EP3301365B1 - Method for controlling an ignition of a heating system, control unit and heating system - Google Patents

Description

The invention relates to a method for controlling an ignition operation of a heating system. The invention also relates to a control unit designed to carry out the method according to the present invention and a heating system with the control unit according to the present invention.

State of the art

Methods for starting the burner of a heating device are known in the prior art. A quantity of fuel in a fuel-air mixture is slowly increased until an ignitable mixture results, so that ignition can take place. The slope of the linear fueling increase is set prior to operation and then remains substantially constant. This has the disadvantage that the point in time of ignition can vary considerably. Ignition that is too early leads to undesirable pressure surges and a loud ignition noise. If the ignition is too late, a required heat output will only be available later.

EP2706300 describes a method for controlling an ignition operation of a heating system.

Disclosure of Invention benefits

The present invention provides a method for controlling an ignition operation of a heating system according to claim 1.

The term "heating system" means at least one device for generating thermal energy, in particular a heater or heating burner, in particular for use in heating a building and/or for generating hot water, preferably by burning a gaseous or liquid fuel. A heating system can also consist of several such devices for generating thermal energy as well as other devices that support the heating operation, such as hot water and fuel storage tanks.

"Ignition operation" is understood to mean an operating phase of the heating system in which the fuel is ignited. A fuel-air mixture is preferably ignited in a burner. In particular, a fuel supply and, if necessary, an air supply are controlled or regulated in the ignition mode. Ignition operation is an essential operating phase of a heating system switch-on process. The ignition operation is advantageously ended as soon as the heating system can be operated as desired, in particular in a controlled operation.

An “operating parameter” should be understood to mean a parameter which is correlated with a quality of a fuel used in the heating system and/or is correlated with a power demand on the heating system. The operating value can directly or indirectly from a parameter describing the quality of the fuel and/or from a directly or indirectly depend on the parameters describing the performance requirement. The operating parameter can be correlated with the calorific value and/or gross calorific value of a fuel. For example, a determined density of the fuel can be an operating parameter. It is also conceivable that a specific operating parameter, for example an ionization current, and/or a time development of the operating parameter under specific, predetermined conditions, is or are an operating parameter. An “operating parameter” can be understood in particular as a parameter which is correlated in particular with the fuel type, in particular an actual fuel type that is currently being used and/or is being supplied to a burner unit of the heating system. A “fuel type” is to be understood in particular as meaning a type and/or a composition of the fuel. The fuel type can particularly preferably correspond to a gas family, such as a second gas family, in particular natural gas, and/or a third gas family, in particular liquid gas. Alternatively and/or additionally, the fuel type can also correspond in particular to fuels from the same gas family and/or fuels within a gas family, such as fuels from different origins and/or different batches, which can at least partially differ in composition. The operating parameter can also be related to a power demand on the heating system. For example, the heating system can be started with a power request, for example with a power request to supply hot water at a temperature of 45°C. The power requirement can follow, for example, from a user input or from a schedule, for example for a heating schedule. The operating parameter or the power requirement can have the value of a burner power parameter and/or be correlated with the burner power parameter.

“Burner power parameter” is to be understood in particular as a parameter which is correlated with the power, in particular a heating power, of the heating system. The output, in particular heating output, of the heating system can advantageously be determined, in particular by the control and/or regulating unit of the heating system, at least on the basis of the burner output parameter. Advantageously, the burner output parameter corresponds to at least one or exactly one measured value representing the output or can be unambiguously assigned to such a measured value. Such a measured value can be, for example, a temperature, an air flow rate, a fan control signal or a fan speed.

The method according to the main claim has the advantage that the ignition operation can be carried out quickly and safely. Ignitions that are too early or too late are avoided by directly or indirectly taking into account the quality of the fuel and/or the power requirement. Operational safety and operational comfort are increased.

Advantageous developments of the method according to the main claim are possible due to the features listed in the subclaims.

The operating parameter is determined in a previous heating operation, which has the advantage that conditions present in an operation taking place before the ignition operation can be detected in this way. This enables a particularly precise adjustment of the ignition operation to the relevant influencing variables. In particular, properties of the fuel currently used in the heating system can be determined in this way. The method is intended to be executed repeatedly. A "previous heating operation" is to be understood as an operating phase of the heating system, in particular an operating phase in which a heating output is provided are in time before the ignition operation. In this sense, a "previous ignition operation" is an ignition operation from a previous iteration of the method, preferably from the last iteration of the method. A previous characteristic value is to be understood as meaning a characteristic value that was recorded or determined before the ignition operation, preferably in a previous ignition operation.

If a first burner performance parameter is determined as a function of the operating parameter, the performance requirement can be met particularly quickly in this way. This further increases operating comfort and ease of use.

The method is further improved if, during ignition operation, the first burner power parameter is largely the same as a starting power, the starting power being selected from a starting power range, in particular a starting power interval, so that the starting power is as close as possible to a power requirement or the power requirement. The starting power range can be selected so that ignition operation is particularly quiet and safe.

If, in ignition mode, a fluid supply parameter is first brought to a starting value and then increased, preferably linearly with a gradient value, until an ignition value of the fluid supply parameter is reached at which a flame in the heating system ignites, this has the advantage that ignition is particularly quiet and reliable is possible. The starting value is preferably selected below the ignition value, ie in such a way that an ignitable fuel-air mixture is not yet present with the fluid supply parameter as the starting value. The ignition value is achieved by increasing the fluid supply parameter. This has the advantage that a loud ignition is avoided. Loud firing occurs when the starting value exceeds the firing value.

A "fluid supply parameter" is to be understood in particular as a scalar parameter which is correlated in particular with at least one fluid supplied, in particular to a burner unit of the heating system, in particular a combustion air flow, a fuel flow and/or a mixture flow, in particular of combustion air and the fuel . A volume flow and/or a mass flow of the at least one fluid can advantageously be inferred, in particular by a control and/or regulating unit of the heating system, at least on the basis of the fluid supply parameter, and/or the volume flow and/or the mass flow of the at least one fluid can be determined. An example of a fluid supply parameter is the specification of an opening width of a fuel valve.

