Patent Application
20240280263
Example embodiments relate to a burner including a control unit and an ignition and ionization electrode for monitoring and igniting the burner flame, in particular in the manner of burners operated with gaseous fuels which serve to heat liquids (service water, for example) and/or air in heating systems and are installed in mobile spaces such as mobile homes and caravans. Example embodiments further relate to a circuit arrangement of a burner. Example embodiments also relate to a method of monitoring and igniting the flame of a burner.
For the safe operation of burners, it is essential that the flame ignites reliably and the flame can be monitored reliably.
Typically, an ignition electrode arranged in the flame area is used for igniting the flame. It is usually coupled to a discharge circuit. If the flame is to be ignited at the burner, the fuel is released and flows out of a burner nozzle as a mixture with air. Simultaneously, a discharge of the discharge circuit occurs via the ignition electrode, generating an ignition spark which ignites the fuel flowing out of the burner nozzle.
Once the flame of the burner is ignited, the flame has to be monitored continuously to ensure that the supply of fuel is stopped when the flame goes out. Usually, an ionization electrode is used to continuously monitor the flame. When the flame is burning, an ionization current is produced between the ionization electrode and an electrical mass typically formed by the burner. The ionization current is continuously monitored. If the flame goes out, this may be detected by a drop and finally a stopping of the ionization current. It is possible to react thereto by stopping the fuel supply. Alternatively, an attempt can be made to re-ignite the burner flame by discharging the ignition electrode again. If this is not successful, the fuel supply has to be stopped.
The prior art also discloses solutions in which the ignition electrode and the ionization electrode are combined in a common electrode. In this case, an AC voltage source is used, and the rectifying effect of the ionization electrode is used to implement the flame monitoring.
The disadvantage of this solution is that an AC voltage source must be provided. Usually, this is only the case if the apparatus in which the burner is used is coupled to an electrical supply network. This is rarely the case for mobile applications such as in mobile homes or camping trailers.
Other solutions in which a common ignition and ionization electrode is used operate without the application of an external voltage to the ionization circuit and use only the flame as a voltage source. The ionization current thus present is monitored.
If only the ionization current is monitored without applying an external voltage, this results in the signal provided by the ionization electrode for detecting the flame reacting very sensitively to deposits or contamination of the ionization electrode. Therefore, the ionization electrode has to be cleaned or even replaced frequently.
The object of the present disclosure is to create a burner with little effort and without an AC voltage source, in which the flame can be ignited reliably and it can then be monitored whether the flame has been ignited and whether it is burning.
To achieve the object, a burner comprising a control unit and an ignition and ionization electrode for igniting and monitoring the burner flame is provided, wherein the ignition and ionization electrode is arranged in the flame area of the burner, is electrically coupled to a discharge circuit and provides an ionization signal when the flame of the burner is switched on, wherein the control unit provides an output signal for actuating the burner on the basis of the ionization signal, and wherein the discharge circuit is connected to a DC voltage source. The present disclosure is based on the basic idea to combine the functions of the ignition electrode and of the ionization electrode in one single electrode. This leads to lower manufacturing costs as only one electrode has to be fabricated and also only one electrode has to be installed. In addition, a single electrode also simplifies maintenance of the burner as only this electrode has to be checked and, if necessary, cleaned and aligned. Furthermore, the burner can be operated with a DC voltage source so that no complex supply with an AC voltage is required.
Advantageously, the supply voltage provided by the DC voltage source is between 8 and 50 V. Therefore, an electrical system voltage of 12 V which is common for mobile homes and camping trailers, is completely sufficient to serve as a supply voltage. Furthermore, electrical systems with 24 or also 48 V as are available in trucks or occasionally also in mobile homes and caravans, would also be conceivable as a supply voltage.
Preferably, a voltage transformer is provided, by means of which the control unit varies the supply voltage of the DC voltage source before the discharge circuit is supplied therewith. An increase in the voltage is advantageous as the reliability is improved when the ignition and ionization electrode is operated with voltages above the usual electrical system voltages. With a higher voltage, the flame can be monitored in a way which is hardly or not at all influenced by the degree of contamination or deposits on the electrode.
Advantageously, the voltage transformer can vary the voltage of the DC voltage source between 100 and 300 V. These values represent a good compromise between, on the one hand, the advantages described above upon ignition and monitoring, and, on the other hand, acceptable costs for the voltage transformer.
The DC voltage source may be a battery or an accumulator. The burner can thus be operated independently of the site infrastructure. Furthermore, no additional current source is required, as the electrical system battery or additional battery anyway installed in the vehicle can serve as a DC voltage source.
Preferably, the discharge energy of the discharge circuit may be adjustable by the control unit by means of frequency change of a pulse width modulation. By means of pulse width modulation, the discharge energy used upon ignition can be adapted to external influences which affect ignition. It is thus ensured that the flame is reliably ignited even under different boundary conditions.
The discharge circuit may comprise a capacitor and an ignition transformer. These components are cost-effective and allow the discharge circuit to be easily constructed such that a long service life is achieved.
Preferably, an operational amplifier is provided which amplifies the ionization signal applied to the control unit when the burner flame is switched on. In particular, the operational amplifier can be used to amplify the DC voltage component of the ionization signal which indicates the existence and indirectly the quality of the flame and can be made available to the control unit.
The object mentioned in the introductory part is furthermore achieved by a circuit arrangement comprising a control unit and an ignition and ionization electrode for igniting and monitoring the burner flame of a burner, wherein the ignition and ionization electrode is arranged in the flame area of the burner, is electrically coupled to a discharge circuit and provides an ionization signal when the flame of the burner is switched on, wherein the control unit provides an output signal for actuating the burner on the basis of the ionization signal, and wherein the discharge circuit is connected to a DC voltage source. Alternatively, the circuit arrangement may be referred to as “ignition and ionization circuit arrangement” of a burner, in particular of a gas burner having an electrode. As in the preceding and following configurations and embodiments, the circuit arrangement is assigned to a burner. Therefore, the circuit arrangement can also be designed in accordance with these aspects. To avoid repetitions, reference is made to the preceding and following explanations.
