Blower

Abstract

In order to effectively suppress adhesion and accumulation of combustion residues and corrosion caused by condensed water, an EGR blower (35) equipped in a diesel engine is provided with: a motor (80) that rotates a rotating shaft (61) inserted through a shaft hole (52a) of a housing (50); an impeller (62); and a sealing device (70) for the shaft hole (52a). The housing (50) has: a lower wall section (51) in which the suction port (51a) is opened; an upper wall section (52) in which a shaft hole (52a) is formed; a suction tube section (53) protruding from the lower wall section (51) toward the upper wall section (52); a spiral peripheral wall part (55) surrounding the suction cylinder part (53); the EGR blower (35) is provided with an impeller (62), a lower wall section (51), and a drain port section (56) that opens in the lower wall section (51), the EGR blower (35) being further provided with a cleaning device (100) that cleans the impeller (62), the cleaning device (100) having: a first cleaning nozzle (101) that sprays a cleaning liquid toward the back surface (62e) of the impeller (62), and a second cleaning nozzle (102) that sprays a cleaning liquid toward the back surface (62e) of the impeller (62); and a second cleaning nozzle (102) that sprays a cleaning liquid toward the blade surface portion (62c) of the impeller (62).

Description

Technical Field

[0001] The present invention relates to a blower, and more particularly to a blower suitable for forming an EGR (Exhaust Gas Recirculation) blower as part of an EGR device in a large or medium diesel engine. Background Art

[0002] As blowers that suck in the gas to be blown and increase its pressure, the following blowers have been known in the past: recirculation blowers that increase the pressure of exhaust gas from a system that outputs power or electricity and recirculates it to the system, auxiliary blowers that increase the pressure of gas supplied to the system (including low-pressure recirculated gas), etc.

[0003] For example, as one of the exhaust emission reduction technologies for diesel engines used in ships, there is known an EGR system that allows a portion of the engine's exhaust gas to flow back to the scavenging side (air supply side) of the engine to recirculate it and reduce NOx (nitrogen oxides) in the exhaust gas. However, the EGR system is provided with an EGR blower that pressurizes a portion of the exhaust gas to a pressure that allows it to be recirculated (for example, refer to Patent Document 1).

[0004] In addition, Patent Documents 2 and 3 describe the following low-pressure EGR system: In a two-stroke diesel engine that is the main engine for large ships, a portion of the low-pressure exhaust gas discharged from the engine and passing through the turbine of the exhaust turbocharger is used as EGR gas, and is returned to the air intake inlet side of the compressor of the turbocharger by an EGR blower.

[0005] In this low-pressure EGR system, part of the exhaust gas is branched into EGR gas at the downstream side of the supercharger or exhaust economizer, and PM (particulate matter) such as soot and SOx (sulfur oxides) formed during the combustion process in the exhaust gas are removed by a scrubber as an exhaust gas cleaning device. Then, the cleaned EGR gas is sent to the suction side of the supercharger at a relatively low pressure and temperature by an EGR blower, typically to the suction port of the compressor of the exhaust turbocharger, mixed with fresh air, and recirculated to the engine (see Non-Patent Document 1).

[0006] In addition, Patent Document 4 states that if low-quality fuel is used in an exhaust turbocharger, combustion residues in the exhaust gas will adhere to the turbine of the turbocharger as dirt, and the dirt is difficult to fall off. In view of this, a blind plate is arranged on the outside of the exhaust inlet, and a water injection cock is arranged above the exhaust inlet, and a cleaning liquid pool is formed in the turbine housing to immerse the blade portion of the impeller in a specific rotation range, and the ship's miscellaneous air is supplied to the air motor used to drive the impeller, so that the impeller rotates at a low speed to remove dirt from the turbine blades.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2011-157959

[0010] Patent Document 2: Japanese Patent Application Publication No. 2018-127706

[0011] Patent Document 3: Japanese Patent Application Publication No. 2013-170520

[0012] Patent Document 4: Japanese Patent Application Laid-Open No. 61-123720

[0013] Non-patent literature

[0014] Non-patent document 1: Journal of the Japan Society of Marine Engineering, Vol. 52, No. 6 (2017) Summary of the invention

[0015] Problem that the invention aims to solve

[0016] However, the conventional blowers and EGR systems equipped with the blowers described in the above-mentioned Patent Documents 1 to 3 have the following problems: combustion residues in the exhaust gas that have not been completely cleaned in the scrubber are easily attached to and accumulated on the impeller of the EGR blower or in its vicinity; and acidic condensed water is easily attached to the EGR path near the EGR blower and causes corrosion.

[0017] Furthermore, although the cost is increased when the entire EGR blower is formed of a material having excellent corrosion resistance, there is also a problem that the corrosion resistance to acidic condensed water and the like is insufficient.

[0018] In this regard, it is conceivable to remove the attached matter and deposits on the impeller by forming a cleaning liquid pool capable of immersing the impeller and rotating the impeller at a low speed, as described in Patent Document 4. However, since the cleaning agent needs to be stored to a predetermined depth, there are the following problems: not only can the cleaning operation be performed only when the engine is stopped, but also the back of the impeller, the surrounding inner wall of the casing (upper side than the cleaning liquid pool) or corrosion protection cannot be reliably cleaned.

[0019] The present invention is made to solve the above-mentioned conventional problems, and an object of the present invention is to provide an EGR blower which can effectively suppress adhesion and accumulation of combustion residues in the blower and corrosion caused by condensed water even during operation of the engine.

[0020] Solutions for solving problems

[0021] In order to achieve the above-mentioned purpose, (1) the blower of the present invention is an EGR blower, which is equipped on a diesel engine as a part of an EGR device, and the diesel engine has the EGR device for recirculating a part of the exhaust gas discharged from the engine body as a part of the combustion gas, and a turbocharger driven by the exhaust gas, and the EGR blower increases the pressure of the part of the recirculated exhaust gas, and is characterized in that the EGR blower is composed of: a housing, which is formed with an axial hole and a gas passage with an intake port and an exhaust port; a motor, which rotates a drive shaft inserted into the axial hole of the housing; an impeller, which is supported by the drive shaft and housed in the housing; and a sealing device, which is able to slide The cam is an airtight container and has an inlet that is adapted to contact the drive shaft and seal the axial hole in a manner that contacts the drive shaft and seals the axial hole. The housing comprises: a lower wall portion having the suction port; an upper wall portion having the axial hole formed therein; an suction cylinder portion that protrudes from the lower wall portion toward the upper wall portion in a truncated cone shape and whose upper end is close to the inlet portion of the impeller; a vortex-shaped peripheral wall portion that surrounds the suction cylinder portion and forms the gas passage; and a drain port portion that opens on the lower wall portion. The EGR blower is provided with a cleaning device for cleaning the impeller, the cleaning device comprising: a first cleaning nozzle that sprays cleaning liquid from the upper wall portion side toward the back side of the impeller facing the upper wall portion; and a second cleaning nozzle that sprays cleaning liquid from the peripheral wall portion side toward the wing portion of the impeller.

