JP2007120450A - Blower system correcting blower rotation speed according to air temperature - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate shift of an air ratio and always maintain the correct air ratio even when air density is changed with a change of air temperature. <P>SOLUTION: The blower system 4 enables adjustment of an air supply amount for combustion by varying blower rotation speed and is provided with a charge air temperature detection device 12 for detecting air temperature for detection combustion, and an air-ratio stabilization control device 7 for controlling the rotation speed of a blower based on the air temperature for detection combustion. The air-ratio stabilization control device 7 is set with air temperature for reference combustion and reference rotation speed for every combustion quantity. When the combustion quantity is changed, the air-ratio stabilization control device calculates correction rotation speed corrected in response to air temperature from the detection combustion air temperature at the present time before the combustion quantity change, the reference combustion air temperature and the reference rotation speed for the combustion quantity after the change of the combustion quantity and adjusts the rotation speed of the blower 5 so that it gets to the calculated correction rotation speed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a blower that corrects the rotational speed of a blower according to the air temperature.

  As described in Japanese Patent Application Laid-Open No. 2002-130185, the amount of blown air is controlled by changing the rotational speed of the blower according to the amount of combustion. In the invention described in Japanese Patent Laid-Open No. 2002-130185, an inverter device is connected to a blower, and the amount of blown air is adjusted by changing the frequency of supplied power. When supplying combustion air to the combustion device, it is necessary to supply the combustion air so that a predetermined air ratio is obtained, and therefore, it is necessary to adjust the blast amount in accordance with the combustion amount set in multiple stages. In this case, if the blower rotation speed is set for each combustion amount, it should be possible to maintain a predetermined air ratio. However, since the specific gravity of air changes due to changes in temperature, the air ratio is There was a problem of shifting.

  Since the air density varies depending on the temperature, when the air temperature increases and the air density decreases, the amount of oxygen in the fixed volume decreases. In order for the fuel to burn, oxygen is required at a certain rate, but if it is set to supply a certain volume of air with respect to the amount of fuel, the amount of oxygen will be reduced by changing the air density. Excess or deficiency occurs. It was necessary to change the setting of the combustion air supply for each season because the amount of oxygen was insufficient in the summer when the temperature was high and the amount of oxygen was excessive in the winter when the temperature was low.

  However, since it is cumbersome to check the air ratio every season and change the setting of the air supply amount, Japanese Patent Laid-Open No. 2002-130185 makes it possible to detect the air flow rate of the blower. In addition, it is described that the rotational speed of the blower is controlled so as to obtain a predetermined air flow rate. And when changing the combustion amount, in order to quickly switch to the blast amount after changing the combustion amount, at the time of switching the combustion amount, the blower rotation speed after switching should be adjusted to be the rotation speed at the same previous combustion amount Has been proposed.

  The change in air temperature due to the change of season changes gradually over a long period of time, so if the blower rotation speed after switching is the rotation speed at the same combustion amount as the previous time, the air ratio will be almost appropriate be able to. However, in this case, if the air temperature is different from the previous combustion amount even if the combustion amount is the same, the problem arises that the air ratio deviates from the appropriate value. For example, in a boiler, the combustion air is preheated by using heat radiation from the periphery of the can body. In this case, the temperature of the combustion air greatly changes due to a change in the amount of heat radiation. Immediately after the start-up when the boiler temperature is low, there is little heat radiation from the boiler, so the combustion air at room temperature is supplied without preheating the air. However, when the boiler burns and the can body temperature rises, the amount of heat released from the boiler increases and the air is preheated, so the combustion air temperature increases. In this case, since the air temperature changes rapidly, the air density changes due to the air temperature change even when the air flow rate is changed to the previous air flow rate when the combustion amount is changed. I couldn't.

In addition, when the combustion amount is set in stages such as high combustion and low combustion, the larger the combustion amount, the larger the heat release amount, so that the combustion air temperature varies depending on the combustion state. Since the combustion air temperature changes after the change of the combustion amount, the combustion air temperature when starting a certain combustion amount is different from the combustion air temperature when ending the combustion amount. Since the required air amount is different even when the combustion amount is the same, there is a problem in that an appropriate air ratio cannot be obtained by adjusting the final blown air amount at the same previous combustion amount when the combustion amount is changed.
JP 2002-130185 A

  The problem to be solved by the present invention is to prevent the air ratio from deviating even when the air density changes due to a change in the air temperature, and to always maintain an appropriate air ratio.