If the gradient value and/or the starting value depend on the operating characteristic, this is a particularly simple and robust way of taking the operating characteristic into account during ignition operation.

The method is further improved if the operating parameter is determined as a function of a or the start value of the fluid supply parameter during ignition operation and/or as a function of a previous start value in a previous ignition operation. If the starting value is determined, for example, in a control process, in particular for approximating the starting value to the ignition value, the quality of the fuel can be determined as a function of the starting value.

If a starting value or the starting value is determined as a function of a previous ignition value of a fluid supply parameter in a previous ignition operation, the starting value can be approximated to the starting value in a particularly simple manner. In this way, the ignition operation can be shortened. The operating comfort or ease of use is increased in this way.

If the operating parameter is determined as a function of a combustion parameter, for example an ionization current, the quality of the fuel can be determined particularly precisely. A "combustion parameter" is to be understood in particular as a scalar parameter which is correlated in particular with a combustion, in particular of the mixture, in particular of the combustion air and the fuel. An example of a combustion parameter is an ionization current, which is measured on a flame of the heating system. Advantageously, the presence and/or quality of combustion can be determined and/or the presence and/or quality of combustion can be determined, in particular by the control and/or regulating unit of the heating system, at least on the basis of the combustion parameter. The combustion parameter advantageously corresponds to at least one or exactly one measured value that depicts and/or characterizes the combustion, or the combustion parameter can be unambiguously assigned to such a measured value. Examples of a measured value that depicts and/or characterizes the combustion are a combustion signal, in particular a light intensity, pollutant emissions, a temperature and/or advantageously an ionization signal.

If the operating parameter is determined as a function of a time profile of the combustion parameter after a change in the fluid supply parameter and/or a first burner output parameter, the precision of the determination of the quality of the fuel is further increased. When there is a change in the fluid supply parameter and/or the first burner output parameter, the time profile of the combustion parameter can be particularly dependent on the quality of the fuel.

The method is further improved when a temporary fluid delivery change over time in the fluid delivery parameter is generated and the Operating parameter is determined as a function of a change in the combustion parameter over time that is correlated with the fluid supply change. A "temporary, temporal fluid supply change" is to be understood as meaning a time-limited variation in the fluid supply parameter, so that it deviates from a largely constant value of the fluid supply parameter before the start of the fluid supply change. The fluid supply parameter is preferably initially increased or decreased over the period of time of the fluid supply change and then regulated to the largely constant value of the fluid supply parameter before the start of the fluid supply change. The fluid supply change is preferably associated with a brief increase in a fluid quantity supplied to the burner unit per unit of time. The duration of the fluid supply change is preferably pulse-like and short compared to the intended time variations of the fluid supply parameter that occur during normal operation of the heating system. It may be possible to determine the calorific value and/or gross calorific value of the fuel from a change in the combustion parameter.

A "pulse", a "pulse-like change" or a "pulse-shaped signal" is understood to mean a time profile of a parameter which is brought from a first value to at least a second value different from the first value within a limited period of time. A "pulse" is also sometimes referred to as a "pulse", particularly in electrical engineering.

In a further advantageous embodiment, the operating parameter is determined as a function of a time profile of the fluid supply parameter, with the heating system being operated in a closed-loop mode after a previous ignition operation. "Closed-loop mode" is to be understood as a control process in which a first operating parameter, which is preferably an actuating signal to a component of the heating system corresponds, for example, to regulate a fuel supply, is set in such a way that a second operating parameter largely assumes the value of a setpoint operating parameter. The first operating parameter is preferably adapted iteratively. The first operating parameter is particularly preferably set as a function of a deviation of the second operating parameter from the setpoint operating parameter. The heating system is preferably operated in a closed-loop mode when a burner output parameter is largely constant or changes sufficiently slowly or slightly. “Operating parameters” are parameters that are used by a control unit of the heating system to control and/or monitor and/or regulate and/or calibrate processes running in the heating system. Examples of "operating parameters" are the fan speed, an ionization current on a flame of the heating system or a desired opening width of a fuel control valve.

The closed-loop mode is advantageously operated after the previous ignition operation. In the closed-loop mode, the fluid delivery parameter can be set directly or indirectly. An operating parameter can be derived from this, from which particularly precise information about the quality of the fuel can be derived.

If the fluid supply parameter is set to a previous ignition value in a previous ignition operation, then regulated to a control value in closed-loop mode and the operating parameter is determined from a comparison between the previous ignition value and the control value, in particular by a size comparison, this is a particularly simple one and robust method to determine the operating characteristic.

The operating parameter is dependent on a time profile of a second burner output parameter with a largely constant first burner output parameter and after a change in the fluid supply parameter determined, this has the advantage that the operating parameter can be determined particularly easily and cheaply. Means for determining a first burner output parameter and/or a second burner output parameter are usually present in heaters and do not have to be retrofitted.

If the first burner output parameter is a detected blower speed, which is kept constant by a control circuit by setting the second burner output parameter and the operating characteristic is determined as a function of a burner output parameter change in the second burner output parameter, the burner output parameter change being correlated with a temporary fluid supply change, the determination of an operating characteristic is which is correlated with a density of the fuel. By changing the fluid supply, for example, a fuel flow to be transported by a blower is increased or a fuel proportion in a fuel-air mixture flow is increased. At a constant fan speed, the fan then requires more power if the fuel has a higher density than air.

If the fluid supply parameter is a valve control signal for a fuel valve and/or one or the combustion parameter is an ionization current and/or one or the second burner performance parameter is a fan speed, then the method is particularly reliable. In particular, a particularly stable closed-loop mode is possible. In particular, efficient ignition operation is possible.

If the fluid supply parameter is a valve control signal for a fuel valve, this has the additional advantage that a particularly reliable and precise setting of a fluid supply or a fuel/air ratio is possible in this way.

If the combustion parameter is an ionization current, this has the advantage that the ionization current has a functional connection to the fuel-air ratio that can be evaluated particularly favorably. This allows precise and reliable regulation and/or control of the heating system with regard to combustion quality and emissions. An "ionization current" is determined by an ionization current measurement on a flame of the heating system.

