Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N1/00—Regulating fuel supply
  • F23N1/02—Regulating fuel supply conjointly with air supply
  • F23N1/022—Regulating fuel supply conjointly with air supply using electronic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
  • F23N5/022—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using electronic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N5/00—Systems for controlling combustion
  • F23N5/24—Preventing development of abnormal or undesired conditions, i.e. safety arrangements
  • F23N5/242—Preventing development of abnormal or undesired conditions, i.e. safety arrangements using electronic means
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2225/00—Measuring
  • F23N2225/08—Measuring temperature
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2225/00—Measuring
  • F23N2225/26—Measuring humidity
  • F23N2225/30—Measuring humidity measuring lambda
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
  • F23N—REGULATING OR CONTROLLING COMBUSTION
  • F23N2239/00—Fuels
  • F23N2239/04—Gaseous fuels

Definitions

• the invention relates to a retrofitting unit for retrofitting a combustion appliance to a gas adaptive combustion appliance. Additionally, the invention relates to a gas adaptive combustion appliance comprising such an oxygen sensor and a method for retrofitting a combustion appliance to a gas adaptive combustion appliance. The invention also relates to a use of a retrofitting unit for retrofitting a combustion appliance to a gas adaptive combustion appliance.
• Pneumatic boilers are known from the prior art.
• the boiler consists of a fan for modulating the boiler power and a fuel gas valve which controls the gas-air ratio.
• a control unit controls the fan speed to set an air to fuel gas ratio.
• the fuel gas valve is a pneumatic valve, the fuel gas flow is dependent on the fan speed.
• pneumatic boilers are set to a specific fuel gas quality. However, the fuel gas quality might differ so that there is a need for gas adaptive boilers.
• Such gas adaptive boilers can be crucial due to the uncertainty in the quality of the future fuel gas supply. Both due to the ban of importing fuel gas from specific countries as well as alternative sources like biogas, with a gas adaptive boiler, the boiler is able to adapt its setting for different gas qualities in order to assure safe and stable operation.
• Gas adaptive combustion appliances were developed to in particular address the broad Wobbe value changes of the fuel supply in Europe and were introduced in 2001.
• the known gas adaptive combustion appliances are fully premixed appliances equipped with an Adaptive Combustion Control Function (ACCF) that are intended to be connected to gas grids where the quality of the distributed gas is likely to vary to a large extent over the lifetime of the appliance including gas grids for natural gases of the second family where up to 20 mol% H2 is added to the natural gas.
• Gas adaptive combustion uses at least one sensor signal to adjust the air fuel mixture to maintain a preset value, such as an ionization signal or an O2 signal.
• the gas adaptive combustion appliance control uses the respective signal and, by controlling the blower and gas valve via for example using a pulse-width modulation (PWM) signal, adjusts the amount of air and gas entering the burner until it the desired value is reached.
• PWM pulse-width modulation
• the gas adaptive combustion allows constant combustion monitoring for optimal efficiency.
• there is a scheduled calibration period which occurs based on run time cycles that confirms the system is operating within predetermined specifications.
• the boiler consists of a fan for modulating the boiler power and a fuel gas valve which controls the gas-air ratio.
• the fuel gas valve can be adjusted manually to set the gas-air ratio at low load.
• a motor driven throttle is located which can electronically adjust the flow through a throttle opening downstream of the fuel gas valve opening and adjusts the gas-air ratio.
• the gas adaptive combustion appliance controls the throttle position and thus the throttle opening by controlling the throttle motor to get a desired gas-air ratio. This ratio is measured with an oxygen sensor in the flue gas.
• Gas adaptive combustion appliances utilize the relationship between the O2 signal and the air-fuel ratio (also known as lambda ⁇ ).
• Gas adaptive combustion appliances have a relationship between O2 and power that can be expressed by an O2 - power curve.
• the flame ionization curve is used as a target setpoint to control the gas valve.
• O2 signal is higher than expected (indicating excess air too high, or lean condition)
• Gas adaptive combustion appliances commonly periodically calibrate to compensate for effects like combustion air temperature/humidity variation, component wear, and fuel composition. Calibration is commonly automatically initiated upon a boiler start several times per month based on an internal counter. When a calibration is required and demand is present, the gas adaptive combustion appliance starts and runs at a constant mid-range firing rate. As an example, the gas valve is opened until lambda equals 1 and a maximum ionization value is reached. This value is then used to shift the ionization setpoint curve. Following this phase, the gas adaptive combustion appliance ramps to low fire and calibrates the minimum opening point of the gas valve. The entire calibration sequence lasts about one minute. In case of using the O2 signal, calibration is done by purging and setting the measured value of O2 related to the 21% O2 of ambient air.
• Ignitions are more reliable with gas-adaptive combustion appliances compared to systems with pneumatic gas / air ratio control where the gas supply rate is pneumatically driven by the air supply rate or vice versa (definition 3.1.201.22 EN 12067-2:2022, 3.117).