[0022] With this structure, in the present invention, when the cleaning liquid is sprayed from the first and second cleaning nozzles toward the upper back surface, the wing surface, and the lower surface of the impeller, the impeller is cleaned, and the cleaning liquid after cleaning is discharged from the drain port. Therefore, even if the engine is in the running state, for example, before it is about to stop, the cleaning operation can be performed, and the impeller and the inner wall of the casing around it can be reliably cleaned. As a result, the following EGR blower is obtained: even during the operation of the engine, the adhesion and accumulation of combustion residues in the EGR blower and the corrosion caused by condensed water can be effectively suppressed.

[0023] It should be noted that, in the case where the impeller is a shield-integrated type, it can also be a structure that is further provided with a third cleaning nozzle, which sprays cleaning liquid from the peripheral wall portion or the lower wall portion side toward the lower surface of the shield of the impeller. In addition, if the impeller is rotated during cleaning, the cleaning liquid sprayed from each cleaning nozzle produces a speed change relative to the impeller and a direction change in the centrifugal direction, thereby enhancing the cleaning effect of the impeller, and the cleaning liquid sprayed from the second cleaning nozzle collides with the wing portion of the impeller and scatters, thereby improving the cleaning effect of the wing portion of the impeller. In addition, even if the cleaning liquid sprayed from the second cleaning nozzle reaches the inner peripheral wall surface of the suction cylinder from the inside of the impeller, the cleaning liquid can also be returned to the cleaning pool, water treatment device, etc. below the scrubber, and the cleaning liquid discharged from the drain port can also be returned to the cleaning pool, water treatment device, etc. In addition, as long as the motor can operate at any speed and drive torque within a predetermined range, the impeller can be controlled to a rotation condition suitable for cleaning.

[0024] (2) In a preferred embodiment of the present invention, the diesel engine may be configured as a main engine of a large ship, and may be configured as a low-pressure EGR blower that increases the pressure of the return gas in the low-pressure EGR line that returns a portion of the exhaust gas after passing through the turbine of the turbocharger to the compressor of the turbocharger. In this case, even if the EGR gas cleaned by the scrubber is at a relatively low pressure and temperature, acidic condensed water adheres to the EGR path near the EGR blower, or combustion residues in the exhaust gas that have not been cleaned adhere to the impeller of the EGR blower or its vicinity, these can be easily cleaned and removed together with the drain.

[0025] (3) A preferred embodiment of the present invention can be configured to further include a mist collection unit, which is disposed between the upper wall portion and the motor and surrounds the shaft hole and the drive shaft, and collects mist leakage from the shaft hole to the atmosphere. In this case, in a housing of an EGR blower that is generally not at such a high pressure, the cleaning fluid enters the sealing portion of the shaft hole during cleaning, and even if mist leakage from the shaft hole to the atmosphere occurs, the leakage can be collected by the mist collection unit.

[0026] (4) A preferred embodiment of the present invention may be a structure in which a heat-resistant anti-corrosion coating having a glass flake layer is applied to the entire area of ​​the inner wall surface of the housing. In this way, for example, the glass flake layer formed by laminating glass flakes of alkali components in a coating film of a heat-resistant coating resin can have sufficient acid resistance and corrosion resistance. In addition, by forming the base material of the inner wall portion of the housing as a large component or further forming the base material of the suction cylinder portion with an iron-based material, it is possible to reduce costs.

[0027] (5) In a preferred embodiment of the present invention, the sealing device may include: a shaft sealing box, which is arranged on the housing in a manner to form the shaft hole and forms an annular groove opening on the inner peripheral surface of the shaft hole; a first sealing ring and a second sealing ring, which are respectively composed of a plurality of divided sealing components that apply force to the drive shaft with a predetermined contact pressure through a clamping spring in a manner to surround the drive shaft in the annular groove, and at least the sliding surface with the drive shaft is formed of a carbon material; a spring receiving plate in the form of an annular plate, which is arranged between the first sealing ring and the second sealing ring in the annular groove in a manner to surround the drive shaft; and a pair of toothed disc spring-shaped fine springs, which are compressed and arranged between the two surfaces of the spring receiving plate and the first sealing ring and the second sealing ring, and apply the first sealing ring and the second sealing ring to the two inner wall surfaces of the annular groove of the shaft sealing box with a predetermined spring pressure.

[0028] Thus, since the sliding surfaces of the first and second seal rings with the clamp spring are made of carbon material, the required corrosion resistance and self-lubricating property can be obtained. The first and second seal rings apply force to the inner wall surfaces of the annular groove of the shaft seal box by a pair of toothed disc spring-like fine springs sandwiching the annular plate-shaped spring receiving plate, so that the first and second seal rings can generate a stable pushing force and friction holding force on the inner wall surfaces of the annular groove by the disc spring-like fine springs with a lower spring constant than the ordinary disc springs. In addition, since the pair of toothed disc spring-like fine springs can be set to a shape that can be bent not only in the axial direction of the drive shaft but also in the radial direction, the pair of toothed disc spring-like fine springs and the annular plate-shaped spring receiving plate between the two springs can be compactly accommodated in a narrow shaft seal box, and at the same time, they can be reliably positioned in the axial direction and the rotation direction, and a positioning holding force can be generated. This positioning holding force plays a role in effectively preventing the first and second seal rings from rotating together with the friction holding force on the inner wall sides of the annular groove.

[0029] (6) The low-pressure EGR device of the diesel engine of the present invention is characterized in that it has the EGR blower described in (2), and is also equipped with: a wet scrubber that purifies the recirculated gas before it is pressurized by the low-pressure EGR blower by water injection in the low-pressure EGR line; a demister that allows the purified recirculated gas to pass to the low-pressure EGR blower side and separates the purified wastewater from the recirculated gas; and a water treatment device with a pump that removes particulate components from the wastewater, adjusts the pH, and then supplies it to the scrubber.

[0030] With this configuration, the cleaning liquid discharged from the low-pressure EGR blower and the cleaning water discharged from the wet scrubber can be introduced into the water treatment device together, and the amount of water used can be effectively suppressed by appropriately circulating them.

[0031] Effects of the Invention

[0032] According to the present invention, it is possible to provide an EGR blower which can effectively suppress adhesion and accumulation of combustion residues in the EGR blower, corrosion due to condensed water, and the like even during operation of the engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The schematic diagram shows the structure of an EGR system of a low-speed diesel engine for a ship including an EGR blower according to an embodiment of the present invention.