In the first aspect of the present invention, combustion air is supplied to a combustion device that performs combustion at values set stepwise such as high combustion and low combustion, and the combustion air is changed by changing the rotational speed of the blower. In a blower that enables adjustment of the air supply amount, a supply air temperature detection device that detects a detected combustion air temperature, which is a temperature of combustion air, and a rotation speed of the blower is controlled based on the detected combustion air temperature An air ratio stability control device is provided, and in the air ratio stability control device, a reference combustion air temperature and a reference rotation speed are set for each combustion amount,
When the combustion amount is constant, the air ratio stability control device corrects the current combustion air temperature, the reference combustion air temperature at the current combustion amount, and the reference rotation speed in accordance with the air temperature. When calculating the corrected rotation speed and adjusting the rotation speed of the blower so that the calculated correction rotation speed is obtained, and when changing the combustion amount, the detected combustion air temperature at the present time and the combustion before changing the combustion amount From the reference combustion air temperature and the reference rotation speed in the combustion amount after the amount change, calculate the corrected rotation speed corresponding to the air temperature and adjust the rotation speed of the blower so as to be the calculated correction rotation speed It is characterized by.

の補正回転数算出式にて行うことを特徴とする空気温度に応じて送風機回転数の補正を行うことを特徴とする。 According to a second aspect of the present invention, in the blower device that corrects the blower rotational speed according to the air temperature, the correction rotational speed is calculated by calculating the high combustion correcting rotational speed and the low combustion correcting rotational speed, respectively. Is what

The correction of the rotational speed of the blower is performed according to the air temperature, which is characterized in that the rotational speed of the blower is corrected.

  According to a third aspect of the present invention, in the blower device that corrects the rotational speed of the blower according to the air temperature, the blower device adjusts the rotational speed of the blower by changing the power supply frequency by the inverter device. Features.

  By implementing the present invention, even when the air density is rapidly changing due to a rapid change in the air temperature or the combustion air temperature is changing due to the combustion amount, the air ratio is changed at the time of switching the combustion amount. It is possible to always maintain an appropriate air ratio.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional explanatory view showing an outline of a blower apparatus for carrying out the present invention, FIG. 2 is a flowchart of the present embodiment, FIGS. 3 and 4 are blower frequencies with respect to combustion state and air temperature in the present embodiment. It is explanatory drawing which showed the relationship.

  FIG. 1 shows a boiler 1 in which a combustion chamber is provided in the center and a water pipe is arranged around the combustion chamber, and a burner 2 is installed at the upper center. The burner 2 performs three-position combustion control of high combustion, low combustion, and stop, a fuel supply device 3 capable of supplying a high combustion fuel amount and a low combustion fuel amount, and a combustion amount corresponding to the combustion amount The blower 4 that supplies the air amount is connected. The blower 4 includes a blower 5 that sends air to the burner 2 through the air duct 11, a motor 6 that rotates the rotor blades of the blower, and an air ratio stability controller 7 that controls the rotational speed of the motor 6. The air ratio stability control device 7 is provided with an inverter device 8 that changes the power supply frequency output to the motor, and an air flow control circuit 9 that determines the frequency output by the inverter device. Determine the air supply volume.

  The boiler burns a flame in a combustion chamber provided in the center, absorbs heat by a water pipe disposed around the combustion chamber, and evaporates can water in the water pipe. The outer surface of the can body made of a water pipe or the like is covered with a heat insulating material, and the periphery thereof is covered with an outer shell, and a number of slit-like air inlets 13 are opened in the outer shell. A space for air preheating is provided between the can body and the outer shell, the blower 5 is connected so as to suck the air in the outer shell, and the air sent to the burner 2 is sent from the air inlet 13 to the boiler can body. It flows around the part, enters the blower 5, passes through the air duct 11, and is sent to the burner 2. In order to detect the temperature of the combustion air preheated around the boiler can body, a supply air temperature detection device 12 is provided downstream of the preheating portion of the combustion air flow, and the detection detected by the supply air temperature detection device 12 The value of the combustion air temperature is output to the air flow control circuit 9 in advance.

The burner combustion amount is controlled based on the steam pressure value in the boiler. When the steam pressure value is low, combustion is high, when the steam pressure value is high, combustion is stopped, and the steam pressure value is in the middle. In some cases, the amount of combustion is controlled at three positions of low combustion. The combustion control device 10 that performs combustion control is connected to the burner 2, the fuel supply device 3, and the blower device 4. The combustion control device 10 determines the amount of combustion, and the fuel supply device 3 receives a signal from the combustion control device. A predetermined amount of fuel is supplied based on Although the combustion air supply amount is also supplied in correspondence with the fuel amount determined by the combustion control device 10, the combustion air supply amount needs to be corrected according to the change in the air density. For this reason, the following correction rotational speed (frequency) calculation formula is set together with the combustion air supply amount in the standard state, and the corrected combustion air amount is supplied.

