JP3977780B2 - gas turbine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas turbine that obtains rotational power of a turbine rotor from a working fluid, and more particularly to cooling air that cools the turbine rotor and seal air flow path structure that seals between the turbine rotor and the stationary blades.
[0002]
[Prior art]
For example, a turbine rotor such as a gas turbine is generally configured by stacking a turbine disk having a plurality of moving blades on the outer peripheral portion and a spacer, and its thermal expansion and contraction and thermal stress are greatly affected by the temperature environment in the center. . If the atmospheric temperature in the center of the turbine rotor is uncertain, it is difficult to estimate the metal temperature in the center of the turbine rotor during steady operation, start-up, or stop of the turbine. In some cases, the turbine rotor and the stationary part (stator blades, casing, etc.) contact each other, the fitting between the turbine disk and the spacer is loosened, or the fitting is tight and the thermal stress exceeding the allowable stress is applied. There is a risk that it will occur.
[0003]
Therefore, conventionally, a cooling flow path in which compressed air from a compressor guided to the center through a connecting shaft with the compressor rotor is divided into each stage as cooling air or wheel space seal air in the turbine rotor. (For example, refer to Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 8-14064
[Problems to be solved by the invention]
As described above, when compressed air is introduced from a compressor rotor connected coaxially through a connecting shaft, it is usual to provide a central hole in the turbine rotor and divert the compressed air flowing through the rotation center to each stage. However, when the center hole is provided, stress concentration in the center hole occurs during turbine operation due to the action of the centrifugal force received by the moving blade provided on the outer periphery. Therefore, a process called “overspin” must be performed at the stage of manufacturing the turbine disk so that the center hole is heat treated by a special method and the centrifugal force during operation is offset by the residual stress. However, this overspin process is very expensive. Also, the presence of the central hole complicates the evaluation of thermal stress and thermal expansion and contraction, and if necessary, the turbine disk may have to be thickened for reinforcement.
[0006]
In each stage, when compressed air that has cooled the turbine disk and spacers is discharged to the gas path, the flow rate and pressure of the compressed air to be discharged are changed to the gas paths at various locations to prevent the high-temperature and high-pressure working fluid from flowing backward. It is necessary to adjust according to the pressure. Therefore, the compressed air that is diverted from the rotation center of the turbine rotor and guided to each stage is adjusted in pressure and flow rate before being released by setting slits or the like. It is difficult to distribute the flow rate accurately. If compressed air is released more than expected at a certain location, the working fluid may enter the turbine rotor at another location. Therefore, in order to prevent the backflow of the working fluid to the turbine rotor, it becomes necessary to assume a large fluctuation in the compressed air flow rate, which becomes a factor of reducing the performance of the gas turbine.
[0007]
Accordingly, an object of the present invention is to provide a gas turbine capable of distributing cooling air and sealing air having an appropriate pressure and flow rate to appropriate positions of the turbine rotor without providing a center hole in the turbine disk.
[0008]
[Means for Solving the Problems]
(1) In order to achieve the above object, the present invention provides a turbine in which a stationary blade attached to the inner peripheral side of a casing and a spacer having a central hole are interposed between turbine disks to which a plurality of moving blades are attached. A gas turbine comprising a rotor and a seal that seals a gap between the stationary blade and the spacer, and first and second cavities formed between the spacer and the turbine disk disposed in front of and behind the spacer, respectively. A compressed air introduction hole for introducing compressed air from outside the casing guided into the stationary blade into one of the first and second cavities through the seal, and the center of the spacer Compressed air from the compressed air introduction hole led to the other of the first and second cavities through the hole is used as a wheel between the spacer and the turbine disk. Characterized in that a jet slit for ejecting a sealing air pace.
[0009]
With the above configuration, first, the compressed air introduced from the stationary blade or the compressed air used for cooling the stationary blade is prevented from leaking to the front and rear wheel spaces through the seal, and the compressed air is introduced through the compressed air introduction hole. And introduced into a first cavity formed between the spacer and, for example, the front turbine disk. The compressed air introduced into the first cavity flows inward in the radial direction, cools the side surfaces of the spacer and the turbine disk that define the first cavity and warms up the side surface of the turbine disk, while passing through the central hole of the spacer. For example, the spacer and the turbine disk that divides into the second cavity formed between the rear-side turbine disk and divides the second cavity when flowing outward in the radial direction are cooled (warmed up at startup). . The compressed air that has passed through the second cavity is finally discharged as a seal air to the gas path through the ejection slit in order to prevent the working fluid from entering the wheel space with the stationary blade.
