Method for starting a burner device and heating device with burner device

Description

[0001] The present invention relates to a method for starting a burner device. Furthermore, the invention relates to a heating device with a burner device that is started using the method.

[0002] To start a vaporizer burner for liquid fuels, it is first necessary to supply heat energy from the outside. The heat energy is usually introduced by an electrically controlled ignition device—the so-called glow plug. Such a glow plug converts electrical energy into heat energy through its ohmic internal resistance. Temperatures of over 1000°C are generated on the surface of the usually ceramic components. DE 10 2004 062 831 A1 and DE 199 24 329 A1, for example, deal with the starting of burner devices in heating systems. EP 0 271 999 A1 discloses a burner device with a control device that uses a temperature signal from the ambient air to control a fan and a fuel valve.

[0003] The object underlying the invention is to propose a method for starting a burner device that is as environmentally friendly as possible. Furthermore, the invention relates to a heating device with a burner device that is started accordingly.

[0004] The invention solves the problem by a method for starting a burner device, wherein a mixture of combustion air and a fuel is burned in the burner device, wherein a combustion process of the burner device is started by a glow plug, and wherein the method comprises at least the following steps: that a temperature of the combustion air is measured, and that a target value of the heating energy of the glow plug is specified as a function of the measured temperature.

[0005] In the prior art, the goal of being able to start the combustion process at any outside temperature is achieved by setting the electrical energy supplied to the glow plug to the lowest temperature values. The invention, however, is based on the realization that lower heating energy can be used at higher temperatures. This means that electrical energy can be saved when outside temperatures are higher. Furthermore, the glow plug is subjected to less strain. In addition, the starting process is shortened at warmer initial temperatures. The temperature-dependent setpoints for the heating energy are determined, for example, based on measurements on the burner device or on the respective type of burner device. In one embodiment, the electrical power of the glow plug is also set according to a predetermined setpoint in addition to the heating energy.

[0006] One embodiment provides that the method further comprises the step of increasing the heating energy of the glow plug until the target heating energy value is exceeded. Alternatively, only the target value is reached and no further increase is made.

[0007] One embodiment includes the method further comprising the steps of: specifying a scaled setpoint for the heating energy as a function of the measured temperature, wherein the scaled setpoint is smaller than the setpoint, and supplying combustion air to the burner device when the scaled setpoint for the heating energy of the glow plug is reached. In one embodiment, the scaled setpoint lies between 50% and 100% of the setpoint. In this embodiment, the combustion air is supplied to the combustion device earlier, before the setpoint for the glow plug has been reached. In one embodiment, the scaled setpoint depends on the properties of the combustion air blower and, in particular, on the time the blower requires to reach a setpoint speed.

[0008] One embodiment provides that the method further comprises the step of: if the desired heating energy value of the glow plug is reached, the fuel is pumped into the burner device. At the moment the glow plug has generated a desired temperature, the fuel is pumped in this embodiment to evaporate with the aid of the glow plug. If this embodiment is combined with the previous one, combustion air is supplied first, followed by fuel. This ensures that combustion air is available for combustion.

[0009] One embodiment includes the method further comprising the steps of: monitoring whether a flame is present in the burner device, specifying a delay time, and operating the glow plug during the delay time after a point in time at which the presence of a flame has been detected. In this embodiment, the glow plug remains active for a certain time even after the flame has been detected so that reliable combustion occurs and the flame does not, for example, go out again because sufficiently stable combustion conditions have not yet developed. In one embodiment, the delay time is specified as a function of the measured temperature. The delay time is longer at lower temperatures and shorter at higher temperatures. This has the advantage of preventing the flame from going out at lower temperatures.At higher temperatures, the glow plug prevents thermoacoustic effects from occurring.

[0010] One embodiment provides that the method further comprises the following steps: that at the beginning of the start-up, the glow plug is switched on and operated at a nominal power, and that at the beginning of the start-up, a path through which the combustion air passes in the burner device is purged with combustion air. In this embodiment, when the combustion process starts, the area in which combustion takes place, e.g., a combustion chamber, is first purged with combustion air so that any remaining residues of flue gas or unburned fuel-air mixture are safely removed. Furthermore, it should be ensured that a temperature sensor, which measures the temperature of the supplied air, is completely surrounded by this fresh air and not by air from the system of the burner device (e.g., a heating device).

[0011] One embodiment of the method, as an extension of the previous embodiment, involves measuring the temperature of the combustion air after purging the path. The combustion air measurement is necessary to determine the setpoint heating output. The measurement takes place here after purging, i.e., after a well-defined baseline state for the burner device has been established.

[0012] One embodiment provides that the method further comprises the following steps: specifying a stabilization time, and starting control of the burner device only after the stabilization time has elapsed after the glow plug has been switched off. The burner device is controlled, for example, depending on a predetermined temperature of the water or the room to be heated. In this embodiment, this control only takes place after a certain time has elapsed, within which the combustion process stabilizes.