• Gas adaptive ignitions can for example begin with the gas valve opening to a fixed point followed by an automatic ramp up until a flame is detected. This feature assures the system will always light at the proper air-fuel ratio.
• pneumatic gas valves open to the same fixed point at every ignition, which is only changed by a manual adjustment of the gas valve. This can lead to light-off issues such as noise or ignition failure over time.
• the object of the invention is to easily retrofit a combustion appliance to a gas adaptive combustion appliance.
• a retrofitting unit for retrofitting a combustion appliance to a gas adaptive combustion appliance
• the retrofitting unit comprises an oxygen sensor comprising a sensing element for measuring an oxygen value in the combustion appliance and a sensor data processing device that is electrically connected to the sensing element and is connectable in regards to data with a data processing device of the combustion appliance for receiving the at least one oxygen value measured by the oxygen sensor.
• the oxygen sensor enables to measure an oxygen value, in particular a flue gas oxygen value.
• the measured oxygen value is used to change a fuel gas flow to maintain a predetermined setting for having a predetermined stable and safe combustion.
• the provision of the oxygen sensor together with a throttle unit described below more in detail enables that the combustion appliance can operate as gas adaptive combustion appliance in which the fuel gas of different quality can be combusted.
• the combustion appliance can be converted into a gas-adaptive combustion appliance with a minimum amount of components or investment.
• the data processing device of the non-gas adaptive combustion appliance can be prepared to be updated towards a gas adaptive combustion appliance. Thus, it is not necessary to change the data processing device for retrofitting purposes.
• the conversion to a gas adaptive combustion appliance is achieved in that the data processing device has a throttle unit control portion that is used to control a throttle unit and a safety unit control portion that is used to communicate with the oxygen sensor.
• a control program for controlling the throttle unit is already integrated in the data processing unit, which enables to retrofit the combustion appliance to a gas adapted combustion appliance by a plug and play mechanism, namely by connecting the oxygen sensor with the data processing device of the combustion appliance.
• the conversion of the combustion appliance to a gas adaptive combustion appliance can also be done in a cost-efficient matter as it is only necessary to connect the oxygen sensor to the data processing device of the combustion appliance. Additionally, it is necessary to add a throttle unit. All other components that a gas adaptive combustion appliance must have like data processing device, fuel valve and fan are already existing in the combustion appliance.
• a connection in respect to data means that two components, in particular the sensor data processing device and the data processing device, communicate with each other by exchanging data.
• the connection can be via wire or wireless.
• the sensor data processing device is used to receive and process the data measured by the sensing element. Thereto, the sensor data processing device is electrically connected to the sensing element so that the data can be exchanged between them in a simple manner.
• the oxygen sensor can be formed as a module. This has the advantage that the oxygen sensor can be simply handled.
• a combustion appliance is a device designed to burn a fuel source in a controlled manner for the purpose of producing heat.
• This device typically comprises a combustion chamber where the combustion reaction occurs and means for conveying air and fuel gas into this chamber.
• the air and fuel in particular fuel gas, can mix before the combustion chamber or inside the combustion chamber.
• the appliance may also include at least one heat exchanger for transferring the heat generated during combustion to a liquid or air, thereby converting the energy from the combustion process into usable heat.
• the combustion appliance may be designed to burn various types of fuels, including but not limited to, natural gas, propane, oil, hydrogen, biogas, or solid fuels such as wood or pellets.
• a combustion appliance can be a boiler, space heater, oven, or a gas water heater.
• a commissioning mode of a combustion appliance is a mode in which the components and/or parameters of the combustion appliance are set so that the combustion appliance can be operated in the operation mode.
• automatic or manual adjustments can be made to components.
• the combustion appliance enables two adjustment possibilities.
• One possibility is to adjust the throttle unit. This can happen automatically by throttle element that is adjusted by a throttle motor.
• Another possibility is to adjust the fuel valve. This can happen manually by manually adjusting an offset element of the fuel valve, namely an offset screw.
• parameters can be determined in the commissioning mode that are used in the operation mode of the combustion appliance.
• flue gas oxygen values are determined during the commissioning mode and stored in a memory of the combustion appliance. Said flue gas oxygen values are used for the operation of the combustion appliance in the operation mode.
• a control unit of the combustion appliance switches from the commissioning mode to the operation mode after all relevant parameters and/or components are determined and/or set.
• the determination of the at least one Wobbe value can be done when the combustion appliance is operated in the commissioning mode and/or when the combustion appliance is operated in the operation mode. In both modes the combustion appliance can be controlled on the determined at least one Wobbe value.
• the Wobbe value is an indicator of the interchangeability of fuel gases. It is used to compare the combustion energy output of different composition fuel gases in an appliance. If two fuels have identical Wobbe values, then for given pressure and valve settings, the energy output will also be identical.
