CN114593076A

CN114593076A - Low-resistance combustion-promoting secondary fan structure

Info

Publication number: CN114593076A
Application number: CN202111611963.1A
Authority: CN
Inventors: 胡炎峰; 张银华; 周伯年
Original assignee: Yuyao Fan General Factory Co ltd
Current assignee: Yuyao Fan General Factory Co ltd
Priority date: 2021-12-27
Filing date: 2021-12-27
Publication date: 2022-06-07
Anticipated expiration: 2041-12-27
Also published as: CN114593076B

Abstract

The invention discloses a low-resistance combustion-promoting secondary fan structure. The sealing device comprises an expansion sleeve, guide rings are mounted at two ends of the expansion sleeve, and the two expansion sleeves are mounted on the air inlet port and the air outlet port respectively through the guide rings. The invention has the beneficial effects that: through the design of the expansion sleeve between the pipeline and the port, the installation error between the port and the pipeline can be compensated, the thermal expansion difference between the port and the pipeline, which is generated due to different wall temperatures, can be compensated, the strength damage, the instability damage and the pipeline pull-off damage are avoided, and the sealing property between the connecting pipeline and the gas inlet and outlet ports is improved; the annular sealing block is arranged at the position of the main shaft extending out of the through hole of the shell for sealing, so that the good air tightness of the shell is ensured, and the air leakage loss of the shell is reduced.

Description

Low-resistance combustion-promoting secondary fan structure

Technical Field

The invention relates to the technical field of ventilators, in particular to a low-resistance combustion-promoting secondary fan structure.

Background

The secondary air fan is a supplementary measure for improving the combustion quality, is an adjusting channel for improving the combustion efficiency, is an indispensable part as long as oxygen is supplemented behind flame, is a stable combustion-supporting effect at present, and has more and more demands on the secondary air fan in the market at present. The secondary fan is specially matched with the primary fan, the air quantity regulation and proportioning between the secondary fan and the primary fan are the key of the boiler combustion technology, and the secondary fan plays a great role in supporting combustion.

Chinese patent grant publication no: CN205261617U, entitled bulletin date 2016, 05 and 25, discloses a secondary fan structure of a boiler, which comprises a gas collecting port, a box body, a secondary fan and a gas supply pipe, wherein the gas collecting port is arranged above the box body, the secondary fan is arranged in the box body, one end of the gas supply pipe is connected with the secondary fan, and the other end of the gas supply pipe is connected to the outside of the box body; and a silencer is arranged on the inner side of the box body and comprises at least two layers of silencing plates made of silencing materials. The defects of the patent are that the air inlet end and the air outlet end of the secondary fan are not provided with a sealing structure when being connected with a pipeline, and when the fan works, the connecting pipeline and the air inlet and outlet ports can generate thermal expansion difference due to different wall temperatures to cause a large amount of air leakage loss.

In summary, there is a need for a low-resistance combustion-promoting secondary air fan structure that can improve the sealing between the connecting duct and the air inlet/outlet port.

Disclosure of Invention

The invention provides a low-resistance combustion-promoting secondary fan structure capable of improving the sealing property between a connecting pipeline and a gas inlet and outlet port, aiming at overcoming the defect that a large amount of gas leakage loss is caused by the fact that the thermal expansion difference is generated between the connecting pipeline and the gas inlet and outlet port due to different wall temperatures when a fan works in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

the utility model provides a short burning secondary fan structure of low resistance, includes the casing, the internally mounted of casing has the rotor subassembly, be equipped with inlet port and the port of giving vent to anger on the casing, inlet port and the port department of giving vent to anger all install sealing device, sealing device includes the inflation cover, the guide ring is all installed at the both ends of inflation cover, and two inflation covers pass through the guide ring and install respectively on inlet port and the port of giving vent to anger.

One ends of the two expansion sleeves are respectively installed on the air inlet port and the air outlet port through guide rings, and the other ends of the two expansion sleeves are respectively connected with the air inlet pipeline and the air outlet pipeline through the guide rings. The expansion sleeve is large in axial flexibility and easy to deform, installation errors between the port and the pipeline can be compensated through the design of the expansion sleeve between the pipeline and the port, thermal expansion differences between the port and the pipeline caused by different wall temperatures can be compensated, axial loads of the port and the pipeline are reduced, accordingly, temperature difference stress between the port and the pipeline is reduced, strength damage, instability damage and pipeline pull-off damage are avoided, and sealing performance between the connecting pipeline and the air inlet and outlet ports is improved.

