JP2005344695A - Small boiler carrying high-speed blower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size of the boiler package of a small boiler such as a small once-through boiler and a vacuum type water heater by improving a blower. <P>SOLUTION: This small boiler carries the high-speed blower 10 having an impeller 11 with a rotary vane 15 directly coupled to a drive motor 13 and having the maximum speed rated value of 10,000 rpm or higher. Also, the impeller 11 is of the cast or forged type. The high-speed blower 10 is desirably an axial type blower or a mixed flow type blower in which the impeller 11, a drive motor 12, and a fixed vane 14 are stored in a same casing 13. Also, the rotational speed of the drive motor 12 is controllably allowed to follow up a load by inverter control. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a small boiler such as a small once-through boiler or a vacuum hot water heater, and more particularly to downsizing of a boiler package.

The average operating load of a small once-through boiler or a vacuum hot water heater is about 30 to 40%, and the operating load fluctuates greatly, and it is required to supply heat stably with respect to the load fluctuation. In order to perform high-efficiency operation while dealing with such load fluctuations, these small boilers generally perform unit control operation using a multi-can arrangement. When placing multiple cans, it is natural that the installation volume of multiple small-capacity cans corresponding to the capacity of one large-capacity can is naturally required, so the boiler package is becoming increasingly smaller. It is out. An example of a small boiler with a multi-can arrangement is disclosed in Patent Document 1 below.
JP-A-9-159102

  When attention is paid to auxiliary equipment other than the boiler main body in the small boiler, the burner occupies the largest volume, and among them, the proportion of the blower is large.

In addition, there is a tendency for the boiler body to be miniaturized per combustion amount, and the combustion chamber load of a small once-through boiler with an evaporation amount of 2 t / h class reaches 5000 kW / m ³ h or more. In addition to this, in the convection heat transfer section where the combustion gas passes through the water tube group, the flow velocity of the combustion gas reaches 50 m / s or more. In view of these pressure losses, a blower that can supply higher-pressure air is required to shorten the flame more than this, but this causes problems of power, cost, and enlargement of the blower.

  Conventionally, a centrifugal fan has been used as a blower (see, for example, Patent Document 1). Further, the size of the blower has been reduced by increasing the rotation speed (high-speed rotation) of the conventional centrifugal blower using a belt-mounted transmission. However, at present, the rotational speed remains at about 5000 rpm due to problems such as the load applied to the bearing, the impeller strength limit, and cost.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a small boiler capable of reducing the size of a boiler package by improving a blower.

  In order to achieve this object, the first characteristic configuration of the small boiler according to the present invention is that an impeller provided with rotating blades is directly connected to a drive motor and is equipped with a high-speed blower whose maximum rated value of rotational speed is 10,000 rpm or more. It is in the point.

  According to said 1st characteristic structure, since the impeller diameter of a high-speed air blower can be made small, the casing dimension which accommodates an impeller and a drive motor can also be made small, and size reduction of a boiler package can be achieved. More specifically, when the air amount, required pressure, and power of the blower are the same, the pressure increase Δp is the square of the product of the impeller diameter d and the rotational speed N as shown in the following formula 1. Since the power P is proportional to the product of the pressure increase Δp and the required air amount Q, the impeller diameter d changes in inverse proportion to the rotational speed N when only the rotational speed N is changed. Note that a and b in Equation 1 are proportional coefficients, respectively.

(Equation 1)
Δp = a · d ² · N ²
P = b · Q · Δp = a · b · Q · d ² · N ²

  For example, when considering a rotation speed of 3600 rpm when a two-pole motor is operated at 60 Hz as a reference, assuming that the impeller diameter and casing dimensions at a rotation speed of 3600 rpm are 100%, the impeller diameter is 36% and the casing dimensions at a rotation speed of 10,000 rpm. Can be reduced to 50% or less. Here, the reduction ratio of the casing dimension is larger than the reduction ratio of the impeller diameter because the air amount is the same in the scroll portion in order to convert the dynamic pressure obtained by accelerating the air with the impeller into the static pressure. If there is, the fluid passage is constant regardless of the rotational speed, so that a value obtained by adding a certain constant value to the impeller diameter is the casing dimension.