[0010]
In this way, by introducing the compressed air from the stationary blade side into the turbine rotor, the compressed air of the appropriate pressure is directly introduced from the compressor through the independent system through the space outside the casing with sufficient space. Can do. Further, since compressed air having an appropriate pressure can be introduced into each stage without going through the turbine rotor center hole, the center hole of the turbine disk can be omitted. In addition, by forming the flow path of such a configuration independently at each stage, it is not necessary to branch the flow path in a complicated manner until it is finally released to the gas path as seal air. Can be adjusted easily and with high accuracy.
[0011]
(2) In the above (1), preferably, the spacer is provided with a guide for guiding the compressed air flowing through the first or second cavity in the radial direction.
[0012]
(3) In the above (1) or (2), preferably, the stationary blade includes a stationary blade diaphragm disposed to face the spacer, and the stationary blade diaphragm flows into the compressed air introduction hole. Of the wheel space between the compressed air outlet hole for extracting compressed air and the spacer and the turbine disk before and after the spacer, the wheel space communicates with the wheel space opposite to the wheel space from which the compressed air from the ejection slit is discharged. And an orifice.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a gas turbine according to the present invention will be described below with reference to the drawings.
The gas turbine according to the present invention supplies high-temperature and high-pressure combustion gas obtained by burning compressed air from a compressor together with fuel in a combustor to the turbine, and obtains rotational power of the turbine rotor by the combustion gas. Yes. The obtained rotational power is transmitted to, for example, a generator rotor that is coaxially connected to the turbine rotor, and converted into electrical energy.
[0014]
FIG. 1 is an axial sectional view showing a detailed structure of a turbine which is a main part of a first embodiment of a gas turbine of the present invention, and FIG. 2 is an enlarged view showing one paragraph of the turbine rotor shown in FIG. 3 is a radial cross-sectional view of a spacer (described later) as viewed in the direction of arrow III in FIG. In the following, the positional relationship corresponding to “left” and “right” in FIGS. 1 and 2 is referred to as “front” and “rear”, and “left-right direction” is referred to as “axial direction”.
1 to 3, the turbine 1 provided in the gas turbine of the present embodiment is provided with a casing 10, a stationary blade 20 provided on the inner peripheral side of the casing 10, and a casing 10 that is rotatably provided. A turbine rotor 30.
[0015]
The casing 10 includes a substantially cylindrical peripheral wall 11 and a shroud 12 provided on the inner peripheral portion of the peripheral wall 11 at predetermined intervals in the axial direction. An outer ring 21 of the stationary blade 20 is supported on the shrouds 12 and 12 adjacent to each other in the axial direction, and a cavity 13 is defined by the stationary blade outer ring 21, the shrouds 12 and 12 adjacent in the axial direction, and the casing peripheral wall 11. ing. A plurality of air introduction holes 14 connected to the cavities 13 are provided in the casing peripheral wall 11. Each air introduction hole 14 is connected to an extraction slit or the like provided in an extraction stage having a required pressure in a compressed air flow path of a compressor (not shown) via an independent pipe (not shown). Yes.
[0016]
The stationary blade outer ring 21 is provided with an opening 23 that allows the cavity 13 and the stationary blade inner passage 22 to communicate with each other. A plurality of stationary blades 20 at each stage are provided in the circumferential direction at a predetermined interval to form a single-stage stationary blade cascade, and are supported via a stationary blade inner ring 24 that connects the inner circumferential sides. A wing diaphragm 25 is provided. The vane inner ring 24 is provided with an opening 27 that communicates the vane inner passage 22 and the cavity 26 in the vane diaphragm 25. In addition, an orifice 28 is provided on the front side wall of the stationary blade diaphragm 25, and a compressed air outlet hole 29 is provided on the inner peripheral side wall.
