Method For Operating A Fuel -Operated Burner

Abstract

The invention relates to A method for operating a fuel-operated burner (3) downstream of an engine (1) and upstream of a catalytic converter (4), comprising an actuation of an ignition apparatus (12) of the burner (3) during a pre-definable preheating phase, without delivering fuel (11) to the burner (3) during the preheating phase, and, after the end of the preheating phase, a timely delivery of fuel (11) to the burner (3) and combustion of the delivered fuel (11) in the burner (3). Further, a computing unit and a computer program product for carrying out such a method are proposed.

Claims

1. A method for operating a burner (3) downstream of an engine (1) and upstream of a catalytic converter (4), the method comprising : actuating a fuel metering device (10) to deliver fuel (11) to the burner (3) starting at a meter time (t.sub.1), actuating an ignition apparatus (12) of the burner (3) such that it ignites at an ignition time (t.sub.0) and subsequently burns for a burning duration (304), determining the meter time (t.sub.1) and/or the ignition time (t.sub.0), such that fuel delivered to the burner (3) at the meter time (t.sub.1) reaches the ignition apparatus (12) at the ignition time or during the burning duration (304).

2. The method according to claim 1, wherein the determining of the meter time (t.sub.1) and/or the ignition time (t.sub.0) is carried out such that fuel delivered to the burner (3) at the meter time (t.sub.1) reaches the ignition apparatus (12) at the ignition time or during the burning duration (304) as a function of a distance between the fuel metering device (10) and the ignition apparatus (12) and/or as a function of a mean advancement speed of the fuel between the fuel metering device (10) and the ignition apparatus (12).

3. The method according to claim 1, comprising the following step before and/or during the actuation of the fuel metering device (10) for delivering fuel (11) to the burner (3), starting at the meter time (t.sub.1): actuating the ignition apparatus (12) of the burner (3) without igniting fuel.

4. The method according to claim 1, comprising the following step before the actuation of the fuel metering device (10) for delivering fuel (11) to the burner (3), starting at the meter time (t.sub.1): actuating a secondary air pump (13) for delivering air to the burner (3).

5. The method according to claim 4 comprising the following steps before the actuation of the secondary air pump (13) for delivering air to the burner (3): actuating the fuel metering device (10) for delivering fuel (11) to the burner (3), actuating the ignition apparatus (12) of the burner (3).

6. The method according to claim 1, wherein the actuation of the ignition apparatus (12) of the burner (3) comprises an actuation of the ignition apparatus (12) with an ignition apparatus actuation duration (303) starting at an ignition apparatus actuating start time (t.sub.2), such that it ignites at the ignition time (t.sub.0).

7. The method according to claim 6, wherein a first actuation of the ignition apparatus (12) of the burner (3) is carried out with a longer ignition apparatus actuation duration (303) than a later second actuation of the ignition apparatus (12) of the burner (3), such that it ignites at the ignition time (t.sub.0) and subsequently burns for the burning duration (304).

8. The method according to claim 1, wherein a spark plug is used as the ignition apparatus (12).

9. A system comprising: a computing unit configured to actuate a fuel metering device (10) to deliver fuel (11) to a burner (3) downstream of an engine (1) and upstream of a catalytic converter (4) starting at a meter time (t.sub.1), actuate an ignition apparatus (12) of the burner (3) such that it ignites at an ignition time (t.sub.0) and subsequently burns for a burning duration (304). determine the meter time (t.sub.1) and/or the ignition time (t.sub.0), such that fuel delivered to the burner (3) at the meter time (t.sub.1) reaches the ignition apparatus (12) at the ignition time or during the burning duration (304).

10. The system of claim 9, further comprising the burner (3).

11. (canceled)

12. A non-transitory computer-readable medium including instructions executable by an electronic processor to perform a set of functions, the set of functions comprising: actuating a fuel metering device (10) to deliver fuel (11) to the burner (3) starting at a meter time (t.sub.1), actuating an ignition apparatus (12) of the burner (3) such that it ignites at an ignition time (t.sub.0) and subsequently burns for a burning duration (304), determining the meter time (t.sub.1) and/or the ignition time (t.sub.0), such that fuel delivered to the burner (3) at the meter time (t.sub.1) reaches the ignition apparatus (12) at the ignition time or during the burning duration (304).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Additional advantages and configurations of the invention result from the description and the enclosed drawing.

[0023] The invention is illustrated schematically in the drawing on the basis of embodiment examples and is described in detail in the following with reference to the drawings.

[0024] FIG. 1 schematically shows an arrangement with an engine, burner, and catalytic converter as can be used in advantageous configurations of the invention.

[0025] FIG. 2 shows a burner, as can be used in configurations of the present invention, in a schematic representation.