Preferably, the expansion sleeve comprises an outer sleeve and an inner sleeve, a port of the inner sleeve is arranged on the inner side wall of the guide ring, an annular mounting groove matched with the port of the outer sleeve is formed in the guide ring, the port of the outer sleeve is arranged in the annular mounting groove of the guide ring, and the outer sleeve is arranged on the outer side of the inner sleeve. The inner sleeve and the outer sleeve are both fixed with the guide ring through threaded connection, the structure is simple, and the processing is convenient. Through the design of the inner sleeve and the outer sleeve, the structural strength of the expansion sleeve is improved, and a good sealing effect and a compensation effect are ensured.

Preferably, the inner sleeve is made of silica gel cloth, and the outer sleeve is made of stainless steel wire cloth. The inner sleeve is made of industrial 2mm silica gel cloth, has the advantages of high temperature resistance, ageing resistance, elasticity and good flexibility, and can solve the problem of connection damage of pipelines and ports caused by good expansion with heat and contraction with cold. The outer sleeve is made of 20-mesh/in stainless steel wire cloth, so that the structural strength of the expansion sleeve is improved, and the good elasticity and flexibility of the expansion sleeve are ensured.

Preferably, the casing includes the spiral case, the side of spiral case is equipped with the inlet box, the inside of spiral case and the inside of inlet box are linked together, the rotor subassembly includes the main shaft, the lateral wall that the one end of main shaft runs through the inlet box just rather than sealed rotation connection, the other end of main shaft runs through the lateral wall of spiral case and rather than sealed rotation connection, install the impeller on the main shaft, the impeller is located inside the spiral case. The fan shell is composed of a volute and an air inlet box which are all formed by welding steel plates made of Q235 materials, and the side faces of the shell are provided with reinforcing flat steel, so that large deformation is avoided in the transportation, installation and operation processes. The main shaft is a monobloc forged shaft and has enough rigidity and strength. An observation door is arranged on the side surface of the volute, so that the working condition in the fan can be observed conveniently; the bottom of spiral case is provided with the deashing door, and the inlet box bottom is provided with the drain, conveniently carries out cleaning work to the casing inside.

Preferably, the inlet port is located on a surface of the inlet box and the outlet port is located on a surface of the volute. The invention relates to a rotating fan which reversely enters 90 degrees and exits 90 degrees, wherein an impeller is a reversely rotating impeller, and gas is sucked into an air inlet box through an air inlet port and is discharged through an air outlet port on a volute under the action of the impeller.

As preferred, the both sides of casing are equipped with the both ends assorted casing through-hole with the main shaft, the tip of main shaft passes the casing through-hole and arranges the outside of casing in, the surface of casing just is located casing through-hole department and installs annular seal piece, annular seal piece cup joints the outside at the main shaft, be equipped with annular seal groove on annular seal piece's the inside wall, install the sealing washer that contacts with the main shaft in the annular seal groove. An annular sealing block (sealing ring) is arranged at the position where the main shaft extends out of the through hole of the shell for sealing, so that the good air tightness of the shell is ensured, and the air leakage loss of the shell is reduced.

Preferably, an outward flange is fixed on the outer side wall of the annular sealing block, an L-shaped pressing plate is arranged on the surface of the shell and annularly distributed around the annular sealing block, the end of one side edge of the L-shaped pressing plate is fixed on the surface of the shell, the outward flange is installed between the surface of the shell and the other side edge of the L-shaped pressing plate, a side through hole is formed in the other side edge of the L-shaped pressing plate, a stud matched with the side through hole is further fixed on the surface of the shell, the stud is arranged in the side through hole and movably connected with the side through hole, a fastening nut is in threaded connection with the stud, and the fastening nut and the outward flange are respectively located on two sides of the other side edge of the L-shaped pressing plate. Wherein L shape clamp plate has certain deformability, and the sealed piece of annular when fixing, through the fastening nut on the double-screw bolt of screwing, can drive another side of L shape clamp plate and take place the bending, and then compresses tightly the turn-ups on the sealed piece of annular on the surface of casing and fix to the purpose of the sealed piece of fixed annular has been reached, simple structure, and the installation is convenient with the dismantlement, and is fixed effectual. Still be equipped with the asbestos board between the surface of annular seal piece and casing, the asbestos board cup joints in the outside of main shaft, reduces the pressure between annular seal piece and the casing, plays the effect of protection annular seal piece and casing.

