DE102004058087A1 - Method for burner start-up in gas heating device involves burner which is supplied with initial value of gas mass which is so small that gas-air mixture cannot ignite and is less than mass of gas corresponding to minimum gas mass - Google Patents

Abstract

The method involves a burner which is supplied with initial value (C2) of gas mass which is less than the mass of gas corresponding to the minimum gas mass. The initial value is so small that the gas-air mixture cannot ignite. The gas mass is increased beyond the minimum load to the target gas mass (C4) and the growth rate is so selected that sufficient mixing of gas and air is ensured.

Description

The The invention relates to a method for starting a burner Gas heater, depending on from a heat request a burner ignition device activated and the burner by subsequent supply of gas and generating a gas-air mixture at the location of the action of the ignition device ignited becomes.

at known method of this type is already a manufacturer side Starting power fixed. This means that the gas valve of the burner for Burner starting process is suddenly opened to a predetermined value and a predetermined amount of gas (gas volume flow) almost abruptly in enters a combustion chamber, the with an inflowing Air quantity an ignitable mixture yields, so that a ignition can be done. In load mode, the amount of gas between an upper Maximum heating power limit (maximum load, gas volume 100%) and a lower limit of minimum heat output (minimum load, typ 35-50%) varied. The value set at the start of the burner is above the minimum load, i. above the for the operation provided lower limit of the amount of gas, so that the ignition a Jump into the load operation represents. This leads to undesirable Pressure surges in the combustion chamber and associated loud noises.

The Invention goes from consideration from that the ignition point and the burner startup process significantly from ambient conditions are dependent. To the for the burner start process relevant Environmental conditions include in particular the backpressure in the exhaust system, (for example also on the exhaust pipe acting wind influences, which can cause a back pressure or a suction effect) and the temperature of the supplied Air volume.

A predetermined starting power, as provided by the prior art, always represents only a compromise solution because Ambient conditions vary between burner locations also by external influences (wind) can change greatly.

Of the Invention is therefore the object of the aforementioned Process to improve so that a easy adjustment of the starting power to the respective ambient conditions is possible.

These The object is achieved by a method having the features of the claim 1 solved. Starting from the above-mentioned method is the burner supplied Gas volume (gas volume flow rate) first to an initial value below a gas amount that is a predetermined Minimum load corresponds, adjusted, whereby the initial value so small chosen that will Do not ignite gas-air mixture yet can. Subsequently the amount of gas is over the amount of gas corresponding to the minimum load is increased until a predetermined target gas quantity, the bigger than is the minimum load corresponding amount of gas is reached, wherein the rate of increase during the increase is chosen so that anytime Ensures adequate mixing of the gas-air mixture is.

at the method according to the invention the amount of gas is first set to an initial value, preferably leaps to this raised. In this condition there is an excess of air. The initial value of Gas quantity is chosen so that the gas-air mixture at the location of the action of the ignition device (for example, at the location of a spark) not yet present in an ignitable mixture ratio, the gas concentration is therefore too low for ignition. Starting from this Initial value, the amount of gas is increased until an ignitable gas-air mixture at the location of the action of the ignition device is present. The increase The amount of gas per time is chosen such that at any time a sufficient Mixing of gas and air in the combustion chamber is present. Once a ignitable mixture is present, this is using the ignition device, for example a generated spark sequence ignited which leads to a soft or gentle ignition without excessive pressure surge. Subsequently the gas quantity is slowly increased up to the target value. On the one hand is one with the inventive method dynamic adaptation of the starting power to the respective ambient conditions possible and on the other hand the previously considered unavoidable pressure surges in the combustion chamber and thus a loud ignition be excluded from the burner. An ignition of the gas heater can be detected by means of a suitable detection device (e.g., ionization sensor or temperature sensor).

Preferably, the amount of gas supplied to the burner is initially set abruptly to the initial value, before, following a ramp function, it is slowly increased. Ignition occurs within the change in gas flow along the ramp function. The initial sudden increase in the amount of gas takes place with the maximum possible actuating speed of a valve used in a valve. Normally, the valve opens in a time of about 100 ms to the predetermined initial value. In the second phase, the amount of gas is increased, with a predetermined increase in gas quantity is maintained per time. Based on a maximum opening of the valve in burner operation with 100% gas volume (max load), the amount of gas in this phase (ramp), for example, increased by 5% per second.

The Slope of the ramp function is preferably adjusted so that the gas-air mixture under consideration ambient conditions of the burner use location within a predetermined safety time is ignited. Through this activities it is ensured that ignition of the Burner takes place before an undesirably large amount of gas in the combustion chamber flown is. is e.g. the initial value is 35% and becomes the valve at an increase rate adjusted by 5% per second, the amount of gas is after two seconds 45% and 60% after a 5 second safety period.