[0017]
The turbine rotor 30 is configured by overlapping a turbine disk 32 having a plurality of moving blades 31 in the axial direction via a spacer 34 having a center hole 33. The turbine disk 32 and the spacer 34 are fastened together by a stacking bolt 35 (see FIG. 3). A plurality of moving blades 31 attached to each turbine disk 32 are fixed radially to the outer peripheral portion of the turbine disk 32 at a predetermined interval in the circumferential direction, thereby constituting a single-stage moving blade cascade.
[0018]
The stationary blade cascade of the same paragraph is located on the front side of each stage blade cascade. The gap between the stationary blade diaphragm 25 of each stage of the stationary blade 20 and the spacer 34 opposed thereto is sealed by seals 36 and 37, and the cavity 38 is formed between the stationary blade diaphragm 25 and the spacer 34 by the seals 36 and 37. A compartment is formed. As the seals 36 and 37, it is preferable to use a contact-type packing having a high sealing effect such as a honeycomb packing or a brush packing so that leakage of sealing air to the front and rear of the stationary blade 20 is suppressed as much as possible.
[0019]
Cavities 39 and 40 are defined by the spacer 22 and the front and rear turbine disks 32 between the spacer 22 and the front and rear turbine disks 32. In the present embodiment, the cavity 39 formed between the front turbine disk 32 and the rear turbine disk 32 is referred to as the first cavity 39 and the second cavity 40, respectively. To do. On the outer peripheral surface of the spacer 34 facing the compressed air outlet hole 29 of the stationary blade diaphragm 25, there is a compressed air introduction hole 41 that communicates the first cavity 39 and the above-described cavity 38 on the outer peripheral side of the spacer, as shown in FIG. In this manner, a plurality of compressed air from the inner peripheral side of the stationary blade diaphragm 25 is introduced into the first cavity 39 through the compressed air introduction hole 41.
[0020]
Further, annular protrusions 42 are provided in the circumferential direction in the first and second cavities 39 and 40 on the side surfaces of the spacer 34 facing the turbine disk 32 before and after. As shown in FIG. 3, the protruding portion 42 is provided with a plurality of slits 43 facing in the radial direction in the circumferential direction. Each slit 43 is arranged so as to be shifted in the circumferential direction from the insertion hole of the stacking bolt 35 so as not to interfere with the stacking bolt 35. A plurality of ejection slits 44 are provided in the circumferential direction on the outer peripheral portion of the spacer 34 to communicate the wheel space between the turbine disk 32 adjacent to the rear side and the second cavity 40. At this time, the opening area of the ejection slit 44 is set so that the required amount of sealing air is ejected in consideration of the pressure of the gas path at the corresponding location.
[0021]
When the gas turbine having the above-described configuration is operated, as indicated by dotted arrows in FIGS. 2 and 3, for example, compressed air extracted from a compressor (not shown) passes through independent pipes from the outer periphery of the casing 10. Through the air introduction hole 14 and introduced into the cavity 13 on the outer peripheral side of the stationary blade 20. The compressed air in the cavity 13 is introduced into the stationary blade inner passage 22 through the opening 23 provided in the stationary blade outer ring 21 to cool the stationary blade 20. The compressed air that has passed through the stationary blade 20 is introduced into a cavity 26 in a stationary blade diaphragm 25 installed on the inner peripheral side of the stationary blade 20. A part of the compressed air introduced into the stationary blade diaphragm 25 is ejected from the orifice 28 provided on the front side, and seals the wheel space with the front turbine disk 32.
[0022]
On the other hand, the other part of the compressed air introduced into the cavity 26 is led out to the cavity 38 between the diaphragm 25 and the spacer 34 through the compressed air lead-out hole 29 provided on the inner peripheral side of the stationary blade diaphragm 25 to be sealed. The air flows into the first cavity 39 formed by the spacer 34 and the front turbine disk 32 through the compressed air introduction hole 41 while being prevented from leaking by being sealed by 36 and 37. When the compressed air in the first cavity 39 flows radially inward through the slit 43 on the front side of the spacer 34, the turbine disk 32 forming the first cavity 39 and the side walls of the spacer 34 are cooled (warming-up at startup). After that, it goes around the second cavity 40 on the rear side of the spacer 34 through the central hole 33 of the spacer 34.