Preferably, bearing seats matched with two ends of the main shaft are fixed on two sides of the shell, the end of the main shaft penetrates through a shell through hole and is installed on the bearing seats and is in sealed rotary connection with the bearing seats, one end of the main shaft is installed inside one of the bearing seats, the other end of the main shaft penetrates through the other bearing seat, a bearing seat cavity is arranged inside the bearing seat, a bearing body is arranged in the bearing seat cavity and is sleeved on the main shaft, and a horizontal vibration measuring point, a vertical vibration measuring point, a cooling water inlet, a cooling water outlet and a temperature measuring hole are respectively arranged on the side wall of the bearing seat cavity. The other end of the main shaft penetrates through the other bearing seat and then is connected with the variable frequency motor through the coupler and the liquid couple in sequence, and the variable frequency motor drives the main shaft to work. The bearing body adopts a rolling bearing, so that the working precision is high. Through the design of the cooling water inlet and the cooling water outlet, cooling water can be introduced into the cavity of the bearing block, so that the cooling effect of the bearing body is achieved; through the design of the temperature measuring hole, a worker can use a temperature measuring element (a platinum thermal resistor) to extend into the temperature measuring hole to measure the temperature of the bearing seat, so that the operation is simple and the detection is convenient; through the design of horizontal vibration measuring point and perpendicular vibration measuring point, the staff can use the vibration measuring probe to carry out the vibration detection on bearing frame horizontal direction and the vertical direction to know the operating condition of bearing frame.

As preferred, still be equipped with the regulating box cover between inlet port and the expansion sleeve rather than corresponding, the one end of regulating box cover is installed in inlet port department, the expansion sleeve of inlet port department passes through the guide ring and installs the other end at the regulating box cover, the internal rotation of regulating box cover is connected with a plurality of pivots, the pivot is parallel to each other and is located same horizontal plane, be fixed with guide vane in the pivot, guide vane's length and the inboard width phase-match of regulating box cover, all guide vane's width sum and the inboard length phase-match of regulating box cover, be equipped with the rotation control device who is connected with the pivot on the regulating box cover. The rotary control device can control the rotating shaft to rotate, so that the guide vanes on the rotating shaft are driven to turn over, the air inlet port is opened and closed, the air quantity, the pressure and the temperature are controlled, and the medium flowing is isolated.

Preferably, the end of the rotating shaft penetrates through the side wall of the adjusting box sleeve and is arranged outside the adjusting box sleeve, a linkage handle is arranged on the end of the rotating shaft, the rotation control device comprises a linkage plate, one end of the linkage handle is fixedly connected with the rotating shaft, the other end of the linkage handle is hinged to the linkage plate, a driving handle and a pointer are fixed on the end of one rotating shaft, the driving handle and the linkage handle are both located at one end of the rotating shaft, the pointer is located at the other end of the rotating shaft, and a dial matched with the pointer in position is arranged on the outer side wall of the adjusting box sleeve. The driving handle can be controlled manually or by an external electric actuator. During operation, the corresponding rotating shafts and the guide blades on the rotating shafts are driven to rotate by the driving handles, and at the moment, the guide blades on other rotating shafts can be driven to synchronously rotate under the transmission action of the linkage handles and the linkage plate, so that the aims of adjusting air volume, pressure and temperature are fulfilled. In the process of rotating the rotating shaft, the pointer on the rotating shaft also rotates along with the rotating shaft, and the pointer and the dial are designed to play a role in indicating so that a worker can directly know the adjusting state at the air inlet port.

