JPH0325640B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a turbo compressor used in a gas turbine or the like, and particularly to a turbo compressor for reducing the surge limit flow rate.

This type of turbo compressor is desired to operate in a small flow rate range in order to improve the fuel efficiency of the gas turbine. For this reason, in the past, as shown in Fig. 1A and B, for example, surging in a small flow area was prevented by giving a pre-swirl to the gas flowing into the compressor and suppressing the suppression angle to the impeller. is prevented. In FIGS. 1A and 1B, 1 is an impeller fixed to an impeller rotating shaft 2, and 3 is a variable inlet guide vane. The variable guide vane 3 is fixed to the shaft 4,
This shaft 4 is pivotally supported by a housing 5 and a bell mouth portion 6. A lever 7 is fixed to the shaft 4, and the lever 7 is connected to a link 9 via a pin 8. As shown in FIG. 1B, the guide vanes 3 are attached to the impeller 1 at approximately equal intervals in the circumferential direction. In order to rotate the guide vanes 3 all at once at the same angle, the aforementioned links 9 are disposed in an annular shape (not shown) corresponding to the guide vanes 3.

When operating the turbo compressor shown in FIGS. 1A and 1B in a small flow range, the link 9 is operated to rotate the guide vane 3 to give a pre-swirl to the gas flowing in from the suction port 10. . As a result, the suppression angle of the inflowing gas at the impeller 1 becomes small, and surging of the turbo compressor is prevented.

While FIGS. 1A and 1B show an example of a non-axisymmetric suction type turbo compressor, FIG. 2 shows a conventional example of an axisymmetric suction type. Here, 11 is an impeller, 12 is a variable inlet guide vane, and the guide vanes 12 are arranged between an outer circumferential wall 13 and an inner circumferential wall 14 at equal intervals in the circumferential direction. Also, Figure 1 A, B
As shown in , the shaft 15, lever 16, pin 1
7. Links 18 are attached to each of the guide vanes 12 to rotate the guide vanes 12 by a desired angle, thereby preventing the occurrence of surging in a small flow rate region.

However, such a conventional turbo compressor requires a complicated link mechanism or ring gear mechanism to rotate all the guide vanes at the same time, resulting in an expensive device. In addition, in the flow between the blades 3 shown by arrows in FIG. 1B, the inner flow IF and the outer flow OF have different speeds.
As a result, a circumferential non-uniform flow with a pressure gradient is generated between each blade, and at a specific rotation speed, this non-uniform flow turns into a vortex flow and excites the impeller 1.
The impeller may be damaged due to resonance.

In order to eliminate such conventional drawbacks, the present invention has a suction port that opens in the radial direction of the impeller,
In a turbo compressor, the gas sucked from the suction port is guided to the impeller through an annular gas passage formed between an inner circumferential wall and an outer circumferential wall, which changes the gas from a radial flow to an axial flow. The passage has a longitudinal cross-sectional shape with a curvature approximately equal to that of the inner peripheral wall,
Further, an annular rectifying plate is arranged to divide the gas flowing into the gas passage into a flow on the inner circumferential wall side and a flow on the outer circumferential wall side, and the annular rectifying plate is arranged around the axis of the impeller, and the rectifying plate is always connected to the inner circumferential wall side. The impeller is positioned approximately midway between the peripheral wall and the outer peripheral wall, and is moved toward the inner peripheral wall along the axis of the impeller during operation in a surging region, so that the gas flowing into the gas passage on the outer peripheral wall side is moved toward the inner peripheral wall side along the axis of the impeller. It is an object of the present invention to provide a turbo compressor that can prevent the occurrence of surging without providing a complicated variable mechanism by increasing the flow rate of gas and increasing the axial velocity of incoming gas at the impeller inlet.

The present invention will be explained in detail below based on the drawings. In the following, parts similar to those in FIGS. 1A and 1B and FIG. 2 are designated by the same reference numerals.

FIG. 3 shows an example of the turbo compressor of the present invention. Here, the reference numeral 21 indicates a rectifying plate, and the lower half of the drawing is in non-operation and the upper half is in operation, that is, the rectifying plate 21
It shows a state where the is away from the impeller 1. Current plate 21
is an annular shape centered on the axis 2' of the impeller 2, for example,
The curvature of the circumferential surface 22 is approximately equal to the curvature of the inner circumferential wall 14. Further, the rectifying plate 21 is connected to the hydraulic actuator 2 via the rod 23.
4, and drives the hydraulic actuator 24 to move the rectifying plate 21 along the axis 2'.
The hydraulic actuator 24 is operated by receiving a control signal from a control circuit (not shown) attached to the gas turbine engine or turbo compressor.