[0023]
When the compressed air in the second cavity 40 flows radially outward through the slits 43 on the rear side of the spacer 34, the side walls of the turbine disk 32 and the spacer 34 forming the second cavity 40 are cooled (warm at startup). Machine). Finally, the compressed air that has cooled the spacer 34 and the side wall of the rear turbine disk 32 seals the wheel space between the diaphragm 25 and the rear turbine disk 32 via the ejection slit 44. It is discharged into the gas path as air.
[0024]
Here, as a comparative example with the present embodiment, the cooling air of the turbine rotor 30 is introduced into the turbine rotor 30 not from the stationary side, that is, from the stationary blade 20 but through a connecting shaft with a compressor (not shown). Configuration examples are shown in FIGS. 4 and 5 correspond to FIGS. 1 and 2, respectively, and the same parts are denoted by the same reference numerals, and the description thereof is omitted.
[0025]
When the compressed air from the compressor is guided into the turbine rotor 3 via a connecting shaft (not shown) with the compressor rotor (not shown), generally, as shown in FIGS. 4 and 5, a turbine disk is used. A central hole 45 is provided in 32, and compressed air is circulated through the rotation center of the turbine rotor 30. The compressed air flowing through the center of rotation of the turbine rotor 30 flows radially outward in the first and second cavities 39 and 40 before and after the spacer 34 in each stage, as indicated by the dotted arrows in FIG. Then, the side wall of the turbine disk 32 is cooled and finally discharged as seal air to the corresponding gas path through the ejection slits 46 and 47 provided in the front and rear portions of the outer peripheral portion of the spacer 34.
[0026]
On the other hand, the compressed air guided from the outside of the casing 10 into the stationary blade 20 flows through the stationary blade passage 22 to cool the stationary blade 20, and then flows into the cavity 26 in the stationary blade diaphragm 25. The gas is discharged as seal air to the corresponding gas path through the orifices 48 and 49 provided before and after.
[0027]
As described above, when the compressed air is introduced from the compressor rotor connected coaxially through the connecting shaft, the compressed air easily flows radially outward due to the centrifugal force in the rotating turbine rotor 30. Usually, the main flow of compressed air is passed through the center of rotation and is divided into each stage. Further, in such a configuration, it is difficult to secure a large number of flow paths for introducing compressed air from the compressor into the turbine rotor 30, so that a complicated flow is generated in the turbine rotor 30 from the main flow formed at the center of rotation. Must be branched and distributed to each stage.
[0028]
However, if the center hole 45 is provided in the turbine disk 32, hoop stress concentrates near the inner wall of the center hole 45 during the turbine operation due to the action of centrifugal force. Therefore, a heat treatment is performed around the center hole 45 in a state where the turbine disk 32 is rotated at the rated rotation or more so that stress remains in the vicinity of the center hole 45 at room temperature and the hoop stress acting during operation is offset by the residual stress. A process called overspin must be implemented. However, this overspin process requires a great deal of cost, which increases the manufacturing cost. In addition, if there is a center hole, the evaluation of thermal stress and thermal expansion / contraction is complicated, and if necessary, the turbine disk 32 may have to be thickened and reinforced, and the processing of the center hole itself is also expensive. It takes.
[0029]
Further, in each stage, when the compressed air that has cooled the turbine disk 32 and the spacer 34 is discharged to the gas path, the flow rate of the compressed air to be discharged is prevented in order to prevent the high-temperature and high-pressure working fluid from flowing back into the turbine rotor 30. It is necessary to adjust the pressure and pressure according to the gas path pressure at each location. In this adjustment, the pressure and flow rate are adjusted before discharge by setting the throttles of the slits 46 and 47, respectively. However, in the case of a multi-branch channel as in this comparative example, only the throttle adjustment of the slits 46 and 47 It is difficult to accurately distribute the flow rate of the compressed air released at each stage. If compressed air is released more than expected at a certain location, the working fluid may enter the turbine rotor 30 at another location. Therefore, in order to prevent the backflow of the working fluid to the turbine rotor 30, it is necessary to introduce sufficiently high-pressure compressed air into the turbine rotor 30 on the assumption that fluctuations in the flow rate of the compressed air are large. The energy required for compressing the air is lost, and the performance of the gas turbine is deteriorated.