A fan speed is a particularly easily detectable and reliable measure of the performance of the heating system.

The use of a control unit for a heating system, which control unit is set up to carry out the method according to the present invention, has the advantage that the heating system can be operated reliably even under changing internal and/or external conditions. This makes it possible to operate the heating system largely without user intervention. This increases the ease of use as well as the availability and reliability of the heating system.

A heating system with a control unit according to the present invention, with at least one fuel valve for a fuel, with an ionization probe on a flame and with a fan with variable fan speed has the advantage that convenient, safe and low-maintenance operation of the heating system is made possible.

drawings

• Figur 1 eine schematische Darstellung des Heizsystem mit einer Steuereinheit,
• Figur 2 eine Abfolge unterschiedlicher Betriebsphasen des Heizsystems, aufweisend einen Zündbetrieb,
• Figur 3 einen Zeitverlauf eines ersten Brennerleistungsparameters in unterschiedlichen Zündbetrieben,
• Figuren 4, 5 und 8 einen Zeitverlauf einer Fluidzufuhrkenngröße und einer Verbrennungskenngröße bei einem Zündbetrieb und unterschiedlichen Varianten des Verfahrens,
• Figur 6 einen Zeitverlauf eines Startwerts der Fluidzufuhrkenngröße bei Zündbetrieben mit unterschiedlichen Brennstoffen,
• Figur 7 einen Zeitverlauf der Fluidzufuhrkenngröße bei Zündbetrieben mit unterschiedlichen Brennstoffen,
• 9 einen Zeitverlauf einer Fluidzufuhrkenngröße und einer Verbrennungskenngröße bei einem Heizbetrieb und
• Figur 10 einen Zeitverlauf der Fluidzufuhrkenngröße und eines zweiten Brennerleistungsparameters in einem Heizbetrieb.

In the drawings are exemplary embodiments of the method for controlling an ignition operation of a heating system according to the present invention, and a control unit according to the present invention and a heating system according to the present invention is shown and described in more detail in the following description. Show it

• figure 1 a schematic representation of the heating system with a control unit,
• figure 2 a sequence of different operating phases of the heating system, including an ignition mode,
• figure 3 a time course of a first burner performance parameter in different ignition operations,
• Figures 4, 5 and 8th a time course of a fluid supply parameter and a combustion parameter in an ignition operation and different variants of the method,
• figure 6 a time course of a start value of the fluid supply parameter during ignition operations with different fuels,
• figure 7 a time course of the fluid supply parameter for ignition operations with different fuels,
• 9 shows a time course of a fluid supply parameter and a combustion parameter in a heating operation and
• figure 10 a time course of the fluid supply parameter and a second burner output parameter in a heating mode.

description

The same parts are given the same reference numbers in the different design variants.

In figure 1 a heater 10 is shown schematically, which is arranged on a memory 12 in the embodiment. The heater 10 has a housing 14 which accommodates different components depending on the degree of equipment.

The essential components are a heat cell 16, a control unit 18, one or more pumps 20 and piping 22, cables or bus lines 24 and holding means 26 in the heater 10. The number and complexity of the individual components also depends on the equipment level of the heater 10.

The heat cell 16 has a burner 28, a heat exchanger 30, a blower 32, a metering device 34 and an air supply system 36, an exhaust system 38 and, when the heat cell 16 is in operation, a flame 40. An ionization probe 42 projects into the flame 40 . The dosing device 34 is designed as a fuel valve 44 . A fan speed 54 of the fan 32 is variably adjustable. The heater 10 and the memory 12 together form a heating system 46. The control unit 18 has a data memory 48, a computing unit 50 and a communication interface 52. The components of the heating system 46 can be controlled via the communication interface 52 . The communication interface 52 allows data to be exchanged with external devices. External devices are, for example, control devices, thermostats and/or devices with computer functionality, for example smartphones.

figure 1 shows a heating system 46 with a control unit 18. In alternative embodiments, the control unit 18 is located outside the housing 14 of the heater 10. The external control unit 18 is designed as a room controller for the heating system 46 in special variants. In preferred embodiments, the control unit 18 is mobile. The external control unit 18 has a communication link to the heater 10 and/or other components of the heating system 46 . The communication connection can be wired and/or wireless, preferably a radio connection, particularly preferably via WLAN, Z-Wave, Bluetooth and/or ZigBee. In further variants, the control unit 18 can consist of several components exist, especially components that are not physically connected. In special variants, at least one or more components of the control unit 18 can be present partially or entirely in the form of software that runs on internal or external devices, in particular on mobile computing units, such as smartphones and tablets, or servers, in particular a cloud. The communication connections are then corresponding software interfaces.

figure 2 illustrates a sequence of different operating phases of the heating system 46. An ignition operation 56 is preceded by a shutdown 58 of the burner 28, a closed loop mode 60 and a previous ignition operation 62. The method according to the present invention is used in ignition operation 56 and previous ignition operation 62 .

The method or ignition operation 56 is started by detecting a power requirement 64 to the heating system 46 . In the exemplary embodiment, the power requirement is a desired heating power, which is sent to the heating system 46 by a room controller. The desired heat output is characterized by a number that describes a desired output in kW. In the exemplary embodiment, the power requirement 64 is determined from this number. For this purpose, a fan speed 54 required for the desired heating output is determined. The control unit 18 has a fan speed characteristic, which assigns the required fan speed 54 to the desired heat output. The power requirement 64 has the value of the required fan speed 54. The values of the fan speed 54 describe the number of revolutions per minute of an impeller of the fan 32. The power requirement 64 is an operating parameter 66. The fan speed characteristic is determined in the laboratory, with the technical properties of the heating system 46 are taken into account.

In the exemplary embodiment, the heating output is set using a first burner output parameter 68 of a second burner output parameter 70 . The first combustor output parameter 68 is a sensed fan speed 54 of the fan 32. The fan 32 includes a Hall effect sensor that senses the number of revolutions per minute of the impeller of the fan 32. The first burner output parameter 68 is determined from a signal from the Hall probe. The second burner performance parameter 70 is a fan control signal 71. The fan control signal 71 is a PWM signal which is sent from the control unit 18 to the fan 32. The second burner power parameter 70 corresponds to a power made available to the blower 32 . A desired fan speed 54 is set by a control circuit in which the second burner output parameter 70 is varied in such a way that the first burner output parameter 68 assumes the value of the desired fan speed 54 .