The invention has the beneficial effects that: through the design of the expansion sleeve between the pipeline and the port, the installation error between the port and the pipeline can be compensated, the thermal expansion difference between the port and the pipeline caused by different wall temperatures can be compensated, and the axial load of the port and the pipeline can be reduced, so that the temperature difference stress between the port and the pipeline is reduced, the strength damage, the instability damage and the pipeline pull-out damage are avoided, and the sealing property between the connecting pipeline and the gas inlet and outlet ports is improved; the annular sealing block is arranged at the position of the main shaft extending out of the through hole of the shell for sealing, so that the good air tightness of the shell is ensured, and the air leakage loss of the shell is reduced; the main shaft is an integrally forged shaft, is connected with the variable frequency motor through the coupler and the liquid couple, is driven by the variable frequency motor to work, and has sufficient rigidity and strength; the bearing body adopts a rolling bearing, so that the working precision is high; the fan shell consists of a volute and an air inlet box which are all formed by welding steel plates made of Q235 materials, and the side surfaces of the shell are provided with reinforced flat steel, so that the fan shell is ensured not to deform greatly in the transportation, installation and operation processes; the structure is simple, and the processing is convenient; the structural strength of the expansion sleeve is improved, and good sealing effect and compensation effect are ensured; the inner sleeve has the advantages of high temperature resistance, ageing resistance, elasticity and good flexibility, and can solve the problem of connection damage of a pipeline and a port due to good expansion with heat and contraction with cold; the outer sleeve improves the structural strength of the expansion sleeve on one hand, and ensures good elasticity and flexibility of the expansion sleeve on the other hand; the structure is simple, the installation and the disassembly are convenient, and the fixing effect is good; the pressure between the annular sealing block and the shell is reduced, and the annular sealing block and the shell are protected; the air quantity, the pressure and the temperature are controlled, and the medium flow is isolated; the worker can directly know the regulation state at the air intake port.

Drawings

FIG. 1 is a schematic diagram of an embodiment of the present invention;

FIG. 2 is a cross-sectional view taken at A-A of FIG. 1;

FIG. 3 is a top view of the sealing device;

FIG. 4 is a cross-sectional view taken at B-B of FIG. 3;

FIG. 5 is an enlarged view at C in FIG. 4;

FIG. 6 is an assembly view of the annular seal block and housing;

FIG. 7 is a front view of the bearing housing;

FIG. 8 is a right side view of the bearing housing;

FIG. 9 is a front view of the adjustment sleeve;

FIG. 10 is a top view of the adjustment sleeve;

fig. 11 is a rear view of the adjustment sleeve.

In the figure: 1. the device comprises a shell, 2, an air inlet port, 3, an air outlet port, 4, a sealing device, 5, an expansion sleeve, 6, a guide ring, 7, an outer sleeve, 8, an inner sleeve, 9, an annular installation groove, 10, a volute, 11, an air inlet box, 12, a main shaft, 13, an impeller, 14, a shell through hole, 15, an annular sealing block, 16, an annular sealing groove, 17, a sealing ring, 18, an outward flange, 19, an L-shaped pressing plate, 20, a side through hole, 21, a stud, 22, a fastening nut, 23, a bearing seat, 24, a bearing seat cavity, 25, a bearing body, 26, a horizontal vibration measuring point, 27, a vertical vibration measuring point, 28, a cooling water inlet, 29, a cooling water outlet, 30, a temperature measuring hole, 31, an adjusting box sleeve, 32, a rotating shaft, 33, a guide blade, 34, a linkage handle and 35, a linkage plate, 36. active handle, 37, pointer, 38 dial.

Detailed Description

The invention is further described with reference to the following figures and detailed description.

In the embodiment shown in fig. 1 and 2, a low-resistance combustion-promoting secondary air fan structure includes a housing 1, a rotor assembly is installed inside the housing 1, an air inlet port 2 and an air outlet port 3 are provided on the housing 1, and sealing devices 4 are installed at the air inlet port 2 and the air outlet port 3, as shown in fig. 3 and 4, the sealing devices 4 include expansion sleeves 5, guide rings 6 are installed at both ends of the expansion sleeves 5, and the two expansion sleeves 5 are installed on the air inlet port 2 and the air outlet port 3 through the guide rings 6, respectively.

As shown in fig. 5, the expansion sleeve 5 includes an outer sleeve 7 and an inner sleeve 8, a port of the inner sleeve 8 is installed on the inner side wall of the guide ring 6, an annular installation groove 9 matched with the port of the outer sleeve 7 is arranged on the guide ring 6, the port of the outer sleeve 7 is installed in the annular installation groove 9 of the guide ring 6, and the outer sleeve 7 is arranged on the outer side of the inner sleeve 8.

The inner sleeve 8 is made of silica gel cloth, and the outer sleeve 7 is made of stainless steel wire cloth.

