Gas turbine suction air filter, a gas turbine using the same and a method for using the same

Abstract: The invention is a gas turbine suction air filter comprising a frame member (3) having an air passing cross section formed in a rectangular shape and a filter cloth (5) contained in said frame member (3). The filter cloth (5) is folded so that a multiplicity of folded faces (7) may be formed along an air passing direction and adjacent ones of said folded faces (7) directly confront each other with only a space being arranged therebetween. The gas turbine air filter has a large capacity due to the large air passing area and dust can be easily removed by an ultrasonic washer because the ultrasonic waves can reach the entire filter cloth.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a gas turbine suction air filter, a gas turbine using this filter and a method for using this filter. Description of the Prior Art A gas turbine generally comprises an air suction portion, a compressor, a combustor and a turbine portion. Air is taken from the air suction portion and is supplied into the compressor to be compressed. The compressed air is sent to the combustor. In the combustor, the compressed air and fuel are mixed together to be burned continuously. By the combustion, a high temperature high pressure combustion gas is generated to be supplied into the turbine portion. By expansion of the combustion gas, moving blades of the turbine portion are driven to rotate a rotor and thereby to generate an electric power. If foreign matters, such as dust, are included in the air to be supplied into the compressor, these foreign matters attach to the blades of the compressor to thereby reduce the compression efficiency. Thus, in order to remove the foreign matters, the air is filtered at the air suction portion. Usually, the air suction portion is provided with a first filter portion which is constructed by a multiplicity of coarse dust filters juxtaposed therein, a second filter portion which is constructed by a multiplicity of medium and high performance filters juxtaposed therein and a third filter portion which is constructed by a multiplicity of ultra-high performance filters juxtaposed therein and, by these filter portions, dust is removed. It is to be noted that, in some gas turbines, the third filter portion is omitted. As there occurs clogging in each of the filters after a long term use, the filter must be replaced. It is the present situation that the coarse dust filter is replaced at an interval of about three months, the medium and high performance filter at an interval of about 6 to 12 months and the ultra-high performance filter at an interval of about 12 months. The filter after used is disposed as an industrial waste. As the gas turbine consumes a large volume of air, a multiplicity of filters are needed. For example, in a usual gas turbine, the first filter portion, the second filter portion and the third filter portion, respectively, have some hundreds of filters therein and each of the filters has an opening area of about 0.35 m 2 . Therefore, in every case of the replacement, a large quantity of industrial waste is discharged and this causes a problem from the viewpoint of the environment preservation. Also, it is not preferable in view of the resource saving to use such large quantity of the filters and moreover this invites an increase in the running cost of the gas turbine. In view of the mentioned problems, trials are being done recently to wash the filter after used for reuse thereof. For the washing, an ultrasonic washer is most appropriate. In the ultrasonic washer, cavitations are generated by the ultrasonic wave. When these cavitations disappear, impulse forces are generated and thereby the dust attaching to the filter cloth is removed. Fig. 5 is a partially cut-out cross sectional view of one prior art example of a medium and high performance filter 51 which is used in the air suction portion. In Fig. 5, air comes from a direction of arrow A and passes through the filter 51. The filter 51 comprises a multiplicity of separators 53 which are made of aluminum or the like. Each of the separators 53 is formed in a corrugated shape and extends perpendicularly to the plane of Fig. 5. A filter cloth 55, which is made of a glass fiber non-woven fabric or the like, is provided between each of the separators 53, 53. The filter cloth 55 is arranged in a serpentine form so as to pass a right hand end and a left hand end of the separator 53 alternately. By this arrangement, area of the filter cloth 55, which is also an air passing area, becomes larger and the dust collection efficiency is enhanced. As the gas turbine consumes a large volume of air, as described above, the multiplicity of the filters 51 are used in the air suction portion. For this reason, the air suction portion becomes extremely large sized. Thus, construction work of the gas turbine needs a wide area of installation space and construction cost also becomes high. In order to mitigate this problem, in the filter 