In the turbo compressor of the present invention configured as described above, the rectifier plate 21 is normally positioned in the gas passage formed between the inner circumferential wall 14 and the outer circumferential wall 13, as shown in the lower half of FIG. In this state, among the flow from the gas suction port 10 toward the impeller 1, the flow on the inner peripheral wall 14 side, that is, the flow toward the inner peripheral wall 14
The gas passing through the gas passage 25 formed between the current plate 21 and the current plate 21 flows from the inlet 26 having the gas inlet width A to the outlet 27 having the gas outlet width B. Further, the flow on the outer peripheral wall 13 side, that is, the gas passing through the gas passage 28 formed between the outer peripheral wall 13 and the rectifier plate 21, flows from the inlet 29 with the gas inlet width C to the outlet 30 with the gas outlet width D. Flowing toward each gas passage 2
Since the curvature of the vertical cross-sectional shape of the current plate 21 is approximately the same as the curvature of the inner circumferential wall 14, the gas inside the flow straightening plates 21 flows in an annular shape without being hindered from changing from a radial flow to an axial flow. It flows as a uniform flow in the circumferential direction along the current plate 21. moreover,
Since these two flows are accelerated when passing through the gas passages 25 and 28, undisturbed gas flows into the impeller 1.

On the other hand, in an operating region where surging occurs, the current plate 21 is moved to a position away from the impeller 1, as shown in the upper side of FIG. That is,
When the aforementioned control circuit detects the occurrence of surging or an operating region where surging is likely to occur and supplies a control signal to the hydraulic actuator 24, the hydraulic actuator 24 operates to move the rod 23 to the left. . As a result, when the current plate 21 moves to the position shown in the upper half of FIG.
Inlet 2 of gas passage 25 formed on inner peripheral wall 14 side
6, the vertical cross-sectional shape of the rectifying plate 21 is the same as that of the inner peripheral wall 14.
, and since the current plate 21 is annular with the axis 2' of the impeller 1 as its center, A
to A', but at outlet 27 near impeller 1.
The width B' remains approximately the same as the non-actuated width B. Therefore, as the width of the inlet 26 decreases, the opening area decreases and the flow rate of gas flowing into the gas passage 25 decreases, but the width of the outlet 27, ie, the opening area, remains almost unchanged, resulting in a decrease in flow velocity.
In other words, the axial velocity at the impeller inlet will be reduced. Moreover, the width of the inlet 29 of the gas passage 28 formed on the outer peripheral wall 13 side is, conversely, from C to C.
C′, but the width of the outlet 30 near the impeller 1
D' is maintained approximately the same as the non-actuated width D for the same reasons as described above. Therefore, gas passage 2
The flow rate of gas flowing into 8 is increased by increasing the inlet width 29,
That is, although the opening area increases, the width of the outlet 30, that is, the opening area remains almost unchanged, so the flow velocity increases. In other words, the axial velocity at the impeller inlet increases. Note that the opening areas of the inlets 26 and 29 on the inner circumferential wall side and the outer circumferential wall side partitioned by the annular rectifier plate 21 described above are determined by the circumferential length and axial width of each portion, Since the circumferential length is constant, it changes depending on the amount of movement of the current plate 21 in the axial direction. On the other hand, the opening areas of the outlets 27 and 30 are hardly affected by the movement of the current plate 21 in the axial direction. Therefore, as shown in FIG. 4, the suppression angle of the incoming gas with respect to the impeller 1 is reduced, allowing operation in a region away from the surging region.
Moreover, since the area of the gas passage 28 is configured to gradually decrease from the inlet 29 to the outlet 30,
The velocity of the flow is gradually increased, the possibility that the flow separates from the wall surface is reduced, and an undisturbed flow flows into the vicinity of the tip of the impeller 1.

FIG. 4 shows the inflow velocity of the flow flowing into the impeller 1, the circumferential velocity of the impeller 1, the relative inflow velocity of the flow with respect to the impeller 1, and the relationship between the direction of each of these velocities and the impeller 1. Here, IS is the gas inflow speed, VPS is the circumferential speed of the impeller 1, RIS is the relative inflow speed of the inflow gas to the impeller 1, and the direction of the relative inflow speed RIS is the direction of the inflow gas to the impeller 1. It corresponds to the suppression angle for . Here, the inflow speed IS and the relative inflow speed RIS shown by broken lines indicate the respective speeds when the baffle plate 21 is not operated, and the inflow speed IS shown by the solid line is near the outer periphery of the impeller when the baffle plate 21 is operated. The relative inflow speed RIS shown by the solid line indicates the relative inflow speed near the outer periphery of the impeller when the current plate 21 is operated. Here, the state indicated by the dotted line in Fig. 4 is
The turbo compressor is set to a small flow rate region that is at the limit where surging occurs, and in this state, the current plate 21 is set to the impeller 1.
When moving away from the impeller and increasing the inflow speed IS of the gas near the outer periphery of the impeller, as shown by the solid line, the relative inflow speed RIS increases as well, as shown by the solid line, and this relative inflow speed RIS
The suppression angle of the impeller 1 to the impeller 1 becomes smaller. Therefore, surging can be avoided. In other words, in operation in the small flow rate range where surging occurs, even if the total flow rate flowing into the turbo compressor is gradually reduced, the inflow velocity near the outer circumference of the impeller will not change as shown by the broken line in Figure 4. Surging can be avoided until the surge limit inflow speed IS is reached, which allows operation in a smaller flow rate range than before.
Fuel efficiency can be improved.