[0034] Figure 2 yes Figure 1 The arrow view in the direction of arrow II in FIG. 1 is a front view of the EGR blower showing a state in which a cleaning device is installed on the housing of the blower according to one embodiment of the present invention.

[0035] Figure 3A yes Figure 2 A view in the direction of arrow IIIa.

[0036] Figure 3B yes Figure 3A A view in the direction of arrow IIIb.

[0037] Figure 4 yes Figure 2 A view in the direction of arrow IV.

[0038] Figure 5 This is a longitudinal cross-sectional view taken on one side in the radial direction of a main portion of a sealing device in an EGR blower according to an embodiment of the present invention.

[0039] Fig. 6A This is a plan view of a disc-spring-like thin spring of a sealing device in an EGR blower according to an embodiment of the present invention, as viewed in the driving axial direction.

[0040] Figure 6B This is a front view of the disc spring-shaped thin spring observed along the driving axis direction.

[0041] Figure 7 This is a plan view of a spring receiving plate in the form of an annular plate of a sealing device in an EGR blower according to an embodiment of the present invention, as viewed in the direction of the driving axis.

[0042] Fig. 8AThis is a plan view of a seal ring of a seal device in an EGR blower according to an embodiment of the present invention as viewed in the direction of the drive shaft.

[0043] Figure 8B This is a front view of the sealing ring obtained by observing it along the driving axis.

[0044] Fig.9A This is a plan view of a main part of a shaft seal case of a sealing device in an EGR blower according to an embodiment of the present invention as viewed in the direction of the drive shaft.

[0045] Fig. 9B This is a front cross-sectional view of the main part of the shaft seal box obtained by observing it along the drive shaft.

[0046] Fig. 10A This is a plan view of the remaining portion of a cover-shaped shaft seal case of a sealing device in an EGR blower according to an embodiment of the present invention, as viewed in the direction of the drive shaft.

[0047] Fig. 10B This is a front cross-sectional view of the remaining cover-shaped portion of the shaft seal box as viewed along the drive shaft direction.

[0048] Fig.11 This is a cross-sectional view of main parts showing the division structure of the upper wall portion of the casing and the arrangement of the mist collecting unit in the EGR blower according to the embodiment of the present invention. DETAILED DESCRIPTION

[0049] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0050] Figures 1 to 11 A case where a blower according to an embodiment of the present invention is provided as an EGR blower in a power system with an EGR device is shown.

[0051] First, its structure will be described.

[0052] like Figure 1 As shown, a power system 1 of the present embodiment includes an engine 10 which is a two-stroke large diesel engine, a turbocharger 20 (exhaust turbocharger), and a low-pressure EGR device 30, all of which are mounted in an engine room of a ship (not shown).

[0053] The engine 10 is an electronically controlled engine that can be used as a main engine of a large ship, for example, and is a low-speed diesel engine of a static pressure supercharging type in which a scavenging tank 13, an exhaust gas receiver 14, a fuel supply unit 15, etc. are mounted on a multi-cylinder engine body 11 having a piston 12 and a crosshead 16. It should be noted that in the present embodiment, the power system 1 is used for a ship, but in addition to being used for a ship, it can also be used as an engine for operating a large generator such as a generator of a power plant.

[0054] The multi-cylinder engine body 11 is provided with a plurality of cylinders 11a (in Figure 1 Only one cylinder is shown in the figure). The multiple cylinders 11a are connected to the scavenging tank 13 via the scavenging port 11b, and on the other hand, exhaust can be discharged to the exhaust receiver 14 when the corresponding exhaust valves 14a are opened. In each cylinder 11a, the air flowing into the cylinder 11a by scavenging is compressed to above the ignition point by the piston 12, and the fuel is injected into the air and burns. At this time, the combustion gas expands and drives the piston 12, and exhaust gas is generated. Then, the exhaust gas from each cylinder 11a is intermittently sent to the exhaust receiver 14.

[0055] Among them, the scavenging tank 13 is a compressed air storage device (scavenging receiver) under a predetermined scavenging pressure, which is used to perform a scavenging effect of discharging the combustion gas in each cylinder 11a of the engine body 11 and filling it with new air. The exhaust receiver 14 is an exhaust storage device, which can store the exhaust gas from each cylinder 11a of the engine body 11 under pressure and alleviate the exhaust pressure fluctuation, and supply the exhaust gas to the turbocharger 20 side at a stable exhaust pressure.

[0056] The fuel supply unit 15 can pump and pressurize the marine diesel fuel purified in the fuel purifier, and inject / supply the fuel into each cylinder 11 a of the engine body 11 when the fuel valve of each cylinder is opened at a predetermined timing.

[0057] The turbocharger 20 includes a turbine 21 and a compressor 22. The turbine 21 is driven to rotate by the exhaust gas supplied to the exhaust inlet from the exhaust receiver 14 side. The compressor 22 is integrally connected to the turbine 21 and is driven to rotate by the turbine 21 to introduce air from the air intake port and compress it to supply it to the scavenging tank 13 side.

[0058] An air cooler 23 (at the bottom) of the turbocharger 20 is provided between the compressor 22 and the scavenging air tank 13. Figure 1The air cooler 23 cools the EGR gas that flows back through the low-pressure EGR device 30 after being pressurized by the compressor 22. In addition, an economizer 25 that recovers exhaust heat is provided at a position downstream of the exhaust outlet of the turbine 21 of the turbocharger 20. The economizer 25 can use the steam generated by heat recovery for miscellaneous steam of the ship, turbine power generation, etc.

[0059] The low-pressure EGR device 30 includes: low-pressure EGR lines Le1~Le3 (hereinafter, also referred to as EGR lines Le), which allow a portion of the lower pressure / low temperature exhaust gas after passing through the economizer 25 to flow back to the air intake side of the compressor 22 of the turbocharger 20 as EGR gas (return gas); an EGR valve 27, which is arranged near the inlet of the low-pressure EGR line Le; a wet scrubber 31, which uses cleaning droplets (such as alkaline cleaning water) to purify the EGR gas after passing through the EGR valve 27; a defogger 32, which separates the purified exhaust gas from the EGR gas after passing through the scrubber 31; and a centrifugal EGR blower 35 (low-pressure EGR blower), which sucks in the low-pressure EGR gas after passing through the defogger 32 and supplies it to the air intake of the compressor 22 of the turbocharger 20.

[0060] The scrubber 31, for example, sprays cleaning droplets on the EGR gas sucked into the recirculation path, i.e., the low-pressure EGR line Le1, from the smoke duct 26 side after passing through the economizer 25, thereby removing PM in the EGR gas and SOx formed during the combustion process. A demister 32 is provided at the bottom side of the scrubber, and the demister 32 separates and collects the droplets after the EGR gas is purified as a drainage portion.