As shown in fig. 1 and 2, the casing 1 includes a volute 10, an air inlet box 11 is disposed on a side surface of the volute 10, an interior of the volute 10 is communicated with an interior of the air inlet box 11, the rotor assembly includes a main shaft 12, one end of the main shaft 12 penetrates through a side wall of the air inlet box 11 and is connected with the air inlet box in a sealed and rotating manner, the other end of the main shaft 12 penetrates through a side wall of the volute 10 and is connected with the air inlet box in a sealed and rotating manner, an impeller 13 is mounted on the main shaft 12, and the impeller 13 is located inside the volute 10.

The inlet port 2 is located on the surface of the inlet box 11 and the outlet port 3 is located on the surface of the volute 10.

As shown in fig. 1 and 6, housing through holes 14 matched with two ends of a spindle 12 are formed in two sides of a housing 1, an end of the spindle 12 penetrates through the housing through hole 14 and is arranged on the outer side of the housing 1, an annular sealing block 15 is installed on the surface of the housing 1 and located at the housing through hole 14, the annular sealing block 15 is sleeved on the outer side of the spindle 12, an annular sealing groove 16 is formed in the inner side wall of the annular sealing block 15, and a sealing ring 17 in contact with the spindle 12 is installed in the annular sealing groove 16.

The outer side wall of the annular sealing block 15 is fixed with an outward flange 18, the surface of the shell 1 is provided with an L-shaped pressing plate 19, the L-shaped pressing plate 19 is annularly distributed around the annular sealing block 15, the end part of one side edge of the L-shaped pressing plate 19 is fixed on the surface of the shell 1, the outward flange 18 is installed between the surface of the shell 1 and the other side edge of the L-shaped pressing plate 19, the other side edge of the L-shaped pressing plate 19 is provided with a side through hole 20, the surface of the shell 1 is further fixed with a stud 21 matched with the side through hole 20, the stud 21 is arranged in the side through hole 20 and movably connected with the side through hole, the stud 21 is in threaded connection with a fastening nut 22, and the fastening nut 22 and the outward flange 18 are respectively located on two sides of the other side edge of the L-shaped pressing plate 19.

As shown in fig. 1, 7 and 8, bearing seats 23 matched with two ends of a main shaft 12 are fixed on two sides of a housing 1, an end portion of the main shaft 12 passes through a housing through hole 14 and is mounted on the bearing seats 23 and is in sealed rotary connection with the bearing seats, one end of the main shaft 12 is mounted inside one of the bearing seats 23, the other end of the main shaft 12 passes through the other bearing seat 23, a bearing seat cavity 24 is arranged inside the bearing seat 23, a bearing body 25 is arranged in the bearing seat cavity 24, the bearing body 25 is sleeved on the main shaft 12, and a horizontal vibration measuring point 26 and a vertical vibration measuring point 27, a cooling water inlet 28, a cooling water outlet 29 and a temperature measuring hole 30 are respectively arranged on the side wall of the bearing seat cavity 24.

As shown in fig. 1, 9, 10 and 11, an adjusting box sleeve 31 is further disposed between the air inlet port 2 and the corresponding expansion sleeve 5, one end of the adjusting box sleeve 31 is mounted at the air inlet port 2, the expansion sleeve 5 at the air inlet port 2 is mounted at the other end of the adjusting box sleeve 31 through a guide ring 6, a plurality of rotating shafts 32 are rotatably connected inside the adjusting box sleeve 31, the rotating shafts 32 are parallel to each other and located on the same horizontal plane, guide blades 33 are fixed on the rotating shafts 32, the lengths of the guide blades 33 are matched with the width of the inner side of the adjusting box sleeve 31, the sum of the widths of all the guide blades 33 is matched with the length of the inner side of the adjusting box sleeve 31, and a rotation control device connected with the rotating shafts 32 is disposed on the adjusting box sleeve 31.

The end part of the rotating shaft 32 penetrates through the side wall of the adjusting box sleeve 31 and is arranged outside the adjusting box sleeve 31, the end part of the rotating shaft 32 is provided with a linkage handle 34, the rotation control device comprises a linkage plate 35, one end of the linkage handle 34 is fixedly connected with the rotating shaft 32, the other end of the linkage handle 34 is hinged with the linkage plate 35, the end part of one rotating shaft 32 is fixedly provided with a driving handle 36 and a pointer 37, the driving handle 36 and the linkage handle 34 are both positioned at one end of the rotating shaft 32, the pointer 37 is positioned at the other end of the rotating shaft 32, and the outer side wall of the adjusting box sleeve 31 is provided with a dial 38 matched with the position of the pointer 37.

