METHOD FOR CONTROLLING A HEATING DEVICE AND HEATING DEVICE

Description

[0001] The present invention relates to a method for controlling a heating device which has a combustion chamber into which combustion air is introduced via a controllable fan. State of the art

[0002] EP 2 888 530 B1 discloses a method for controlling a heating device having a combustion chamber into which combustion air is introduced via a controllable fan. In the disclosed method, a static pressure and / or a power consumption, as well as a speed of the fan, are measured. From the measured static pressure and / or the measured power consumption, in conjunction with the measured speed, a pressure coefficient and / or a power coefficient is then determined. Based on the determined pressure coefficient and / or the determined power coefficient, a volume flow coefficient is then determined with the aid of reference values ​​for the pressure coefficient and / or the power coefficient, from which a volume flow of the combustion air is in turn determined. Disclosure of the invention

[0003] The present invention according to the independent claims has the advantage that a calibration of the reference values ​​for the operating coefficient, for example a pressure coefficient and / or a power coefficient, is carried out, whereby occurring control deviations, which may occur, for example, due to wear phenomena and / or friction losses on the fan, can be taken into account.

[0004] The features listed in the subclaims enable advantageous developments of the invention according to the main claim. It is advantageous if the reference values ​​for the operating coefficient are stored as a function of the volume flow coefficient, preferably in the form of a characteristic curve, wherein the reference values ​​for the operating coefficient, in particular the characteristic curve, are adjusted by calibration.

[0005] By calibrating using a calibration function, the calibration can also be adjusted relatively easily.

[0006] It is particularly advantageous if a calibration parameter is determined for the calibration, whereby a particularly efficient calibration can be carried out during operation of the heating device.

[0007] It is advantageous if the fan is set to a first speed, preferably corresponding to a large volume flow, and a first operating coefficient is determined, whereby an initial value for calibration can be determined particularly easily.

[0008] It is also advantageous if a second speed for a desired, preferably low, volume flow is determined from a relationship that is based on a constant ratio between volume flow and speed, whereby a second speed for a desired volume flow can be determined with little computational effort.

[0009] It is particularly advantageous if the fan is set to the second speed, preferably corresponding to the low volume flow, and a second operating coefficient is determined, whereby a suitable comparison value for calibration can be provided particularly easily.

[0010] Advantageously, the calibration parameter is determined from a comparison between the first operating coefficient and the second operating coefficient, which enables a particularly simple determination of the calibration parameter.

[0011] It is particularly advantageous if the calibration is carried out when the heating device is connected to a power supply and / or a sensor, preferably an ionization sensor, detects an unexpected flame behavior in the combustion chamber, thereby enabling particularly efficient and safe operation of the heating device.

[0012] The invention also relates to a heating device with a control unit which is designed to carry out a method according to the preceding description, thereby increasing the efficiency and safety of the heating device. Drawings

[0013] Embodiments of the invention are shown schematically in the drawings and explained in more detail in the following description. Fig. 1 a schematic representation of an embodiment of a heating device, Fig. 2 a schematic representation of another embodiment of a heating device, Fig. 3 a schematic representation of possible characteristic curves for the pressure coefficient H and a power coefficient P, Fig. 4 a schematic representation of the relationship between volume flow V and speed N Fig. 5 a schematic representation of a calibrated characteristic curve with calibrated power coefficients P̂ compared to a non-calibrated characteristic curve with power coefficient P Description of the embodiments

[0014] In Fig. 1 A schematic representation of an embodiment of a heating device 10 is shown. The heating device 10 has a fan 12, a burner 14, a heat exchanger 16, an exhaust duct 18, and an exhaust pipe 20. Combustion air is conveyed into a combustion chamber 22 of the heating device via the fan 12. The burner 14 and the heat exchanger 16 are also arranged in the combustion chamber. Fuel, such as a gas, is conveyed to the burner 14. In the heat exchanger 16, the heat released in the burner 14 is transferred to a heating medium, such as heating water.

[0015] In the illustrated embodiment, the heating device 10 has a pressure sensor 30 and a speed sensor 26, which are connected to a control unit 32. According to the present method, a static pressure h, which represents an operating variable of the heating device 10, is measured by means of the pressure sensor 30. In turn, a speed N of the fan 12, or of a fan wheel 24, is measured by means of the speed sensor 26. In the illustrated case, the speed sensor is a Hall sensor 28.