  In the first characteristic configuration, the high rotation speed required for downsizing the blower is realized by directly connecting the impeller to the drive motor. In other words, in the configuration using the conventional belt-mounted transmission, the rotational speed is limited to about 5000 rpm, but this characteristic configuration makes it possible to realize the rotational speed of 10,000 rpm or more.

  The second characteristic configuration is that, in addition to the first characteristic configuration, the impeller is made of cast metal, forged metal, or engineering plastic.

  According to said 2nd characteristic structure, the following problems can be solved. That is, when the blower is rotated at a higher speed and the impeller diameter is reduced, a rotational balance is strictly required. Therefore, in the assembly structure by welding (see FIG. 12), it is difficult to process the impeller. If is made of cast metal, forged metal or engineering plastic by injection molding, the problem is solved. Further, for example, a high-speed centrifugal impeller having a curved structure with a curved inlet portion and a straight outlet portion as shown in FIG. 13 and an axial flow impeller with blades having a blade shape as shown in FIG. It becomes possible to produce a simple blade shape.

  In the third feature configuration, in addition to the first or second feature configuration, the high-speed blower is an axial flow type in which the impeller, the drive motor, and the fixed blade are housed in the same casing. It is in the point which is a blower or a mixed flow type blower.

  According to the third characteristic configuration, by using an axial flow type or mixed flow type (centrifugal and axial flow type) blower as the high-speed blower, the air that has flowed in is highly efficient despite the miniaturization. The pressure can be boosted and sent out. That is, in the case of an axial blower, as shown in FIG. 6, the inflowing air is accelerated in the axial rotation direction by the impeller rotor blades, and is further efficiently decelerated by the rear stationary blades. The air that has passed through the fixed blades cools the drive motor while turning in the casing, and is decelerated as the flow path cross-sectional area further increases behind the drive motor. In this way, the inflowing air efficiently converts the velocity energy into pressure energy, is boosted, and is sent out of the casing. In the case of a mixed flow type blower, as shown in FIG. 10, the inflowing air is accelerated in the centrifugal direction and the axial rotation direction by the impeller rotor blades, and is further efficiently decelerated by the rear stationary blades. The direction velocity component is efficiently converted in the axial rotation direction. The air that has passed through the fixed blades cools the drive motor while turning in the casing, and is decelerated as the flow path cross-sectional area further increases behind the drive motor. In this way, the inflowing air efficiently converts the velocity energy into pressure energy, is boosted, and is sent out of the casing. Furthermore, since the drive motor can be reduced in size by increasing the rotation speed of the blower, the drive motor that has been conventionally arranged outside the casing can be accommodated in the casing, and the drive motor is efficiently cooled by the air flowing in the casing. be able to.

  The fourth characteristic configuration is that, in addition to the third characteristic configuration, the fixed blade and the casing are made of cast metal or engineering plastic.

  According to the fourth feature configuration, the following problems can be solved. That is, when the high-speed blower is a mixed flow type, the portion covering the impeller of the casing is a cylindrical streamlined type (see FIG. 10), and the fixed vane serving as the diffuser is a wing shape or a streamlined type (see FIG. 14). In the assembly structure by welding, it becomes difficult to process the casing and the fixed blade. However, if the casing and the fixed blade are made of metal formed by casting or engineering plastic by injection molding, the problem is solved.

  The fifth feature configuration is that, in addition to any one of the feature configurations described above, the rotational speed of the drive motor can be load-followed by inverter control.