[0061] The EGR blower 35 comprises: a vortex-type casing 50 into which the EGR gas after passing through the defogger 32 is introduced; a hub-shaped rotating shaft 61 (driving shaft) which is inserted into the casing 50 in a rotatable manner; an impeller 62 which is supported by the rotating shaft 61 and accommodated in the casing 50; and a sealing device 70 which contacts the outer peripheral surface of the rotating shaft 61 in a slidable manner and seals the shaft hole 52a described later.

[0062] like Figures 1 to 4 and Fig.11 As shown, the shell 50 has: a lower wall portion 51 with a suction port 51a; an upper wall portion 52 with an axial hole 52a; a suction cylinder portion 53 protruding in a cone shape from the lower wall portion 51 toward the upper wall portion 52 and with the upper end 53a close to the inlet side of the impeller 62; a vortex-shaped peripheral wall portion 55 that surrounds the suction cylinder portion 53 and forms a gas passage 54 that is a part of the EGR line Le; and a drainage port portion 56 opened in the lower wall portion 51.

[0063] The impeller 62 housed in the casing 50 and supported on the hub-shaped rotating shaft 61 is a shroud-integrated impeller, which comprises: a downward-facing inlet portion 62a, which surrounds the protruding upper end 53a of the suction cylinder 53 on the inner end side of the gas passage 54 in a rotatable manner; an outlet portion 62b, which opens in a radially outward direction toward the vortex-shaped peripheral wall portion 55; a plurality of wing portions 62c, which extend from the inlet portion 62a side to the outlet portion 62b and are spaced apart from each other at equal angles; a shroud 62d, which covers the lower surface side of the plurality of wing portions 62c; and a back surface 62e, which faces the upper wall portion 52 of the casing 50.

[0064] like Figure 3A and Figure 3B As shown, the casing 50 has a discharge port 57 a (blow-out port) opened on the outer end portion 55 a side of the spiral peripheral wall portion 55 , and the gas passage 54 is a spiral passage surrounding the suction cylinder portion 53 .

[0065] In addition, Figure 1 A motor 80 is disposed on the upper side of the housing 50 for rotating the hub-shaped rotating shaft 61. Figure 5 As shown, the motor 80 is fastened to the annular motor mounting portion 52p protruding from the detachable central thick plate portion 52c of the upper wall portion 52. The motor 80 includes an output shaft 81 and a motor body 82 driving the output shaft 81. The output shaft 81 is embedded inside the hub-shaped rotating shaft 61, abuts against the rotating shaft 61 via a retainer 63, and is integrally bolted to the rotating shaft 61 by a fastening bolt and a plug-shaped washer.

[0066] Although the motor body 82 is not shown in detail, it is, for example, an inverter-integrated electric motor controlled by a variable voltage variable frequency method (hereinafter referred to as a VVVF method), which can operate at any driving speed and driving torque within a predetermined range, thereby being controlled to a driving state suitable for the operating conditions of the engine 10 and the cleaning conditions described later. However, the motor body 82 may be a pneumatic motor instead of an electric motor.

[0067] When the impeller 62 is driven to rotate in the housing 50 by the output shaft 81 of the motor 80 via the hub-shaped rotating shaft 61, the EGR gas introduced into the gas passage 54 after cleaning on the scrubber 31 side is blown to the air inlet of the compressor 22 of the turbocharger 20, pressurized by the compressor 22 to be able to scavenge, and recirculated to the engine 10 via the air cooler 23.

[0068] like Figure 2As shown, a cleaning device 100 for cleaning the impeller 62 and the inner wall 58 of the housing 50 near the impeller 62 is installed on the housing 50, and the cleaning device 100 has: a first cleaning nozzle 101, which sprays cleaning liquid from the upper wall 52 side toward the back side 62e of the impeller 62 facing the upper wall 52; a second cleaning nozzle 102, which sprays cleaning liquid from the peripheral wall 55 side toward the wing portion 62c of the impeller 62; and a third cleaning nozzle 103, which sprays cleaning liquid from the peripheral wall 55 or the lower wall 51 side toward the lower surface of the shield 62d of the impeller 62. The cleaning device 100 also has: a cleaning liquid distribution pipe 104, one end side of which is connected to the supply source of the cleaning liquid (for example, the pump 36 and the water treatment device 37 described later) is a collecting pipe, and the other end side is three branch pipes; and a valve 105, which is provided on one end side of the cleaning liquid distribution pipe 104.

[0069] The first cleaning nozzle 101 forms an inclination angle θ1 from the upper side near the outer peripheral radius position of the impeller 62 relative to the back side 62e of the impeller 62 to the vertical upper side, and can spray cleaning liquid in the spray direction D1 toward the center side of the impeller 62, and its spray flow rate can be adjusted by a valve 105 with a built-in spherical valve body, etc. It should be noted that the spray direction D1 of the cleaning liquid from the first cleaning nozzle 101 can also be set to form a predetermined cross angle relative to the radial direction of the back side 62e and tilted toward the circumferential direction of the impeller 62. In this case, the cleaning liquid can be sprayed in the direction of the rotating shaft 61 that deviates from the hub shape, and the relative speed of the cleaning liquid relative to the rotation of the impeller 62 at the impact site can also be increased or decreased. In addition, the intensity of the spray of the cleaning liquid can be changed, for example, by the valve 105, the pump 36 or by an additional spray control valve, a booster pump, etc., and the temperature of the spray of the cleaning liquid can be changed by switching the supply device of the cleaning liquid, using steam heat, etc. The spraying of the cleaning fluid is not limited to the spraying of liquid only, but can also be the spraying of a mixed fluid of liquid and gas, pressurized superheated steam, etc., and the spraying form can be one or more fan-shaped, cone-shaped, or other jet forms.

[0070] The second cleaning nozzle 102 is arranged near the setting height of the wing portion 62c in the rotation axis direction of the impeller 62 in a manner that is located further outward than the outer periphery of the impeller 62, and forms a predetermined inclination angle at least in the circumferential direction relative to the wing portion 62c of the impeller 62, and sprays the cleaning liquid in the spray direction D2 toward the center side of the impeller 62. In addition, the spray flow rate of the second cleaning nozzle 102 can be adjusted by the valve 105, and can be changed at a certain ratio relative to the spray flow rate of the first cleaning nozzle 101. It should be noted that the spray direction D2 of the cleaning liquid from the second cleaning nozzle 102 is shown as a spray direction close to the horizontal direction, but it can also be set to form an inclination angle in the up and down direction to the rotation axis direction of the impeller 62 according to the shape of the wing portion 62c to improve the cleaning effect.