• the gross Wobbe index or value is defined as the volume-basis gross calorific value, at specified reference conditions, divided by the square root of the relative density at the same specified metering reference conditions. In common usage, and in the absence of any other qualifier, the term Wobbe index is taken to mean the quantity that is identified here as gross Wobbe index or value (Definition 3.5 ISO 6976:2016).
• the net Wobbe index or value is the volume-basis net calorific value, at specified reference conditions, divided by the square root of the relative density at the same specified metering reference conditions (Definition 3.6 ISO 6976:2016). Both Wobbe indices can be used for the purpose of comparison, as long as the same type of index is used for the respective comparison.
• the Wobbe index or value is expressed in MJ/Nm 3 .
• An operation mode is a mode of the combustion appliance which is present after the commissioning is finalized.
• the parameters determined and set in the commissioning mode are used to operate the combustion appliance.
• the outputted heat of the combustion appliance outputs is used in different kind of applications like for central heating and/or domestic water heating. Further application fields of the combustion appliance can be to provide process heating. Processing heating is used in commercial use for industrial processes that needs heat. In said case a constant heat output has to be provided.
• a starting mode of the combustion appliance is a mode in which the air and fuel gas mixtures is ignited in the combustion chamber by the burner.
• the combustion appliance can be in a standby mode in which the combustion appliance is switched on but the burner is not working.
• the combustion appliance can be in commissioning or in an operation mode in which it has a specific power output. At normal operation the boiler determines its power output by modulation.
• a failure state of the combustion appliance is a combustion appliance state in which a combustion appliance component malfunctions so that the combustion appliance does not operate as expected.
• a combustion appliance failure state is a state in which inadequate conditions, e.g. insufficient fuel or air, are present so that the burner does not start and thus the combustion appliance does not operate as expected.
• a failure state covers a failed ignition or no ignition.
• a failure state can be present when the measured air to fuel gas mixture does not correspond to the expected air to fuel gas mixture so that the combustion appliance does not operate as expected.
• Another advantage of the invention is that by considering the oxygen value a commissioning time in case of ignition failure is reduced.
• a failure free state of the combustion appliance is a combustion appliance state in which the combustion appliance operates as expected.
• the combustion appliance in particular a data processing unit of the combustion appliance, can determine the flue gas oxygen value which is a measure for air to fuel gas ratio.
• the data processing unit can control the combustion appliance on the basis of the determined air to fuel gas ratio.
• the combustion appliance can be easily controlled by measuring the flue gas oxygen value.
• the oxygen value can be measured in the flue gas.
• a burner of the combustion appliance combusted the mixed air and fuel gas being in the combustion chamber.
• the oxygen value of the combusted gas being in the combustion chamber of the combustion appliance can be measured.
• the oxygen value of a non-combusted gas for example of the air and fuel gas mixture can be measured.
• the oxygen value can be measured in the combustion chamber before the burner combusts the air and fuel gas mixture and/or in a part of the gas flow path being upstream of the combustion chamber.
• the retrofitting unit can comprise a throttle unit for controlling a fuel gas flow from a fuel gas valve of the combustion appliance.
• the throttle unit is used for adapting the combustion appliance to the gas adaptive appliance by controlling the fuel gas flow that passes the fuel gas valve as it is described more in detail.
• the throttle unit and the oxygen sensor can be separated components and/or can be separately connected to the data processing device of the combustion appliance.
• the throttle unit comprises a throttle element for controlling a throttle opening cross section through which the fuel gas flows.
• the throttle unit has the advantage that the fuel gas flow coming from the fuel gas valve can be controlled independent of the fan speed.
• the data processing device can control the throttle unit and/or the fan and/or the fuel gas valve dependent on the measured at least one oxygen value.
• the stepper valve comprises a stepper motor, also known as step motor or stepping motor, which is an electrical motor that rotates in a series of small angular steps.
• the stepper motor thus divides a full revolution into a number of equidistant steps.
• the stepper motor consists of several "toothed" electromagnets arranged as a stator around a central rotor. These electromagnets are activated by an external driver circuit or a microcontroller. Each step rotates the shaft through a fixed angle.
• the circular arrangement of electromagnets is divided into groups referred to as phases.
• a stepper motor can be precisely rotated through a specific angle by activating the electromagnets one after the other.
• the controllable pneumatic valve is a valve wherein a fluid flow rate is controlled by varying the size of the flow passage via a restrictor.
• the restrictor is directed by a signal from an actuator.
• Typical examples of controllable pneumatic valves are solenoid valves, in particular proportional solenoid valves.
• the proportional control solenoid valve utilizes a solenoid as an actuator for variable valve positioning.
• a normally closed solenoid control valve with zero current fed to the coil, the spring pushes the plunger downwards to a fully closed position. Applying current to the coil generates a magnetic field to move the plunger upward against the return spring.
• 100% duty cycle power is fully fed to the solenoid and the solenoid valve is open.
