GB2327492A

GB2327492A - Combustion control method

Info

Publication number: GB2327492A
Application number: GB9811505A
Authority: GB
Inventors: Si-Hwan Kim
Original assignee: Daewoo Electronics Co Ltd
Current assignee: WiniaDaewoo Co Ltd
Priority date: 1997-05-28
Filing date: 1998-05-28
Publication date: 1999-01-27
Also published as: GB9811505D0; KR19980085384A; JPH10332141A; KR100243899B1

Abstract

A combustion control method for a gas boiler establishes reference wind pressure, reference fan driving voltage, and reference flame voltage in an initial ignition time. The established reference wind pressure is compared with the wind pressure from sensor 250 in the present state. A fan driving voltage is changed according to the comparison result of the wind pressures. The fan driving voltage is changed to track the flame voltage from infrared sensor 200 in the present state to the reference flame voltage. When the flame voltage in the present state reaches the reference flame voltage, a normal fan driving voltage is set to the fan driving voltage at that time, and a normal flame voltage is set to the flame voltage at that time. Under the establishment of the normal fan driving voltage, the flame voltage in the present state is compared with the normal flame voltage. According to the comparison of the flame voltages, the fan driving voltage is changed so that the flame voltage in the present state follows the normal flame voltage.

Description

2327492 COMBUSTION CONTROL METHOD

Background of the Invention 1. Field of the Invention

The present invention relates to a combustion control method of boilers, incinerators, and like equipment wherein fuel is burned, more particularly to a combustion control method of a gas boiler which recognizes a combustion state in a burner by using air pressure in an exhaust duct, fan driving voltage, and flame voltage, and which controls air flow depending on the combustion state.

2. Description of the Prior Art

The efficient control of combustion relates to the is efficient control of the fuel and combustion oxidant, usually air. Efficient control of combustion is essential in the power industry, chemical industry, and various other process industries. The control of combustion can be used in not only the industrial application, but also boilers at apartments or houses. In general, boilers are classified as a gas boiler or an oil boiler according to the fuel to being used. Especially, because the gas boiler uses gas as the fuel, it does not generate waste gas which contaminates the environment in comparison with the oil boiler. Further, the gas boiler is easy to manage. Accordingly, it has been widely used in many houses or apartments.

The gas boiler uses a liquefied petroleum gas(LPG) or a liquefied natural gas (LNG), and heats the water with high 1 is temperature heat. generated by the fuel combustion in the burner. The heated water with high temperature is circulated through pipes installed in the room, and then heats the space of the room. Also, the boiler may supply warm water to a kitchen or bathroom.

FIG. 1 shows a conventional gas boiler, and the operation of the gas boiler is simply described below. When the user operates the boiler, a pre-purge process is run in the boiler. The pre-purge process is to completely exhaust the harmful gas remaining in a combustion room 10 and an exhaust duct 15 by the circulation of a fan 5 for a predetermined time. As soon as the pre-purge process is done, the fuel gas (LPG or LNG) is supplied to the boiler through a pipe. A gas valve 20 connected to the pipe adjusts pressure of the fuel gas to the predetermined pressure level and provides the gas to a burner 25. Under the supplement of the fuel gas, high voltage is provided to an ignition transformer 30 depending on the control signal generated f rom a MICOM (not shown in f igures) The ignition transformer 30 generates a spark discharge at an ignition plug. The combustion is started by igniting the fuel gas caused by the spark discharge.

The ignition state is detected by an infrared ray sensor 35 installed on the outside wall of the combustion room 10. That is, the infrared ray sensor 35 detects flame condition in the burner, e.g., change of wavelength depending on the color of the flame. The color of flame may be yellow or blue. If the flame color is blue, the infrared ray sensor 35 provides an electrical signal which corresponds to perfect combustion. The 2 MICOM determines the ignition process to be completely done when the MICOM receives the electric signal of perfect combustion.

is A combustion heat generated by the combustion process in the burner 25 applies heat to water passing through a heat exchanger 40 installed on an upper part of the combustion room 10. If the heated water has a predetermined temperature set by the user, the MICOM drives a circulating pump 45. The circulating pump forces the heated water to flow through the pipe installed around the room by the circulating force, and then the room is heated. A number of sensors for detecting the temperature of the heated water (not shown in the figures) are installed on the surface of the pipe lying adjacent to the heat exchanger 40. When the user wants to use the warm water, the MICOM detects a moving direction of water flowing through the pipe connected with a flow switch 50 and prevents heated water from flowing through the pipe for heating the room by changing the flowing route of the water. On the other hand, the burned gas is exhausted through an exhaust hood 55 installed at the upper part of the combustion room 10 and the exhaust duct 15 connected to an exhaust hole 60 toward the outside.

