JP2010169052A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent clogging of unburnt fuel in a front end face of an oxidation catalyst 13, when the oxidation catalyst 13 is disposed upstream of a DPF 14 of an exhaust passage 10 and fuel is supplied to the oxidation catalyst 13 by using a fuel addition valve 15 or the like in regeneration of the DPF 14. <P>SOLUTION: After temperature sensors 24, 25 are disposed respectively in front of and behind the oxidation catalyst 13 and it is confirmed that a condition of an inlet temperature of oxidation catalyst is lower than an outlet temperature of oxidation catalyst is satisfied, the fuel is supplied to the oxidation catalyst 13. If the above condition is not satisfied, the fuel supply is halted. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine having a filter for collecting PM (Particulate Matter), which is particulate matter in exhaust gas, in an exhaust passage, and particularly relates to a regeneration technique for the filter.

  In an internal combustion engine such as a diesel engine, a PM collection filter is disposed in an exhaust passage to collect PM contained in exhaust discharged from the engine, thereby preventing the release of PM into the atmosphere.

  In such a filter, since the exhaust resistance gradually increases due to the accumulation of the collected PM, it is necessary to regenerate the filter by burning and removing the accumulated PM in a timely manner.

  For this reason, an oxidation catalyst is arranged on the upstream side of the filter, and when the filter is regenerated, fuel is supplied to the oxidation catalyst to generate oxidation heat, thereby raising the temperature of the downstream filter to a temperature at which PM can be combusted. Thus, PM is removed by combustion (filter regeneration).

  Patent Document 1 discloses a regeneration technique for a PM collection filter as described above. When the filter is regenerated (when the amount of accumulated PM exceeds a predetermined value), the temperature on the inlet side of the oxidation catalyst is changed. The fuel supply to the oxidation catalyst is started on the condition that the activation temperature of the oxidation catalyst (250 ° C.) or higher, and then the inlet side temperature of the oxidation catalyst is set lower than the activation temperature during regeneration. When the temperature drops below 200 ° C., the fuel supply is stopped.

JP 2006-274907 A

  However, as a condition for supplying the regeneration fuel, it is not possible to accurately determine the activation of the oxidation catalyst simply by determining the temperature on the inlet side of the oxidation catalyst alone. If the activity of the oxidation catalyst is low, the supplied regeneration catalyst Fuel may clog the front end face of the oxidation catalyst. When the front end face of the oxidation catalyst is clogged, the output is reduced due to an increase in back pressure.

  In view of such a situation, an object of the present invention is to prevent unburned fuel from being clogged in the front end face of an oxidation catalyst during regeneration of a PM collection filter.

  For this reason, in the present invention, attention is paid to the fact that the outlet side becomes a high temperature atmosphere with respect to the inlet side of the oxidation catalyst due to the activation of the oxidation catalyst (generation of oxidation heat). Detection means for detecting is provided, and at least one of the fuel supply conditions is that the temperature on the inlet side of the oxidation catalyst exceeds the temperature on the outlet side of the oxidation catalyst.

  According to the present invention, with respect to the oxidation catalyst, since the inlet side temperature is less than the outlet side temperature, after confirming the activity of the oxidation catalyst, the fuel for regeneration is supplied, and the front end face of the oxidation catalyst is clogged. Can be prevented.

The system diagram of the diesel engine which shows one Embodiment of this invention Flow chart of DPF regeneration control

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a system diagram of an internal combustion engine (here, a diesel engine) showing an embodiment of the present invention.

  The intake passage 2 of the diesel engine 1 is provided with an intake compressor of a supercharger (turbocharger) 3, and the intake air is supercharged by the intake compressor, cooled by the intercooler 4, passed through the intake throttle valve 5, It flows into the combustion chamber of each cylinder through the intake manifold 6. The fuel is increased in pressure by a common rail type fuel injection device, that is, by a high pressure fuel pump (not shown), sent to the common rail 7, and then directly injected into the combustion chamber by the fuel injection valve 8 of each cylinder. Here, the air flowing into the combustion chamber and the injected fuel are combusted by compression ignition.