  According to the fifth characteristic configuration described above, both the load follow-up control and the size reduction of the blower can be achieved by performing the rotation speed control, which is conventionally performed using the belt-mounted transmission, by inverter control. As a result, it is possible to solve the problems of the conventional belt-mounted transmission and realize load following control. Incidentally, as a problem of the conventional belt-mounted transmission, as shown in FIG. 15, a force that is continuously pulled to the drive motor side acts on the pulley of the impeller shaft, and particularly in a small once-through boiler that repeatedly starts and stops, It can be mentioned that the burden on the shaft and bearings becomes severe during startup.

  The sixth characteristic configuration is that, in addition to any one of the above-described characteristic configurations, the bearing that supports the rotation shaft of the drive motor is an air bearing or a ceramic bearing.

  According to the sixth characteristic configuration, it is possible to prevent the life of the rotating shaft from being shortened due to the high rotation of the drive motor.

  The seventh feature configuration is that, in addition to any one of the feature configurations described above, the drive motor is a permanent magnet synchronous motor.

  According to the seventh characteristic configuration, since the permanent magnet synchronous motor is more efficient and smaller than the induction motor, it contributes to the downsizing of the blower, and as a result, the boiler package can be further downsized.

  An embodiment of a small boiler according to the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 shows a schematic configuration diagram of a vacuum hot water heater 100 having a capacity of 580 kW equipped with a small high-speed blower as an example of a small boiler according to the present invention. In the vacuum hot water heater 100 shown in FIG. 1, the blower 20 is the same centrifugal blower as the conventional centrifugal blower shown in FIG. 12A, but the impeller 21 is directly connected to the drive motor 22, and the rotational speed of the blower is By making the (maximum rating) a high-speed rotation specification of 10,000 rpm or more, the volume reduction rate can be reduced by 50% or more with respect to the conventional centrifugal blower, and as a result, the casing of the boiler body 1 is obtained. The boiler casing 2 and the boiler package are also downsized. Here, a boiler package means the occupied part of the whole boiler containing the boiler casing 2 of the boiler main body 1, the air blower 20 provided in the outer side of the boiler casing 2, and the burner 3. FIG.

  Moreover, although not shown in figure, the rotation speed of the air blower 20 can be controlled by providing the inverter which drives the air blower 20 separately from the vacuum hot water heater 100, and controlling the output of the said inverter. Therefore, the load following operation with respect to the load fluctuation of the vacuum hot water heater 100 by the inverter control can be performed.

  The blower 20 uses an air bearing or a ceramic bearing as a bearing (not shown) that supports the rotation shaft of the drive motor 22. The drive motor 22 is preferably configured using a permanent magnet synchronous motor. Furthermore, the impeller 21 (including the rotating blades) of the blower 20 is manufactured by casting. As the material of the impeller 21, it is preferable to use AC3A (silmine) of an aluminum alloy. By using an aluminum alloy as the material of the impeller 21, although the yield strength is inferior to that of general structural steel (SS), the specific gravity is one third, so there is a margin for the allowable stress generated in the impeller during high-speed rotation. Can be made.

  Since the structure of the vacuum hot water heater itself is the same as that of the present invention (see FIG. 2), the detailed description is omitted. However, in the schematic configuration diagram of the conventional vacuum hot water heater shown in FIG. 2, a simple internal structure of the vacuum hot water heater is partially shown.

  Next, for comparison, FIG. 2 shows a schematic configuration diagram of a conventional vacuum hot water heater 200 having the same capacity. As shown in FIG. 2, in the vacuum hot water heater, since the burner 3 is disposed near the vertical center of the furnace, the blower 40 is disposed below the burner 3. This is because if the blower 40 is disposed on the upper side of the burner 3, it interferes with the heat exchanger 5, and if it is disposed on the lateral side of the burner 3, the lateral width of the boiler increases. Therefore, in the conventional vacuum hot water heater 200, the length of the leg of the can body 4 is extended to dispose the can body 4 from the bottom of the boiler casing 2 in order to dispose the large-diameter blower 40 below the burner 3. It becomes a structure which raises significantly, and the boiler casing 2 becomes high.