[0026] FIG. 3 schematically shows temporal profiles of fuel metering and ignition as can occur in advantageous configurations of a method according to the invention.

DETAILED DESCRIPTION

[0027] In FIG. 1, an arrangement with an engine, burner, and catalytic converter as can be used in advantageous configurations of the invention is shown schematically and bears the overall reference numeral 100.

[0028] In the illustrated example, a four-cylinder engine 1, a turbocharger 2 (optional), a burner 3, a three-way catalytic converter 4 (TWC), a gasoline particulate filter 5 (OPF), and a muffler 6 are arranged, wherein further components can also be provided within the scope of the invention that are not shown here. For example, several catalytic converters can also be provided, and the arrangement of the individual components with respect to one another, unless otherwise specified, need not necessarily correspond to the order shown. It is essential that the engine 1 is arranged on the remaining components and that the burner 3 is installed on the catalytic converter 4 in as close proximity to the latter as possible. In the case of several catalytic converters, the burner 3 is to be provided in the vicinity of the catalytic converter to be heated in order to achieve as efficient a delivery of heat as possible. In particular, several burners can then also be used.

[0029] As mentioned above, the catalytic converter 4 is configured so as to convert pollutants that can be contained in an exhaust gas of the engine 1 (but also of the burner 3). However, the catalytic converter 4 can only perform this task from a certain minimum temperature (so-called light-off temperature). As already explained, the burner 3 is therefore intended to heat the catalytic converter 4 as quickly as possible over the light-off temperature and thereby expel as few pollutant contents as possible from its own exhaust gas.

[0030] In FIG. 2, such a burner 3 is shown in greater detail schematically.

[0031] To operate the burner 3, for example, air 7 is conveyed via a secondary air pump 13 (SLP) into a burner jacket 8, is twisted via a swirl grid 9, and is guided to an injection valve 10 as a fuel metering device. Fuel 11 is delivered to the air 7 via the injection valve by means of a fuel pump (EKP) 14, which can also be considered part of the fuel metering device. Through the swirling and injection angles, a combustible fuel-air mixture is generated and guided to a spark plug 12 as the ignition apparatus. Here, the mixture is ignited and combusted in the combustion chamber. Hot burning gases or burning exhaust gas 31 are introduced into the exhaust system downstream of the engine 1 and upstream of the catalytic converter 4 to be heated.

[0032] In the context of a preferred embodiment of the present invention, fuel metering and ignition are now matched to one another such that fuel delivered to the burner at a meter time reaches the spark plug 12 at the ignition time or during the burning duration.

[0033] Referring now to FIG. 3, to actuate in particular the spark plug 12 and the injection valve 10, a computing unit 300, e.g. a so-called BCU (burner control unit) is provided, which is in particular configured so as to carry out a preferred embodiment of a method according to the invention. For explanation, an injection path 301 and an ignition path 302 are plotted against time t.

[0034] A desired ignition time is denoted with t.sub.0. In particular, the spark plug 12 of the burner 3 is actuated so as to ignite at the ignition time t.sub.0 in that the spark plug 12 or its ignition coil is actuated with an ignition apparatus actuation time 303 as the charging time starting at an ignition apparatus actuation start time t.sub.2. After ignition at the ignition time t.sub.0, the spark plug 12 burns over a burning duration 304.

[0035] According to a preferred embodiment of the invention, the fuel metering and ignition are now matched to one another such that the spark plug 12 ignites no later than when the fuel-air mixture cloud caused by the fuel metering arrives there. To this end, the injection valve 10 for delivering fuel 11 to the burner 3 is actuated, starting at a meter time t.sub.1. Depending on the amount of fuel to be metered, the actuation takes an actuation duration 305 up to an actuation end time t.sub.3. The temporal interval between the meter time t.sub.1 and the ignition time t.sub.0 is set to correspond to a “time of flight” 306 of the fuel from the injection valve 10 to the spark plug 12. The time of flight depends in particular on the specific geometric distance and the current mean advancement speed, which is essentially set by the airflow from the secondary air pump 13 or its speed.

[0036] As already explained above, in addition to this synchronous fuel metering and ignition, further measures can be taken in order to enable as safe and as emission-free operation of the burner 3 as possible. In particular, different preheating measures can be taken.

[0037] According to an advantageous embodiment, prior to the above-described ignition, the spark plug 12 of the burner 3 can be operated without fuel during a preheating period in order to heat the burning chamber of the burner 3 at least in the immediate vicinity of the spark plug 12, which facilitates or assists the ignition during an initial phase of the normal operating period.

[0038] In order to ensure a safe combustion, especially at the start of the injection, for example at the start (especially for the first injection), a longer ignition coil charging time for the spark plug can be provided and thus ultimately a safe ignition can be ensured.

[0039] Finally, once a safe combustion has finally been established in operation, the ignition can also be turned off entirely.