However, the conventional gas boiler has a problem that the gas boiler stops doing the combustion operation due to a head wind blowing into the exhaust duct. That is, the flame in the burner may be extinguished during the combustion process or the gas is imperfectly burned. Further, the conventional gas boiler has another problem that the gas is imperfectly 3 burned due to a favorable wind blowing from the inside the gas boiler to the combustion room. That is, when favorable wind blows to the boiler during the combustion process, the gas is imperfectly burned due to the over supply of air. The head wind represents an air flow in a condition that the exhaust gas is prevented from blowing out due to the air flow from the exterior through the exhaust duct 15, and the favorable wind represents an air flow in the other condition that the air flow generated from the inner space of the gas boiler is over supplied into the combustion room, and the gas is imperfectly burned.

Slizmary of the Invention Therefore, the present invention is developed to solve the above problems. An object of the present invention is to provide the combustion control method for a gas boiler which, in one embodiment, prevents extinguist or inperfect cstion of the flame due to the head wind durin the ction state.

9 Another object of the present invention is to provide the combustion control method for the gas boiler which, in one embodiment, prevents the inperfect combustion of the flame due to the favourable wind during the combustion operation of the gas boiler. Still another object of the present invention is to provide the combustion control method for the gas boiler which, in one embodiment, provides the optimal caTb-Lstion state by controlling the fan driving voltage according to the combustion state in the gas boiler. Still another object of the present invention is to provide the combustion control method for -the gas boiler which, in- one embodiment L-LY 4 burnP. the fuel gas by comparing the fan driving voltage, the flame voltage, and wind pressure with the established reference data and altering the fan driving voltage.

The combustion control method according to the present invention is applied to the gas boiler having a MICOM for controlling all processes of the gas boiler, a gas valve, an infrared ray sensor, a sensor for detecting the wind pressure, a fan, a circulating pump, etc. The MICOM has an embedded program for controlling the whole process in the gas boiler. The gas valve regulates a gas flow depending on the control signal obtained from the MICOM. The infrared ray sensor detects the color of flame and provides an electric signal according to the color of the flame generated from a burner during the combustion process to the MICOM. The sensor for detecting the wind pressure is installed at one side of an exhaust duct and detects a wind pressure blowing through the exhaust pipe. The fan operates by a fan driving part, provides air for combustion into the combustion room, and exhausts burnt air from the burner to the exterior. The circulating pump forces the heated water to circulate through the pipe for heating.

The combustion control method of the gas boiler according to the present invention performs as follows. First, in a step for establishing the reference data(S100), a reference wind pressure P of the gas boiler, a reference fan driving voltage V, and a reference flame voltage F are provided to and saved in the MICOM. The procedure continues to a step for comparing the wind pressures (S200). In the step for comparing the wind pressures, the reference wind pressure P is compared with the wind pressure by the fan after the ignition procedure is completed. In the step for altering the fan driving voltage(S300), the fan driving voltage is changed according to the result of the step for comparing with the wind pressures (S200). After the step for altering the fan driving voltage(S300) is completed, the procedure advances to a step for establishing normal combustion data(S500) in which the MICOM sets the fan driving voltage V1 in the present state to a normal fan driving voltage CV in normal combustion process, and sets the flame voltage F1 in the present state to a normal flame voltage CF in normal combustion process. After the step for establishing normal combustion data(S500), the procedure advances to a combustion step(S600) in which the fuel gas is burned during the predetermined time. In the combustion step( S600), after the lapse of the predetermined time the procedure advances to the step for comparing with the flame voltages(S700) in which the normal flame voltage CF in the normal combustion state is compared with the flame voltage F1 in the present combustion process. The procedure advances to the step for tracking the normal flame voltage(S800) in which the fan driving voltage is changed according to the comparison result of the flame voltages so that the MICOM tracks the flame voltage F1 to the normal flame voltage CF. After the step for tracking the normal flame voltage(S800) is completed, the procedure returns to the combustion step(S600).