  On the other hand, in the vacuum hot water heater 100 according to the present invention shown in FIG. 1, since the blower 20 has a small diameter, the extension of the leg length of the can body 4 is shortened, and the boiler package is moved in the height direction and the length direction. Can be made smaller. Hereinafter, with respect to a specific example of downsizing according to the present invention, with reference to a comparison table shown in FIG. explain.

As shown in FIG. 3, in the conventional vacuum hot water heater 200, the size of the blower 40 is such that the diameter φ is 600 mm, the width W is 500 mm, and the volume V is 0.14 m ^3. In the vacuum hot water heater 100, the dimensions of the blower 20 are such that the diameter φ is 300 mm, the width W is 500 mm, the volume V is 0.04 m ^3, and the volume reduction rate is about 70%. As a result, in the conventional vacuum hot water heater 200, the dimensions of the boiler package are as follows: the width W is 800 mm, the height H is 1700 mm, the length L is 2200 mm, and the volume V is 2.99 m ³ . In the vacuum hot water heater 100 according to the present invention, the dimensions of the boiler package are as follows: the width W is 800 mm, the height H is 1400 mm, the length L is 1900 mm, the volume V is 2.13 m ³ , and the volume reduction rate is about 30%. The size is reduced.

Second Embodiment
4 and 5 show schematic configuration diagrams of small once-through boilers 300 and 400 having a capacity of 470 kW (evaporation amount: 0.75 t / h) equipped with a small high-speed blower as another example of the small boiler according to the present invention. . In the small once-through boiler 300 shown in FIG. 4, the blower 20 is a centrifugal blower similar to the conventional one as in the first embodiment, but the impeller is directly connected to the drive motor, and the rotational speed (maximum rating) of the blower is set. By adopting a high-speed rotation specification of 10,000 rpm or more, the volume reduction rate is reduced by 50% or more with respect to the conventional centrifugal blower, and as a result, a boiler casing 2 that is a casing of the boiler body 1, and The boiler casing 2 and the boiler package including the external burner 3 and the blower 20 are also downsized. In addition, about the structure and control method of the centrifugal air blower 20, since it is the same as that of 1st Embodiment, the overlapping description is abbreviate | omitted.

  Further, in the small once-through boiler 400 shown in FIG. 5, the blower 10 is an axial blower, and as shown in FIG. 6, the impeller 11 is directly connected to the drive motor 12, and the rotational speed (maximum rating) of the blower is set to 10,000 rpm. By doing in the above, size reduction is attained compared with the conventional air blower 40, As a result, the boiler casing 2 and the boiler package of a boiler main-body part are also reduced in size, respectively. In FIG. 7, the schematic diagram which compared the external shape of the conventional centrifugal air blower and the high-speed axial flow air blower 10 is shown.

  The blower 10 used in the small once-through boiler 400 shown in FIG. 5 is an axial flow blower as described above, and has the following structure. That is, as shown in FIG. 6, in the axial flow fan 10, the impeller 11 provided with the rotating blades, the drive motor 12, and the fixed blade 14 are accommodated in the same casing 13. In the example shown in FIG. 6, the fixed blade 14 is attached to the casing 13.

  Moreover, the impeller (including rotating blades) 11, the fixed blade 14, and the casing 13 of the axial flow fan 10 are manufactured by casting. Here, the material of the impeller 11 is preferably an aluminum alloy AC3A (Silmine), and the material of the fixed blade 14 and the casing 13 is a carbon steel cast steel product (SC) or a stainless steel cast steel product (SUSF). Etc. are preferably used. By using an aluminum alloy as the material of the impeller, although the yield strength is inferior to that of general structural steel (SS), the specific gravity is one third, so there is a margin for the allowable stress generated in the impeller 11 during high-speed rotation. Can be made.

  The axial blower 10 uses an air bearing or a ceramic bearing as a bearing (not shown) that supports the rotating shaft of the drive motor 12 as in the first embodiment. The drive motor 12 is preferably configured using a permanent magnet synchronous motor.