• duty cycle describes the proportion of on time to the cycle duration interval in a pulse-width modulation for controlling a load.
• Pulse-width modulation in other words is a method of controlling the average power or amplitude delivered by an electrical signal.
• a low duty cycle corresponds to low power, because the power is off for most of the time.
• Duty cycle is expressed in percent, with 100% being fully on.
• Duty cycles between 0 to 100 percent range proportionally change the flow of the valve. For example, a duty cycle of 50% fed to the solenoid moves the spring and the plunger to 50% of the operating range.
• the data processing device can control the throttle unit and/or the fan and/or the fuel gas valve dependent on the at least one oxygen value received from the oxygen sensor.
• the data processing device can comprise a throttle unit control portion for controlling the position of a throttle element of the throttle unit.
• Providing the throttle control portion has the advantage that the throttle unit has only to be connected in regard to data to the data processing device. In other words, the installer does not have to perform any other actions for configuring the throttle unit to the data processing device.
• the oxygen sensor can be arranged in the combustion chamber.
• the oxygen sensor can easily measure the flue gas oxygen value and/or can quickly response to oxygen value changes in the combustion chamber.
• the oxygen sensor can be arranged upstream of the burner, in an air flow path. This is possible as the method does not need the flue gas to detect a change in oxygen.
• a retrofitting unit which comprises a sensing element for measuring an oxygen value, in particular a flue gas oxygen value, in the combustion appliance and a sensor data processing device that is connected to the sensing element, for retrofitting a combustion appliance to a gas adaptive combustion appliance.
• the throttle unit 6 controls the fuel flow, in particular the fuel gas flow, coming from the fuel valve 5.
• the throttle unit 6 comprises a throttle motor 22 and a throttle element 21 shown in figure 2 .
• the throttle motor 22 changes the position of the throttle element 21.
• the throttle element 21 delimits a throttle opening cross section through which the fuel flow, in particular the fuel gas, can flow.
• the fuel flow that passes through the throttle unit 6 depends on the position of the throttle element 21.
• the throttle unit 6 is electrically connected with a data processing unit 9 of the combustion appliance 1 as is indicated with dotted line in figure 1 .
• the throttle element position depends on the instruction that is received from the data processing unit 9.
• the data processing unit 9 transmits a throttle position signal P to the throttle unit 6, in particular the throttle motor 22.
• the throttle motor 22 changes the position of the throttle element 21 according to the received throttle position signal P.
• the data processing device 9 comprises a processor and/or can be used to set the power state of the combustion appliance 1. Thereto, the data processing device 9 sends at least one operation signal S1-S4 to the fan 4 to set the fan speed. In particular, the data processing device 9 can set the combustion appliance 1 to operate in a minimum power state, a maximum power state or a power state that is between the maximum and minimum power state.
• the combustion appliance 1 also comprises a manifold 13.
• the manifold 13 is arranged upstream of a burner 7 of the combustion appliance 1 and is used to mix the fuel, in particular fuel gas, passing the throttle unit 6 with air provided by the fan 4.
• the combustible mixed gas is burned in a combustion chamber 18 of the combustion appliance 1 by the burner 7.
• the combustion appliance 1 comprises a heat exchanger 12 that surrounds the combustion chamber 18 and that is used to transfer the heat to a liquid, in particular water, that is used for a central heating and/or for domestic hot water.
• the flue gas leaves the combustion chamber 18 via an exhaust flue path 17.
• a sensor heating manager can be executed in a tenth step G10. Additionally in an eleventh step G11 a sensor calibration manager and in a twelfth step G12 a throttle starting positioning manager can be executed.
• the sensor heating manager ensures that the sensor heating, i.e. the heating of the sensing element 19 is turned on or off. If the oxygen sensor 8 is not heated, the sensor needs to be calibrated. The calibration takes a few seconds; however, heating may take a few minutes. During operation of the combustion appliance 1 there are moments where no heat demand is expected, this means, the heating can be turned off resulting in energy savings.
• the sensor calibration manager can calibrate the oxygen sensor 8 in the eleventh step G11 to prevent discomfort for the user.
• the data processing device 9 ensures that each 72 hours the oxygen sensor 8 is calibrated. By tracking a calibration timer, the most optimal moment can be found.
• a calibration is done in air, wherein the percentage of oxygen in air is known.
• the calibration can be done in a pre-purge and/or post-purge process.
• the throttle starting positioning manager, the sensor heating manager and the sensor calibration manager can be executed after the ninth method step G9. Additionally, said managers can be executed in cases after it is determined in the sixth step G6 that the combustion appliance has been commissioned. In particular, the managers can be executed before it is determined in a fourteenth step G14 whether a heat demand is present.
• a sixteenth method step G16 is initiated in which the starting behavior of the combustion appliance 1 is set. Likewise, to the seventh step G7 one part of the setting of the starting behavior can be to determine the fuel gas quality.