[0016] Based on the measured static pressure h and the measured speed N, an operating coefficient, in this case a pressure coefficient H, is determined by the control unit 32 using the following formula: H = g × h N 2 × D 2

[0017] Where g is the acceleration due to gravity and D is the diameter of the impeller 24 of the fan 12. Both quantities are known and stored in a memory 34 of the control unit 32.

[0018] A volume flow coefficient F is then determined based on reference values ​​for the operating coefficient, in this case the pressure coefficient H.

[0019] The reference values ​​for the operating coefficient, in this case the pressure coefficient H, are stored in the memory 34 of the control unit 32 as a function of the volume flow coefficient F. The reference values ​​were determined using a reference fan with at least similar geometric dimensions to the fan 12.

[0020] Finally, a volume flow V̇ of the combustion air is determined using the volume flow coefficient F using the following formula: F = V ˙ N × D 3

[0021] Thus, the volume flow V can be determined relatively easily by measuring the operating variable, in this case the static pressure h, of the heating device 10 and the speed N of the fan 12. Knowing the volume flow V makes it possible to adapt it to the amount of fuel supplied by controlling the fan 12 accordingly, so that clean and low-emission combustion can take place.

[0022] In Fig. 2 A schematic representation of a further embodiment of a heating device 10 is shown. The heating device 10 shown is different from the heating device 10 shown in Fig. 1 The heating device 10 shown is slightly modified. Identical and corresponding elements are provided with the same reference numerals.

[0023] In addition to detecting the rotational speed N of the fan 12 via the rotational speed sensor 26, in this exemplary embodiment, a power consumption W, which also represents an operating variable of the heating device 10, is measured via a power sensor 36. The power consumption W is a power W that is supplied to a motor of the fan 12. The power sensor 36 is located within the control unit 32.

[0024] Based on the measured power consumption W and the measured speed N, an operating coefficient, in this case a power coefficient P, is determined by the control unit 32 using the following formula: P = W ρ × N 3 × D 5

[0025] This is ρ the density of the combustion air and D the diameter of the fan wheel 24. The diameter D of the fan wheel 24 is known and stored in the memory 34 of the control unit 32. The density ρ The combustion air is assumed to be constant and stored in the storage unit as a fixed value, such as 1.2928 g / dm 3 for air in this case. Alternatively, it would also be conceivable that the density ρ of the combustion air is determined as a function of the temperature T of the combustion air and / or the static pressure h. Thus, the static pressure h could be determined with a pressure sensor 30 as shown in Fig. 1 also for the embodiment in Fig. 2 The temperature T of the combustion air could be measured with a temperature sensor located upstream of the burner.

[0026] A volume flow coefficient F is then determined based on reference values ​​for the operating coefficient, in this case the performance coefficient P.

[0027] The reference values ​​for the operating coefficient, in this case the performance coefficient P, are stored in a memory 34 of the control unit 32 as a function of the volume flow coefficient F. The reference values ​​were determined using a reference fan with at least similar geometric dimensions to the fan 12.

[0028] Finally, a volume flow of the combustion air is determined based on the volume flow coefficient F using formula (4).

[0029] This also applies to the embodiment of the heating device 10 from Fig. 2 The volume flow V can be determined relatively easily by measuring the operating variable, in this case the power consumption P, of the heating device 10 and the speed N of the fan 12. By knowing the volume flow V, it is now also possible for this exemplary embodiment to adapt it to the amount of fuel supplied by appropriately controlling the fan 12, so that clean and low-emission combustion can take place.

[0030] In both embodiments, the reference values ​​for the operating coefficients are stored as characteristic curves depending on the volume flow coefficient F in the memory 34 of the control unit 32. Accordingly, in Fig. 3 Characteristic curves for the pressure coefficient H and a power coefficient P are shown schematically.

[0031] The present method has the advantage of calibrating the reference values ​​for the operating coefficient. This allows changes in the speed N of the fan 12, which may occur due to wear, for example, on a bearing of the fan wheel 24, to be taken into account, allowing the volume flow V to be determined more accurately. The more accurate determination of the volume flow V, in turn, allows the ratio between supplied combustion air and supplied fuel to be controlled more precisely, allowing combustion to be even cleaner and with lower emissions. Thus, the present method increases the efficiency and also the safety of the heating system.

[0032] This calibration can be performed for both the reference values ​​of the pressure coefficient H and the reference values ​​of the performance coefficient P. To avoid repetition, however, only the calibration of the reference values ​​of the performance coefficient P for the example from Fig. 2 A calibration of the reference values ​​of the pressure coefficient H for the example from Fig. 1 is done analogously.