  In addition, although not shown, an inverter that drives the axial flow fan 10 is provided separately from the small once-through boiler 300, and the rotational speed of the axial flow fan 10 can be controlled by controlling the output of the inverter. it can. Therefore, the load following operation with respect to the load fluctuation of the small once-through boiler 300 by the inverter control becomes possible.

  Since the structure of the small once-through boiler itself is the same as that of the conventional one (see FIG. 8), a detailed description is omitted. However, in the schematic configuration diagram of the conventional small once-through boiler shown in FIG. 8, a simple internal structure of the small once-through boiler is partially shown.

  Next, for comparison, FIG. 8 shows a schematic configuration diagram of a conventional small once-through boiler 500 having the same capacity. Hereinafter, specific examples of downsizing according to the present invention will be described with reference to a comparison table shown in FIG. 9, using specific numerical values, taking as an example a cylindrical slim type for multi-can installation with a can width of 900 mm or less. To do.

As shown in FIG. 9, in the conventional small once-through boiler 500, the centrifugal blower 40 has a diameter φ of 600 mm, a width W of 500 mm, and a volume V of 0.14 m ^3. In the small once-through boilers 300 and 400, the dimensions of the centrifugal blower 20 and the axial blower 10 are as follows: the diameter φ is 300 mm, the width W is 500 mm, the volume V is 0.04 m ^3, and the volume reduction rate is about 70. %. As a result, in the conventional small once-through boiler 500, the dimensions of the boiler package are as follows: the width W is 800 mm, the height H is 1800 mm, the length L is 1600 mm, and the volume V is 2.30 m ^3. In the small once-through boilers 300 and 400 according to the invention, the dimensions of the boiler package are as follows: width W is 800 mm, height H is 1800 mm, length L is 1200 mm, volume V is 1.73 m ³ , and boiler package volume reduction rate is 25 % And downsizing. In this embodiment, since the height of the boiler package is not changed, the package installation area is also reduced by about 25%.

  Hereinafter, another embodiment will be described.

  <1> In the first embodiment, the case where the centrifugal blower is used as the high-speed small blower 20 has been described. However, the high-speed small blower 20 is illustrated in FIG. You may replace with the mixed flow type air blower 30. FIG.

  <2> In the second embodiment, the case where the centrifugal blower and the axial flow blower are used as the high-speed small blowers 20 and 10 has been described. However, the high-speed small blowers 20 and 10 are mixed flow type shown in FIG. You may replace with the air blower 30.

  <3> In each of the above embodiments, the case where the aluminum alloy AC3A (silmine) is used as the material of the impellers 11 and 21 has been described. However, the material of the impellers 11 and 21 is limited to that of the above embodiments. It is not a thing. For example, the material of the impellers 11 and 21 may be a forged product instead of a cast product. In this case, as a material of the impellers 11 and 21, for example, A2014 (duralumin) can be used. The material of the impellers 11 and 21 may be engineering plastics by injection molding other than castings and forgings. There are engineering plastics that are used for industrial applications compared to general-purpose plastics. Among them, those having excellent heat resistance, rigidity, and impact resistance due to glass fiber reinforcement can be used. Examples thereof include PPE (modified polyphenylene ether), PET (polyethylene terephthalate), and PPS (polyphenylene sulfide). Although these engineering plastics have a lower yield strength than general structural steel (SS), they have a specific gravity of ¼, so that allowance can be given to the allowable stress generated in the impeller during high-speed rotation.

  <4> In the second embodiment, the case where a cast such as a carbon steel cast steel product (SC) or a stainless steel cast steel product (SUSF) is used as the material of the fixed blade 14 and the casing 13 of the axial flow fan 10 will be described. However, the material of the fixed blade 14 and the casing 13 is not limited to that of the above embodiment. For example, engineering plastics by injection molding similar to the above <3> may be used.