  In the case of boilers, in order to obtain an optimal combustion state without being affected by individual differences or installation environment, the combustion air supply amount is set during a test operation performed immediately after installation. In the setting at the time of trial operation, at the time of low combustion, by finding the point at which the combustion state is optimal by increasing or decreasing the rotation speed of the blower, it is input to the air ratio stability controller 7 as the low combustion reference rotation speed, The combustion air temperature at the time of setting is detected and input to the air ratio stability control device 7 as the reference combustion air temperature for low combustion. Similarly, at the time of high combustion, the point at which the combustion state becomes optimal is found by increasing / decreasing the rotation speed of the blower, and is input to the air ratio stability control device 7 as the high combustion reference rotation speed and set. The combustion air temperature at the time is detected and input to the air ratio stability control device 7 as the reference combustion air temperature for high combustion.

  This will be described based on the flowchart of FIG. First, the air flow control circuit 9 reads the detected combustion air temperature detected by the supply air temperature detection device 12 and calculates the corrected rotational speed. If you know the current combustion air temperature, you can use the corrected rotational speed calculation formula that substitutes the reference rotational speed for low combustion and the standard combustion air temperature to calculate the corrected rotational speed for low combustion. The high combustion correction rotational speed can be calculated using a correction rotational speed calculation formula in which the rotational speed and the reference combustion air temperature are substituted.

  Further, the blast amount control circuit 9 reads a combustion command output from the combustion control device 10. When the 3-position combustion control is performed, the combustion command is one of high combustion / low combustion / stop. The value of the blower rotational speed (corrected rotational speed) to be output to the inverter device 8 is determined in accordance with the read combustion command. If the combustion command is high combustion, the high rotational speed for combustion is output and low combustion is performed. If there is, output a low combustion correction rotational speed. Further, when a command to stop combustion is output, the output of the rotation speed 0, that is, the operation of the blower is stopped. In the inverter device 8, the value of the power supply frequency supplied to the motor 6 is changed according to the rotational speed command from the blower amount control circuit 8, and a predetermined amount of air is supplied by adjusting the blower rotational speed. The above control is repeated, and if the air temperature changes, the rotational speed is corrected at that time. Although the present embodiment shows the case of three-position combustion control, the concept of the present invention control can be applied even when the combustion control other than the three-position combustion control is performed. For example, in the case of four-position combustion control in which medium combustion is performed in addition to high combustion and low combustion, the correction rotation speed for medium combustion may be calculated.

  Next, an example of air flow control will be described with reference to FIGS. In this embodiment, the reference combustion speed (frequency) for low combustion set during the test operation is 25 Hz, the reference combustion air temperature for low combustion, which is the combustion air temperature at the time of setting, is 30 ° C., and the reference rotation speed for high combustion is set. (Frequency) is 55 Hz, and the standard combustion air temperature for high combustion is 40 ° C. Since the amount of heat for preheating the combustion air differs between low combustion and high combustion, the combustion air temperature is higher during high combustion. Moreover, the combustion air temperature change is modeled and it demonstrates as what changed as the figure. Note that the rotational speed of the blower 5 and the power supply frequency supplied to the motor 6 are in a substantially proportional relationship, and in an actual apparatus, setting based on the frequency is widely performed. The value is set with the value of the power supply frequency.

  3 and 4 start from a state where combustion is stopped, respectively, low combustion starts at points A and I, transitions to high combustion at points C and K, and low combustion again at points E and M. High combustion occurs at points G and O. FIG. 3 is in the summer when the temperature is high, and initially the combustion of the boiler is stopped, and the combustion air temperature is not preheated. In this state, the temperature detected by the supply air temperature detection device 12 is equal to the boiler chamber temperature and is 35 ° C. When the combustion is stopped, the blower frequency is 0 Hz because the blower is also stopped.

  Since low combustion is performed from the point A, it is necessary to supply air for low combustion. At this time, the detected combustion air temperature detected by the supply air temperature detection device 12 is 35 ° C., which is 5 ° C. higher than the low combustion reference combustion air temperature of 30 ° C. As the air temperature rises, the amount of oxygen in the fixed volume decreases from the reference time, so that the amount of oxygen will be insufficient unless more air is supplied than at the reference time. The blower amount control circuit 9 calculates the corrected rotational speed at low combustion by substituting a value into the corrected rotational speed calculation formula.