In the turbo compressor shown in FIG. 3, when the baffle plate 21 is moved in a direction away from the impeller 1, a small amount of fluid with low energy flows into the vicinity of the root of the impeller 1, causing a stall. can also be considered. However, in this type of turbo compressor, the vicinity of the root of the impeller 1 is located on the outside of the bend in the flow path in which the fluid flowing from the axial direction toward the impeller 1 bends outward in the radial direction. , is a place where stalls are theoretically unlikely to occur,
It does not cause surging of the entire turbo compressor.

Note that it is of course possible to operate the current plate by using a pneumatic actuator or other means instead of the hydraulic actuator.

As explained above, the present invention has a suction port that opens in the radial direction of an impeller, and has a gap between an inner circumferential wall and an outer circumferential wall that converts the gas sucked in from the suction port from a radial flow to an axial flow. In a turbo compressor in which the gas is guided to the impeller through a formed annular gas passage, the gas passage has a vertical cross-sectional shape with a curvature approximately equal to that of the inner circumferential wall, and the gas flowing into the gas passage is An annular rectifying plate is arranged around the axis of the impeller to divide the flow into the inner peripheral wall side and the outer peripheral wall side, and the rectifying plate is normally placed approximately halfway between the inner peripheral wall and the outer peripheral wall. At the same time, during operation in a surging generation area, the impeller is moved toward the inner circumferential wall side along the axis of the impeller, so when the current plate is not in operation, the annular current plate prevents the incoming gas from being disturbed. It increases the flow rate of the gas that flows into the car and into the gas passage on the outer peripheral wall during operation, increasing the axial velocity of the inflowing gas at the impeller inlet, making it possible to operate in an area away from the area where surging occurs. Become.

Therefore, unlike conventional variable inlet guide vanes using annular links, there is no non-uniform flow of fluid in the circumferential direction, so there is no resonance of the impeller at a specific rotation speed, and there is no need for complicated inlet guide vanes. It is also possible to prevent the occurrence of surging without providing a variable mechanism.

[Brief explanation of drawings]

1A and 2 are sectional views showing the configuration of two examples of conventional turbo compressors, FIG. 1B is a sectional view taken along line A-A in FIG. 1A, and FIG. 3 is a turbo compressor of the present invention. FIG. 4 is a cross-sectional view showing an example of the structure of FIG. 4, and FIG. 4 is a diagram showing the relationship among the impeller, the circumferential speed of the impeller, the gas inflow speed, and the relative gas inflow speed. 1... Impeller, 2... Impeller shaft, 3... Variable inlet guide vane, 4... Shaft, 5... Housing, 6...
Bell mouth section, 7... lever, 8... pin, 9...
... Link, 10 ... Suction port, 11 ... Impeller, 1
2... Variable guide vane, 13... Outer peripheral wall, 14... Inner peripheral wall, 15... Shaft, 16... Lever, 17... Pin, 18... Link, 21... Current plate, 22...
Surrounding surface, 23... Rod, 24... Hydraulic actuator, 25, 28... Gas passage, 26, 29...
Entrance, 27, 30...exit.

Claims (1)

[Claims] 1 having a suction port opening in the radial direction of the impeller,
In a turbo compressor, the gas sucked from the suction port is guided to the impeller through an annular gas passage formed between an inner circumferential wall and an outer circumferential wall, which changes the gas from a radial flow to an axial flow. The passage has a longitudinal cross-sectional shape with a curvature approximately equal to that of the inner peripheral wall,
Further, an annular rectifying plate is arranged to divide the gas flowing into the gas passage into a flow on the inner circumferential wall side and a flow on the outer circumferential wall side, and the annular rectifying plate is arranged around the axis of the impeller, and the rectifying plate is always connected to the inner circumferential wall side. A turbo compressor characterized in that the turbo compressor is located approximately midway between a peripheral wall and an outer peripheral wall, and is moved toward the inner peripheral wall along the axis of the impeller when operating in a surging generation region.