In the ignition mode 56 the power requirement 64 is compared to a starting power range 72 . Starting power range 72 is a set of possible starting powers 74 at which particularly advantageous ignition operation 56 is possible. In particular, a quiet and safe ignition operation 56 is possible with a starting power 74 in the starting power range 72 . The takeoff power 74 is selected from the takeoff power range 72 to be as close to the power requirement 64 as possible.

In the exemplary embodiment, the starting power range 72 is a starting power interval 76 . The starting power interval 76 has a minimum starting power 78 and a maximum starting power 80 . If the power requirement 64 is within the starting power interval 76, the power requirement 64 is selected as the starting power 74. In ignition mode 56 is the desired fan speed 54 or the first burner power parameter 68 is set to the power requirement 64 as quickly as possible.

If the power requirement 64 is greater than the maximum starting power 80, the maximum starting power 80 is selected as the starting power 74. If the power requirement 64 is less than the minimum starting power 78, the minimum starting power 78 is selected as the starting power 74. In the ignition mode 56, the desired fan speed 54 or the first burner power parameter 68 is set to the power requirement 64 as quickly as possible. After the fuel/air mixture has been ignited, the desired fan speed 54 or the first burner power parameter 68 is modulated to the power requirement 64 . The desired blower speed 54 or the first burner power parameter 68 is changed from the starting power 74 to the power requirement 64 in such a way that the heating system 46 can be operated quietly and safely.

figure 3 12 illustrates a time course of the first burner output parameter 68 for three different ignition modes 56a, 56b, 56c, each with different output requirements 64. A first abscissa axis 82 shows a time. The first abscissa axis 82 is interrupted at two points and shows periods of time in which an ignition operation 56a, 56c or 56c is carried out. The first burner power parameter 68 is shown on a first ordinate axis 84 . In ignition mode 56a, the power requirement 64 is starting power interval 76. In ignition mode 56b, the power requirement 64 is above the maximum starting power 80. The first burner power parameter 68 is initially increased to the maximum starting power 80 as quickly as possible. The first burner output parameter 68 is kept constant until ignition has taken place. In the exemplary embodiment, ignition is detected using the ionization probe 42 (see below). Subsequently, the first burner performance parameter 68 with a linear Ramp set to power demand 64 value. In the exemplary embodiment, the heating system 46 is operated in the closed-loop mode 60 (see below) in order to minimize the emissions produced during combustion. The first burner power parameter 68 is therefore increased at such a rate that a stable closed-loop mode 60 is possible. In alternative variants, it is possible for the first burner output parameter 68 to be selected using a time profile stored in the control unit 18 . It is conceivable, for example, for a relationship or characteristic curve to be stored in control unit 18, which assigns a suitable gradient to power requirement 64 for an increase or decrease in burner power parameter 68 after ignition. In the ignition mode 56c, the power requirement 64 is below the minimum starting power 78. The first burner power parameter 68 is initially increased to the minimum starting power 78 as quickly as possible. After ignition, the first burner output parameter 68 is reduced to the value of the output request 64 with a linear ramp.

In the exemplary embodiment, the starting power range 72 is a starting power interval 76. In alternative embodiments, the starting power range 72 is a set of discrete power points and/or at least one power interval. In particular, it is conceivable that the starting power range 72 has a first starting power and a second starting power. The selection of the starting power range 72 is based on the technical properties of the heating system 46 and is selected in such a way that the heating system 46 can always be operated as desired. In particular, the starting power range 72 is selected in such a way that the heating system 46 can be operated with quiet and safe ignition operation 56 . The starting power range 72 is advantageously established in laboratory tests and stored in the control unit 18 . It is also conceivable that the starting power range 72 is updated while the heating system 46 is in operation. For example, the ignition mode can be 56 calibrated in a particular phase of operation, and the take-off power range 72 updated if necessary.

In the exemplary embodiment, in the ignition mode 56 the fuel valve 44 is opened as soon as the first burner output parameter 68 has largely reached the value of the starting output 74 . figure 4 shows the time profile of a valve control signal 86. A second abscissa axis 88 depicts a time. A second ordinate axis 90 shows the valve control signal 86 and an ionization current 92.

The valve control signal 86 is a control signal which is sent to the fuel valve 44 and describes a desired opening width of the fuel valve 44 . The valve control signal 86 can be characterized by an indication of the desired opening width of the fuel valve 44 . The desired opening width of fuel valve 44 is described in the exemplary embodiment with a percentage between 0% and 100%, with an opening width of 0% corresponding to a completely closed fuel valve 44 and an opening width of 100% corresponding to a completely open fuel valve 44. By "increase or decrease the valve control signal 86" it is meant that the valve control signal 86 is changed to increase or decrease the desired fuel valve 44 opening compared to a last desired fuel valve 44 opening. The valve control signal 86 is a fluid supply parameter 94.

The ionization current 92 is an electrical current measured by the ionization probe 42 on the flame 40 of the burner 28 . The ionization current 92 is a combustion parameter 96. The detected ionization current 92 is received by the control unit 18. In the exemplary embodiment, the ionization current 92 largely continuously recorded. The ionization current 92 is stored at least in sections as a function of time in the control unit 18 .

First, the fluid supply parameter 94 is brought to a starting value 98 as quickly as possible. In figure 4 the starting value is 98 30%. The start value 98 is determined during start-up or during a first ignition operation 56 depending on the first burner power parameter 68 or depending on the starting power 74 . A starting value characteristic curve is stored in the control unit 18 and assigns the starting value 98 to the first burner output parameter 68 . The starting value 98 is selected in such a way that a non-ignitable fuel/air mixture is produced given the burner output parameters 68 that are present. The initial value characteristic was determined empirically in laboratory tests. In the case of later ignition operations 56, the starting value 98 is determined on the basis of previous ignition operations 62 (see below).