• the combustion appliance 1 is prepared for the standby mode or the stop of the combustion appliance 1.
• the combustion appliance 1 is prepared such that a restart of the combustion appliance1 is done by using the correct parameters.
• the method step G18 is explained more in detail in figure 8 .
• FIG 4 shows a method for determining a throttle element position of the throttle unit 6. Said figure shows the specifics of the eighth method step G8 shown in figure 3 .
• the throttle position setting is started.
• the data processing device 9 outputs a first operating signal S1 that causes that the combustion appliance 1 is operated in a maximum power state. Specifically, the first operating signal S1 is sent to the fan 4 to operate the combustion appliance 1 in the maximum power state. Additionally, the data processing device 9 receives a first flue gas oxygen value O1 measured by the oxygen sensor 8 when the combustion appliance is operated in the maximum power state.
• the throttle element position of the throttle unit 6 corresponds to the throttle element position that is set in the fourth method step G4.
• the data processing device checks whether the measured first flue gas oxygen value O1 fulfils a test condition.
• the test condition comprises a check whether the first flue gas oxygen value O1 is arranged in a predetermined flue gas oxygen range assigned to maximum power state of the combustion appliance for a predetermined time-period.
• the predetermined flue gas oxygen band and the predetermined time-period can be saved in a memory of the combustion appliance 1, in particular data processing device 9.
• the throttle element position is adjusted in a fourth sub-step T4.
• the throttle element position can be automatically adjusted.
• the data processing device 9, in particular the throttle unit control portion 26, sends out a throttle position signal P to change the throttle element position of the throttle element 21 and thus to change the fuel gas flowing through the throttle unit 6.
• the sub-steps T3 and T4 are repeated until the test condition is fulfilled.
• the throttle position of the throttle unit 6 is stored in the memory in a fifth sub-step T5.
• the data processing device 9 outputs a second operating signal S2 that causes the combustion appliance 1 to operate in a minimum power state. Specifically, the data processing device 9 outputs the second operating signal S2 to the fan 4 to operate the combustion appliance 1 in the minimum power state. Additionally, the data processing device 9 receives a second flue gas oxygen value O2 from the oxygen sensor 8 when the combustion appliance is operated in the minimum power state.
• the throttle element position of the throttle unit 6 that is set when the combustion appliance 1 is operated in the minimum power state corresponds to the throttle element position that fulfils the test condition of the third method sub-step T3.
• the data processing device 9 determines whether the received second flue gas oxygen value O2 fulfils a further test condition.
• the further test condition comprises a check whether the second flue gas oxygen value O2 is arranged in a predetermined further flue gas oxygen range assigned to a minimum power state of the combustion appliance 1 for a predetermined further time-period.
• the predetermined further flue gas oxygen band and the predetermined further time-period can be saved in a memory of the combustion appliance 1.
• the fuel valve 5 is adjusted in an eighth sub-step T8.
• the fuel valve 5 can be manually adjusted by an installer by adjusting an offset screw of the fuel valve 5.
• the fuel valve 5 can be automatically adjusted by the data processing device 9.
• the sub-steps T7 and T8 are repeated until the further test condition is fulfilled.
• the throttle element position determination is finished.
• the boundary table is created in the nineth method step G9.
• the creation of the boundary table is shown in figure 5 more in detail. As is discussed above, the boundary table is created when the combustion appliance 1 is operated in the commissioning mode. Said table is used in an operating mode as is explained below more in detail.
• a first sub-step C1 the data processing device 9 starts with creating the boundary table. Said creation can only be done when the combustion appliance 1 is operated in the commissioning mode. In other words, the determined values of the table cannot be changed, when the combustion appliance 1 is operated in the operation mode.
• a second sub-step C2 the data processing device 9 receives information about a third power state stored in a memory of the combustion appliance 1.
• the third power state is between the maximum power state and the minimum power state.
• the data processing device sends a third operation signal S3, in particular to the fan, to cause the combustion appliance 1 to be operated in the third power state.
• the data processing device 9 receives in a fourth sub-step C4 a third flue gas oxygen value 03. Additionally, the data processing device 9 determines in the fourth sub-step C4 an upper threshold value and a lower threshold value with respect to the third flue gas oxygen value 03. The measured third flue gas oxygen value O3 and the determined upper and lower threshold value are stored in a fifth sub-step C5.
• a sixth sub-step C6 the data processing device 9 determines whether the table is complete. If not, the data processing device sends a fourth operation signal S4, which results in that the combustion appliance 1 operates in power state that is between a maximum power state and a minimum power state, so that the combustion appliance 1 is operated in a fourth power state.
• the fourth power state differs from the first to third power state.
• the data processing device 9 receives the fourth power state value from the memory likewise to the third power state described in sub-step C2.
• the sub-steps C4-C7 are repeated for all power states of the combustion appliance 1 that are stored in the memory as discussed above for sub-step C2. After the boundary table is created the boundary table creation method is finished in the eighth sub-step C8.