  Exhaust gas after combustion in the engine 1 is discharged to the exhaust passage 10 via the exhaust manifold 9, but a part of the exhaust is discharged from the exhaust manifold 9 as EGR gas by the EGR device, that is, the EGR passage 11. Is recirculated to the intake manifold 6 via the EGR control valve 12. Further, the exhaust discharged to the exhaust passage 10 passes through the exhaust turbine of the supercharger 3 and drives it.

  An oxidation catalyst 13 having an oxidation function and a diesel particulate filter (hereinafter referred to as DPF) 14 for collecting PM in the exhaust are arranged in series downstream of the exhaust turbine in the exhaust passage 10 for exhaust purification. .

  The DPF 14 is made of, for example, a porous ceramic honeycomb structure carrier, and a large number of passages communicating the upstream side and the downstream side are arranged side by side, and the upstream end and the downstream end are alternately sealed in adjacent passages. Wall flow type filter. Therefore, the exhaust gas flows from the passage where the upstream end is open and the downstream end is sealed, passes through the passage wall (its pore), and flows out to the passage where the upstream end is sealed and the downstream end is open. In addition, PM in the exhaust is collected on the passage wall. In such a DPF 14, the exhaust resistance gradually increases due to the accumulation of the collected PM. Therefore, it is necessary to regenerate the DPF 14 in a timely manner as described later.

  The oxidation catalyst 13 is, for example, a porous ceramic honeycomb structure supporting a noble metal (oxidation catalyst) such as platinum (Pt), etc. In order to regenerate the DPF 14, the reducing component in the exhaust gas is oxidized. This is used to generate oxidation heat and raise the temperature of the downstream DPF 14. Further, a noble metal (oxidation catalyst) may be supported on the DPF 14 to have an oxidation function.

  An electromagnetic fuel addition valve 15 that can add fuel (reducing agent) to the exhaust gas flowing into the oxidation catalyst 13 is provided upstream of the oxidation catalyst 13 in the exhaust passage 10. However, as will be described later, when the fuel for regeneration is supplied by the post injection of the direct injection type fuel injection valve 8, the fuel addition valve 15 can be omitted.

  An electronic control unit (hereinafter referred to as ECU) 20 of the engine 1 is constituted by a microcomputer, and includes a CPU, a ROM, a RAM, an input / output interface, and the like.

  In order to control the engine 1, the ECU 20 includes an accelerator opening sensor 21 for detecting the accelerator opening Acc, a rotational speed sensor 22 for detecting the engine rotational speed NE, an air flow meter 23 for detecting the intake air amount Qa, a temperature Signals are input from the sensors 24, 25, 26 and the differential pressure sensor 27.

  The temperature sensor 24 is provided on the inlet side of the oxidation catalyst 13 and detects the oxidation catalyst inlet side temperature T1 from the exhaust temperature on the oxidation catalyst inlet side. Hereinafter, this is referred to as an oxidation catalyst inlet side temperature sensor.

  The temperature sensor 25 is provided on the outlet side of the oxidation catalyst 13 and detects the oxidation catalyst outlet side temperature T2 from the exhaust temperature on the oxidation catalyst outlet side. Hereinafter, this is referred to as an oxidation catalyst outlet side temperature sensor.

  The temperature sensor 26 is provided on the outlet side of the DPF 14 and detects the DPF temperature T3 from the exhaust temperature on the DPF outlet side. Hereinafter, this is referred to as a DPF temperature sensor. Instead of detecting the exhaust temperature on the DPF outlet side, a temperature sensor (thermocouple) may be directly embedded in the DPF 14 to detect the carrier temperature.

  The differential pressure sensor 27 detects a differential pressure across the DPF 14 (DPF upstream pressure−DPF downstream pressure) ΔP. Note that pressure sensors may be provided before and after the DPF 14 to obtain an output difference between the two sensors, and the differential pressure may be calculated based on the difference.

  Based on these input signals, the ECU 20 performs arithmetic processing according to a predetermined program, a fuel injection command signal for the fuel injection control (fuel injection timing and fuel injection amount control) of the fuel injection valve 8, and the intake throttle valve 5 In addition to outputting an opening degree command signal for opening degree control and an opening degree command signal for opening degree control (EGR amount control) of the EGR control valve 12, fuel for fuel supply control for regeneration of the fuel addition valve 15 Outputs an addition command signal.