The fluid supply parameter 94 is then increased linearly with a slope value 100. In figure four, the slope value 100 is 15% per second. Gradient value 100 is determined as a function of operating characteristic 66 , operating characteristic 66 being recorded before ignition operation 56 . During start-up or during the first ignition operation 56, the operating characteristic 66 is determined as a function of the first burner power parameter 68 or as a function of the starting power 74. A first gradient value characteristic curve is stored in the control unit 18 and assigns the gradient value 100 to the first burner output parameter 68 . The gradient value 100 is selected in such a way that the fuel-air mixture does not ignite too quickly under typical internal and external conditions. The first gradient value characteristic was determined empirically in laboratory tests. In the case of later ignition operations 56, the slope value 100 is determined on the basis of a previous heating operation 102. A previous heating operation 102 may include a previous ignition operation 62 and/or a closed loop mode 60 and/or a Shutdown 58 include (see figure 2 ). In comparison to a slope value 100 determined from the previous heating operation 102, a slope value 100 determined from the first slope value characteristic curve is smaller.

The linear increase in the fluid supply parameter 94 is stopped at an ignition value 104 . The control unit 18 checks the course of the combustion parameter 96 over time. As soon as the fuel-air mixture ignites, an ionization current 92 is present. figure 4 shows the course over time of the ionization current 92 or the combustion parameter 96. Before the ignition, the ionization current 92 has the value 0; there is no ionization current 92 present. During ignition, the ionization current 92 increases rapidly and reaches a maximum at a first point in time 106 . Subsequently, the ionization current 92 falls and stabilizes at a certain value. During ignition operation 56, the control unit determines the maximum of the ionization current 92 or the first point in time 106. As soon as the first point in time 106 is present, the linear increase in the fluid supply parameter 94 is stopped. The value of the fluid supply parameter 94 present at the first point in time is the ignition value 104. The fluid supply parameter 94 is then kept largely constant at the ignition value 104. In the exemplary embodiment, the ignition value 104 is 60%. The ignition value 104 generally depends on the external and internal conditions of the heating system. In particular, the ignition value 104 can depend on a quality of a fuel used in the heating system 46 and/or on the power requirement 64 or the first burner power parameter 68 .

In the exemplary embodiment, start value 98 is determined as a function of a previous ignition value 108 . The previous ignition value 108 is determined in the previous ignition mode 62 . figure 5 shows the fluid supply parameter 94 and the combustion parameter 96 over time during a previous ignition operation 62 and an ignition operation 56. After the previous ignition operation 62, the previous ignition value 108 has a previous starting value 110 compared. If an amount of a difference between the previous ignition value 108 and the previous starting value 110 deviates too much from a safety distance 112, the starting value 98 ignition operation 56 is changed. The safety distance 112 is a known value stored in the control unit 18 which depends on the first burner output parameter 68 . The safety distance 112 as a function of the first burner performance parameter 68 was determined empirically in laboratory tests. The safety distance 112 ensures quiet and safe ignition. In figure five, the safety margin 112 is 10%. If the absolute value of the difference between the previous ignition value 108 and the previous start value 110 differs from the safety distance 112 by more than 4%, the start value 98 is changed in comparison to the previous start value 110 in the ignition operation 56 . If the absolute value of the difference between the previous ignition value 108 and the previous start value 110 is greater than the safety margin 112 , the start value 98 is determined from the sum of the previous start value 110 and a change step 114 . If the absolute value of the difference between the previous ignition value 108 and the previous start value 110 is less than the safety margin 112 , the start value 98 is determined by the change step 114 being subtracted from the previous start value 110 . In the exemplary embodiment, changing step 114 depends on first burner output parameter 68 . In figure 5 the change step 114 is 5%. In this way, when the method is repeated, the start value 98 is set iteratively in such a way that a distance between the start value 98 and the ignition value 104 largely equals the safety distance 112 .

In alternative specific embodiments, a first time interval 116 between a second point in time 118 and a third point in time 120 is compared with a desired ignition duration 122 stored in control unit 18 . In a variant of the exemplary embodiment, the desired ignition duration 122 is 2 seconds. In other variants, the desired ignition duration is 122 between 0.1 seconds and 10 seconds, preferably between 1 second and 5 seconds. In other embodiments, the ignition duration 112 depends on the first burner power parameter 68 . The ignition duration 112 is determined empirically in such a way that rapid, quiet and reliable ignition is ensured. If first time interval 116 is shorter than ignition duration 112 by at least one predefined threshold, start value 98 is determined by subtracting a change step 114 from previous start value 110 . If the first time interval 116 is at least one predetermined threshold longer than that after 112, the start value 98 is determined by adding the change step 114 to the previous start value 110. In this way, the starting value 98 is set iteratively in such a way that the first time interval 116 largely corresponds to the desired ignition duration 122 .

figure 6 shows a time development of the start value 98 in three different operating phases 124a, 124b and 124c. A time is plotted on a third abscissa axis 126 . The starting value 98 is shown on a third ordinate axis 127 . In the three different operating phases 124, the heating system 46 is operated with a constant first operating parameter 68 of 3000. In each of the three different operating phases 124, the heating system 46 was operated several times in the ignition mode 56. In each of the three different operating phases 124, the heating system 46 was operated with a different fuel. Otherwise, there are largely constant internal and external conditions in each operating phase in the individual ignition operation 56 . For this reason, the start value 98 determined as a function of the previous ignition value 108 stabilizes at a fixed value. In the operating phase 124a, the fuel is a burner test gas G25. A first starting value 98a is 43%. In the operating phase 124b, the fuel is a burner test gas G271. The burner test gas G271 is leaner than the burner test gas G25. Burner test gas G271 has a lower calorific value than burner test gas G25. A second starting value 98b is 48%. In the Operating phase 124c, the fuel is a burner test gas G21. The burner test gas G21 is richer than the burner test gas G25. The burner test gas G21 has a higher calorific value than the burner test gas G25. A third starting value 98c is 38%.