[0030]
On the other hand, in the present embodiment, as described above, the compressed air is guided from the stationary blade 20 side into the turbine rotor 30 through an independent system passing through the space outside the casing 10 with sufficient space. Thus, compressed air having an appropriate pressure can be directly introduced into each stage of the turbine rotor 30 from the compressor. Since compressed air having an appropriate pressure can be introduced into each stage of the turbine rotor 30 without going through the rotor center hole, the center hole of the turbine disk 32 can be omitted. In addition, since it is not necessary to provide a center hole, the evaluation of the rotor center temperature can be facilitated. In addition, an independent flow path having the above-described configuration is formed in each stage, so that the gas path can finally be used as seal air. Since it is not necessary to branch each flow path in the turbine rotor 30 until it is released into the turbine, the flow rate and pressure of the sealing air can be adjusted easily and with high accuracy. Therefore, high energy efficiency can be ensured, the performance or size of the gas turbine can be improved, and the reliability can be improved. Furthermore, since the center hole of the turbine disk 32 can be omitted and the flow path of the compressed air can be simplified, the structure of the turbine rotor 30 can be simplified and the strength can be improved, and the reliability can be improved in terms of strength. Can do.
[0031]
FIG. 6 is an axial sectional view showing the detailed structure of the turbine which is the main part of the second embodiment of the gas turbine of the present invention, and FIG. 7 is a radial sectional view of the spacer as viewed from the arrow VII in FIG. 6 and FIG. 7 correspond to FIG. 1 and FIG. 3 of the first embodiment, and the same parts as those in FIG. 1 and FIG.
[0032]
As shown in FIGS. 6 and 7, in the present embodiment, a plurality of guides arranged in the circumferential direction in the first and second cavities 39 and 40 are formed on the side surfaces of the spacer 34 facing the turbine disk 32 before and after the spacer 34. A plurality of guide channels 51 are formed between the guides 50. The plurality of guide channels 51 are reduced in diameter in the radial direction. Each guide channel 51 is arranged so as to be shifted in the circumferential direction from the insertion hole of the stacking bolt 35 so as not to interfere with the stacking bolt 35. Other configurations are the same as those of the first embodiment described above.
[0033]
Also in this embodiment, the flow of compressed air is substantially the same as that of the first embodiment, but the compressed air that has flowed into the first cavity 39 via the stationary blade 20 as shown by the dotted arrows in FIG. Is guided by the guide 50 and flows radially inward through the guide channel 51 while actively suppressing the circumferential velocity component. The compressed air that has flowed into the second cavity 40 via the center hole 33 also flows radially outward through the guide channel 51 while being guided by the guide 50 and suppressing the circumferential velocity component. Therefore, the same effect as that of the first embodiment described above can be obtained.
[0034]
Further, when the inner diameter of the spacer 34 is relatively large, the path to the center hole 33 becomes longer, and the compressed air forms a free vortex in the first cavity 39, and the compressed air becomes closer to the center hole 34. The circumferential speed component increases. As a result, in the region on the inner peripheral side of the first cavity 39, a flow accompanied by a backflow occurs in the flowing compressed air, which may increase the pressure loss. This can be solved to some extent by reducing the diameter of the spacer 34 as much as possible. However, in the present embodiment, as described above, the diameter of the spacer 34 is reduced as much as possible, and the guide 50 has a structure in the first cavity 39. By guiding the compressed air in the radial direction and actively suppressing the growth of the circumferential velocity component, the pressure loss can be more effectively reduced.
[0035]
In the second embodiment, the state in which the guides 50 are provided on both the front and rear surfaces of the spacer 34 is illustrated. However, the guides 50 may be provided at least in the first cavity 39. The guide 50 in the cavity 40 may be omitted or replaced with the protruding portion 42 described in the first embodiment. In this case, the same effect is obtained.