  In such an exhaust system of the engine 1, PM contained in the exhaust is collected by the DPF 14 and is prevented from being released into the atmosphere.

  When the engine load increases and the exhaust temperature becomes high, the PM collected and deposited in the DPF 14 is oxidized and removed by exposure to the high-temperature exhaust, but the engine load is low for a long time. If it continues, PM will not be oxidized and removed in the meantime.

  Therefore, the PM accumulation amount of the DPF 14 gradually increases, and due to the clogging of the DPF 14, the exhaust resistance increases and the output of the engine 1 decreases.

  Therefore, the oxidation catalyst 13 is disposed on the upstream side of the DPF 14, and the downstream DPF 14 is heated as much as possible by the heat of oxidation by the oxidation catalyst 13, so that the PM collected and deposited in the DPF 14 is burned and removed in a possible range. While aiming (continuous regeneration), the fuel addition valve 15 is actuated to supply fuel to the oxidation catalyst 13 in a timely manner (when the regeneration time is determined, for example, when the PM accumulation amount of the DPF 14 reaches a predetermined value). By supplying and generating greater oxidation heat in the oxidation catalyst 13, the downstream DPF 14 is heated to a temperature at which PM can be combusted and the PM collected and deposited in the DPF 14 is surely removed by combustion (forced) Playback).

  On the other hand, when the activity of the oxidation catalyst 13 is low, if the fuel is supplied from the fuel addition valve 15 to the oxidation catalyst 13, the supplied fuel becomes “soot” without being oxidized, and the front end surface of the oxidation catalyst 13. The clogging may cause a decrease in output due to an increase in back pressure.

Therefore, here, the oxidation catalyst inlet side temperature sensor 24 and the oxidation catalyst outlet side temperature sensor 25 are provided to detect the oxidation catalyst inlet side temperature T1 and the oxidation catalyst outlet side temperature T2,
Oxidation catalyst inlet side temperature T1 <Oxidation catalyst outlet side temperature T2
If the above condition is satisfied, the fuel supply condition for regeneration is satisfied. If the condition is not satisfied, the fuel for regeneration is not supplied to prevent the front end face of the oxidation catalyst 13 from being clogged.

  Next, DPF regeneration control by the ECU 20 in the present embodiment based on the above purpose will be described with reference to the flowchart of FIG. Note that the DPF regeneration control routine of FIG. 2 is executed in time synchronization every predetermined time.

  In S1, it is determined based on the value of the regeneration flag F whether the DPF regeneration is in progress (the DPF regeneration is requested).

  The reproducing flag F indicates whether or not the DPF is being reproduced. Specifically, when the value is 1, the reproduction is being performed, and when the value is 0, the reproduction is not being performed. The initial setting value is 0.

  If DPF regeneration is not in progress (if F = 0), the process proceeds to S2.

  In S2, the PM accumulation amount of the DPF is calculated based on the differential pressure ΔP before and after the DPF detected by the differential pressure sensor 27 in order to determine whether or not it is the regeneration timing. As the PM deposition amount increases, the front-rear differential pressure ΔP increases. However, the front-rear differential pressure ΔP also depends on the exhaust flow rate (≈intake air amount), and therefore, the PM deposition from the DPF front-rear differential pressure ΔP and the intake air amount Qa. Calculate the amount.

  In S3, it is determined whether or not it is the regeneration time by comparing the PM accumulation amount calculated in S2 with a predetermined threshold PM1 for regeneration time determination. As a result of the comparison, if the PM accumulation amount <PM1, it is determined that it is not the regeneration time, and this routine is terminated.

  If the PM accumulation amount ≧ PM1, it is determined that it is the regeneration time (regeneration request is present), the process proceeds to S4, and the regeneration flag F = 1 is set.

  Instead of calculating the PM accumulation amount and comparing it with the predetermined value PM1, the differential pressure before and after the DPF when PM accumulation amount = PM1 is obtained and mapped for each exhaust flow rate (intake air amount). The DPF front-rear differential pressure ΔP detected by the differential pressure sensor 27 is compared with the front-rear differential pressure ΔPm1 corresponding to the regeneration timing at the current exhaust flow rate (intake air amount) obtained from the map, and when ΔP ≧ ΔPm1, You may make it judge that it is a reproduction | regeneration time.