The combustion control method for the gas boiler according to one embodiment of the present invention establishes the- optimal 6 1 wind pressure required in the normal combustion process by comparing the reference wind pressure with the wind pressure in the ignition process. After the normal wind pressure is established, the MICOM compares the normal flame voltage with the flame voltage. The MICOM controls the flame voltage in the present state so as to track the normal flame voltage so that the fuel gas is completely burned. That is, the flame voltage remains at the normal flame voltage as the fuel gas is completely burned. For keeping the flame voltage at the predetermined value, the MICOM controls the fan driving voltage in the gas boiler. Therefore, the combustion control method.for the gas boiler according to me anbodiment of the present invention prevents the flame from being extinguished due to the head wind during the combustion process. Further, the combustion is control method for the gas boiler according to one embodiment of the present invention prevents the fuel gas from imperfect combustion caused by the favorable wind. Therefore, the combustion control method for the gas boiler suppresses the production of pollutant caused by the imperfect combustion.

Brief description of the drawings

The above objects and other advantages of the present invention will become more apparent by describing the preferred embodiment thereof with reference to the attached drawings in which:

FIG. 1 is a schematic view of a conventional gas boiler; FIG. 2 is a partial block diagram of the gas boiler for controlling the combustion; 7 FIG. 3 is a schematic procedure block diagram showing the combustion control method for the gas boiler according to one embodiment of the present invention; FIG. 4 is a flowchart for describing the combustion control method for the gas boiler according to one elment of the present invention; FIG. 5 is a detailed procedure block diagram showing the combustion control method for the gas boiler according to me embodiment of the'present invention.

Detailed Description of the Preferred Embodiment

A description of the combustion control method for the gas boiler according to one anbodiment of the present invention will be given below in detail with reference to the accompanying drawings of is an embodiment of the present invention.

FIG. 2 is a partial block diagram of the gas boiler for controlling combustion. FIG. 3 is a schematic procedure block diagram showing the combustion control method for the gas boiler according to one wbodiment of the present invention. FIG. 4 is a flowchart for describing the combustion control method for the gas boiler according to one &nbodt of the present invention. FIG. 5 is a detailed procedure block diagram showing the combustion control method for the gas boiler according to one embodiment of the present invention.

The combustion control method for the gas boiler is applied to the gas boiler having a control MICOM 100, a gas valve 150, an infrared ray sensor 200, a sensor for detecting the wind pressure 250, a fan 300, a fan driving part 350, and 8 a circulating pump 400. The gas boiler has various reference data established by considering the normal combustion state in the design step. The MICOM 100 has an embedded program for controlling the whole process in the gas boiler. The gas valve 150 regulates a gas flow depending on the control signal obtained from the MICOM 100. The infrared ray sensor 200 detects the color of flame and provides an electric signal according to the color of the flame generated from a burner during the combustion process to the MICOM. That is, the infrared sensor detects the flame voltage depending on the combustion state and provides the flame voltage to the MICOM 100. An ignition transformer 550 generates a high voltage according to the control signal of the MICOM 100 and supplies the high voltage to an ignition plug. The sensor for detecting the wind pressure 250 installed at one side of an exhaust duct detects a wind pressure blowing through the exhaust duct, and provides the wind pressure to the MICOM 100. The circulating pump 400 forces the heated water to circulate through the pipe for heating. The fan 300 provides air for combustion into the combustion room, and exhausts burned air from the burner to the exterior by the fan driving part 350. The fan driving part 350 controls rotations per minute (R.P.M.) of the fan 300 by supplying the predetermined voltage to the fan 300. A detector for the circulation of fan 450 detects the R.P. M. of the fan 300 and provides the R.P.M. to the MICOM 100. The R.P.M. of the fan is saved in the memory of the MICOM 100. A display 500 shows the operation state of the gas boiler. An input part 600 is used to provide temperature data, time data, etc. for 9 controlling the operation of the gas boiler.

