Method for the targeted ageing of a catalytic converter by means of a test bench

Abstract

The invention relates to a method for the targeted ageing of a catalytic converter (2) by means of a test bench (1) comprising the catalytic converter (2) and an internal combustion engine (3), wherein the internal combustion engine (3) has at least two combustion chambers (5, 6), namely a first combustion chamber (5) and a second combustion chamber (6). An ageing phase is carried out in which the internal combustion engine (3) is operated in a fired manner, as a result of which the internal combustion engine (3) provides an overall lean exhaust gas which forms an exhaust gas mass flow which is conducted through the catalytic converter (2). During a first part of the ageing phase, the internal combustion engine (3) is operated in a fired manner in that the first combustion chamber (5) and the second combustion chamber (6) are operated in a fired manner, as a result of which the internal combustion engine (3) provides the overall lean exhaust gas which forms the exhaust gas mass flow which, during the first part, has a base temperature of less than 900 degrees Celsius and is conducted through the catalytic converter (2).

Description

[0001] 24-3927 PIF

[0002] 1

[0003] Method for the targeted aging of a catalyst using a test bench

[0004] The invention relates to a method for the targeted aging of a catalyst using a test bench.

[0005] CN 101790624 B discloses a method for verifying the aging state of a catalyst on board a vehicle. DE 102018 126767 B4 discloses a method for monitoring the effectiveness of a three-way catalyst. DE 102018 130990 A1 discloses a method for aging a component of an exhaust aftertreatment system. WO 2010 / 022747 A1 discloses a method for generating aging gas for aging exhaust aftertreatment components. Furthermore, EP 1 521 903 B1 discloses a method for artificially aging a catalyst device used on a catalyst test bench.

[0006] The object of the present invention is to provide a method by which a catalyst can be aged in a particularly advantageous and targeted manner using a test rig.

[0007] This problem is solved according to the invention by a method having the features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

[0008] The invention relates to a method for the targeted and artificial aging of a catalyst. The method according to the invention is carried out using a test rig, in particular a stationary and thus completely immobile one, which is a device distinct from a vehicle. In other words, the aging of the catalyst can be specifically induced by means of the method according to the invention. The feature that the catalyst can be specifically and artificially aged by means of the method according to the invention means that the aging of the catalyst that can be effected or is effected by means of the method is brought about by means of the test rig and does not result from the operation of a vehicle in which the catalyst is installed. The test rig includes the catalyst and an internal combustion engine or combustion engine.

[0009] 2

[0010] The process involves an internal combustion engine which, as will be explained in more detail below, produces exhaust gas. The catalyst is designed to treat the exhaust gas, specifically to catalytically support and / or effect at least one chemical reaction in which at least one chemical compound contained in the exhaust gas, also referred to as a starting compound, or in particular several chemical compounds contained in the exhaust gas, also referred to as starting compounds, is converted into a chemical compound different from the respective starting compound, also referred to as a result compound. The starting compound is or comprises, for example, carbon monoxide (CO) and / or unburned hydrocarbons (HC) and / or nitrogen (NOx).In other words, the catalyst is designed to catalytically support and / or initiate chemical reactions by which carbon monoxide (CO) contained in the exhaust gas is converted into carbon dioxide (CO2), unburned hydrocarbons (HC) contained in the exhaust gas are converted into carbon dioxide and water (H2O), and nitrogen oxides contained in the exhaust gas, such as nitric oxide (NO), are converted into nitrogen (N2) and carbon dioxide. Thus, the catalyst is designed as a three-way catalyst. The conversion of the respective reactant compound into the respective result compound is also referred to as "conversion" or "reaction." Therefore, the catalyst is designed for a conversion, that is, for the reaction of at least one reactant compound into at least one different result compound.As will be explained in more detail below, the process uses the exhaust gas of the internal combustion engine as an aging gas, with which the catalyst is specifically aged.

[0011] In this process, the internal combustion engine has several, and therefore at least or exactly two, combustion chambers, namely a first combustion chamber and a second combustion chamber. For example, each combustion chamber is partially bounded by a respective cylinder of the internal combustion engine and partially by a respective, translationally movable cylinder on the piston of the internal combustion engine, so that, for example, the internal combustion engine is designed as a reciprocating piston engine.