  In addition, regarding the calculation method of the PM accumulation amount, during the engine operation, the PM amount discharged from the engine is obtained for each unit time based on the engine operation condition, and this is multiplied by a predetermined collection efficiency to obtain a unit time. A method may be employed in which the PM deposition amount is obtained every time, or a decrease due to continuous regeneration is further obtained, and these are integrated to calculate the PM deposition amount.

  After the PM accumulation amount ≧ PM1 is determined to be the regeneration time and the regeneration flag F = 1 is set in S4, the process proceeds to S5. Further, in the routine after the next time, since F = 1 in the determination of the reproducing flag F in S1, the process proceeds to S5 as it is.

  In S5, the temperature sensors 24 and 25 detect the temperatures before and after the oxidation catalyst, that is, the oxidation catalyst inlet side temperature T1 and the oxidation catalyst outlet side temperature T2.

  In S6, as one of the fuel supply conditions for regeneration, the oxidation catalyst inlet side temperature T1 is equal to or higher than a predetermined value TC1 (T1 ≧ TC1) and / or the oxidation catalyst outlet side temperature T2 is equal to or higher than a predetermined value TC2 (T2 ≧ TC2). ). This is to determine whether or not the exhaust temperature serving as a base is equal to or higher than a predetermined value in order to burn PM in the DPF. In particular, for the oxidation catalyst inlet side temperature T1, it is determined whether or not the exhaust temperature atmosphere is such that the oxidation catalyst can be activated. As for the oxidation catalyst outlet side temperature T2, it is determined whether the temperature of the exhaust gas flowing into the base DPF is equal to or higher than a predetermined value when the DPF is heated.

  Note that it may be determined whether only the oxidation catalyst inlet side temperature T1 is T1 ≧ TC1, or only the oxidation catalyst outlet side temperature T2 may be determined whether T2 ≧ TC2 or not. Whether both T1 ≧ TC1 and T2 ≧ TC2 may be determined for both the catalyst inlet side temperature T1 and the oxidation catalyst outlet side temperature T2.

  If the determination in S6 is YES, the process proceeds to S7 in order to determine another fuel supply condition for regeneration. In the case of NO, the process proceeds to S10, the fuel supply by the fuel addition valve 15 is stopped (stopped), and the rise of the exhaust temperature is waited.

  In S7, as one of the supply conditions of the regeneration fuel, the oxidation catalyst inlet side temperature T1 and the oxidation catalyst outlet side temperature T2 are compared to determine whether or not T1 <T2.

  When T1 <T2, the oxidation catalyst inlet side temperature T1 is higher than the oxidation catalyst outlet side temperature T2, which means that the oxidation catalyst is activated and generates heat of oxidation. (There is no risk of clogging of the front end face of the oxidation catalyst). Therefore, when T1 <T2, the process proceeds to S8 and S9 to supply fuel to the oxidation catalyst.

  In S8, the DPF temperature T3 is detected by the temperature sensor 26.

  In S9, the fuel supply amount (fuel addition amount) by the fuel addition valve 15 is set so that the DPF temperature T3 becomes the target temperature, and the fuel addition valve 15 is operated according to this set value.

  More specifically, the target temperature is variably set according to the elapsed time from the start of regeneration, etc., so that the target temperature is gradually increased and finally the temperature at which PM can be efficiently burned (for example, 600 ° C.) On the other hand, the actual temperature detected by the temperature sensor 26 is compared with the target temperature. If the actual temperature is less than the target temperature, the amount of fuel supplied by the fuel addition valve 15 is increased. If the actual temperature is greater than the target temperature, Performs feedback control so as to reduce the amount of fuel supplied by the fuel addition valve 15 to achieve the target temperature.

  In the case of T1 ≧ T2, the oxidation catalyst inlet side temperature T1 is lower than the oxidation catalyst outlet side temperature T2, which means that the oxidation catalyst is not activated and does not generate oxidation heat. If fuel is supplied, unburned fuel may be clogged in the front end face of the oxidation catalyst. Therefore, if T1 ≧ T2, the process proceeds to S10.

