously from a position above a predetermined height above the blade root toward the blade root and at a position below a predetermined height below the blade tip. The axial flow compressor according to claim 1, characterized in that the axial flow compressor is formed so as to be continuously increased toward the tip end portion. 3. The camber of the moving blade and the stationary blade increases continuously from the position above a predetermined height above the blade root toward the blade root and at the position below a predetermined height below the blade tip. The axial flow compressor according to claim 1, characterized in that the axial flow compressor is formed so as to be continuously increased toward the tip end portion.