• Figure 6 shows a diagram showing a flue gas oxygen curve dependent on a power state of the combustion appliance. Specifically, figure 6 shows curves that are determined on the basis of the values that are determined in the method shown in figure 5 .
• Figure 6 shows the dependency of flue gas oxygen values 01-04 from the power state of the combustion appliance. Specifically, figure 6 shows the first flue gas oxygen value O1 when the combustion appliance 1 is in the maximum power state and the second flue gas oxygen value O2 when the combustion appliance 1 is in the minimum power state.
• figure 6 shows upper thresholds 2 and lower thresholds 3.
• Each of the upper thresholds 2 and the lower thresholds 3 are assigned to one measured flue gas oxygen value.
• the upper and lower threshold curve defines a flue gas oxygen band that is used to control the combustion appliance as is explained more in detail in figure 7 .
• Figure 7 shows a flow chart relating to a combustion control of the combustion appliance 1 in the operation mode. That means, the method steps are performed after the combustion appliance 1 is commissioned. Specifically, figure 7 shows the method sub-steps that are executed in the seventh method step G17 shown in figure 3 .
• a burner off condition can result if there is no heat demand request and/or if a burner could not be started for a predetermined number of times. If the burner off condition is fulfilled, the combustion appliance 1 prepared for a standby mode or a stop in the third sub-step N3. This transition process is shown in figure 8 more in detail.
• the oxygen sensor 8 measures the flue gas oxygen value in the combustion chamber 18 in a fourth sub-step N4. Specifically, the data processing device 9 receives the measured flue gas oxygen value in the fourth sub-step N4.
• an adjusting process is started in a sixth sub-step N6.
• said adjustment process it is checked in a seventh sub-step N7 whether the fan speed is above a fan threshold value. If this is not the case, the method is continued at the second sub-step N2.
• Figure 10 shows an overview of a system 10 comprising several combustion appliances, namely a first combustion appliance 1a, a second combustion appliance 1b, a third combustion appliance 1c and a fourth combustion appliance 1d.
• a first combustion appliance 1a a second combustion appliance 1b
• a third combustion appliance 1c a fourth combustion appliance 1d.
• all combustion appliances 1a, 1b, 1c, 1d are in an operating mode.
• the combustion appliances are arranged in a cascade and are connected in parallel to each other.
• a first sub-step B1 the method for detecting blockage is initiated. As mentioned above this can happen when the combustion appliances are in a starting process, i.e. the ignition phase is initiated.
• the data processing device 9 detects whether the flue gas path 17 is blocked. Thereto, the data processing device 9 uses the oxygen values measured by the oxygen sensor 8.
• the blockage detection can be performed before the burner combusts the air to fuel gas mixture or after combustion. In the following, it is assumed that the detection is performed after the combustion so that the oxygen sensor 8 measures flue gas oxygen values.
• Figure 13 shows a diagram illustrating how blockage in the flue gas path can be determined according to a first variant.
• the diagram shows the correlation between a factor indicating the blockage, namely the load loss in the flue gas path, and a time between the time when the fuel gas valve 5 is opened and a time when the oxygen sensor 8 measures a flue gas oxygen value that is above a predetermined threshold.
• the predetermined threshold is that the flue gas oxygen value has to be equal or greater than 7,5%.
• Figure 14 shows a diagram illustrating how blockage in the flue gas path can be determined according to a second variant.
• the diagram shows the correlation between a factor indicating the blockage, namely the load loss in the flue gas path, and measured oxygen values.
• the data processing device 9 ensures that the oxygen sensor measures the flue gas oxygen value at a predetermined time-period after the fuel valve 5 is opened. For example, the data processing device can ensure that the oxygen value is measured after 2,4 seconds after the fuel valve 5 is opened.
• increasing oxygen values correlate to increasing load loss.
• V1 in particular a measured oxygen value, that is measured after the predetermined time-period
• the data processing device 9 detects the load loss and thus blockage of the flue gas path. This can be done in the second sub-step B2 discussed above in figure 12 .
• Figure 15 shows a diagram illustrating how blockage in the flue gas path 17 can be determined according to a third variant.
• the diagram shows the correlation between a factor indicating the blockage, namely the load loss in the flue gas path, and a gradient of the oxygen value.
• the data processing device 9 receives several oxygen values and determines at least one gradient dependent on the received oxygen values. Additionally, the data processing device determines the minimum gradient value during the starting phase of the combustion appliance 1.
• the determined value V1 corresponds to the determined minimum gradient.
• the load loss and thus the blockage of the flue gas path can be determined after the minimum gradient is determined. This can be done in the second sub-step B2 discussed above in figure 12 .
• the data processing device 9 determines in the second sub-step D2 that the combustion appliance 1 is in a failure state
• the data processing device 9 transmits a failure signal to a display device of the combustion appliance in a third sub-step D3.