51 for the gas turbine, as compared with general filters, such as those for air conditioning in a building, a pitch P, as shown in Fig. 5, between each of the separators 53 is made smaller. Hence, the air passing area becomes large and number of pieces of the filters 51 to be used for the air suction portion is reduced and thereby a smaller size of the air suction portion is attained. For example, while the separator pitch in the general filter is 10 to 15 mm, the separator pitch P in the filter 51 for the gas turbine air suction portion is about 5 mm. By this arrangement, while the capacity, or the air passing volume per filter, of the general filter is 35 to 50 m 3 /minute, that of the gas turbine air suction portion is attained as high as about 50 to 70 m 3 /minute. However, even though the filter 51 in which the separator pitch P is so made smaller is washed by the ultrasonic washer, transmission of the ultrasonic wave is obstructed by the separator 53 so that the ultrasonic wave may hardly reach the entire portion of the filter cloth 55 and there is a problem that the dust is not sufficiently removed. This problem makes the reuse of the filter 51 for the gas turbine air suction portion difficult, as compared with the general filter. Also, as mentioned above, the prior art filter 51 for use in the gas turbine suction air portion, after used, is disposed as the industrial waste not to be reused and this increases the running cost of the gas turbine having the air suction portion mounted with the filter 51. SUMMARY OF THE INVENTION In view of the mentioned problems in the prior art, it is an object of the present invention to provide a gas turbine suction air filter and a method for using the same by which a large capacity is realized and still dust can be easily removed by an ultrasonic washer. Also, it is another object of the present invention to provide a gas turbine in which the filter of the present invention is used. In order to achieve the mentioned objects, the present invention provides a gas turbine suction air filter comprising a frame member having an air passing cross section formed in a rectangular or cylindrical shape and a filter cloth contained in the frame member, in which the filter cloth is folded so that a multiplicity of folded faces are formed in series and adjacent ones of the folded faces directly confront each other with only a space being arranged therebetween. In the mentioned filter, as the filter cloth is folded so that the multiplicity of the folded faces may be formed along the air passing direction, the air passing area is large and hence the capacity is large. Also, in this filter, as the adjacent ones of the folded faces directly confront each other with only a space being arranged between them and there is provided no intervening member, such as a separator, between the adjacent ones of the folded faces, the ultrasonic wave reaches to the entire filter cloth. Thus, a sufficient dust removal can be attained by the ultrasonic washer. It is preferable that the frame member constituting the mentioned filter of the present invention is made of a metal material. In the metal material, the ultrasonic wave transmission is less damped. Also, as the metal material is excellent in the strength and rigidity, thickness of the frame member can be made smaller as compared with the frame member constructed of a wooden material, a synthetic resin or the like. That is, in the frame member of the filter of the present invention, less damping of the ultrasonic wave is effected for the reason not only of the material but also of the thickness of the member. Thus, in this filter, even though the air passing area is large, the ultrasonic wave is easily reachable to the entire filter cloth. This metal frame member is appropriate for use in the filter of a large capacity, or more concretely of a capacity (air volume passing through an opening area of 0.35 m 2 ) of 50 m 3 /minute or more. The frame member is preferably constructed of a stainless steel which effects less damping of the ultrasonic wave, is excellent in the strength and rigidity and is also excellent in the corrosion resistance. The filter cloth is preferably made of a non-woven fabric including a synthetic resin fiber. As compared with the glass fiber, the synthetic resin fiber is more flexible and the fibers are entangled more densely. Thus, there is no need to use such a binder for adhesion of the fibers as used in the glass fiber non-woven fabric. Also, there is no case where the binder dissolves into the wash liquid to loosen the fibers, as in the case of the glass fiber non-woven fabric. The filter cloth may be constructed of a combination of the synthetic resin fiber and the glass fiber but, even in such case, it is preferable that the ratio of the synthetic resin fiber to the entire fibers is 50% or more in volume. The synthetic resin fiber is preferably a polypropylene or polyester fiber as it is produced in a large scale to be less expensive and generates no poisonous gas when it is burned for