  In S10, the fuel supply by the fuel addition valve 15 is stopped (stopped) in order to prevent clogging of the front end face of the oxidation catalyst due to the fuel supply.

  As described above, by confirming that the oxidation catalyst inlet side temperature T1 is higher than the oxidation catalyst outlet side temperature T2 as at least one of the fuel supply conditions, the activity of the oxidation catalyst is confirmed, and then the fuel supply for regeneration is supplied. Therefore, clogging of the front end face of the oxidation catalyst can be prevented in advance.

  During fuel supply by the fuel addition valve 15 at S8 and S9 (during addition amount control) or during fuel supply stop at S10, the process proceeds to S11.

  In S11, in order to determine whether or not the regeneration is completed, the PM accumulation amount of the DPF is calculated based on the DPF front-rear differential pressure ΔP detected by the differential pressure sensor 27, similarly to S2.

  In S12, it is determined whether or not regeneration is completed by comparing the PM accumulation amount calculated in S11 with a predetermined threshold PM2 for regeneration completion. As a result of the comparison, if PM accumulation amount> PM2, it is determined that regeneration is not completed, and this routine is terminated.

  When the PM accumulation amount ≧ PM2, it is determined that the regeneration is completed, the process proceeds to S13, the fuel supply by the fuel addition valve 15 is completely stopped, and at the same time, the regeneration flag F = 0 is reset, and this routine is executed. finish.

  Instead of calculating the PM accumulation amount and comparing it with the predetermined value PM2, the differential pressure before and after the DPF when PM accumulation amount = PM2 is obtained and mapped for each exhaust flow rate (intake air amount). The DPF front-rear differential pressure ΔP detected by the differential pressure sensor 27 is compared with the front-rear differential pressure ΔPm2 corresponding to the completion of regeneration at the current exhaust flow rate (intake air amount) obtained from the map, and when ΔP ≦ ΔPm2, It may be determined that the reproduction has been completed.

  In addition, regarding the calculation method of the PM deposition amount, during the DPF regeneration, the PM removal amount is obtained based on the DPF temperature or the DPF temperature and the exhaust flow rate, etc. for each unit time. A method of calculating the PM deposition amount by calculating the PM removal amount and subtracting the PM removal amount by regeneration from the PM deposition amount at the start of regeneration may be adopted.

  The determination of whether or not regeneration is complete can also be made based on the elapsed time from the start of regeneration, the fuel supply time, or the total amount of fuel supply.

  According to the present embodiment, the oxidation catalyst inlet side temperature T1 and the oxidation catalyst outlet side temperature T2 are detected, and that the oxidation catalyst outlet side temperature T1 exceeds the oxidation catalyst outlet side temperature T2 is at least one of the fuel supply conditions. Thus, after confirming the activity of the oxidation catalyst, the fuel for regeneration is supplied, and the front end face of the oxidation catalyst can be prevented from being clogged.

  In addition, if a pressure sensor is provided before and after the oxidation catalyst to detect clogging of the front end surface from pressure loss and the fuel supply is stopped, excessive clogging can be avoided. In addition, it is necessary to newly install a pressure sensor on the inlet side of the oxidation catalyst, which not only increases the cost, but can only be detected after clogging occurs, and clogging cannot be prevented beforehand.

  In this regard, as in this embodiment, the temperature sensor before and after the oxidation catalyst is mounted by setting at least one of the fuel supply conditions that the oxidation catalyst outlet side temperature T1 is higher than the oxidation catalyst outlet side temperature T2. In many cases, there is no need to install a new one, so that an increase in cost can be suppressed and clogging can be prevented in advance.

  Further, according to the present embodiment, it is possible to determine that at least one of the oxidation catalyst inlet side temperature T1 and the oxidation catalyst outlet side temperature T2 is equal to or higher than a predetermined temperature, In consideration of the exhaust gas temperature, the fuel supply conditions for regeneration can be made more appropriate.

In the above embodiment,
Oxidation catalyst inlet side temperature T1 <Oxidation catalyst outlet side temperature T2
Is the fuel supply condition,
Oxidation catalyst inlet side temperature T1 + α <Oxidation catalyst outlet side temperature T2
May be the fuel supply condition.