A start value 98 determined using the previous ignition value 108 depends on the quality of the fuel. In the exemplary embodiment, the greater the starting value 98, the lower the calorific value of the fuel. The starting value 98 can be used as the operating parameter 66. It is conceivable that a difference from the previous ignition value 108 and the previous starting value 110 is used as the operating characteristic 66, in particular taking into account the safety distance 112. It is also conceivable that a first time interval 116 is used as the operating characteristic 66, in particular taking into account the desired ignition duration 112.

In the exemplary embodiment, the gradient value 100 is selected as a function of the starting value 98. The seed value 98 is compared to the previous seed value 110. The difference between the starting value 98 and the previous starting value 110 is an operating parameter 66 . A linear relationship is stored in the control unit 18, which assigns the amount of the difference between the previous starting value 110 and the starting value 98 to a change in slope value. If the absolute value of the difference between the previous starting value 110 and the starting value 98 is 0, a slope value change of 0 is assigned. If the absolute value of the difference between the previous starting value 110 and the starting value 98 is 1%, then a gradient value change of 0.5% per second is assigned. The greater the magnitude of the difference between the previous starting value 110 and the starting value 98, the greater the slope value change. If the starting value 98 is greater than the previous start value 110, the slope value 100 is determined by adding the slope value change to a previous slope value 128. If the start value 98 is less than the previous start value 110, the slope value 100 is determined by subtracting the slope value change from the previous slope value 128.

In variants, any other functional relationship is used, which assigns the slope value change to the difference between the previous starting value 110 and the starting value 98 . The type of functional relationship depends on the technical properties of the heating system 46. The functional relationship is preferably determined empirically in laboratory tests.

In further variants of the embodiment, a second gradient value characteristic is stored in the control unit 18 . The second gradient value characteristic assigns the gradient value 100 to the start value 110 . The second slope value characteristic is preferably determined empirically in laboratory tests.

figure 7 shows the time profile of valve control signal 86 for three different ignition operations 56d, 56e and 56f. In the ignition mode 56d, the fuel is the burner test gas G25. The slope value 100 is 7.5% per second. In ignition mode 56e, the fuel is burner test gas G271. The slope value 100 is 10% per second. In the ignition mode 56f, the fuel is the burner test gas G21. The slope value 100 is 5% per second.

In further specific embodiments, the operating parameter 66 is determined as a function of a time profile of the fluid supply parameter 94 . In a particularly preferred embodiment, the fluid supply parameter 94 is initially set to a previous ignition value 108 in a previous ignition operation 102 set. The heating system 46 is then operated in a closed-loop mode 60 . In the closed-loop mode 60, the fluid supply parameter 94 is regulated to a control value 130. In the preferred embodiment, the operating characteristic 66 is determined by subtracting the previous firing value 108 from the control value 130 .

In the closed-loop mode 60, the fan speed 54 or the first burner output parameter 68 is kept largely constant. The valve control signal 86 is set in such a way that the ionization current 92 largely assumes the value of a target ionization. In the closed-loop mode 60, the detected ionization current 92 is compared continuously to the target ionization. In alternative embodiments, the current ionization current 92 is compared to the target ionization at time intervals, preferably periodically. The time intervals are preferably short compared to time scales typical for regulation and/or control of the heating system 46, for example between 10 ms and 10,000 ms, in particular between 100 ms and 1000 ms. The target ionization depends on the fan speed 54 . In the preferred embodiment, the required target ionization is determined as a function of fan speed 54 by a target ionization characteristic stored in control unit 18 . The target ionization characteristic is determined by laboratory tests and adapted to the requirements of the heating system 46. It is conceivable that the target ionization characteristic or the target ionization is determined by special methods during operation of the heating system 46, in particular by methods for calibrating the heating system 46. The target ionization is a target combustion parameter.

If the currently detected ionization current 92 is less than the target ionization, the valve control signal 86 is increased in the exemplary embodiment. If the current ionization current 92 is greater than the target ionization, the valve control signal 86 is lowered. In the exemplary embodiment, the valve control signal 86 becomes all the stronger increased or decreased, the greater the deviation of the current ionization current 92 from the target ionization. A linear relationship is stored in the control unit 18, which assigns a change in the valve control signal 86 to a difference in the ionization current 92 from the target ionization. If the amount of the difference between the ionization current 92 and the setpoint ionization is less than an ionization threshold, the valve control signal 86 is not changed. The ionization threshold is a value stored in the control unit 18 to take into account measurement inaccuracies or signal noise of the detected ionization current 92 . In the exemplary embodiment, the ionization threshold depends on the first burner output parameter 68 .

In variants of the preferred embodiment, the relationship stored in control unit 18 between the difference between ionization current 92 and target ionization and the change in valve control signal 86 has the form of any monotonically increasing function, in particular linear and/or quadratic and/or exponential and/or a power function. In preferred embodiments, the fluid supply parameter 94 is changed and/or increased or decreased the more, the greater the deviation of the currently detected combustion parameter 96 from the target combustion parameter.

A change in the valve control signal 86 changes a fuel-air ratio in a fuel-air mixture supplied to the burner 28 . The sensed ionization current 92 changes as a function of the change in the valve control signal 86. In this way, the valve control signal 86 can be iteratively changed so that the sensed ionization current 92 closely equals the target ionization. The set valve control signal 86, in which the detected ionization current 96 largely equals the setpoint ionization, is detected by the control unit 18 as a control value 130.

figure 8 illustrates the most preferred embodiment. figure 8 FIG. 12 shows the course over time of the ionization current 92 and of the valve control signal 86. First, a previous ignition operation 62 takes place. After the ignition, the closed-loop mode 60 is started from a fourth point in time 132 . The valve control signal is regulated down from the previous ignition value 108 to the regulation value 130 . If the control value 130 is lower than the previous ignition value 108, this indicates that the fuel has a higher calorific value than assumed. If the control value 130 is lower than the previous firing value 108, this indicates that the previous slope value 128 is too high. If the control value 130 is higher than the previous ignition value 108, this indicates that the fuel has a lower calorific value than assumed. If the control value 130 is higher than the previous firing value 108, this indicates that the previous slope 128 is too low.