[0071] The third cleaning nozzle 103 forms a predetermined inclination angle at least in the vertical direction relative to the lower surface of the shroud 62d of the impeller 62 from the outside of the outer radius of the impeller 62, and can spray cleaning liquid in the injection direction D3 toward the center side of the impeller 62. In addition, the injection flow rate of the third cleaning nozzle 103 can be adjusted by the valve 105, and can change at a roughly constant ratio relative to the injection flow rates of the first cleaning nozzle 101 and the second cleaning nozzle 102. It should be noted that the injection direction D3 of the cleaning liquid from the third cleaning nozzle 103 is illustrated as a spray direction inclined at least toward the vertical upper side (one side of the rotation axis of the impeller 62), and of course, it can be set to be inclined toward the circumference of the impeller 62 according to the shape of the shroud 62d to improve the cleaning effect.

[0072] The cleaning device 100 is arranged on the small radius area side of the spiral wall portion 55 of the housing 50, and the drain port portion 56 is arranged close to the large radius area side of the spiral wall portion 55. That is, the cleaning liquid sprayed from the first cleaning nozzle 101, the second cleaning nozzle 102 and the third cleaning nozzle 103 is scattered or forced and flows down along the centrifugal direction by the rotation of the air supply direction of the impeller 62, and is drained to the drain port portion 56. A drain pipe not shown in the figure is connected to the drain port portion 56, through which the cleaning liquid can be returned to the washing water pool or water treatment device 37 below the scrubber 31 and the demister 32. It should be noted that in order to easily drain water from the drain port portion 56, the lower wall portion 51 can also be slightly inclined relative to the horizontal plane so that the drain port portion 56 side becomes lower.

[0073] like Figure 5 As shown, the hub-shaped rotating shaft 61 is a covered cylindrical body that can be connected to the output shaft 81 of the motor 80 in a manner that allows it to rotate as a whole, and has: a roughly cylindrical body 61a with a step, which is engaged with the output shaft 81 of the motor 80 with a predetermined engagement pressure; a plug-shaped gasket 61b, which is concentrically engaged with one end of the roughly cylindrical body 61a in the impeller 62 and closes one end of it; an annular spacer 61c, which can position the roughly cylindrical body 61a and the plug-shaped gasket 61b relative to the output shaft 81 of the motor 80; a bolt 61d, which fastens the roughly cylindrical body 61a, the plug-shaped gasket 61b and the spacer 61c to the output shaft 81 of the motor 80 as a whole; and a stop pin 61e.

[0074] like Figures 5 to 9AAs shown in Figures 9B, the sealing device 70 comprises: a shaft sealing box 71, which has an annular groove 71h formed on the inner peripheral surface of the shaft hole 52a; a first sealing ring 73A and a second sealing ring 73B, which are accommodated in the annular groove 71h; a circular ring-shaped spring receiving plate 74, which is arranged between the first and second sealing rings 73A and 73B in the annular groove 71h in a manner of surrounding the hub-shaped rotating shaft 61; and a pair of toothed disc spring-shaped wire springs 75A and 75B, which are compressed and arranged between the two surfaces of the spring receiving plate 74 and the first and second sealing rings 73A and 73B, so as to apply force to the first and second sealing rings 73A and 73B against the two inner wall surfaces of the annular groove 71h of the shaft sealing box 71 with a predetermined spring pressure.

[0075] like Figure 5 , Fig.9A , 9B and Fig. 10A , 10B As shown, the shaft seal box 71 is composed of a box body 71A and an annular side plate 71B integrally fastened to the box body 71A by a plurality of side plate mounting screws 76. The box body 71A and the side plate 71B form the shaft hole 52a and the annular groove 71h.

[0076] like Fig.9A , 9B As shown, the box body 71A has: a circular recess 71v, which is open to a side that becomes the impeller 62 side after installation; a circular center hole 71a, which passes through the inner fixed part of the circular recess 71v; a flange 71f, which is located on the open end side of the circular recess 71v; a plurality of side plate mounting holes 71g and a plurality of fixing bolt holes 71hb; and a stop pin mounting hole 71ia.

[0077] like Fig. 10A , 10B As shown, the annular plate-shaped side plate 71B has: a circular center hole 71b, whose inner diameter is the same as that of the circular center hole 71a of the box body 71A; a plurality of mounting threaded holes 71ha, which are formed at the same radial position as the plurality of side plate mounting holes 71g at the same angular intervals in a manner that enables a plurality of side plate mounting screws 76 to be inserted and threadedly engaged with the plurality of side plate mounting holes 71g of the box body 71A; and a stop pin mounting hole 71ib.

[0078] The shaft seal case 71 composed of the case body 71A and the annular side plate 71B is integrally fastened by a plurality of side plate mounting screws 76 in a state where the circular center holes 71A and 71b are positioned so that the circular center holes 71A and 71b are located on the same central axis.

[0079] The shaft seal box 71 is integrally fastened to the central thick plate portion 52c of the upper wall portion 52 by inserting a plurality of fixing bolts 77 through a plurality of fixing bolt holes 71hb formed on the flange 71f of the box body 71A and screwing them to the central thick plate portion 52c of the upper wall portion 52, thereby sandwiching a gasket 78. During this fastening, the box body 71A and the annular plate-shaped side plate 71B are arranged and positionally adjusted so that the circular center holes 71A and 71b are located on the rotation center axis C1 of the hub-shaped rotating shaft 61 and the output shaft 81 of the motor 80.

[0080] In addition, the circular central side thick plate portion 52c of the upper wall portion 52 is formed to have a larger diameter than the impeller 62. By removing a plurality of mounting bolts 52b relative to the outer peripheral side portion of the upper wall portion 52 of the casing 50 and removing the central side thick plate portion 52c, the rotating action portion from the motor 80 to the impeller 62 can be separated from the fixed portion including the rest of the casing 50.

[0081] like Figure 5 and Fig. 8A , 8B As shown, the first and second sealing rings 73A, 73B are respectively composed of a plurality of split sealing components 73sA, 73sb which are divided into two parts. The split sealing components 73sA, 73sb are applied to the hub-shaped rotating shaft 61 with a predetermined contact pressure by a clamping spring 72 in a manner of surrounding the hub-shaped rotating shaft 61 in an annular groove 71h. The sliding surfaces of the two split sealing components 73sA, 73sb at least with the hub-shaped rotating shaft 61 are formed of carbon material.

[0082] In addition, if Figure 5 , Fig.9A , 9B and Fig. 10A , 10B As shown, a plurality of stop pins 71pA and 71pb are provided on the first and second seal rings 73A and 73B. The stop pins 71pA and 71pb extend from the inner wall surfaces Fs1 and Fs2 (see FIG. Fig.9A , 9B , Fig. 10A , 10B ) protrudes parallel to the rotation center axis C1.