  That is, the activity of the oxidation catalyst is more reliably determined by setting at least one of the fuel supply conditions that the oxidation catalyst outlet side temperature T2 exceeds the oxidation catalyst outlet side temperature T1 by a predetermined value α or more. Then, by supplying the fuel, clogging of the front end face of the oxidation catalyst can be prevented more reliably.

  In the above embodiment (flow of FIG. 2), the fuel supply condition for regeneration is determined only for the oxidation catalyst inlet side temperature T1 and the outlet side temperature T2, but it is not during idle operation or deceleration operation. May be added as a fuel supply condition.

  In the above embodiment, the fuel addition valve 15 is provided on the upstream side of the oxidation catalyst 13 in the exhaust passage 10 as the regeneration fuel supply means, and the ECU 20 controls the fuel addition valve 15 to Although the fuel is supplied, the fuel addition valve 15 is eliminated, and the fuel is supplied to the oxidation catalyst 13 using the direct injection fuel injection valve 8 that injects the fuel into the cylinder of the engine 1. You can also.

  That is, after the main injection in the vicinity of the compression top dead center of the fuel injection valve 8, post-injection for additionally injecting fuel in the expansion stroke or exhaust stroke from the fuel injection valve 8 is performed, and the post-injected fuel The fuel is supplied to the oxidation catalyst 13 by being discharged into the exhaust passage 10 with almost no combustion in the cylinder.

  As described above, when post injection is used as the regeneration fuel supply means, the post injection amount and / or the post injection timing are controlled when the DPF temperature T3 is controlled to be the target temperature in S9 of the flow of FIG. By controlling this, it is possible to control the DPF temperature.

  Further, when raising the temperature of the DPF 14 by supplying fuel for regeneration, control for increasing the combustion temperature by closing control of the EGR control valve 12 or control for suppressing exhaust cooling by closing control of the intake throttle valve 5 may be used together. Needless to say good things.

  In the above embodiment, the exhaust gas purification device for a diesel engine has been described. However, the engine type is not limited to this, and a filter is disposed in the exhaust passage to collect PM, and the regeneration of this filter is performed. As long as the engine performs timely, it can be applied to any engine.

DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Intake passage 3 Supercharger 4 Intercooler 5 Intake throttle valve 6 Intake manifold 7 Common rail 8 Fuel injection valve 9 Exhaust manifold 10 Exhaust passage 11 EGR passage 12 EGR control valve 13 Oxidation catalyst 14 DPF
20 ECU
21 Accelerator opening sensor 22 Rotation speed sensor 23 Air flow meter 24 Oxidation catalyst inlet side temperature sensor 25 Oxidation catalyst outlet side temperature sensor 26 DPF temperature sensor 27 Differential pressure sensor

Claims (5)

A filter that is disposed in an exhaust passage of the internal combustion engine and collects PM in the exhaust; and an oxidation catalyst that is disposed on the upstream side of the filter in the exhaust passage. In an exhaust gas purification apparatus for an internal combustion engine, comprising a fuel supply means for regeneration for supplying fuel,
Providing a temperature detecting means for detecting the temperature of the inlet side and outlet side of the oxidation catalyst;
The regeneration fuel supply means uses at least one of the fuel supply conditions that the temperature on the outlet side is higher than the temperature on the inlet side detected by the temperature detection means. apparatus.   The regeneration fuel supply means sets at least one of the fuel supply conditions that the temperature on the outlet side exceeds the temperature on the inlet side detected by the temperature detection means by a predetermined value or more. The exhaust emission control device for an internal combustion engine according to claim 1.   The regeneration fuel supply means is another fuel supply condition that at least one of the inlet-side temperature and the outlet-side temperature detected by the temperature detecting means is equal to or higher than a predetermined temperature. The exhaust emission control device for an internal combustion engine according to claim 1 or 2, characterized by the above.   The fuel supply means for regeneration has a fuel addition valve upstream of the oxidation catalyst in the exhaust passage, and controls the fuel addition valve to supply fuel to the oxidation catalyst. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3.   The regeneration fuel supply means performs the oxidation catalyst by post injection that injects fuel in the expansion stroke or exhaust stroke from the fuel injection valve after the main injection of the fuel injection valve that injects fuel into the cylinder of the internal combustion engine. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein fuel is supplied to the engine.

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