[0013] According to a further teaching, the invention relates to a heating device for heating air and / or for heating a liquid, comprising a burner device which generates thermal energy by combustion of a fuel-air mixture, comprising a heat exchanger which transfers the thermal energy generated by the burner device to air and / or the liquid, and comprising a control device, wherein the burner device has a glow plug, a combustion air blower, a fuel pump and a temperature sensor for measuring the temperature of the combustion air, and wherein the control device is designed such that it carries out the method according to one of the aforementioned or following embodiments.

[0014] One embodiment of the heating device provides that the burner device further comprises a sensor for detecting a flame in the burner device.

[0015] The above and following embodiments and explanations of the method also apply accordingly to the heating device that implements the method. To avoid repetition, reference is made to the remaining description.

[0016] In detail, there are numerous possibilities for designing and developing the method according to the invention and the heating device. Reference is made, on the one hand, to the patent claims subordinate to the independent patent claims and, on the other hand, to the following description of exemplary embodiments in conjunction with the drawings. They show: Fig. 1 is a schematic representation of the heating device, Fig. 2 is a schematic representation of the burner device and Fig. 3 is a schematic representation of the start-up process of the burner device.

[0017] In the Fig. 1A heating device is shown very schematically. A fuel-air mixture is burned in a burner device 1, and the thermal energy released is transferred to air or a medium, e.g., process water, in a heat exchanger 2. In particular, the flue gas generated in the burner device 1 is fed to the heat exchanger 2. The start-up process of the burner device 1, described below, is controlled by the control device 3.

[0018] The Fig. 2The schematically illustrated burner device has a combustion chamber in which the fuel-air mixture is burned and the resulting flue gas (see the arrow on the right) is discharged to the right here to be transferred to the room air or, for example, to domestic water via the heat exchanger. The combustion process is started by the glow plug 100. It is indicated here that the glow plug 100 is subjected to a pulse-modulated electrical voltage. The temperature then established at the glow plug 100 leads to the evaporation of a fuel, e.g., diesel fuel, and thereby to the generation of a fuel-air mixture. The required combustion air (indicated by the left arrow) is supplied by the combustion air blower 101. The fuel is introduced into the combustion chamber by a fuel pump 102.This occurs particularly in the immediate vicinity of the glow plug 100, so that the liquid fuel evaporates in the temperature environment created by the glow plug 100. After a certain period of time, a self-sustaining flame (symbolically indicated here) has developed, and the glow plug 100 can be switched off. Sensor 104 in the combustion chamber is used to detect the flame.

[0019] For the start-up process described below, a temperature sensor 103 is provided which measures the temperature of the supplied combustion air. Fig. 1 The signals from the sensors for the flame 104 and for the combustion air temperature 103 are fed to the control device 3 shown. Furthermore, the control device 3 controls the glow plug 100—or more precisely, the control of the glow plug 100—the fuel pump 102, and the combustion air blower 101.

[0020] The Fig. 3shows a schematic example of a burner start-up sequence. The start-up phase takes place between times 1 and 7.

[0021] The top row (a) shows the rated power of the glow plug over time t. At the beginning of the process, at time 1, the glow plug is switched on and operated at its rated power, which is controlled by measuring current and voltage and setting a PWM voltage (an electrical voltage controlled by pulse width modulation). At time 6, i.e., before the end of the start-up phase, the glow plug is switched off.

[0022] Line b) shows the heating energy curve of the glow plug as a function of time t. The energy calculation is performed, for example, by numerical integration of the power. The ramp-like curve can be seen, which peaks at time 6. As long as the glow plug power is controlled constantly between times 3 and 4, it can be assumed that the energy increase is linear. A scaled setpoint and a setpoint for the heating energy are also plotted.

[0023] Line c) shows the control of the combustion air fan in relation to the target speed. The fan is initially operated between times 1 and 2 and then switched off. Only at time 3 is the fan switched on again, after which it is operated continuously. It is indicated that the speed and thus the speed of the fan is higher between times 1 and 2 than after time 3, i.e., during normal operation of the burner device. A target speed is specified for normal operation. In one embodiment, the target speed is specified as a function of the measured combustion air temperature.

[0024] Line d) shows the activation of the fuel supply. Fuel is introduced into the combustion chamber starting at time 4 and continuing beyond the end of the start-up phase.

[0025] Line e) refers to the sensor for detecting the flame. The point in time at which the flame is detected, and thus the beginning of the combustion phase, is designated as point in time 5. From point in time 5 onward, combustion occurs continuously, or a flame is continuously present.

[0026] The following describes the interaction of the individual components or events when starting the burning process.