[0033] The calibration of the reference width of the power coefficient P is carried out using a calibration function f 2 ( A 2 ), which results in a calibrated power coefficient P: P ^ = P + c 1 − c 2 ⋅ f 1 A 1 ⋅ 1 f 2 A 2

[0034] The parameters c 1 and c 2 are manually adjusted during manufacture of the heating device 10 for the fan 12.

[0035] The function f 1 ( A1 ) is an adaptation function that takes into account specific properties of the present blower 12. In the present embodiment, this is: f 1 A 1 = A 1 ⋅ c 3 + c 4

[0036] These include c 3 and c 4 Parameters that are set during the manufacture of the heating device 10 depending on the type of fan 12 used. In this case, c 3 = 0.025 and c 4 = 0.5.

[0037] The parameter A 1 is an adjustment parameter and is also set manually during the manufacture of the heating device 10 for the blower 12 and makes it possible to take into account the specific characteristics of the blower 12 in question, since even individual blowers of the same type may have manufacturing differences.

[0038] The function f 2 ( A2 ), however, is a calibration function that takes into account wear phenomena, such as those on a bearing of the fan 12. In the present embodiment, this is: f 2 A 2 = 2 ⋅ V ˙ − V ˙ low V ˙ high − V ˙ low − V ˙ − V ˙ low V ˙ high − V ˙ low 2 ⋅ 20 − A 2 + A 2 ⋅ c 5 + c 6

[0039] These include c 5 and c 5 parameters that are set during the manufacture of the heater 10 depending on the type of fan 12 used. This allows the calibration function to be adapted to the wear behavior of the fan. In this case, c 5 = 0.035 and c 4 = 0.3.

[0040] The parameter A 2 is a calibration parameter and is determined by the present method, allowing for particularly efficient calibration during operation of the heating device 10. Thus, wear phenomena are taken into account to the extent that they occur, allowing for particularly precise control of the heating device 10.

[0041] In a first process step, the blower 12 is set to a first, preferably a large volume flow V̇ high The corresponding speed N high is set, and a first performance coefficient P high is determined. Influences resulting from wear are less noticeable at high speeds of the fan 12 than at low speeds. This circumstance can be advantageously utilized by determining the performance coefficient P high at a high speed N high, which provides a good starting point for calibration.

[0042] Preferably, the fan 12 is set to the first speed N high between 3000 and 6000 revolutions per minute, in the illustrated case 5000 revolutions per minute. This enables a particularly efficient determination of the performance coefficient P high.

[0043] In the present case, the power consumption W high of the fan 12 is measured at the set first speed N high, whereupon the power coefficient P high is determined by means of formula (3) in conjunction with the set first speed N high and the measured power consumption W high.

[0044] In addition, the power coefficient P high is then calculated using the available reference values ​​or characteristic curves ( Fig. 3 ), a volume flow coefficient F high is determined for the performance coefficients P. From the volume flow coefficient F high, a first volume flow is then calculated using formula (2) V̇ high certainly.

[0045] In a further process step, a second speed N low is set for a desired, in this case low, volume flow V̇ low determined from a relationship that assumes a constant ratio between volume flow V and speed N as follows: V ˙ low N low = V ˙ high N high = const .

[0046] In this case, the desired volume flow V̇ low Using the relationship described in formula (7), the desired volume flow V̇ low , the previously determined first volume flow V̇ high and the already known first speed N high, the second speed N low is then determined as follows: N low = N high V ˙ high ⋅ V ˙ low

[0047] This makes it particularly easy to determine the second speed N low, with little computational effort required.

[0048] In Fig. 4 is shown a schematic representation of the relationship between volume flow V and speed N. As already described, a constant relationship between volume flow V and speed N exists for the present method. The arrows indicate the way in which the second speed N low is determined according to the previous description. It can also be seen that the desired volume flow V̇ low in this case is lower than the first volume flow V̇ low . Accordingly, in the present case, the second speed N low is lower than the first speed N high .

[0049] In a further process step, the blower 12 is now set to the second, in this case the low, volume flow V̇ low The corresponding speed N low is set, and a second operating coefficient P low is determined. This allows for the advantage of the fact that influences resulting from wear are more noticeable at lower speeds. Thus, by determining the performance coefficient P low at a low speed N low, a comparison value suitable for calibration can be determined particularly easily.

[0050] Preferably, the fan 12 is set to the second speed N low between 920 and 1700 revolutions per minute, in the illustrated case 1000 revolutions per minute. This enables a particularly efficient determination of the performance coefficient P low.