  <5> In the second embodiment, the case where the fixed blade 14 of the axial-flow fan 10 is attached to the casing 13 has been described. For example, the fixed blade 14 is schematically illustrated in FIG. You may fix to the drive motor 12 side.

  <6> In each of the above embodiments, the vacuum hot water heater and the small once-through boiler are exemplified as the small boiler according to the present invention. However, the small boiler according to the present invention is not limited to the above embodiment. By applying the present invention to a small boiler with a limited installation area and installation volume, it is possible to achieve the same miniaturization as in the above embodiment. Moreover, in each said embodiment, the dimension illustrated and the attachment positional relationship of a small air blower are examples, and can be suitably changed along the meaning of this invention.

The schematic block diagram which shows one structural example of the vacuum hot water heater as 1st Embodiment of the small boiler which concerns on this invention Schematic configuration diagram showing one configuration example of a conventional vacuum hot water heater Comparison table of dimensions of vacuum hot water heater according to the present invention and conventional vacuum hot water heater The schematic block diagram which shows the 1st structural example of the small once-through boiler as 2nd Embodiment of the small boiler which concerns on this invention. The schematic block diagram which shows the 2nd structural example of the small once-through boiler as 2nd Embodiment of the small boiler which concerns on this invention. Sectional drawing which shows one structural example of the axial flow type air blower used for the small boiler which concerns on this invention Schematic comparing the outline of a conventional centrifugal blower and the high-speed axial blower used in the small boiler according to the present invention. Schematic configuration diagram showing a configuration example of a conventional small once-through boiler Size comparison table of small once-through boiler according to the present invention and conventional small once-through boiler Sectional drawing which shows one structural example of the mixed flow type air blower used for the small boiler which concerns on this invention Sectional drawing which shows the other structural example of the axial-flow type air blower used for the small boiler which concerns on this invention. Cross-sectional view of relevant parts showing an example configuration of an impeller of a blower formed with an assembly structure by welding Cross-sectional view of main parts and front view of main parts showing one configuration example of a high-speed centrifugal impeller Cross-sectional view of main part and front view of main part showing one configuration example of high-speed axial flow impeller The figure which shows the conventional air blower provided with the belt hanging transmission

Explanation of symbols

1: Boiler body 2: Boiler casing 3: Burner 4: Can body 5: Heat exchanger 6: Water pipe 7: Chimney 8: Hot water pipe 9: Air passage 10: High-speed small axial flow blower 11, 21: Impeller 12, 22: Drive motor 13, 23: Blower casing 14: Fixed blade 15: Rotating blade 20: High speed small centrifugal blower 24: Suction silencer 30: High speed small mixed flow blower 40: Conventional centrifugal blower 100: The present invention Small boiler (vacuum hot water heater)
200: Conventional small boiler (vacuum hot water heater)
300, 400: Small boiler according to the present invention (small once-through boiler)
500: Conventional small boiler (small once-through boiler)

Claims (7)

  A small boiler characterized in that an impeller provided with rotating blades is directly connected to a drive motor and is equipped with a high-speed blower having a maximum rated value of rotational speed of 10,000 rpm or more.   2. The small boiler according to claim 1, wherein the impeller is made of cast metal, forged metal, or engineering plastic.   The small fan according to claim 1 or 2, wherein the high-speed blower is an axial flow blower or a mixed flow blower in which the impeller, the drive motor, and the fixed blade are accommodated in the same casing. boiler.   4. The small boiler according to claim 3, wherein the fixed blade and the casing are made of cast metal or engineering plastic.   The small boiler according to any one of claims 1 to 4, wherein the rotational speed of the drive motor can be load-followed by inverter control.   The small boiler according to any one of claims 1 to 5, wherein the bearing that supports the rotating shaft of the drive motor is an air bearing or a ceramic bearing.   The small boiler according to any one of claims 1 to 6, wherein the drive motor is a permanent magnet synchronous motor.

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