[0027] Simultaneously with the glow plug being switched on at time 1, the combustion air blower is started and operated until the combustion path, in particular the combustion chamber, has been flushed with fresh air. Therefore, the blower is switched off at time 2. The duration between times 1 and 2 can be adjusted to ensure that fresh air reaches the temperature sensor. The specified time therefore depends on how long it takes to supply the fresh air. Therefore, the duration can be measured based on the conditions of the burner device installed in the heater, for example. Alternatively, the duration is specified depending on a maximum exhaust gas or fresh air path, depending on the respective line cross-sections and the properties of the fresh air blower, e.g. the blower speed and / or the generateable volume flow.

[0028] After the fan is switched off, the combustion air temperature is determined based on the temperature sensor measurement. This occurs at time 2. Based on the temperature, three setpoints for controlling the glow plug are determined, e.g., calculated by interpolation – preferably using a data table and / or, for example, a relationship described by mathematical formulas. This is a setpoint for the heating energy and a scaled setpoint, which is preferably between 50% and 100% of the setpoint. Finally, there is the setpoint for the delay time, which decreases with increasing measured temperature (see further explanations).The setpoint for the heating energy or the energy setpoint depends on the temperature of the combustion air, in that a higher temperature is associated with a lower setpoint and a lower temperature with a higher setpoint. The warmer the combustion air, the less heat energy the glow plug needs to produce. The relationships between the setpoint and the temperature of the combustion air are determined, for example, from comparative measurements. The scaled setpoint is determined, for example, based on a scaling value between 0.5 and 1 and the setpoint. Relevant for the scaling value is the time required by the combustion air fan to reach the setpoint speed required for operation. If the fan accelerates quickly, the time can be shorter. If the fan only increases its speed slowly, the delay time must be longer.As can be seen in line b), the glow plug is controlled so that its heating energy continuously increases. The power and energy are continuously monitored by measuring voltage and current.

[0029] At the time at which the scaled target value for the heating energy has been reached, i.e. here at time 3, the fan for the combustion air is switched on. If the target value is subsequently reached at time 4, the pump device is started, so that combustion air and fuel are present in the combustion chamber. Furthermore, the fan has preferably reached its target speed at time 4. In one embodiment, the heating energy of the glow plug is no longer determined after this time 4. For example, the calculation of the energy is set from the measured values ​​for current and voltage. The heating energy of the glow plug increases through further control, starting from the nominal or target power above the target value.

[0030] At time 5, it is detected that a flame is present, meaning that the mixture of combustion air and fuel has ignited. The glow plug, which is still active, supports the development of the flame during a delay period from time 5 to time 6. At time 6, the glow plug is switched off.

[0031] A stabilization period extends up to time 7, after which it is assumed that a combustion condition has been established that allows controlled operation of the burner device or heater. List of reference symbols

[0032] 1 Burner device 2 heat exchanger 3 Control device 100 Glow plug 101 Combustion air blower 102 fuel pump 103 Temperature sensor 104 Sensor for detecting a flame

Claims

1. A method of starting a burner device (1), wherein a mixture of combustion air and a fuel is burnt in the burner device (1), wherein a burning process of the burner device (1) is started by a glow element (100), and wherein the method comprises at least the following steps: a temperature of the combustion air is measured, and a set value of the heating energy of the glow element (100) is specified as a function of the measured temperature.

2. The method according to claim 1, wherein the method further comprises the following steps: a scaled set value of the heating energy is specified as a function of the measured temperature, wherein the scaled set value is smaller than the set value, the combustion air is conveyed into the burner device (1) in the event that the scaled set value of the heating energy of the glow element (100) is reached, and the fuel is conveyed into the burner device (1) in the event that the set value of the heating energy of the glow element (100) is reached.

3. The method according to claim 1 or 2, wherein the method further comprises the following steps: it is monitored in the burner device (1) whether a flame is present, a delay time is specified, and the glow element (100) is operated during the delay time after a time at which the presence of a flame has been determined.

4. The method according to any of claims 1 to 3, wherein the method further comprises the following steps: the glow element (100) is switched on at the beginning of the starting process and is operated at a rated power, a path passing the combustion air in the burner device (1) is purged with combustion air at the beginning of the starting process, and the temperature of the combustion air is measured after the purging of the path.

5. The method according to any of claims 1 to 4, wherein the method further comprises the following steps: a stabilization time is specified, and a regulation of the burner device (1) is started only after the stabilization time has elapsed after switching off of the glow element (100).

6. A heating device for heating air and / or heating a liquid, comprising a burner device (1) which generates thermal energy by the combustion of a fuel-air mixture, comprising a heat exchanger (2) which transfers the thermal energy generated by the burner device (1) to the air and / or liquid, and comprising a control device (3), wherein the burner device (1) includes a glow element (100), a combustion air fan (101), a fuel pump (102), and a temperature sensor (103) for measuring the temperature of the combustion air, and wherein the control device (3) is configured so as to perform the method according to any of claims 1 to 5.