The combustion control method of the gas boiler according to one embodiment of the present invention perfo=m as follews...In the abovementioned gas boiler, first, the procedure advances to a step for establishing the reference data(S100) in which a reference wind pressure P, a reference fan driving voltage V, and a reference flame voltage F are provided to and saved in the memory of the MICOM 100.

After the step for establishing the reference data S100 is completed, an ignition process is to start. The fuel gas is supplied to the burner of the combustion room through the gas valve 150 according to the control of the MICOM 100. After that, the air for combustion process is supplied to the combustion room by the fan 300 depending on the driving signal of the fan driving part 350. Under the supplement of the fuel gas, the ignition transformer 550 generates the high voltage according to the control of the MICOM 100. The high voltage of the ignition transformer 550 generates the spark discharge at the ignition plug. The fuel gas is ignited by the spark discharge. Under this condition, the sensor for detecting the wind pressure 250 measures the wind pressure P1 of the fan in the present state and provides the wind pressure P1 of the fan to the MICOM 100. The MICOM 100 executes the step for comparing the wind pressures S200 in which the reference wind pressure P is compared with the wind pressure P1 of the fan. In the step for comparing the wind pressures S200, the MICOM determines the favorable wind state when the wind pressure Pi of the fan is higher than the reference wind pressure P, or is 1 is -the head wind state when the wind pressure P1 of the fan is lower than the reference wind pressure P.

The procedure advances to a step S300 in which the fan driving voltage is altered in the ignition process. The step for altering the fan driving voltage S300 has a step S330 for decreasing the fan driving voltage in the favorable wind state, a step S360 for increasing the fan driving voltage in the head wind state, and a step S390 for substituting the normal combustion data for the reference data.

In the step for comparing the wind pressures S200, when the wind pressure Pi of the fan is higher than the reference wind pressure P, the fan driving voltage V1 is decreased until the reference flame voltage F is higher than the flame voltage F1 in the present state. That is, if the result of the step for comparing the wind pressures S200 is the favorable wind state that air is over supplied to the combustion room, the MICOM decreases the R.P.M. of the fan to decrease the amount of air flow. The decrement of the R.P.M. of the fan may be achieved by the decrement of the fan driving voltage Vi. Accordingly as the fan driving voltage V1 is decreased, the R.P.M. of the fan 300 is decreased, and thus the amount of air flow is also decreased. The MICOM 100 executes the step S330 in which the fan driving voltage in the favorable wind state is decreased until the f lame voltage F1 is equal to or lower than the reference flame voltage F.

In the step for comparing the wind pressures S200, when the wind pressure Pi of the fan is lower than the reference wind pressure P, the fan driving voltage V1 is increased until 11 the reference flame voltage F is lower than the flame voltage F1 in the present state. That is, if the result of the step for comparing the wind pressures S200 is the head wind state that the air less supplies to the combustion room, the MICOM increases the R.P.M. of the fan 300 to increase the amount of air flow. The increment of the R.P.M. of the fan 300 may be accomplished by the increment of the fan driving voltage Vi. The increment of the fan driving voltage V1 may be confirmed by measuring the flame voltage Fl. Accordingly as the fan driving voltage V1 is increased, the R.P.M. of the fan 300 are increased, and thus the amount of air flow is also increased. The R.P.M. of the fan is continued to increase until the flame voltage F1 is equal to or higher than the reference flame voltage F. That is, the MICOM 100 executes the step S360 in is which the fan driving voltage in the head wind state is increased until the flame voltage F1 is equal to or higher than the reference flame voltage F.

After the step for altering the fan driving voltage S300 is completed, the procedure advances to a step for establishing normal combustion data S500 in which the MICOM sets the fan driving voltage V1 in the present state to a normal fan driving voltage CV, and sets the flame voltage FI in the present state to a normal flame voltage CF.