[0083] The plurality of stop pins 71pA and 71pb are respectively engaged with the first and second seal rings 73A and 73B in a concave-convex manner in the axial direction of the hub-shaped rotating shaft 61 .

[0084] like Figure 5 and Fig. 6A , 6BAs shown, a pair of toothed disc spring-shaped thin springs 75A and 75B respectively have multiple arc portions 75r extending in the circumferential direction, multiple inner claw portions 75c, and two end portions 75e1 and 75e2 bent into a cantilever hook shape, and the two end portions 75e1 and 75e2 have a free shape separated in a manner of being separated by a predetermined gap d in the circumferential direction.

[0085] In addition, a pair of toothed disc spring-shaped hair springs 75A, 75B are provided to engage with the inner surface 71c (refer to Figure 5 , Fig.9A , 9B ) is crimped into a radially reduced diameter state and embedded in the shaft seal box 71. In this embedded state, a plurality of inner cam portions 75c are separated from each other at approximately equal angles, thereby being able to apply force to the entire circumferential area of ​​the first and second sealing rings 73A and 73B with uniform side pressure.

[0086] For the annular spring receiving plate 74, as Figure 5 and Figure 7 As shown, a plurality of through holes 74h and arc-shaped cutouts 74n are formed at equal intervals, and the cutouts 74n can be used to adjust the angular position of the annular spring receiving plate 74 in the circumferential direction. For example, the cutouts 74n are arranged at a position that can be visually viewed from the inspection hole 110 with an opening and closing cover arranged on the front side of the housing 50 in the blower installation posture.

[0087] In addition, the radial clearance of the inner diameter side of the annular plate-shaped spring receiving plate 74 relative to the hub-shaped rotating shaft 61 is larger than the radial clearance of the outer diameter side of the annular plate-shaped spring receiving plate 74 relative to the inner surface 71c of the annular groove 71h, and the size of the annular plate-shaped spring receiving plate 74 is set in a manner that does not contact the hub-shaped rotating shaft 61.

[0088] Furthermore, a mist collecting unit 90 is provided between the upper wall portion 52 and the motor 80 . The mist collecting unit 90 surrounds the shaft hole 52 a and the hub-shaped rotating shaft 61 from the radial outside and collects mist leakage from the shaft hole 52 a to the atmosphere.

[0089] The mist collection unit 90 comprises: an annular protrusion 91, which protrudes from the upper wall portion 52 at a height of the motor mounting reference surface Mt and is close to the mounting plate 83 of the motor 80 in a manner that surrounds the axial hole 52a and the hub-shaped rotating shaft 61; and a plurality of filter-shaped mist collectors 92, which are arranged at equal angular intervals on the annular protrusion 91. The mist collection unit 90 is capable of collecting mist leakage that leaks from the axial hole 52a to the atmosphere side through the sliding gap between the sealing device 70 and the hub-shaped rotating shaft 61.

[0090] In addition, on the housing 50, a coating such as Figure 2 The heat-resistant anticorrosion coating 58i shown in the partially enlarged view in FIG. 5 has a glass flake layer 58f configured in multiple layers in a coating film 58r of a heat-resistant or thermosetting coating resin. The glass flake layer 58f is formed by spraying and coating, for example, flaky glass flakes of an alkali component uniformly dispersed in the coating film of the coating resin in multiple layers, thereby making the anticorrosion coating 58i function as an acid-resistant heat-resistant lining.

[0091] In addition, a heat-resistant anti-corrosion coating 58i is also applied to the inner circumferential wall surface 53b and the outer circumferential wall surface 53c of the suction cylinder portion 53 of the housing 50. That is, the entire area of ​​the inner wall 58 of the housing 50 mentioned here refers to the entire area of ​​the gas passage 54 formed as a part of the EGR line Le in the housing 50, and may include the inner circumferential wall surface 53b of the suction cylinder portion 53, the anti-corrosion coating 57i of the inner wall of the blow-out cylinder portion 57 forming the exhaust port 57a, etc.

[0092] In the entire region of the inner wall 58 of the housing 50 coated with the anti-corrosion coating 58i, the base materials of the lower wall 51, the upper wall 52, the suction cylinder 53, the peripheral wall 55, etc. of the housing 50 are formed of an iron-based material, for example, a general structural rolled steel material. On the other hand, the hub-shaped rotating shaft 61 (including the bolt 61d and the plug-shaped washer 61b) and the impeller 62 are each formed of, for example, stainless steel having excellent strength and corrosion resistance.

[0093] Thus, in the present embodiment, the diesel engine 10 is configured as a main engine of a large ship, and is provided with an EGR blower, which refluxes a portion of the exhaust gas after passing through the turbine 21 of the turbocharger 20 to the low-pressure EGR line Le of the compressor 22 of the turbocharger 20, pressurizes the reflux gas in the low-pressure EGR line Le to the supply pressure to the compressor 22, and supplies air.

[0094] Next, the action will be described.

[0095] In the EGR blower 35 of the present embodiment configured as described above and the low-pressure EGR device 30 equipped with the EGR blower 35, the housing 50 includes: the suction cylinder 53 protruding from the lower wall 51 in a truncated cone shape, the upper end 53a of which is inserted into the inlet 62a of the impeller 62 and close to the inlet 62a; the spiral peripheral wall 55 surrounding the suction cylinder 53 and forming the gas passage 54; and the drainage port 56 opening on the lower wall 51, so that when the cleaning liquid is sprayed from the first to third cleaning nozzles 101 to 103 toward the back surface 62e of the impeller 62, the wing surface 62c, and the lower surface of the shroud 62s, respectively, the impeller 62 is cleaned, and the cleaning liquid after cleaning is discharged from the drainage port 56. Therefore, even in the operating state of the engine 10, for example, just before stopping, the cleaning operation can be performed, and the impeller 62 and the inner wall 58 of the housing 50 around it can be reliably cleaned. As a result, even during the operation of the engine 10 , adhesion and accumulation of combustion residues in the EGR blower 35 , corrosion due to condensed water, and the like can be effectively suppressed.

[0096] In addition, if the impeller 62 is rotated in the air supply direction during cleaning, the cleaning liquid sprayed from the first and third cleaning nozzles 101 and 103 produces a relative speed change with respect to the impeller 62 and a direction change in the centrifugal direction, thereby enhancing the cleaning effect of the impeller 62, and the cleaning liquid sprayed from the second cleaning nozzle 102 collides with the wing portion 62c of the impeller 62 and scatters, thereby improving the cleaning effect of the wing portion 62c of the impeller 62.

[0097] In addition, even if the cleaning liquid sprayed from the second cleaning nozzle 102 reaches the inner peripheral wall surface 53b of the suction cylinder 53 from the inside of the impeller 62, the cleaning liquid can be returned to the cleaning pool or water treatment device 37 below the scrubber 31 and the demister 32, and the cleaning liquid discharged from the drain port 56 can also be returned to the cleaning pool, the water treatment device 37, etc. In addition, the VVVF type motor 80 can operate at any rotation speed and driving torque within a predetermined range, so the impeller 62 can be controlled to a rotation condition suitable for cleaning.