To the Purpose of temporal change of the ignition point within the safety period can be both the limit value as well the slope of the ramp function or both can be varied.

In Further development of the invention is provided that the temperature of the burner supplied Air detected and as a predictor of variation the limit and / or slope of the ramp function becomes. The air temperature can thus as a predictor control technology in the Process for burner start of a gas heater are involved. The Other ambient conditions, in particular the exhaust gas pressure, for example, in Course of a test of the burner by subsequent correction the slope of the ramp function are taken into account.

A a particularly simple procedure can be achieve in development of the invention in that an im essential linear ramp function is set.

going For example, assume that at maximum load of the burner a gas quantity of 100% and at minimum load a gas quantity of 35% -50% is supplied, For example, as an initial value, a gas volume is set. the 3% -15%, preferably 5%, below the amount of gas corresponding to the minimum load with the amount of gas subsequently being 2% -20% per second, preferably 5% per second, increasing and increasing the amount of gas at the burner start on a target gas quantity from 5% to 20%, preferably 10%, over the minimum load corresponding amount of gas is limited.

The ignition device For example, it can be activated by a pilot flame ignited or a glow wire to glow is brought. The pilot flame can after the ignition continue to burn permanently. Preferably, however, the ignition device activated by a spark sequence is started, with the gas-air mixture at the location of the spark ignites. The spark sequence can then after detecting the ignition to be ended.

In the following the invention is based on an in 1 illustrated curve diagram explained in more detail.

In 1 four curves are schematically illustrated over a time axis t, of which the curve A is a heat request, the curve B the Zündfunkenfolge generated at burner start, the curve C modulator drive, ie the amount of gas supplied to the burner and the curve D the flame indicating ionization signal represents an ionization sensor.

From the diagram according to 1 It can be seen that upon detection of a heat request (curve A) at time t1 immediately the spark sequence (curve B) is generated. At a point t2 which is shifted in time from t1, the gas valve is suddenly increased to an initial value C2, which is below the minimum load. Thereafter, the gas valve is opened relatively slowly according to a ramp function. At the in 1 illustrated method example, the ignition takes place at the time t3 at the gas quantity C3, which can be seen by a sudden change in the ionization signal (curve D). After the ignition point C3, the gas valve is further opened along the ramp function until C4 is reached above the minimum load.

These process management allows on the one hand, a consideration the environmental influences and on the other hand a very quiet start without pressure surges.

To the Purpose of adapting the starting power to the ambient conditions can both the amplitude of the initial gas value C2 and the slope the ramp function, i. the duration of the relatively slow increase in gas volume, be changed. In extreme cases, the amplitude of the sudden opening of the Gas valve in the first start phase, i. the gas quantity C2, to zero or set close to zero.

Claims (8)

A method for burner start of a gas heater, wherein activated in response to a heat request, a burner ignition and the burner is ignited by subsequent supply of gas and generating a gas-air mixture at the location of the action of the ignition device, characterized in that the burner thereby initially supplied gas quantity to an initial value (C2) below a Gas set, which corresponds to a predetermined minimum load is set, wherein the initial value (C2) is chosen so small that the gas-air mixture can not ignite, and then as long as over the minimum load corresponding amount of gas is increased until a predetermined Target gas quantity (C4), which is greater than the minimum load corresponding amount of gas is reached, the rate of increase during the increase is chosen so that at any time sufficient mixing of the gas-air mixture is ensured. Method according to claim 1, characterized in that that the supplied to the burner Gas quantity first is set abruptly to the initial value (C2) before it, following a ramp function, is increased slowly. Method according to claim 2, characterized in that that the Ramp function selected that will Gas-air mixture taking into account Ambient conditions of the burner site ignited within a specified safety time becomes. Method according to claim 3, characterized that to temporal change of the ignition point within the safety period the initial value (C2) and / or the Slope of the ramp function can be varied. Method according to claim 4, characterized in that that the Temperature of the burner supplied Air detected and as an influence variable for the variation of the Limit and / or the slope of the ramp function is used. Method according to one of claims 2 to 5, characterized that one linear ramp function is set. Method according to one of claims 1 to 6, wherein the one Maximum load of the burner corresponding amount of gas 100 and the Minimum load corresponding amount of gas corresponding to 35% -50%, characterized that as Initial value (C2) is set a gas amount, the 3% -15%, preferably 5%, below which the minimum load corresponds to the gas quantity, that the gas quantity subsequently by 1% -20% per second, preferably 5% per second, is increased, and that the given Target gas quantity 5% -20%, preferably 10%, over the minimum load corresponding amount of gas is. Method according to one of claims 1 to 7, characterized that the Ignition device activated will, by a spark sequence is started, wherein the gas-air mixture is ignited at the location of the sparks.