However, in the step comparing the wind pressures S200, when the wind pressure Pi of the fan is equal to the reference wind pressure P, the MICOM 100 executes the step for substituting the normal combustion data for the reference data S390 in which the normal fan driving voltage CV is substituted 12 for the reference fan driving voltage V, and the normal flame voltage CF is substituted for the reference flame voltage CF. By setting the normal fan driving voltage CV and the normal flame voltage CF in the step for establishing the normal combustion data S500 or the step for substituting the normal combustion data for the reference data S390, the procedure advances to a combustion step S600 in which the fuel gas is burned during the predetermined time. When the combustion step S600 is started, the infrared ray sensor 200 measures the flame voltage Fl in the combustion process. The MICOM 100 compares the flame voltage FI with the reference flame voltage CF(S700). The normal flame voltage CF is voltage value of the flame in the normal combustion state in which the color of the flame is blue. By establishing the normal fan driving voltage as described above, the MICOM watches the change of the flame voltage F1 in the present state by referring to the normal flame voltage CF. The MICOM 100 recognizes the combustion state according to the electric signal from the infrared rays sensor 200. When the color of the flame is yellow, the combustion state is imperfect combustion, but when the color of the flame is blue, the combustion state is perfect combustion. That is, the MICOM 100 determines the combustion state according to the voltage value or the current value from the infrared rays sensor 200.

The procedure advances to a step S800 in which the fan driving voltage V1 is changed according to the result of the step S700 for comparing the flame voltages so that the flame voltage F1 follows the normal flame voltage CF. The step S800 for tracking the normal flame voltage has a step S830 for decreasing the fan driving voltage in combustion, a step S860 for increasing the fan driving voltage in combustion, and a step S890 for keeping the fan driving voltage at the normal fan driving voltage.

When the flame voltage V1 is higher than the normal flame voltage CF in the step for comparing the flame voltages S700, the MICOM 100 decreases the fan driving voltage V1 until the flame voltage F1 reaches to the reference flame voltage CF(S830). That is, to prevent the air from being over supplied to the combustion room, the MICOM decreases the fan driving voltage V1 until the flame voltage FI is equal to the normal flame voltage CF.

On the other hand, the flame voltage F1 in the combustion state is lower than the normal flame voltage CF, the MICOM 100 increases the fan driving voltage V1 until the flame voltage F1 is higher than the normal flame voltage CF (S860). That is, when the f lame voltage F1 measured by the infrared rays sensor 200 is lower than the normal flame voltage CF, the air for combustion is insufficiently supplied to the combustion room. Therefore, to sufficiently supply the air to the combustion room, the MICOM 100 increases the fan driving voltage V1 until the f lame voltage F1 is equal to the normal f lame voltage CF When the flame voltage F1 is equal to the normal flame voltage 25 CF in the step for comparing the flame voltages S700, the MICOM 100 sets the fan driving voltage V1 in the present state to the normal fan driving voltage CV(S890).

After the step for tracking the normal flame voltage S800 14 is completed, the MICOM 100 returns to the combustion step S600. In FIG. 4, a capital letter "All represents the normal combustion state.

is As described above, the combustion state of the gas boiler in one embodiment of the present invention is controlled by regulating the amount of the air flow according to the change of the fan driving voltage. When the interrupt signal of the boiler is provided to the MICOM during the combustion process, the MICOM 100 stops supplying the fuel gas to the burner, and then the flame is extinguished. However, the MICOM continues to operate the fan 300 for exhausting the burned gas and the circulating pump 400 for forcing the heated water to circulate. That is, when the interrupt signal is provided to the MICOM, the postpurge process is executed like the conventional process. The combustion control method for the gas boiler according to me euk)odiment of the present invention establishes the optimal wind pressure required in the normal combustion process by comparing the reference wind pressure with the wind pressure in the ignition process. After the normal wind pressure is established, the MICOM compares the normal flame voltage with the flame voltage. The MICOM controls the flame voltage in the present state so as to track the normal flame voltage so that the fuel gas is completely burned. That is, the flame voltage remains at the normal flame voltage as the fuel gas is completely burned. For keeping the flame voltage at the predetermined value, the MICOM controls the fan driving voltage in the gas boiler. Therefore, the combustion control method for the gas boiler according to one embodiment of the present invention prevents the f Lame is from being extinguished by the head wind during the combustion process. Further, the combustion control method for the gas boiler according tp one embodirmnt of the present invention prevents the fuel gas from imperfect combustion caused by the favorable wind.