The invention relates to a rotary fan which reversely advances by 90 degrees and outputs by 90 degrees, and an impeller 13 is a reversely rotating impeller. The main shaft 12 is an integrally forged shaft, is installed and fixed through a rolling bearing, has enough rigidity and strength, is connected with the variable frequency motor through a coupler and a liquid couple, and is driven by the variable frequency motor to work.

The casing 1 comprises a volute 10 and an air inlet box 11, which are all formed by welding steel plates made of Q235 materials, and the side surfaces of the casing 1 are provided with reinforced flat steel, so that large deformation is avoided in the transportation, installation and operation processes.

Through the design of the expansion sleeve 5 between the pipeline and the port, the installation error between the port and the pipeline can be compensated, the thermal expansion difference between the port and the pipeline, which is generated due to different wall temperatures, can be compensated, and the axial load of the port and the pipeline is reduced, so that the temperature difference stress between the port and the pipeline is reduced, the strength damage, the instability damage and the pipeline pull-off damage are avoided, and the sealing property between the connecting pipeline and the air inlet/outlet port is improved.

An annular sealing block 15 (a sealing ring 17) is arranged at the position, extending out of the shell through hole 14, of the main shaft 12 for sealing, so that good air tightness of the shell 1 is guaranteed, and air leakage loss of the shell 1 is reduced.

In operation, the variable frequency motor drives the main shaft 12 and the impeller 13 thereon to rotate, so that air is sucked into the air inlet box 11 through the air inlet port 2 and discharged through the air outlet port 3 on the volute casing 10. When the air volume needs to be adjusted, the driving handle 36 drives the corresponding rotating shaft 32 and the guide blades 33 thereon to rotate (the driving handle 36 can be controlled manually or by an external electric actuator), and at this time, under the transmission action of the linkage handle 34 and the linkage plate 35, the guide blades 33 on other rotating shafts 32 can be driven to synchronously rotate, so that the purpose of adjusting the air volume is achieved. During the rotation of the rotating shaft 32, the pointer 37 on the rotating shaft 32 also rotates along with the rotating shaft 32, and through the design of the pointer 37 and the dial 38, the pointer functions as an indication, so that the working state at the air inlet port 2 can be directly known by the staff.

Claims

1. The utility model provides a short burning secondary fan structure of low resistance, characterized by includes casing (1), the internally mounted of casing (1) has the rotor subassembly, be equipped with inlet port (2) and the port of giving vent to anger (3) on casing (1), inlet port (2) and the port of giving vent to anger (3) department all install sealing device (4), sealing device (4) are including inflation cover (5), guide ring (6) are all installed at the both ends of inflation cover (5), and two inflation covers (5) are installed respectively on inlet port (2) and the port of giving vent to anger (3) through guide ring (6).

2. The low-resistance combustion-promoting secondary fan structure as claimed in claim 1, wherein the expansion sleeve (5) comprises an outer sleeve (7) and an inner sleeve (8), the port of the inner sleeve (8) is installed on the inner side wall of the guide ring (6), the guide ring (6) is provided with an annular installation groove (9) matched with the port of the outer sleeve (7), the port of the outer sleeve (7) is installed in the annular installation groove (9) of the guide ring (6), and the outer sleeve (7) is arranged on the outer side of the inner sleeve (8).

3. The structure of the low-resistance combustion-promoting secondary air fan as claimed in claim 2, wherein the inner sleeve (8) is made of silica gel cloth, and the outer sleeve (7) is made of stainless steel wire cloth.

4. The low-resistance combustion-promoting secondary fan structure according to claim 1, wherein the casing (1) comprises a volute (10), an air inlet box (11) is arranged on the side surface of the volute (10), the interior of the volute (10) is communicated with the interior of the air inlet box (11), the rotor assembly comprises a main shaft (12), one end of the main shaft (12) penetrates through the side wall of the air inlet box (11) and is in sealed and rotating connection with the air inlet box, the other end of the main shaft (12) penetrates through the side wall of the volute (10) and is in sealed and rotating connection with the air inlet box, an impeller (13) is mounted on the main shaft (12), and the impeller (13) is located inside the volute (10).