[0012] In the method according to the invention, an aging phase is carried out at least once. During the aging phase, the internal combustion engine is fired up. 24-3927 PIF

[0013] 3

[0014] The engine is operated in a lean manner, producing an overall lean exhaust gas flow that forms an exhaust mass flow which is passed through the catalyst during the aging phase. This means that during the aging phase, the exhaust mass flow, and thus the overall lean exhaust gas flow of the internal combustion engine, is passed through the catalyst. The fact that the exhaust gas of the internal combustion engine is lean overall, and preferably continuously and thus without interruption, during the aging phase means that the exhaust gas, particularly with regard to its residual oxygen content, has a composition that results from lean operation of the internal combustion engine when considering the engine as a whole.In other words, during the aging phase, the internal combustion engine as a whole, that is, considered holistically, and in particular continuously and without interruption, operates in a lean condition. This means that, when considering the engine holistically, it operates with a lean air-fuel ratio, which is greater than 1. Specifically, during the aging phase, the overall air-fuel ratio with which the internal combustion engine is operated is greater than 1.01.

[0015] The aging phase has at least or exactly two parts: a first part and a second part. During the first part of the aging phase, the internal combustion engine is operated by firing the first combustion chamber and the second combustion chamber, in particular all combustion chambers, of the internal combustion engine. This results in the internal combustion engine as a whole, that is, when considering the engine in its entirety, providing a lean exhaust gas. This exhaust gas mass flow, which during the first part of the aging phase, in particular continuously and / or constantly, has a base temperature of less than 900 degrees Celsius and is passed through the catalysts. The base temperature is also referred to as the "first temperature".It is conceivable that during the first part of the aging phase, the exhaust gas mass flow exhibits a consistently lower base temperature compared to 900 degrees Celsius, and thus remains constant. Furthermore, it is conceivable that during the first part of the aging phase, the base temperature is at least substantially constant. 24-3927 PIF.

[0016] 4

[0017] The characteristic that the respective combustion chamber is fired, that is, operated in a fired process, means that combustion processes take place in the respective combustion chamber, specifically such that a combustion process occurs within each operating cycle of the internal combustion engine. During this combustion process, a fuel-air mixture, also simply referred to as a mixture, is combusted in the respective combustion chamber, specifically ignited and burned, resulting in the exhaust gas of the internal combustion engine. The respective mixture comprises at least air and, for example, a liquid fuel.

[0018] The second part of the aging phase follows, for example, directly from the first part. The fact that the second part of the aging phase preferably follows directly from the first part means that no other, further part of the aging phase lies between the first and second parts. During the second part of the aging phase, the internal combustion engine is operated with combustion, whereby the first combustion chamber is fired and the second combustion chamber is operated without combustion. In each fired combustion chamber, air and fuel are introduced into the respective combustion chamber.The characteristic that the second combustion chamber is operated without fuel, particularly continuously and thus without interruption, during the second part of the aging phase, means that combustion does not occur in the second combustion chamber during this second part of the aging phase. During this unfired operation of the second combustion chamber, fuel is not introduced into the second combustion chamber.In the unfired operation of the second combustion chamber, only the air is passed through it, specifically pumped through it, with respect to the fuel and air. During the second part of the aging phase, the first combustion chamber provides the exhaust gas resulting from the combustion processes taking place there. During this second part of the aging phase, the second combustion chamber provides the air that is passed through it. Thus, during the second part of the aging phase, the internal combustion engine provides the overall lean exhaust gas, which forms the exhaust mass flow that is passed through the catalytic converter.This means that although during the second part of the aging phase the first combustion chamber is fired and the second combustion chamber is operated unfired, the exhaust gas of the internal combustion engine as a whole, that is, when considering the internal combustion engine as a whole, in particular, continues, 24-3927 PIF.