Therefore, the combustion control method for the gas boiler suppresses the production of pollutants caused by the imperfect combustion.

The combustion control method for the gas boiler according to one embodt of -the present invention- provides the optimLrn combustion state by actively controlling the amount of air flow provided to the combustion room. The amount of the air flow is regulated by changing the fan driving voltage or the R.P.M. of the fan according to the combustion state. The combustion state is changed due to an external reason such as the head wind or favorable wind that affects the combustion state fuel gas in the burner which is installed in the combustion room.

In the above, the present invention is described in detail by using the preferred embodiment, but the invention is not limited in the above embodiment. It should be obvious to people skilled in the conventional art that modifications can be made to the anood=rp-r.t of rne invention as describedabove without departing from the scope of the invention. However, the invention is limited by the accompanying claims below.

16 CLA" 1. A combustion control method for a gas boiler having a gas valve which regulates an amount of gas flow depending on a control signal obtained from a MICOM having an embedded program for controlling a whole process; an infrared ray sensor which provides an electric signal according to a color of a flame at a burner during the combustion process to the MICOM; a sensor for detecting wind pressure which is installed at a side of the exhaust duct and measures the wind pressure passing through the exhaust duct; a fan driving part which drives a fan for providing an amount of air flow to a combustion room and for exhausting the burned gas from the burner; and a circulating pump for forcing water to circulate through the heating pipes, is the combustion control method of the gas boiler comprising the steps of:

establishing the reference data 5100 in which reference wind pressure P, reference fan driving voltage V, and reference flame voltage P of the gas boiler are provided to and saved in the MICOM; comparing the wind pressures S200 in which the MICOM compares the reference wind pressure P with a wind pressure Pi of the fan when the initial ignition procedure is completed; altering the fan driving voltage S300 according to the result of the comparison of the wind pressures S200; establishing the normal combustion data SSOO in which the fan driving voltage V1 in the present state is set to the normal fan driving voltage CV, and the flame voltage FI in the 17 is present state is set to the normal flame voltage W after the step for altering the fan driving voltage S300 is completed; burning the fuel gas S600 in which the fuel gas is burned during the predetermined time after the step for establishing the normal combustion data SSOO is completed; comparing the flame voltages S700 in which the normal flame voltage CF in the normal combustion state is compared with the flame voltage F1 in the present combustion process after the lapse of a predetermined time; and tracking the normal flame voltage S800 in which the fan driving voltage is changed according to the comparison result of the flame voltages so that the MICOM tracks the flame voltage FI to the normal flame voltage CF; and wherein when said step for tracking the normal flame voltage S800 is completed, the procedure returns to the combustion step S600.

2. The combustion control method for the gas boiler as claimed in claim 1, wherein said step for altering the fan driving voltage S300 comprises:

a step S330 in which the fan driving voltage V1 is decreased until the reference flame voltage F is higher than the flame voltage Fi when the wind pressure Pi of the fan is higher than the reference wind pressure P in the step for comparing the wind pressures S200; a step S360 in which the fan driving voltage is increased until the reference flame voltage Fis higher than the flame voltage F1 when the wind pressure of the-fan P1 is lower than 1 the reference wind pressure P in the step for comparing the wind pressures S200; and a step 5390 in which the normal fan driving voltage CV is substituted for the reference fan driving voltage V when the wind pressure of the fan Pi is equal to the reference pressure P in the step for comparing the wind pressures S200.

is 3. The combustion control method for the gas boiler as claimed in claim 1 or 2, wherein said step for tracking the normal flame voltage S800 comprises:

a step S830 in which the fan driving voltage V1 is decreased until the flame voltage Fi is lower than the normal flame voltage CF when the flame voltage Fi in the combustion process is higher than the normal flame voltage CF; a step S860 in which the fan driving voltage V1 is increased until the flame voltage FI is higher than the normal flame voltage CF when the flame voltage FI in the combustion process is lower than the normal flame voltage CF; and a step S890 in which the fan driving voltage V1 is substituted for the normal fan driving voltage CV when the flame voltage Fi in the combustion process is equal to the normal flame voltage CF.

4. A cstion control method for a gas boiler substantially as hereinbefore described with reference to any one of Figures 2 to 5 of the acccying drawings.

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