disposal. Further, in place of the synthetic resin fiber, a porous sheet made of a synthetic resin may be used. The porous sheet made of the synthetic resin has numerous minute pores for passing of air and uses no fiber. Hence, there occurs no loosening of the fiber. In the porous sheet of the synthetic resin, there is a need to form numerous minute air holes for securing a filter performance and, in view of the strength and manufacturing process, it is preferable to use a polytetrafluoroethylene resin as a base material. Also, the frame member formed in a cylindrical form has an air passing portion at a cylinder portion of the cylindrical shape and the filter cloth formed in a cylindrical form and contained in the frame member, in which the filter cloth is a non-woven fabric including a synthetic resin fiber. In the filter so constructed, air to be filtered can flow uniformly in the entire filter cloth through the air passing portion of the frame member formed in the cylindrical shape. Also, in addition to the wash by the ultrasonic wave, the pulse type air wash can be combined and a sufficient dust removal can be performed. Further, the filter cloth is constructed of a non-woven fabric including a synthetic resin fiber and thereby the ultrasonic wash can be done repeatedly in the wash liquid. In this case, the ratio of the synthetic resin fiber to the entire fibers is preferable to be 50% or more in volume. The synthetic resin fiber is preferably a polypropylene or polyester fiber as it is produced in a large scale to be less expensive and generates no poisonous gas when it is burned for. disposal. A gas turbine mounted with the mentioned filter of the present invention can contribute in the resource saving and in the environment preservation. Also, in this gas turbine, the running cost is reduced, as the filter can be washed by the ultrasonic washer so as to be reused. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partially cut-out cross sectional view of a gas turbine suction air filter of one embodiment according to the present invention. Fig. 2 is an enlarged view of a portion of a filter cloth used in the filter of Fig. 1. Figs. 3(a) and (b) show a gas turbine suction air filter of another embodiment according to the present invention, wherein Fig. 3(a) is a partially cut-out side view and Fig. 3(b) is a transverse cross sectional view. Fig. 4 is a partially cut-out cross sectional view of a gas turbine of another embodiment according to the present invention. Fig. 5 is a partially cut-out cross sectional view of a gas turbine suction air filter in the prior art. DESCRIPTION OF THE PREFERRED EMBODIMENTS Herebelow, the present invention will be described concretely based on embodiments and with reference to the appended figures, where appropriate. Fig. 1 is a partially cut-out cross sectional view of a gas turbine suction air filter 1 of one embodiment according to the present invention. This filter 1 comprises a box-like frame member 3 and a filter cloth 5 contained in the frame member 3. In Fig. 1, direction A shows an air flow direction. The frame member 3, when seen in the front view or in the direction A, has a square shape having one side of length L, shown in Fig. 1, of about 0.6 m, for example. Also, the frame member 3 has depth D of about 0.3 m and thickness T of about 1 mm, both for example. Needless to mention, the shape and dimensions of the frame member 3 are not limited to those mentioned above. In the air suction portion of the gas turbine, there are provided a multiplicity of the filters 1 juxtaposed in the upward and downward directions of Fig. 1 and in the perpendicular direction to the plane of Fig. 1, so that a filter portion of the gas turbine is formed. The frame member 3 is made of a metal material. The metal material effects less damping of an ultrasonic wave transmission therein and, being excellent in the strength and rigidity, can make the frame member 3 in a thinner material. By the frame member 3 made in the thinner material, the ultrasonic wave transmission in the frame member 3 is less damped. As described later, while the filter cloth 5 is folded, as the frame member 3 is constructed of the metal material, the ultrasonic wave is easily reachable to the entire filter cloth 5. Thus, dust removal of the filter cloth 5 can be done securely by an ultrasonic washer. Also, in the frame member 3 made of the metal material, no absorption of wash liquid, as seen in a frame member made of a wooden material, occurs. In the ultrasonic washer, the frame member 3 is dipped in the wash liquid to be washed. Hence, it is preferable that the frame member 3 is constructed of a metal material which is excellent in the corrosion resistance. A stainless steel, an aluminum alloy, a titanium alloy, etc. are named as the preferable metal material. Among them, the stainless steel is most preferable as it is produced in a large scale to be obtainable less expensively. Fig. 2 is an enlarged view of a portion of the filter cloth 5 used in the filter 1 of Fig. 1. As shown