The object mentioned in the introductory part is furthermore achieved by a method of monitoring and igniting the flame of a burner, comprising the following steps:
With regard to the resulting advantages, reference is made to the above explanations as to the burner.
Advantageously, the supply voltage of the DC voltage electrode in step a) can be varied by the control unit using a voltage transformer as a function of one or more of the following influencing factors: the burner, the burner temperature and the degree of contamination or the deposits on the ignition and ionization electrode which can be estimated on the basis of the service life or the resistance of a protective circuit. As already explained above, taking these external influencing factors into account has a positive effect on successful ignition of the flame and a reliable monitoring of the flame.
Preferably, the discharge energy upon ignition of the flame in step b) can be varied by the control unit as a function of the ambient temperature and/or the air humidity. By adapting the discharge energy, it is ensured that a clean ignition spark flashes over between the electrode and the burner and the burner flame is reliably ignited in a wide variety of situations.
Preferably, as soon as the control unit detects in step d) that the amplified ionization signal is below a predetermined limit value, the fuel supply can be stopped or after a further discharge of the discharge circuit, it can be checked whether an ionization signal above the limit value is detected by the control unit. This ensures that no unburned fuel flows out of the burner when the flame goes out, which can be detected by a drop in the ionization signal. Alternatively to the switching-off of the fuel supply, an attempt can be made to re-ignite the fuel flowing out by an automatic new ignition to be able to continue operation without causing any loss of comfort. Alternatively, an attempt can be made to stabilize the burning behavior or, for example, to achieve a certain calorific value (so-called lambda-value) by controlling the supply of air and/or fuel.
The present disclosure is described below with reference to an embodiment which is represented in the accompanying drawing and in which:
The burner serves to heat air and/or water and can be installed in mobile homes and caravans, for example.
The ignition and ionization electrode 20 is arranged in the flame area of the burner nozzle 10 and generates an ionization signal when the flame is switched on, which is transmitted to a control unit 40 via a protective circuit 22 and an operational amplifier 30. The ignition and ionization electrode 20 and the protective circuit 22 are electrically coupled to a discharge circuit 50.
The discharge circuit 50 comprises a capacitor 52 and an ignition transformer 54.
The discharge circuit 50 and the protective circuit 22 are supplied by a supply voltage of a DC voltage source 70 converted by a voltage transformer 60.
The supply voltage of the DC voltage source 70 can be between 8 and 50 V. It is conceivable to use a battery 72 or an accumulator 74 as a DC voltage source 70. Alternatively, it is possible to use a power supply unit.
In the illustrated embodiment, the supply voltage of the DC voltage source 70 is variably converted by the control unit 40 by means of the voltage transformer 60. This can be done by pulse width modulation, the frequency of which is in the range of a few kHz to 1 MHz. It is then conceivable that the voltage can be varied between 100 to 300 V, but is usually 180 V.
Varying the supply voltage of the DC voltage source 70 by means of the voltage transformer 60 can be carried out depending on different influencing factors such as the burner type, the burner temperature and the degree of contamination or the deposits on the ignition and ionization electrode 20. The degree of contamination and the deposits on the electrode are estimated on the basis of the service life and on the basis of the resistance present in the protective circuit 22.
It is also conceivable to introduce a voltage divider and a low-pass filter to be able to measure the voltage converted by the voltage transformer 60 by means of the control unit 40.
In addition, the control unit 40 can comprise a proportional-integral-derivative controller or a proportional-integral controller by means of which the converted voltage can be adjusted to a set value.
To ignite the burner flame, the control unit 40 releases the fuel supply so that the fuel-air mixture flows out at the burner nozzle 10. Simultaneously, ignition takes place by a discharge of the discharge circuit 50 via the ignition and ionization electrode 20.
The discharge energy of the discharge circuit 50 released upon ignition can be adjusted variably by the control unit 40. The discharge energy can be varied by changing the number of discharges per second. Typically, the discharge frequency is in the range from 8 to 50 Hz.
In this configuration, it is conceivable to control the discharge energy of the discharge circuit 50 by means of the control unit 40 as a function of external influencing factors such as the ambient temperature and/or the air temperature.
When the burner flame burns, an ionization signal is generated at the ignition and ionization electrode 20. At the same time, the converted supply voltage of the DC voltage source 70 is applied to the protective circuit 22 as an external voltage. The operational amplifier 30 amplifies the DC voltage component of the ionization signal which is present at the ignition and ionization electrode 20 due to the rectifier property of the flame.
The control unit 40 detects the amplified ionization signal which is present at the burner nozzle 10 due to the burner flame, and outputs an output signal depending on the ionization signal, which controls the gas supply to the burner nozzle 10. If there is no ionization signal at the control unit 40 or an ionization signal the value of which is below a predetermined limit value when the fuel supply is released, the control unit 40 stops the further fuel supply. This prevents further fuel from flowing out of the burner nozzle which would then not be burned.
According to an alternative, the control unit 40 reactivates the discharge circuit 50 when the ionization signal falls below a predetermined limit value. In case a stable flame is then generated again at the burner nozzle 10, an ionization signal is again applied to the control unit 40, and the burner can continue to be operated. In case no ionization signal is detected after an ignition attempt, the control unit 40 stops the further supply of fuel.
While the disclosure has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 120 436.4 | Aug 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/071157 | 7/28/2022 | WO |