5. The low-resistance combustion-promoting secondary air fan structure as claimed in claim 4, wherein the air inlet port (2) is located on the surface of the air inlet box (11), and the air outlet port (3) is located on the surface of the volute (10).

6. The low-resistance combustion-promoting secondary air fan structure according to claim 4, wherein casing through holes (14) matched with two ends of the main shaft (12) are formed in two sides of the casing (1), the end portion of the main shaft (12) penetrates through the casing through holes (14) and is arranged on the outer side of the casing (1), an annular sealing block (15) is installed on the surface of the casing (1) and located at the casing through holes (14), the annular sealing block (15) is sleeved on the outer side of the main shaft (12), an annular sealing groove (16) is formed in the inner side wall of the annular sealing block (15), and a sealing ring (17) in contact with the main shaft (12) is installed in the annular sealing groove (16).

7. The low-resistance combustion-promoting secondary fan structure as claimed in claim 6, wherein an outward flange (18) is fixed on the outer side wall of the annular sealing block (15), an L-shaped pressing plate (19) is arranged on the surface of the shell (1), the L-shaped pressing plate (19) is annularly distributed around the annular sealing block (15), the end of one side edge of the L-shaped pressing plate (19) is fixed on the surface of the shell (1), the outward flange (18) is installed between the surface of the shell (1) and the other side edge of the L-shaped pressing plate (19), a side through hole (20) is arranged on the other side edge of the L-shaped pressing plate (19), a stud (21) matched with the side through hole (20) is further fixed on the surface of the shell (1), the stud (21) is arranged in the side through hole (20) and movably connected with the side through hole, and a fastening nut (22) is in threaded connection with the stud (21), the fastening nut (22) and the flanging (18) are respectively positioned at two sides of the other side edge of the L-shaped pressing plate (19).

8. The low-resistance combustion-promoting secondary fan structure as claimed in claim 4, wherein bearing seats (23) matched with two ends of the main shaft (12) are fixed on two sides of the shell (1), the end portion of the main shaft (12) penetrates through a shell through hole (14) to be mounted on the bearing seats (23) and is in sealed rotary connection with the bearing seats, one end of the main shaft (12) is mounted inside one of the bearing seats (23), the other end of the main shaft (12) penetrates through the other bearing seat (23), a bearing seat cavity (24) is arranged inside the bearing seat (23), a bearing body (25) is arranged in the bearing seat cavity (24), the bearing body (25) is sleeved on the main shaft (12), a horizontal vibration measuring point (26) and a vertical vibration measuring point (27) are respectively arranged on the side wall of the bearing seat cavity (24), and a cooling water inlet (28), A cooling water outlet (29) and a temperature measuring hole (30).

9. The low drag combustion-promoting overfire air blower structure of claim 1, an adjusting box sleeve (31) is also arranged between the air inlet port (2) and the corresponding expansion sleeve (5), one end of the adjusting box sleeve (31) is arranged at the air inlet port (2), the expansion sleeve (5) at the air inlet port (2) is arranged at the other end of the adjusting box sleeve (31) through a guide ring (6), a plurality of rotating shafts (32) are rotatably connected inside the adjusting box sleeve (31), the rotating shafts (32) are parallel to each other and are positioned on the same horizontal plane, guide blades (33) are fixed on the rotating shafts (32), the length of the guide vanes (33) is matched with the width of the inner side of the adjusting box sleeve (31), the sum of the widths of all the guide vanes (33) is matched with the length of the inner side of the adjusting box sleeve (31), and a rotation control device connected with the rotating shaft (32) is arranged on the adjusting box sleeve (31).

10. The low drag combustion-promoting overfire air blower structure of claim 9, the end part of the rotating shaft (32) penetrates through the side wall of the adjusting box sleeve (31) and is arranged outside the adjusting box sleeve (31), a linkage handle (34) is arranged at the end part of the rotating shaft (32), the rotation control device comprises a linkage plate (35), one end of the linkage handle (34) is fixedly connected with the rotating shaft (32), the other end of the linkage handle (34) is hinged with the linkage plate (35), a driving handle (36) and a pointer (37) are fixed at the end part of one rotating shaft (32), the driving handle (36) and the linkage handle (34) are both positioned at one end of the rotating shaft (32), the pointer (37) is positioned at the other end of the rotating shaft (32), and a dial (38) matched with the pointer (37) in position is arranged on the outer side wall of the adjusting box sleeve (31).