  Since the correction speed for low combustion = 25 × (273 + 35) / (273 + 30) = 25.4, the blower amount control circuit 9 sends a command to the inverter device 8 so that the output frequency is 25.4 Hz. The inverter device 8 sets the power frequency supplied to the motor 6 to 25.4 Hz, and increases the blower rotational speed by 0.4 Hz from the low combustion reference rotational speed. By setting the air blower frequency to 25.4 Hz instead of 25 Hz, the air supply amount was increased to compensate for the decrease in the oxygen amount in a certain volume due to the decrease in the air density due to the increase in air temperature. Can be supplied, and stable combustion can be performed. At this time, the correction rotational speed in the case of high combustion is also calculated in the control program. However, since the output is not performed, description such as calculation of the high combustion correction rotational speed is omitted.

  When combustion starts, the temperature of the can increases, and the amount of heat leaking from the can increases as the temperature of the can increases. The combustion air flowing around the can body toward the blower 5 absorbs heat from the can body, and thus the temperature rises. The combustion air temperature starts to rise from point B, and the correction amount of rotation for low combustion that changes with the rise in the detected combustion air temperature detected by the supply air temperature detection device 12 in the air flow control circuit 9. The value of the blower frequency output to the inverter device 8 is changed according to the value of.

  The combustion air temperature at the time point C is 40 ° C., and the combustion is low until point C. Therefore, the blower frequency at this time is the low combustion correction rotational speed = 25 × (273 + 40) / (273 + 30) = 25.8 Hz. In order to change the combustion amount from point C to high combustion, the air supply control circuit 9 sets the combustion air supply amount for high combustion. In this case, the blower frequency output from the air flow control circuit 9 to the inverter device is a value for the high combustion calculated from the detected combustion air temperature at point C, the high combustion reference combustion air temperature, and the high combustion reference rotational speed. This is the corrected rotation speed. Here, since the reference combustion air temperature and the detected combustion air temperature accidentally have the same value, the high combustion correction rotational speed = 55 × (273 + 40) / (273 + 40) = 55, and the air flow control circuit 9 is A command is output to change the blower frequency to 55.0 Hz.

  Since the combustion air temperature changes with a change in the amount of heat released from the boiler, the detected combustion air temperature continues to rise even after the blower frequency is changed to 55.0 Hz. It has risen to 55 ° C. When the detected combustion air temperature rises, the high combustion correction rotational speed also rises, so that the blower frequency rises to 57.6 Hz at the point D. The combustion air temperature is determined by the amount of heat released from the can body. Here, the combustion air temperature does not change after reaching 55 ° C., and the blower frequency is constant during that time.

  At point E, the combustion amount is changed from high combustion to low combustion. In this case, the corrected rotational speed is a value calculated from the detected combustion air temperature at the point E detected by the supply air temperature detecting device, the low combustion reference combustion air temperature, and the low combustion reference rotational speed. Low combustion correction rotational speed = 25 × (273 + 55) / (273 + 30) = 27.1 Hz. The air flow control circuit 9 outputs a command to the inverter device 8 so as to change the frequency to 27.1 Hz. Since the combustion air preheating amount at the time of low combustion stays only at about 10 ° C. from room temperature, the detected combustion air temperature decreases toward point F, and the blower frequency also decreases to point F. Since the detected combustion air temperature after point F is stable at 45 ° C., the blower frequency also maintains a value of 26.2 Hz.

  When the combustion state is changed from low combustion to high combustion at point G, the blower frequency in this case also becomes 55.9 Hz, which is a high combustion value corresponding to the detected combustion air temperature at point G. After that, since the detected combustion air temperature has increased to 55 ° C. at the point P, the blower frequency has also been increased to 57.6 Hz.

  Since the combustion air temperature at the point C at which the first low combustion ends is 40 ° C., the optimum blower frequency at the end of the low combustion is 25.8 Hz. However, since the combustion air temperature at the point E at which the second low combustion is started is 55 ° C., the optimum blower frequency at the start of the low combustion is 27.1 Hz. Similarly, since the combustion air temperature at the point E when the first high combustion ends is 55 ° C., the optimum blower frequency at the end of the high combustion is 57.6 Hz. Since the combustion air temperature at the point G at which the second high combustion starts is 45 ° C., the optimum blower frequency at the start of the high combustion is 55.9 Hz. In the control according to the present invention, when changing the combustion amount, the corrected rotation speed is calculated from the detected combustion air temperature at the time before the combustion amount is changed, and the reference combustion air temperature and the reference rotation speed in the combustion amount after the combustion amount is changed. Since the rotational speed of the blower is adjusted so that the calculated corrected rotational speed is obtained, even when the combustion air temperature changes, the optimal air ratio can always be obtained.