[0098] Since the blower of the present embodiment acts as the EGR blower 35 to increase the pressure of the reflux gas in the low-pressure EGR line Le, even if the EGR gas cleaned by the scrubber 31 is at a lower pressure and a lower temperature, acidic condensed water attached to the EGR path Le near the EGR blower 35, or combustion residues in the uncleaned exhaust gas attached to the impeller 62 of the EGR blower 35 or its vicinity, can be easily cleaned and removed together with the drainage.

[0099] Moreover, in the present embodiment, since a mist collecting unit 90 for collecting mist leakage from the shaft hole 52a to the atmosphere is provided between the upper wall portion 52 and the motor 80, even if the cleaning fluid enters the sealing portion of the shaft hole 52a during cleaning and generates mist leakage from the shaft hole 52a to the atmosphere, the leakage can be reliably collected by the mist collecting unit 90 in the housing 50 of the EGR blower 35, which is usually not at such a high pressure.

[0100] In addition, in this embodiment, since the heat-resistant anticorrosion coating 58i having the glass flake layer 58f is applied to the entire area of ​​the inner wall 58 of the housing 50, sufficient acid resistance and corrosion resistance can be obtained. In addition, by forming the base material 58s (at the inner wall of the inner wall 58 of the housing 50 to be a large part) Figure 2 The partially enlarged figure shows the base material 51s of the lower wall portion 51), or further forming the base material of the suction cylinder portion 53 with an iron-based material, which can achieve cost reduction.

[0101] In addition, in this embodiment, since at least the sliding surfaces of the inner peripheral sides of the first and second seal rings 73A and 73B with clamp springs in the sealing device 70 are made of carbon material, the required corrosion resistance and self-lubricating properties can be obtained. In addition, the first and second seal rings 73A and 73B are pressed against the inner wall surfaces ( 71h ) of the annular groove 71h of the shaft seal box 71 by a pair of toothed disc spring-shaped fine springs 75A and 75B sandwiching the annular plate-shaped spring receiving plate 74. Fig.9A , 9B , Fig. 10A , 10B The first and second sealing rings 73A and 73B exert a stable pushing force and friction retaining force on the two inner wall surfaces of the annular groove 71h by means of the toothed disc spring-like fine springs 75A and 75B having a lower spring constant than the ordinary disc spring.

[0102] In addition, since a pair of toothed disc spring-like fine springs 75A and 75B are arranged to be bendable not only in the axial direction but also in the radial direction of the hub-shaped rotating shaft 61, the pair of toothed disc spring-like fine springs 75A and 75B and the annular plate-shaped spring receiving plate 74 between the two springs can be compactly accommodated in the narrow shaft seal box 71, and at the same time, they can be reliably positioned in the axial and rotational directions, and a positioning and retaining force can be generated. This positioning and retaining force, together with the friction retaining force on the two inner wall sides of the annular groove 71h and the anti-rotation force of the anti-rotation pins 71pA and 71pb, effectively prevents the first and second sealing rings 73A and 73B from rotating.

[0103] In addition, the low-pressure EGR device 30 of the marine diesel engine 10 of the present embodiment comprises: a wet scrubber 31, which purifies the EGR gas before the pressure is increased by the EGR blower 35 by water injection in the low-pressure EGR line Le; a demister 32, which allows the purified EGR gas to pass to the EGR blower 35 side and separates the purified wastewater from the gas; and a water treatment device 37 with a pump, which removes particulate components from the wastewater, adjusts the pH, and supplies it to the scrubber again, so that the cleaning liquid discharged from the EGR blower 35 and the cleaning water discharged from the wet scrubber 31 can be introduced into the water treatment device 37 together, and by properly circulating them, the amount of water used can be effectively suppressed.

[0104] As described above, in the present embodiment, adhesion and accumulation of combustion residues in the EGR blower 35 and corrosion due to condensed water can be effectively suppressed even during the operation of the engine 10 .

[0105] It should be noted that in the EGR blower 35 of the above-mentioned embodiment, the output shaft 81 of the motor 80 is inserted into the hub-shaped rotating shaft 61, and the two are integrated by bolting, but the combination form of the impeller 62 and the motor 80 is not particularly limited as long as it can be driven to rotate.

[0106] In addition, in one embodiment described above, the impeller 62 formed of a specific stainless steel material having particularly excellent corrosion resistance is cleaned as the main object by spraying the cleaning agent from the first to third cleaning nozzles 101 to 103, and the inner wall 58 of the housing 50 is cleaned only near the impeller 62 by spraying the cleaning liquid. However, the cleaning range can be appropriately set according to the tendency of dirt to adhere and accumulate. In addition, the spray direction of the cleaning liquid is inclined only toward the rotation center axis C1 side of the impeller 62, but it is also possible, for example, to make the first to third cleaning nozzles 101 to 103 have spray ports facing different directions, respectively, to clean a wide range of the inner wall 58, and further, it is also possible to consider offsetting the influence on the rotation of the impeller 62, or conversely spraying the cleaning agent to apply force or become resistance in the direction of rotation.

[0107] Furthermore, in one embodiment, the engine 10 is used for ships, but the present invention can also be applied to large engines other than ships, for example, stationary engines for operating generators.

[0108] As described above, the present invention can provide an EGR blower that can effectively suppress the adhesion and accumulation of combustion residues in the blower and corrosion caused by condensed water during the operation of the engine. This is useful for all EGR blowers that constitute part of the EGR device in large or medium-sized diesel engines.

[0109] Description of reference numerals:

[0110] 1 Powertrain

[0111] 10Engine (diesel engine, marine diesel engine, main engine)

[0112] 11 Engine body (internal combustion engine body)

[0113] 11a Cylinder (cylinder)

[0114] 11b scavenging port

[0115] 12 Piston

[0116] 13 Scavenge air tank (scavenge air receiver)

[0117] 14 Exhaust receiver (exhaust storage)

[0118] 14a Exhaust valve

[0119] 15 Fuel supply unit

[0120] 16 Phillips

[0121] 20 Turbocharger (exhaust turbocharger)

[0122] 21 Turbine

[0123] 22 Compressor

[0124] 23 Air Cooler

[0125] 25 Energy Saver

[0126] 26 Smoke Road

[0127] 27EGR valve

[0128] 30 Low-pressure EGR device

[0129] 31 Scrubber (wet scrubber)

[0130] 32 demister

[0131] 35EGR blower (low pressure EGR blower)