• the failure state of the combustion appliance comprising the failure type is displayed on the display device in the third sub-step D3.
• the data processing device 9 ensures in the third sub-step D3 that the commissioning mode or operating mode or starting mode of the combustion appliance is stopped.
• the data processing device 9 then initiates a couple of re-attempts which can ultimately lead to stop the combustion appliance. However, it depends on the failure state whether the data processing device 9 initiates the re-attempts.
• the starting behavior executed in the seventh step G7 or sixteenth step G16 shown in fig. 3 is continued. Thereto, it is referred to the aforementioned statements referring to the setting of the combustion appliance 1 in the starting behavior.
• Figure 17 shows a diagram showing different states of the combustion appliance 1 during a commissioning mode.
• the diagram shows a curve 32 of oxygen values that are measured by the oxygen sensor 8 and transmitted to the data processing device 9. Additionally, the diagram shows the time of a start attempt of the combustion appliance 1. As is evident from fig. 17 , the time of a start attempt signal O has a rectangular shape, indicating that the fuel valve 5 is opened.
• a lower threshold 24, an upper threshold 23 and a further upper threshold 25 are shown in the diagram.
• the threshold values relate to oxygen values.
• the lower threshold 24 corresponds to an oxygen value that is smaller than the oxygen value corresponding to the upper threshold 23.
• the oxygen value of the upper threshold 23 is smaller than the oxygen value corresponding to the further upper threshold 25.
• the data processing device 9 determines a combustion appliance state dependent on the oxygen value measured by the oxygen sensor 8. As is explained below more in detail, the data processing device 9 can also consider other combustion parameters for the determination of the combustion appliance state. Dependent on the oxygen value it can be differentiated between the following states.
• the data processing device 9 determines that no fuel gas is present and thus determines a combustion failure state.
• the further upper threshold can be 20% of oxygen. Said state is indicated as "State A" in the diagram. Said state is present for example during a time period until the time point t1.
• the data processing device 9 transmits a failure signal to the display device of the combustion appliance stating that no fuel gas is present and/or that the fuel gas supply to the appliance is interrupted. Additionally, the data processing device 9 ensures that the starting mode of the combustion appliance 1 is aborted and the combustion appliance 1 is switched to blocking or locking mode.
• a locking mode is the result of a failure state and requires a manual reset of the combustion appliance 1.
• a blocking mode is the result of a failure state and is a temporary block of the combustion appliance 1, wherein the combustion appliance 1 will resume an operation mode at a later time, automatically.
• a starting mode of the combustion appliance is a mode in which the air and fuel gas mixtures being in the combustion chamber is ignited in the combustion chamber.
• the data processing device 9 determines that the fuel gas is not sufficiently present and thus determines a combustion appliance failure state. Specifically, the data processing device 9 determines that the air to fuel gas ratio is not correct. Said state is indicated as "State B" in the diagram. To solve the problem, the fuel valve can be adjusted either automatically or manually by the installer.
• the upper threshold 23 can be 10% of oxygen in the measured gas. State B is present for example in the time period between time point t2 and time point t3.
• the data processing device 9 transmits a failure signal to the display device of the combustion appliance stating that the wrong air to fuel gas ration is detected and thus the air and fuel gas mixture being in the combustion chamber is too lean. Additionally, the failure signal comprises the information to the installer to adjust the fuel valve 5 shown in figure 5 .
• the data processing device 1 ensures that the starting mode of the combustion appliance 1 is aborted and the combustion appliance 1 is switched to blocking or locking mode or the throttle unit is adjusted such that richer start conditions are achieved during next ignition attempt.
• the data processing device 9 determines that sufficient fuel gas is present or in other words that the measured oxygen value is in the correct range. Said state is indicated as "State C" in the diagram and for example is present in the time period between time point t4 and time point t5. Additionally, the data processing device checks whether the combustion appliance1 is ignited. If the combustion appliance is not ignited and thus no flame is detected, the data processing device 9 determines that a combustion appliance component is malfunctioning and thus determines a combustion appliance failure state. At this point the data processing device 9 knows that the fan and fuel valve are operating. Most likely the ignition probe, ignition transformer and/or wire harness is malfunctioning. Said information is displayed on the display device of the combustion appliance.
• the data processing device 9 transmits a failure signal to the display device of the combustion appliance stating that a correct air to fuel gas ratio is detected and that the installer should check for a component malfunctioning or wrong parameter setting.
• the data processing device 9 ensures that the starting mode of the combustion appliance 1 is aborted and the combustion appliance 1 is switched to blocking or locking mode.
• the data processing device 9 determines that the measured oxygen value is in the correct range and that the combustion appliance is ignited, the data processing device 9 determines that the combustion appliance 1 is in a failure free state so that the starting process or operation mode can be continued.
• the data processing device 9 determines that the air and fuel gas mixture is too rich to start. Said state is indicated as "State D" in the diagram and for example is present in the time period between time point t6 and time point t7.