[0019] 5

[0020] The mixture is lean. This occurs primarily because, viewed individually, the fired operation of the first combustion chamber compensates for the unfired operation of the second combustion chamber, such that during the second part of the aging phase, the exhaust gas of the internal combustion engine as a whole—that is, when considering the engine as a whole—is consistently lean. For example, during the second part of the aging phase, the first combustion chamber is operated rich, meaning with a rich air-fuel ratio (lambda), thereby at least partially compensating for the excess air resulting from the unfired operation of the second combustion chamber. The unfired operation of the second combustion chamber during the second part of the aging phase, while the first combustion chamber is fired, is also referred to as the second combustion chamber being shut off or blocked.Especially when the respective combustion chamber is partially formed by the aforementioned cylinder, the deactivation of the second combustion chamber is also referred to as "cylinder deactivation." Thus, during the second part of the aging phase, the second combustion chamber is deactivated, specifically cylinder deactivation, while the first combustion chamber continues to operate. This allows, for example, unburned hydrocarbons from the first combustion chamber to enter the exhaust gas of the internal combustion engine and thus the catalytic converter, while oxygen from the second combustion chamber enters the exhaust gas and thus the catalytic converter. Therefore, during the second part of the aging phase, the unburned hydrocarbons can react with the oxygen in the exhaust gas in the catalytic converter, oxidizing them—that is, burning them—within the catalytic converter.This results in a peak temperature, higher than the base temperature, occurring at least temporarily, and in particular at least once, and especially several times, within the second part of the aging phase of the catalyst. The process according to the invention makes it possible to age the catalyst in a particularly simple and targeted manner, thereby bringing it, for example, into a so-called limiting catalyst state, i.e., converting it into a so-called limiting catalyst.

[0021] The invention is based in particular on the following considerations and findings: the catalyst or its catalytically effective volume for conversion has an extent also referred to as "length", which runs along a flow direction in which the catalyst or its 24-3927 PIF

[0022] 6

[0023] The volume, also referred to as the catalyst volume, is the volume through which the exhaust gas mass flow can pass or is passing. The catalyst can thus be divided, at least conceptually, into two sub-sections: a first sub-section and a second sub-section, which connects to the first sub-section in the direction of the exhaust gas mass flow through the catalyst. Therefore, the second sub-section is located downstream of the first sub-section in the direction of the exhaust gas mass flow passing through the catalyst, and the first sub-section is thus located upstream of the second sub-section in the direction of the exhaust gas mass flow passing through the catalyst.In principle, it would be conceivable for the catalyst sections to be directly connected to one another, so that there is no gap between them that is free of the catalyst and thus free of a coating catalytically effective for the conversion described above. It is conceivable that the sections are formed as a single unit, i.e., from a single piece. Furthermore, it would be conceivable that the sections are spaced apart from each other in the direction of the exhaust gas mass flow through the catalyst, particularly completely, so that a gap exists between them in the direction of the exhaust gas mass flow that is completely free of a coating catalytically effective for the conversion described above. In this case, for example, the first section would form a first individual catalyst and the second section a second catalyst.In other words, the sub-areas can then be viewed, for example, as individual catalysts, and it is conceivable that the individual catalysts are arranged in a common housing.

[0024] The method according to the invention can advantageously impair, and in particular reduce, both the ability of the catalyst to store oxygen contained in the exhaust gas, also referred to as "oxygen storage capacity," and the performance or efficiency of the catalyst to carry out the aforementioned conversion, also referred to as "conversion capacity" or "conversion efficiency." The oxygen storage capacity is also referred to as oxygen storage capacity (OSO). The conversion capacity is also referred to as catalytic efficiency. With regard to the oxygen storage capacity and the conversion efficiency, the method makes it possible to reduce the oxygen storage capacity of the first sub-area very quickly, in particular to a minimum, without, however, the 24-3927 PIF

[0025] 7

[0026] The conversion efficiency of the catalyst as a whole cannot be excessively reduced. For example, it is possible to rapidly reduce the oxygen storage capacity in the first part of the catalyst, particularly to a minimum, without excessively reducing the overall conversion efficiency of the catalyst. Thus, while the oxygen storage capacity of at least the first part, and especially of the catalyst as a whole, is already at a very low level, specifically at the aforementioned minimum, the overall conversion efficiency of the catalyst, although reduced compared to a new catalyst, is still at such a high or good level that the catalyst as a whole is still able to carry out the conversion at a fairly high conversion rate.Starting from this point, by further carrying out the process, the conversion rate can ultimately be reduced in the event of impairment, in particular until the conversion rate reaches a target value, which can, for example, be predefined or predetermined. The process thus makes it possible to very quickly reduce the oxygen storage capacity in the first part of the catalyst, in particular to the aforementioned minimum and / or to a first target value, without unduly affecting the overall conversion rate of the catalyst. Furthermore, by continuing to carry out the process, the conversion rate is reduced even further, and thus the conversion rate can also be brought to a second target value, which can, for example, be predefined or predetermined.Since, when the conversion rate of the catalyst is reduced overall, the oxygen storage capacity in the first part of the catalyst is already at its minimum, the conversion rate can be selectively adjusted to the second target value without undesirably impairing the oxygen storage capacity. The method according to the invention thus makes it possible to easily adjust the oxygen storage capacity to the first target value and the conversion rate to the second target value. For this purpose, the method can simply be carried out for a certain period of time, and in particular until the conversion rate reaches the second target value, because the oxygen storage capacity will reach the first target value, especially its minimum, before this point.Once the target values ​​for oxygen storage capacity and conversion performance are reached, the process can simply be terminated, and the catalyst then exhibits, for example, the limiting catalyst state. Compared to the conventional solution, the catalyst can thus be brought into the limiting catalyst state (PIF) particularly easily, quickly, and precisely.24-3927