  FIG. 4 is in the winter when the temperature is low. In this case as well, when the correction rotational speed is calculated for each air temperature as in FIG. 3, the result is as shown in FIG. In the summer when the temperature is high, the blower frequency is larger than the reference value. In the winter when the temperature is low, the blower frequency is smaller than the reference value.

  In the case of FIG. 4, the combustion air temperature at the time point K at which the first low combustion ends is 10 ° C., so the optimum blower frequency at the end of the low combustion is 23.3 Hz. And since the air temperature for combustion in the point M which starts the low combustion of the 2nd time is 25 degreeC, the optimal air blower frequency at the time of the low combustion start is 24.6 Hz. Similarly, since the combustion air temperature at the point M at which the first high combustion ends is 25 ° C., the optimum blower frequency at the end of the high combustion is 52.4 Hz. Since the combustion air temperature at the point O where the second high combustion is started is 15 ° C., the optimum blower frequency at the start of the high combustion is 50.6 Hz. In this case as well, the corrected rotational speed is calculated from the detected combustion air temperature at the time before the change of the combustion amount, the reference combustion air temperature and the reference rotational speed at the combustion amount after the change of the combustion amount, and becomes the calculated corrected rotational speed. Thus, since the rotation speed of the blower is adjusted, even when the combustion air temperature is changed, it is possible to always obtain an optimum air ratio.

  When changing the combustion amount, when controlling the blower speed at the same previous combustion amount, if the combustion air temperature is not the same between the previous and current, there is a problem that the air ratio collapses. It was. However, as described above, the corrected rotation corrected according to the air temperature from the detected combustion air temperature at the present time before the combustion amount change, the reference combustion air temperature and the reference rotation speed in the combustion amount after the combustion amount change. By calculating the number, even when the air temperature is changing, the optimum air ratio can always be maintained, and stable combustion can be performed.

Partial sectional explanatory drawing which showed the outline | summary of the air blower which implements this invention Flow chart of this embodiment Explanatory diagram showing the relationship of the blower frequency to the combustion state and air temperature Explanatory diagram showing the relationship of the blower frequency to the combustion state and air temperature

Explanation of symbols

1 boiler
2 Burner
3 Fuel supply device
4 Blowers
5 Blower
6 Motor
7 Air ratio stability controller
8 Inverter device
9 Air flow control circuit
10 Combustion control device
11 Air Duct 12 Supply Air Temperature Detection Device
13 Air inlet

Claims (3)

Combustion air is supplied to a combustion device that performs combustion at values set in stages, such as high combustion and low combustion, and the amount of combustion air supply can be adjusted by changing the rotational speed of the blower In the blower, an air supply temperature detector that detects the detected combustion air temperature, which is the temperature of the combustion air, and an air ratio stability controller that controls the rotational speed of the blower based on the detected combustion air temperature are provided. In the specific stability control device, the reference combustion air temperature and the reference rotation speed are set for each combustion amount,
When the combustion amount is constant, the air ratio stability control device corrects the current combustion air temperature, the reference combustion air temperature at the current combustion amount, and the reference rotation speed in accordance with the air temperature. When calculating the corrected rotation speed and adjusting the rotation speed of the blower so that the calculated correction rotation speed is obtained, and when changing the combustion amount, the detected combustion air temperature at the present time and the combustion before changing the combustion amount From the reference combustion air temperature and the reference rotation speed in the combustion amount after the amount change, calculate the corrected rotation speed corresponding to the air temperature and adjust the rotation speed of the blower so as to be the calculated correction rotation speed A blower that corrects the rotational speed of the blower according to the air temperature. In the air blower that corrects the blower rotation speed according to the air temperature according to claim 1, the calculation of the correction rotation speed is to calculate the correction rotation speed for high combustion and the correction rotation speed for low combustion, respectively.

An air blower that corrects the rotational speed of the blower according to the air temperature, which is performed using a formula for calculating the rotational speed of the air.   3. A blower that corrects the rotational speed of the blower according to the air temperature according to claim 1 or 2, wherein the blower adjusts the rotational speed of the blower by changing a power supply frequency by an inverter device. A blower that corrects the rotational speed of the blower according to the air temperature.

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