In order to determine gradient value 100 for ignition operation 56 , operating parameter 66 is determined as the difference between previous ignition value 108 and control value 130 . The control unit checks whether the absolute value of the operating characteristic 66 is greater than a characteristic value threshold. The characteristic value threshold is a characteristic value that is stored in the control unit 18 and depends on the first burner output parameter 68 . Measurement inaccuracies or measurement errors and usual fluctuations in the valve control signal 86 are taken into account with the aid of the characteristic value threshold. If the operating characteristic 66 does not exceed the characteristic threshold, the previous gradient value 128 is used as the gradient value 100 . If the operating characteristic 66 exceeds the characteristic threshold, the previous gradient value 128 is recalculated. The gradient value 100 is selected by the control unit 18 using an analytical calculation method in such a way that the fluid supply parameter 86, starting from the starting value 98, after the desired ignition duration 122 assumes the control value 130 (see FIG figure 8 ). In this way, a slope value 100 that is smaller than the previous one is determined Gradient value 128 if control value 130 is less than previous ignition value 108. If control value 130 is greater than previous ignition value 108, a gradient value 100 is determined that is greater than previous gradient value 128.

In alternative embodiments, it is conceivable that a relationship is stored in the control unit 18 which assigns the gradient value 100 or the gradient value change to the operating characteristic value 66 . In particular, a linear relationship is conceivable, which assigns a gradient value change to the operating characteristic value 66 . Operating parameter 66 can be calculated by subtracting previous ignition value 108 from control value 130 . If the operating parameter 66 is 0, a gradient value change of 0 is assigned to it. If the operating parameter 66 is 1%, then a gradient value change of 0.5% per second is assigned. The greater the operating parameter 66, the greater the change in slope value. The slope value 100 is determined by adding the slope value change to the previous slope value 128 . If the control value 130 is less than the previous ignition value 108, then the operating parameter 66 is negative. The slope value 100 is reduced compared to the previous slope value 128. If the control value 130 is greater than the previous ignition value 108, then the operating parameter 66 is positive. The slope value 100 is increased compared to the previous slope value 128. In further embodiments, any other functional relationships between the operating characteristic value 66 and the gradient value 100 can be used. The type of functional relationship depends on the technical properties of the heating system 46.

In further variants, a temporary fluid supply change 134 over time is generated in the fluid supply parameter 94 in the previous heating operation 102, and the operating parameter 66 is generated as a function of a change associated with the fluid supply change 134 correlated temporal combustion parameter change 136 of the combustion parameter 96 is determined. These variants are preferably carried out with a largely constant first burner output parameter 68 .

figure 9 13 illustrates a fluid delivery change 134 of the valve control signal 86 and a combustion characteristic change 136 of the ionization current 92 during a closed loop mode 60. At the fluid delivery change 134, the largely constant valve control signal 86 is increased by a pulse height 138 as quickly as possible and after a pulse width 140 as quickly as possible again reduced to an initial value of the valve control signal 86. The pulse height 138 is selected depending on the first burner output parameter 68 . In figure 9 the pulse height is 138 5%. Depending on the first burner output parameter 68, the pulse height 138 can assume values between 0.5% and 20%. The pulse width is 140 in figure 9 40ms. In alternative embodiments, the pulse width 140 has values between 1 ms and 2000 ms, in particular between 10 ms and 200 ms, preferably 100 ms.

The fluid delivery change 134 results in the combustion characteristic change 136 . The change in combustion parameter 136 is correlated with a calorific value of the fuel. The greater the calorific value of the fuel, the smaller a first signal height 142 or first signal area 144 of the change in combustion parameter 136. The greater the calorific value of the fuel, the lower slope value 100 should be. In variants of the method, the operating parameter 66 is a first signal level 142 and/or a first signal area 144 of the combustion parameter change 136. In this way, the gradient value 100 can be adapted to the calorific value of the fuel. The control unit 18 has a relationship which gives the operating characteristic value 66 the gradient value 100 or the Assigns slope value change. The slope value 100 or slope value change is preferably the smaller the larger the operating parameter 66 is.

The combustion characteristic change 136 also depends on the magnitude of the fluid delivery change 134 . In preferred embodiments, the operating characteristic 66 is the first signal level 142 divided by the pulse level 138. In further preferred embodiments, the operating characteristic 66 is the first signal area 144 divided by a pulse area 146.

In further variants, in which the heating system 46 is intended to be operated with a finite number of different types of fuel, in particular with two different types of fuel, the control unit 18 has different sets of operating parameters, which are each provided for operation with one type of fuel. If the heating system 46 is operated with a specific set of operating parameters and a fluid supply parameter 94 and/or a first burner output parameter 68 is varied, the combustion parameter 96 will behave differently depending on whether the set of operating parameters matches the fuel used. From the behavior of the combustion parameter 96, conclusions can be drawn about the type of fuel used. The type of fuel can be determined quickly and reliably in this way, particularly when there are two different types of fuel. In such variants, the operating parameter 66 can be a slope value 100, which is stored in the control unit 18 as a function of the type of fuel.

In further variants, the first burner output parameter 68 is kept constant in a previous heating operation 102 . A transient fluid delivery change 134 is generated and a burner performance parameter change 148 is sensed. In preferred variants, the first burner power parameter is 68 the detected fan speed 54 and the second burner power parameter 70 a PWM signal, which is sent from the control unit 18 to the fan 32. The second burner power parameter 70 corresponds to the power made available to the blower 32 . The fluid supply change 134 briefly increases a proportion of fuel in a fuel-air mixture transported by the blower 32 . If the mass density of the fuel is greater than the mass density of air, the mass flow through the blower 32 increases for a short time. In order to keep the first burner output parameter 68 constant, the blower 32 needs a higher output for a short time. The second burner output parameter 70 rises briefly, resulting in a burner output parameter change 148 with a positive second signal level 150 . figure 10 FIG. 14 shows a fluid supply change 134 and a positive burner output parameter change 148. A fourth abscissa axis 154 shows a time. The valve control signal 86 and the second burner output parameter 70 are shown on a fourth ordinate axis 156 .

If the mass density of the fuel is lower than the mass density of air, the mass flow through the blower 32 drops briefly. The blower 32 requires less power for a short time. The second burner power parameter 70 drops briefly. This results in a negative second signal level 150 of the burner power parameter change 148 .