in Fig. 1, the filter cloth 5 is formed in pleats or folded portions, wherein a multiplicity of pleat faces or folded faces 7 are formed in series along the air passing direction. Thus, this filter cloth 5 has a large area for passing of air. The filter 1 comprising this filter cloth 5 is of a large capacity and is appropriately used in the gas turbine that consumes a large volume of air. In view of the application to the gas turbine, the capacity (volume of air passing through an opening area of 0.35 m 2 ) is preferable to be 50 m 3 /minute or more, most preferably 60 m 3 /minute or more. As is clear from a comparison between Fig. 1 and Fig. 5, width W of the pleat face 7 in Fig. 2 is extremely small as compared with the folded width of the filter cloth 55 of the filter 51 in the prior art. Accordingly, when the filter cloth 5 is washed by the ultrasonic washer, the ultrasonic wave is easily reachable to the entire filter cloth 5. Also, as the adjacent ones of the pleat faces directly confront each other with only a space being arranged between them and there is no intervening member, such as the separator 53, between adjacent pleat faces 7, 7, there occurs no case where the intervening member obstructs the ultrasonic wave transmission. Thereby, the dust removal by the ultrasonic wave becomes facilitated. That is, while there had been a difficulty in the washing of the filter 1 in the prior art, reuse of the filter 1 in the gas turbine can be accelerated in the present invention. . The width W of the pleat face 7 is preferably 3 mm or more and 50 mm or less, most preferably 10 mm or more and 30 mm or less. By the width W selected in the mentioned range, the easiness in the dust removal and the high capacity are consistent with each other. The filter cloth 5 may be either a woven fabric or a non-woven fabric but the non-woven fabric is usually used. As a preferable fiber used for the filter cloth 5, a fiber made of a synthetic resin is named. As the synthetic resin fiber has a flexibility higher than a glass fiber, in the non-woven fabric made of the synthetic resin fiber, the fibers are entangled densely with each other to hardly loosen. Even if the filter 1 is dipped in the wash liquid of the ultrasonic washer, therefore, the filter cloth 5 is hardly damaged. The synthetic resin fiber is preferably a polypropylene fiber or a polyester fiber for the reason that it is produced in a large scale to be obtainable less expensively and, even if burned for disposal, does not generate a poisonous gas. Furthermore, in place of the synthetic resin fiber, a porous sheet made of a synthetic resin may be used. The synthetic resin porous sheet has a multiplicity of air passing pores and, using no fiber, hardly loosens. Thus, even if the filter 1 is dipped in the wash liquid of the ultrasonic washer, the filter cloth 5 is hardly damaged. As there is a need to form the multiplicity of air passing pores for securing a filter performance, as well as in view of the strength and manufacturing process, the synthetic resin porous sheet is preferably made of a polytetrafluoroethylene resin as a base material. The filter cloth 5 may also be constructed by a combination of the synthetic resin fiber and the glass fiber but, in this case, it is preferable that the ratio of the synthetic resin fiber to the entire fibers is 50% or more in volume, most preferably 70% or more in volume. The adjacent pleat faces 7, 7 may be joined together by thread and thereby a position deviation of the filter cloth 5 caused by water pressure or the like at the time of washing can be suppressed. Also, there may be provided a rib in the frame member 3 and, by this rib also, the position deviation of the filter cloth 5 due to the water pressure or the like at the time of washing can be suppressed. Figs. 3(a) and (b) show a gas turbine suction air filter of another embodiment according to the present invention. In Figs. 3(a) and (b), numeral 33 designates a frame member, formed in a cylindrical shape, made of a porous member, such as a punching metal. This porous member forming the frame member 33 is employed to have a porosity of 40 to 60%. In the frame member 33, there is contained a filter cloth 5, formed in a cylindrical shape, made of a synthetic resin non-woven fabric, in which pleat faces or folded faces 7, like in the embodiment shown in Figs. 1 and 2, are formed in series. In the filter so constructed, air to be filtered flows in directions of arrows A shown in Figs. 3(a) and (b) to pass through the frame member 33 to be filtered. It is to be noted that, while this filter formed in the cylindrical shape is dipped in a wash liquid to be washed by an ultrasonic washer for reuse thereof, a pulse type air wash (back wash) as a combination with the wash by the ultrasonic washer may be employed for removing dust attaching to the filter by blowing a back wash air in a pulsing form from downstream of the filter. Fig. 4 is a partially cut-out cross sectional view of a gas turbine 9 of another embodiment according to the present