[0027] 8

[0028] The invention avoids the influences of arbitrariness and chance that occur in conventional methods. In other words, the inventive method allows the oxygen storage capacity to be quickly brought to a desired level, for example, to the first target value and, in particular, to the minimum, after which the conversion power can be specifically adjusted to the desired second target value. This allows the catalyst to be brought to the limiting catalyst state quickly, precisely, and without arbitrary or random events.

[0029] To age the catalyst particularly advantageously, simply, quickly, and in a controlled manner, it is preferably provided that the exhaust gas mass flow rate during the aging phase is at most 1000 kilograms per hour, and in particular less than 1000 kilograms per hour. More preferably, it is provided that the exhaust gas mass flow rate during the aging phase is at most 400 kilograms per hour, in particular at most 350 kilograms per hour, and most preferably at most 300 kilograms per hour. Preferably, the exhaust gas mass flow rate during the aging phase is at most 300 kilograms per hour.This results in a relatively low exhaust gas mass flow, which rapidly reduces the oxygen storage capacity, particularly of the first section of the catalyst and thus of the catalyst as a whole. This allows it to be brought down to the first target value, specifically to the minimum, without excessively reducing the overall conversion efficiency of the catalyst. By subsequently repeating the process, the overall efficiency of the catalyst can then be further reduced and thus brought down to the second target value.

[0030] Another embodiment is characterized by the fact that a regeneration phase is carried out at least once after the aging phase. During the regeneration phase, the internal combustion engine is operated under load, resulting in an overall rich exhaust gas. This means that during the regeneration phase, the internal combustion engine is operated in a rich, i.e., comprehensive, and in particular continuously and thus without interruption, fuel-rich conditions, so that the exhaust gas during the regeneration phase has a composition resulting from the fact that the internal combustion engine is operated in a rich, i.e., comprehensive, and in particular continuously and without interruption, fuel-rich conditions.

[0031] 9

[0032] The combustion air-fuel ratio is less than 1, particularly less than 0.99. This results in the rich exhaust gas forming an exhaust gas mass flow during the regeneration phase, which is passed through the catalyst and has a temperature, particularly a constant temperature, also referred to as the "second temperature," which is less than 900 degrees Celsius. For example, the second temperature can be lower than the base temperature. Preferably, the second temperature is greater than 600 degrees Celsius. Preferably, the second temperature is 800 degrees Celsius. The regeneration phase counteracts the aging caused by the aging phase, as the regeneration phase regenerates the catalyst, also simply called the catalytic converter.The regeneration phase serves to stabilize the catalytic converter's properties, specifically its oxygen storage capacity (OSC) and conversion efficiency, through a partial regeneration. This allows the catalytic converter to be used immediately without having to deal with random regeneration cycles.

[0033] Preferably, the aging phase is carried out several times in succession, in particular such that the regeneration phase is carried out once between each successive aging phase. In simplified terms, one regeneration phase is performed between each successive aging phase, which advantageously reduces the oxygen storage capacity and the conversion rate, thus allowing the catalyst to be brought to the limiting catalyst state particularly quickly and easily.