[0132] 37 Water treatment device

[0133] 50 Shell

[0134] 51 Lower wall

[0135] 51a Inlet

[0136] 52 Upper wall

[0137] 52a shaft hole

[0138] 52b Multiple mounting bolts

[0139] 52c Central side thick plate part

[0140] 53 Suction cylinder

[0141] 53a upper end

[0142] 53b inner wall surface

[0143] 53c peripheral wall

[0144] 54 Gas passage

[0145] 55 peripheral wall portion (peripheral wall portion on the vortex)

[0146] 55a Outer end

[0147] 56 Drainage outlet

[0148] 57 Blow out tube

[0149] 57a Exhaust port (blow-out port)

[0150] 57i, 58i anti-corrosion coating

[0151] 58 inner wall (inner wall surface part)

[0152] 58f glass flake layer

[0153] 58r coating

[0154] 61 Rotating shaft (driving shaft)

[0155] 61a roughly cylindrical

[0156] 61b Washer

[0157] 61c Spacer

[0158] 61d bolt

[0159] 62 Impeller

[0160] 62a Entrance Department

[0161] 62b Export

[0162] 62c Wing face

[0163] 62d shield

[0164] 62e back (upper back)

[0165] 62s shroud (covering the lower side of the wing section)

[0166] 63 retaining ring

[0167] 70 Sealing device

[0168] 71 shaft seal box

[0169] 71A Box body

[0170] 71B Side Panel

[0171] 71A, 71b center hole

[0172] 71c inside

[0173] 71f flange

[0174] 71g side panel mounting holes

[0175] 71h annular groove

[0176] 71ha mounting threaded hole

[0177] 71hb fixing bolt hole

[0178] 71iA, 71ib anti-rotation pin installation hole

[0179] 71pA, 71pb stop pin

[0180] 71v round recess

[0181] 72 clamping spring

[0182] 73A First sealing ring

[0183] 73B Second sealing ring

[0184] 73sA, 73sb split sealing components

[0185] 74 Spring receiving plate

[0186] 74h through hole

[0187] 74n cut

[0188] 75A, 75B fine spring (fine spring in the shape of a disc spring with teeth)

[0189] 75c inner claw part

[0190] 75e1, 75e2 ends

[0191] 75r arc part

[0192] 76 Side panel mounting screws

[0193] 77 fixing bolt

[0194] 80 motor

[0195] 81 Output shaft (drive shaft)

[0196] 82 Motor body

[0197] 83 Mounting plate

[0198] 90 Mist Collection Units

[0199] 91 annular convex part

[0200] 92 Mist Collector

[0201] 100 cleaning device

[0202] 101 First cleaning nozzle (back cleaning nozzle)

[0203] 102 Second cleaning nozzle (wing cleaning nozzle)

[0204] 103 The third cleaning nozzle (lower surface cleaning nozzle)

[0205] 104 cleaning liquid distribution pipe

[0206] 105 valve

[0207] 110 Inspection hole

[0208] C1 Rotation center axis

[0209] D1, D2, D3 Spray direction (spray direction of cleaning fluid)

[0210] Fs1, Fs2 inner wall

[0211] Le, Le1, Le2, Le3 Low-pressure EGR line (exhaust gas recirculation path)

[0212] Mt Motor mounting reference surface

[0213] θ1 tilt angle

Claims

1. An EGR blower, which is equipped on a diesel engine as a part of an EGR device, the diesel engine comprising the EGR device for recirculating a part of exhaust gas discharged from an engine body as a part of combustion gas, and a turbocharger driven by the exhaust gas, the EGR blower pressurizes a part of the recirculated exhaust gas, characterized in that: The EGR blower comprises: a housing formed with an axial hole and a gas passage having a suction port and a discharge port; a motor that rotates a drive shaft inserted through the shaft hole of the housing; an impeller supported by the drive shaft and received in the housing; and a sealing device that slidably contacts the drive shaft and seals the shaft hole, The housing comprises: a lower wall portion having the suction port; an upper wall portion having the shaft hole; a suction cylinder portion protruding from the lower wall portion toward the upper wall portion in a truncated cone shape and with the upper end close to the inlet portion of the impeller; a vortex-shaped peripheral wall portion surrounding the suction cylinder portion and forming the gas passage; and a drain port portion opening on the lower wall portion. The EGR blower is provided with a cleaning device for cleaning the impeller, and the cleaning device comprises: a first cleaning nozzle, which sprays cleaning liquid from the upper wall side toward the back side of the impeller facing the upper wall; and a second cleaning nozzle, which sprays cleaning liquid from the peripheral wall side toward the wing portion of the impeller.

2. The EGR blower according to claim 1, characterized in that: The diesel engine is configured as the main engine of a large ship. The low-pressure EGR blower is configured to return a part of the exhaust gas after passing through the turbine of the turbocharger to the compressor of the turbocharger in a low-pressure EGR line and to increase the pressure of the return gas in the low-pressure EGR line.

3. The EGR blower according to claim 1 or 2, characterized in that: The EGR blower further includes a mist collecting unit that is provided between the upper wall portion and the motor, surrounds the shaft hole and the drive shaft, and collects mist leakage that leaks from the shaft hole to the atmosphere.

4. The EGR blower according to claim 1 or 2, characterized in that: A heat-resistant anticorrosion coating having a glass flake layer is applied to the entire area of ​​the inner wall surface of the housing.

5. The EGR blower according to claim 1 or 2, characterized in that: The sealing device comprises: A shaft seal box, which is arranged on the housing in a manner of forming the shaft hole and has an annular groove opened on the inner peripheral surface of the shaft hole; The first seal ring and the second seal ring are respectively composed of a plurality of divided seal members that are biased against the drive shaft at a predetermined contact pressure by a clamp spring in a manner of surrounding the drive shaft in the annular groove, and at least the sliding surface with the drive shaft is formed of a carbon material; a spring receiving plate in the shape of an annular plate, which is disposed between the first sealing ring and the second sealing ring in the annular groove in a manner of surrounding the drive shaft; and A pair of toothed disc spring-shaped thin springs are compressed and arranged between the two surfaces of the spring receiving plate and the first sealing ring and the second sealing ring, and the first sealing ring and the second sealing ring are forced to the two inner wall surfaces of the annular groove of the shaft seal box with a predetermined spring pressure.

6. A low-pressure EGR device for a diesel engine, characterized in that: The EGR blower according to claim 2 is provided, and further comprising: a wet scrubber that purifies the recirculated gas before it is pressurized by the low-pressure EGR blower by water injection in the low-pressure EGR line; a demister that passes the purified reflow gas toward the low-pressure EGR blower and separates the purified drain water from the reflow gas; and A water treatment device with a pump removes particulate components from the wastewater, adjusts the pH, and supplies the wastewater to the scrubber again.

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