invention. The gas turbine 9 comprises an air suction portion 11, a duct 13, a compressor 15, a combustor 17 and a turbine portion 19. Air taken from the air suction portion 11 is supplied into the compressor 15 via the duct 13 to be compressed. The compressed air is sent to the combustor 17. In the combustor 17, the compressed air and fuel are mixed together to be burned continuously. By the combustion, a high temperature high pressure combustion gas is generated to be supplied into the turbine portion 19. By expansion of the combustion gas, moving blades of the turbine portion 19 are driven to rotate a rotor and thereby to generate an electric power. The air suction portion 11 comprises a first filter portion 21, a second filter portion 23 and a third filter portion 25. The first filter portion 21 is constructed by a multiplicity of coarse dust filters 27 juxtaposed therein. The second filter portion 23 is constructed by a multiplicity of medium and high performance filters 29 juxtaposed therein. The third filter portion 25 is constructed by a multiplicity of ultra-high performance filters 31 juxtaposed therein. The structure of the medium and high performance filter 29 and the ultra-high performance filter 31, respectively, is approximately same as that of the filter 1 shown in Fig. 1 and there is no intervening member between the pleat faces 7, 7. Thus, while the medium and high performance filter 29 and the ultra-high performance filter 31, respectively, have a large capacity, reuse of the filters by the ultrasonic washing is possible. Needless to mention, the coarse dust filter 27 may be constructed similarly to the filter 1 shown in Fig. 1. According to the filter of the present invention as described above, the filter cloth is constructed to be folded with the multiplicity of the folded faces being formed along the air passing direction and the adjacent ones of the folded faces directly confront each other with only a space being arranged therebetween and no intervening member is arranged between the adjacent folded faces. Further, the filter cloth has a large capacity. Hence, it is appropriate for use in the gas turbine that consumes a large volume of air and still enables an easy dust removal when it is washed by the ultrasonic washer. Reuse of this

Claims: A gas turbine suction air filter comprising a frame member (3;33) having an air passing cross section formed in a rectangular or cylindrical shape and a filter cloth (5) contained in said frame member (3;33), characterized in that said filter cloth (5) is folded so that a multiplicity of folded faces (7) are formed in series and adjacent ones of said folded faces (7) directly confront each other with only a space being arranged therebetween. A gas turbine suction air filter as claimed in claim 1, characterized in that said frame member (3;33) is made of a metal material. A gas turbine suction air filter as claimed in claim 2, characterized in that said metal material is a stainless steel. A gas turbine suction air filter as claimed in claim 1, 2 or 3, characterized in that said filter cloth (5) is a non-woven fabric including a synthetic resin fiber. A gas turbine suction air filter as claimed in claim 4, characterized in that a ratio of said synthetic resin fiber to entire fibers constituting said filter cloth (5) is 50% or more in volume. A gas turbine suction air filter as claimed in claim 4 or 5, characterized in that said synthetic resin fiber is made of a polypropylene or a polyester. A gas turbine suction air filter as claimed in any one of claims 1 to 6, characterized in that said frame member (33) formed in a cylindrical form has an air passing portion at a cylinder portion of said cylindrical shape and said filter cloth (5) is formed in a cylindrical form. A gas turbine suction air filter as claimed in claim 1, 2 or 3, characterized in that said filter cloth (5) is a porous sheet made of a synthetic resin. A gas turbine suction air filter as claimed in claim 8, characterized in that said porous sheet is made of a polytetrafluoroethylene resin. A gas turbine suction air filter as claimed in any one of claims 1 to 9, characterized in that said filter is washable by an ultrasonic washer to be reused. A gas turbine mounted with a gas turbine suction air filter as claimed in any one of claim 1 to 10. A method of using a gas turbine suction air filter, characterized in that said gas turbine suction air filter as claimed in any one of claims 1 to 10 is washed by an ultrasonic washer to be reused.

Inventors: ADACHI TATSUO, AOTA TOYOSEI, DOI YOSHIYUKI, HARA SATOSI, ISOHASI KENJI, MAEHATA SHIGERU, OKUNO KATSUTOSHI, ADACHI, TATSUO, AOTA, TOYOSEI, DOI, YOSHIYUKI, HARA, SATOSI, ISOHASI, KENJI, MAEHATA, SHIGERU, OKUNO, KATSUTOSHI, Aota, Toyosei, c/oTakasago Mach. Works of Mitsub., Doi, Yoshiyuki, c/oTakasago Mach. Works of Mitsub., Okuno, Katsutoshi, c/oTakasago Mach.Works of Mitsu
Applicants: MITSUBISHI HEAVY IND LTD, MITSUBISHI HEAVY INDUSTRIES, LTD.
Application year: 2001
Main classification: F02M35
IPC codes: F02C7, B01D46