[0034] To achieve particularly advantageous aging of the catalyst, a further embodiment of the invention provides that the internal combustion engine is operated under fire during the regeneration phase, specifically by operating the first and second combustion chambers continuously. It is preferably provided that, during the regeneration phase, unfired operation of a combustion chamber of the internal combustion engine, and thus, for example, of a cylinder forming a combustion chamber of the internal combustion engine, is omitted, particularly continuously. Thus, for example, the first and second combustion chambers are each operated with a rich mixture, i.e., with a rich air-fuel ratio, resulting in the rich exhaust gas during the regeneration phase. 24-3927 PIF

[0035] 10

[0036] Another embodiment is characterized in that the regeneration phase lasts at least two minutes. Preferably, the regeneration phase lasts less than ten minutes. For example, the regeneration phase lasts ten minutes, and for example, the regeneration phase lasts at most ten minutes. This allows the catalyst to be brought to the limiting catalyst state particularly quickly and easily.

[0037] In a further, particularly advantageous embodiment of the invention, it is provided that the regeneration phase lasts shorter than the aging phase, which allows the catalyst to be brought into the limiting catalyst state particularly quickly.

[0038] In a further, particularly advantageous embodiment of the invention, it is provided that during the regeneration phase, unfired operation of a combustion chamber of the internal combustion engine is omitted, in particular continuously, whereby the oxygen storage capacity and the conversion performance can be brought particularly advantageously and specifically to the respective target values.

[0039] In order to bring the catalyst into the limiting catalyst state particularly quickly and easily, a further embodiment of the invention provides that the aging phase lasts at least 60 minutes.

[0040] During the second part of the aging phase, for example, the second combustion chamber is repeatedly shut off, with the second combustion chamber being operated in the same way as the first combustion chamber between two shut-off cycles. During the second part of the aging phase, the second combustion chamber is shut off at least ten times, in particular at least 20 times, and more than ten times, in particular more than 20 times. During the second part of the aging phase, the second combustion chamber is shut off at most 100 times, in particular at most 80 times, and most especially at most 50 times, in particular less than 50 times. This allows the catalyst to be aged particularly advantageously and brought into the limiting catalyst state particularly quickly and easily.

[0041] Finally, it has proven particularly advantageous if the second part of the aging phase is at least temporarily and at least once, especially 24-3927 PIF

[0042] 11

[0043] The peak temperature of the catalyst is repeatedly exceeded by more than 1000 degrees Celsius. Preferably, the peak temperature is at least 1050 degrees Celsius. For example, the peak temperature is greater than 1100 degrees, and in particular greater than 1130 degrees Celsius. In other words, during the second part of the aging phase, the internal combustion engine is operated in such a way that the exhaust gas mass flow reaches the peak temperature at least temporarily, and in particular several times in quick succession.

[0044] The process according to the invention enables targeted and artificial aging of the catalyst, in particular to bring the catalyst, for example designed as a three-way catalyst, to the limiting catalyst state with regard to oxygen storage capacity and conversion performance, i.e., to a level of the, for example, predetermined limiting catalyst. Subsequently, it is possible, for example, to use the catalyst aged by means of the process according to the invention and thus exhibiting the limiting catalyst state, i.e., by carrying out tests on the catalyst aged by means of the process.These tests can provide information and data that, for example, in a vehicle equipped with a catalytic converter system, allows for the precise determination of whether and / or when the system has aged to such an extent due to vehicle operation that it reaches the critical condition. In other words, this information and data can be used to program the vehicle's control unit, enabling it to accurately detect whether and / or when the catalytic converter system has reached this critical condition. Consequently, measures can be taken to ensure low-emission operation of the vehicle.

[0045] Preferably, the exhaust gas mass flow rate during the regeneration phase is at most 1000 kilograms per hour, and in particular less than 1000 kilograms per hour. For example, the exhaust gas mass flow rate during the regeneration phase is less than 800 kilograms per hour.

[0046] It is conceivable that during the aging phase, the exhaust gas, and thus the exhaust gas mass flow, is passed through the catalyst at a space velocity of at most 5,550,001 / h, based on the first section of the catalyst. 24-3927 PIF

[0047] 12

[0048] During the second part of the aging phase, the formation of the second combustion chamber is carried out and the internal combustion engine as a whole, that is, considered holistically, is operated so lean, that is, with such a lean, in particular global, combustion air ratio, that the peak temperature is preferably at least 1000 degrees Celsius.