The second signal level 150 or a second signal area 152 (see figure 10 ) are correlated with the mass density of the fuel. The mass density of the fuel allows conclusions to be drawn about a type of fuel and/or a calorific value of the fuel. In such variants of the method, the operating parameter 66 is a second signal height 150 and/or a second signal area 152 of the burner performance parameter change 148. In this way, the slope value 100 can affect the mass density and/or indirectly or be adjusted directly to the calorific value of the fuel. The control unit 18 has a relationship which assigns the gradient value 100 or the gradient value change to the operating characteristic value 66 . The slope value 100 or slope value change is preferably the smaller the larger the operating parameter 66 is.

The burner power parameter change 148 also depends on the magnitude of the fluid supply change 134 . In preferred embodiments, the operating characteristic 66 is the second signal level 150 divided by the pulse level 138. In further preferred embodiments, the operating characteristic 66 is the second signal area 152 divided by a pulse area 146.

In the embodiments presented above, different methods for determining the operating characteristic 66 are presented. It is conceivable that several different methods are used in particular embodiments. In this way, it is possible to compare operating parameters 66 determined differently with one another. Conclusions about an operating state of the heating system 46 can be drawn from a comparison of differently determined operating parameters 66 . It is also conceivable that operating characteristic values 66 determined differently are used to check the operating characteristic value 66 . In this way, the ignition operation 56 can be controlled particularly precisely and reliably.

In the exemplary embodiment and other specific embodiments, slope value 100 is set as a function of operating characteristic value 66 . In variants it is conceivable that the starting value 98 is selected as a function of the operating parameter 66 . For example, if the slope value 100 is a function of an operating characteristic value 66, which is determined from a difference between a previous ignition value 108 and a control value 130 (see figure 8 ), determined, it is conceivable that the start value 98 also depends on the Operating parameter 66 depends. For example, a change in starting value 98 compared to a previous starting value 110 may be proportional to operating characteristic 66 .

Claims (17)

1. Method for controlling an ignition operation (56) of a heating system (46), an operating parameter (66) recorded before the ignition operation (56) being taken into account, characterized in that the operating parameter (66) is determined in a previous heating operation (102), wherein the operating parameter (66) is suitable for determining
   a quality of a fuel used in the heating system (46), in particular a calorific value of the fuel and/or a fuel type of the fuel, and/or the operating parameter (66) is suitable for determining an output requirement (64) for the heating system (46).
2. Method according to Claim 1, characterized in that, in the ignition operation (56), a first burner output parameter (68) is determined as a function of the operating parameter (66).
3. Method according to Claim 2, characterized in that, in the ignition operation (56), the first burner output parameter (68) largely equates to a starting output (74), wherein the starting output (74) is selected from a starting output range (72), in particular a starting output interval (76), such that the starting output (74) is as close as possible to an or the output requirement (64) .
4. Method according to one of the preceding claims, characterized in that, in the ignition operation (56), a fluid supply characteristic value (94) is firstly brought to a starting value (98) and is then increased, preferably linearly with a slope value (100), until an ignition value (104) of the fluid supply characteristic value (94) is reached, at which a flame (40) in the heating system (46) ignites.
5. Method according to Claim 4, characterized in that the slope value (100) and/or the starting value (98) depend(s) on the operating parameter (66).
6. Method according to one of the preceding claims, characterized in that the operating parameter (66) is determined as a function of a or the starting value (98) of the fluid supply characteristic value (94) in the ignition operation (56) and/or as a function of a previous starting value (98) in a previous ignition operation (62).
7. Method according to one of the preceding claims, characterized in that a or the starting value (98) is determined as a function of a previous ignition value (100) of a or the fluid supply characteristic value (94) in a or the previous ignition operation (62).
8. Method according to one of the preceding claims, characterized in that the operating parameter (66) is determined as a function of a combustion characteristic value (96), for example an ionization current (92).
9. Method according to Claim 8, characterized in that the operating parameter (66) is determined as a function of a time profile of the combustion characteristic value (96) after a change in the fluid supply characteristic value (94) and/or a first burner output parameter (68).
10. Method according to Claim 9, characterized in that a temporary fluid supply change (134) over time in the fluid supply characteristic value (94) is generated, and the operating parameter (66) is determined as a function of a combustion characteristic value change (136) over time in the combustion characteristic value (96) that is correlated with the fluid supply change (134).
11. Method according to one of the preceding claims, characterized in that the operating parameter (66) is determined as a function of a time profile of the fluid supply characteristic value (94), the heating system (46) having been operated in a closed-loop mode (60) after a previous ignition operation (62).
12. Method according to Claim 11, characterized in that the fluid supply characteristic value is set to a previous ignition value (108) in a previous ignition operation (62), is then regulated to a control value (130) in the closed-loop mode (60), and the operating parameter (66) is determined from a comparison between the previous ignition value (108) and the control value (130), in particular a magnitude comparison.
13. Method according to one of the preceding claims, characterized in that the operating parameter (66) is determined as a function of a time profile of a second burner output parameter (70) with a largely constant first burner output parameter (68) and following a change in the fluid supply characteristic value (94).
14. Method according to Claim 13, characterized in that the first burner output parameter (68) is a recorded fan rotational speed (54), which is kept constant by a control loop by adjusting the second burner output parameter (70), and the operating parameter (66) is determined as a function of a burner output parameter change (148) in the second burner output parameter (70), wherein the burner output parameter change (148) is correlated with a temporary fluid supply change (134).
15. Method according to one of the preceding claims, characterized in that a or the fluid supply characteristic value (94) is a valve control signal (86) for a fuel valve (44) and/or a or the combustion characteristic value (96) is an ionization current (92) and/or a or the second burner output parameter (70) is a fan control signal (71).
16. Control unit (18) for a heating system (46), wherein the control unit (18) is set up in such a way that a method according to one of the preceding claims can be carried out.
17. Heating system (46) having a control unit (18) according to Claim 16, having at least one fuel valve (44) for a fuel, having an ionization probe (42) on a flame (40) and having a fan (32) with a variable fan rotational speed (54).

Images