• the data processing device 9 displays in the display that components malfunctioning is not expected to be the cause for the failure state. This helps the installer to find the reason for the failure state of the combustion appliance 1.
• the data processing device 9 transmits a failure signal to the display device of the combustion appliance stating that a wrong air to fuel gas ratio is detected and that the detected air and fuel gas mixture is too rich. Additionally, the installer is informed to adjust the fuel valve 5 shown in figure 1 to resolve the combustion appliance failure state. Further, the data processing device 9 ensures that the starting mode of the combustion appliance 1 is aborted and the combustion appliance 1 is switched to blocking or locking mode. Alternatively, the throttle element position is adjusted such that leaner start conditions can be achieved during the next ignition attempt.
• Fig. 18 shows a calibration of the oxygen sensor for a situation in which the oxygen sensor 8 is always heated.
• the calibration process described below occurs in the fifth step G5 shown in fig. 3
• the time-period in which exists a heat demand, the time-period in which the calibration time is expired, the time-period in which the oxygen sensor is heated and the time-period in which the burner is operated are indicated with black filled rectangles.
• the data processing device 9 initiates a calibration of an oxygen sensor 8 for calibrating the oxygen sensor 8. Thereto, the safety unit control portion 28 of the data processing device 9 transmits a control signal to the sensor data processing unit 20 of the oxygen sensor 8. Additionally, the data processing device 9 initiates a purging of the combustion chamber 18. Thereto, the data processing device 9 transmits a control signal to the fan 5 to run the fan 5 at a predetermined speed for a predetermined time. The data processing device 9 ensures that the calibration initiation and the purging initiation is set such that the oxygen sensor 8 is calibrated during the purging of the combustion chamber 18. Additionally, the data processing device 9 ensures that the burner 7 is stopped during the calibration and/or purging of the combustion chamber 18. As the data processing device 9 knows when a heat request will occur, the data processing device can determine the time when to initiate pre-purging or post-purging to calibrate the oxygen sensor 8.
• the oxygen sensor 8 is always heated. There exists a heat demand between the first time point t1 and a second time point t2. At said two time points the calibration time-period is not expired. Thus, the burner is operated between the two time-periods t1 and t2.
• the data processing device 9 initiates purging of the combustion chamber 18.
• the data processing device 9 initiates a calibration of the oxygen sensor 8 that is ended at a fourth time point t4.
• the purging can be finished. Alternatively, the purging can be continued until the fifth time point t5.
• Fig. 19 shows a calibration of the oxygen sensor for a situation in which the oxygen sensor is not constantly heated. The initiation of the calibration and purging is done in the same way as it is described in fig. 18 .
• the heat demands can be prescheduled so that the data processing device 9 knows when there will be a heat demand for the combustion appliance 1.
• the data processing device can initiate an oxygen sensor heating and a pre-purging at a first time point t1 that is before the second time point t2 when the heat demand starts.
• the data processing device can select the first time point t1 that the oxygen sensor 8 is heated up and calibrated at the second time point t2.
• the combustion appliance 1 can output heat at the time point t2 without waiting that the oxygen sensor is heated up or calibrated.
• the data processing device 9 determines that the calibration time is expired at a sixth time point. Thus, the data processing device 9 ensures that the oxygen sensor 8 is calibrated when the next heat demand is received. This is the case for the second heat demand that is received at the seventh time-period t7.
• the data processing device 9 initiates a pre-purge and a calibration of the oxygen sensor 8 at the seventh time-period t7.
• the calibration and the pre-purging are ended at an eighth time-period t8 so that the burner starts at the eighth time-period t8.
• Fig. 20 shows a calibration of the oxygen sensor for a situation in which the oxygen sensor is heated for a predetermined time.
• the predetermined time can be 1h.
• the initiation of the calibration and purging is done in the same way as it is described in fig. 18 .
• the data processing device initiates to start heating the sensor at a first time point t1. Additionally, the data processing device 9 initiates a pre-purging and calibration of the oxygen sensor 8 at the first time point t1. The pre-purging and the calibration are ended at the second time point t2 so that the burner starts to combust the air and fuel mixture in the combustion chamber 18. The burner is stopped at the end of the heat demand at the third time point t3. The data processing device initiates at the third time point t3 a post-purging and at a fourth time point t4 a calibration of the oxygen sensor 8. The calibration is ended at a fifth time point t5.
• the third heat demand is present at a tenth time-period t10. However, at the tenth time-period the oxygen sensor is still heated, and the calibration time is not expired. Thus, there is no need for a pre-purging and the burner starts at the tenth time-period t10. The burner is stopped at the end of the heat demand, namely at an eleventh time-period t11. The data processing device then initiates a post-purging and a new calibration of the oxygen sensor 8.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Regulation And Control Of Combustion (AREA)

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• 2024
  • 2024-02-06 EP EP24155996.2A patent/EP4600554A1/de active Pending

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