[0051] In the present case, the power consumption W low of the fan 12 is measured at the set second speed N low , whereupon the power coefficient P low is determined by means of formula (3) in conjunction with the set second speed N low and the measured power consumption W low .

[0052] In a further process step, the calibration parameter is now determined from a comparison between the first operating coefficient P high and the second operating coefficient P low, which enables a particularly simple determination of the calibration parameter with little computational effort.

[0053] In the present case, the comparison between the first performance coefficient P high and the second performance coefficient P low is carried out by forming a ratio, in particular a quotient, of the second performance coefficient P low and the first performance coefficient P high, wherein an adaptation to the previously described specific properties of the present blower 12 is carried out for both: f 2 A 2 = P low + c 1 − c 2 ⋅ f 1 A 1 P high + c 1 − c 2 ⋅ f 1 A 1

[0054] From formula (6) we get V̇ = V̇ low : f 2 A 2 = A 2 ⋅ c 5 + c 6

[0055] The parameters are c 5 and c 6 are already known, since they are set during the manufacture of the heating device 10, as already described. If the value for f 2 ( A 2 ) into the relationship (10), the calibration parameter A 2 determine numerically.

[0056] Using the calibration parameter determined by the present method A 2, the reference values ​​stored in the memory for the performance coefficient, or the characteristic curve, can now be calibrated using formulas (4) to (6), whereby changes in the speed N of the fan 12, which can occur due to wear, for example on a bearing of the fan wheel 24, can be taken into account and whereby the volume flow V can be determined more precisely.

[0057] In Fig. 5 is a schematic representation of a calibrated characteristic curve with calibrated power coefficients P̂ compared to a non-calibrated characteristic curve with non-calibrated performance coefficients P. For illustration purposes, the volume flow coefficients F low and F high are shown, which are calculated using formula (2) for the corresponding volume flows V̇ low and V̇ highcan be determined. It can be seen that a stronger calibration is obtained for lower volume flows than for higher volume flows. Thus, the present method enables a very realistic calibration.

[0058] In the present method, the calibration is always carried out when the heating device 10 is connected to a power supply or when a sensor, for example an ionization sensor, detects an unexpected flame behavior in the combustion chamber, thereby enabling particularly efficient and safe operation of the heating device 10.

Claims

1. Method for regulating a heating device (10) which has a combustion chamber (22), into which combustion air is introduced via a controllable blower (12), wherein an operating variable (W, h) and a speed (N) of the blower are measured, wherein an operating coefficient (P, H) is determined based on the measured operating variable (W, h) and the measured speed (N), wherein a volume flow coefficient (F) is determined based on reference values for the operating coefficient (P, H), wherein a volume flow (V˙) of the combustion air is determined based on the volume flow coefficient (F), characterized in that the reference values for the operating coefficient (P, H) are calibrated, and in that the calibration is performed using a calibration function (f2).

2. Method according to Claim 1, characterized in that the reference values for the operating coefficient (P, H) are stored on the basis of the volume flow coefficient (F), preferably in the form of a characteristic curve, wherein the reference values for the operating coefficient (P, H), in particular the characteristic curve, are adapted by means of the calibration.

3. Method according to one of the preceding claims, characterized in that a calibration parameter (A2) is determined for the calibration.

4. Method according to one of the preceding claims, characterized in that the blower (12) is set to a first speed (Nhigh) and a first operating coefficient (Phigh) is determined.

5. Method according to one of the preceding claims, characterized in that a second speed (Nlow) is determined for a desired volume flow (V˙low) from a relationship based on a constant ratio between volume flow (V˙) and speed (N).

6. Method according to Claim 5, characterized in that the blower (12) is set to the second speed (Nlow), preferably corresponding to the desired volume flow (V˙low) and a second operating coefficient (Plow) is determined.

7. Method according to Claim 6, characterized in that the calibration parameter (A2) is determined from a comparison between the first operating coefficient (Phigh) and the second operating coefficient (Plow).

8. Method according to one of the preceding claims, characterized in that the calibration is carried out when the heating device (10) is connected to a power supply system and / or a sensor, preferably an ionization sensor, detects an unexpected flame behaviour in the combustion chamber (22).

9. Heating device (10) having a control unit (32), which is configured to carry out a method according to one of the preceding claims.

10. Heating device (10) according to Claim 9, comprising a pressure sensor (30) and a speed sensor (26), which are connected to the control unit (32).