[0036]
In the above description, the compressed air via the stationary blade 20 is guided to the first cavity 39. However, in some cases, the compressed air may be guided to the second cavity 40. In short, the compressed air introduction hole is introduced so that compressed air from outside the casing 10 guided into the stationary blade 20 is introduced into one of the first and second cavities 39 and 40 through the seals 36 and 37. 41 should just be provided. The ejection slit 44 allows the compressed air from the compressed air introduction hole 41 guided to the other of the first and second cavities 39 and 40 through the center hole 33 of the spacer 34 to flow into the spacer 34 and the turbine disk. What is necessary is just to provide so that it may eject as the sealing air of the wheel space between 32. Therefore, when the compressed air is introduced from the stationary blade 20 into the second cavity 40, the ejection slit 44 may be provided on the front side of the outer peripheral portion of the spacer 34. However, an orifice 28 for ejecting seal air is provided on the side of the front and rear side walls of the stationary blade diaphragm 25 where seal air from the ejection slit 44 is not ejected. That is, in the orifice 28, the internal cavity 26 communicates with the wheel space on the opposite side of the wheel space from which the compressed air from the ejection slit 44 is discharged, of the wheel space between the spacer 34 and the turbine disk 32 before and after the spacer 34. In addition, it may be provided on the stationary blade diaphragm 25. In this case, the same effect as described above can be obtained.
[0037]
1 to 7 illustrate the turbine rotor 30 that rotates integrally, the present invention can also be applied to a so-called two-shaft turbine in which the rotation shaft is divided. In particular, in a twin-shaft turbine, the high-pressure turbine rotor and the low-pressure turbine rotor are often blocked by a partition wall, and it is difficult to introduce compressed air from the high-pressure turbine rotor to the low-pressure turbine rotor. It is effective to apply
[0038]
【The invention's effect】
As described above, according to the present invention, since the center hole of the turbine disk can be omitted, it is possible to provide a gas turbine that is less expensive and can be manufactured at a lower cost. In addition, flow distribution can be facilitated by directly supplying compressed air to each stage of the turbine rotor by an independent system without complicatedly branching the flow path in the turbine rotor, thus improving reliability. be able to. Furthermore, since the center hole of the turbine disk can be omitted and the flow path can be simplified, the structure of the turbine rotor can be simplified and the strength can be improved, and the reliability can also be improved in terms of strength.
[Brief description of the drawings]
FIG. 1 is an axial sectional view showing a detailed structure of a turbine that is a main part of a first embodiment of a gas turbine of the present invention.
FIG. 2 is an enlarged view showing one paragraph of the turbine rotor shown in FIG. 1;
3 is a radial cross-sectional view of the spacer as viewed in the direction of arrow III in FIG. 1. FIG.
FIG. 4 is a diagram showing a configuration example when a turbine rotor central hole is provided as a comparative example with the present embodiment.
FIG. 5 is a diagram showing a configuration example when a turbine rotor central hole is provided as a comparative example with the present embodiment.
FIG. 6 is an axial sectional view showing a detailed structure of a turbine that is a main part of a second embodiment of the gas turbine of the present invention.
7 is a radial cross-sectional view of the spacer as viewed in the direction of arrow VII in FIG. 6;
[Explanation of symbols]
10 casing 20 stator blade 25 stator blade diaphragm 28 orifice 29 compressed air outlet hole 30 turbine rotor 31 rotor blade 32 turbine disk 33 center hole 34 spacers 36, 37 seal 39 first cavity 40 second cavity 41 compressed air introduction hole 44 Ejection slit 50 guide

Claims (3)

A stationary blade attached to the inner peripheral side of the casing, a turbine rotor having a spacer having a center hole interposed between turbine disks to which a plurality of moving blades are attached, and a seal for sealing a gap between the stationary blade and the spacer In a gas turbine with
First and second cavities respectively formed between the spacer and the turbine disk disposed before and after the spacer;
A compressed air introduction hole for introducing compressed air from outside the casing guided into the stationary blade into one of the first and second cavities through the seal;
Compressed air from the compressed air introduction hole led to the other of the first and second cavities through the central hole of the spacer is ejected as seal air for the wheel space between the spacer and the turbine disk. A gas turbine comprising an ejection slit. The gas turbine according to claim 1, wherein the spacer is provided with a guide for guiding the compressed air flowing through the first or second cavity in a radial direction. 3. The gas turbine according to claim 1, wherein the stationary blade includes a stationary blade diaphragm disposed to face the spacer, and the stationary blade diaphragm derives compressed air flowing into the compressed air introduction hole. A compressed air outlet hole, and an orifice communicating with a wheel space on the opposite side of the wheel space from which the compressed air is discharged from the ejection slit among wheel spaces of the spacer and the turbine disk before and after the spacer are provided. A gas turbine characterized by that.

Images