[0049] Further insights and considerations underlying the invention are that modern motor vehicles use on-board diagnostics (OBD) to monitor emissions during operation. This helps prevent excessive increases in emissions. In particular, it is desirable to recognize that an exhaust aftertreatment system, such as a catalytic converter system for treating the exhaust gas of an internal combustion engine, can reach a state during the vehicle's operation in which exhaust aftertreatment is no longer as effective as desired. This state is, for example, the aforementioned limiting state of the catalytic converter. Using so-called OSC diagnostics, an OSC level can be measured, based on which conclusions can be drawn about the catalytic effectiveness of the catalytic converter system.If the catalytic converter system has aged to the point where it can no longer adequately treat the exhaust gas, then the catalytic converter system is in its limiting state. Ideally, on-board diagnostics should be able to distinguish between different states of such a catalytic converter system with sufficient precision, meaning with sufficient accuracy, one of which is the limiting state. On-board diagnostics are usually subject to tolerances, making it difficult to differentiate between these states. Since chemical components used in a catalytic converter that contribute to oxygen storage are more stable with age than chemical components that contribute to conversion, deliberately bringing a catalytic converter into its limiting state is typically not straightforward.Common methods for the targeted aging of catalysts, in order to bring these catalysts into the limiting catalyst state, reduce both the oxygen storage capacity (OSO) and the catalytic effectiveness, and thus the conversion performance, without any particular differentiation.

[0050] The aforementioned problems and disadvantages can be avoided by the invention. The aging of the catalyst achievable by means of the inventive method is an artificial limit catalyst aging, which the24-3927 PIF

[0051] 13

[0052] The oxygen storage capacity is advantageously reduced to a limit value, thus lowering the first target value, resulting in impaired operation with regard to oxygen storage capacity. The method allows data to be generated from the aged catalyst to detect such impaired operation using appropriate diagnostics. Furthermore, the method of selectively aging the catalyst enables high discriminatory power, allowing, for example, the OBD (On-Board Diagnostics) system in a vehicle to differentiate between the aforementioned states. A second state is, for example, a fully broken-in state, and a third state is, for example, an intermediate state in which the catalyst system can treat the exhaust gas better than in the limit state, but worse than in the fully broken-in state.The inventive method can be carried out in a time- and cost-efficient and reproducible manner, which allows the catalyst to be aged advantageously and in a targeted manner.

[0053] The low base temperature of less than 900 degrees Celsius (°C) ensures minimal aging, which only becomes significant due to the isolation of the first section of the catalyst. This low base temperature of less than 900 degrees Celsius allows for advantageous, increased thermal aging of the entire catalyst. Due to the preferably low exhaust gas mass flow and the preferably short isolation of the second combustion chamber, the first section of the catalyst is primarily, or even predominantly, affected by aging. Because of the low amount of reactants associated with the low exhaust gas mass flow and the isolation of the second combustion chamber, as well as the low space velocity, an exothermic temperature is concentrated in the first section of the catalyst. The peak temperature is, for example, in the range of 1051 degrees Celsius.The second section of the catalyst, however, has the same or a similar base temperature as the first section and only experiences waste heat from the first section without itself experiencing or generating any significant exothermic activity. Subsequent catalysts are thus aged more gently. In other words, the second section of the catalyst ages more gently than the first. Through the targeted thermal aging of the first section of the catalyst with the lean exhaust gas, the oxygen storage capacity and thus the catalytic efficiency, and consequently the conversion performance, are significantly reduced in a short time. The process according to the invention is characterized in particular by the fact that the oxygen storage capacity of at least or especially of the first section of the 24-3927 PIF is significantly reduced.

[0054] 14

[0055] The catalyst's oxidation state can be reduced within a few hours, particularly to the minimum and / or the first target value. The catalytic efficiency (conversion rate) of the entire catalyst, however, experiences only moderate degradation up to this point. A subsequent, further repetition of the process then serves to precisely adjust the conversion rate, especially to the second target value, so that the limiting catalyst state can be achieved particularly easily. The underlying reason for this is that lean exhaust gas causes continuous and significant aging of the catalyst. Certain catalyst technologies can also exhibit accelerated aging with rich exhaust gas.

[0056] The test bench is an engine test bench comprising the internal combustion engine and the catalytic converter. For example, the internal combustion engine is initially operated at a load point, particularly one that is constant at least at this point. This results in an exhaust gas mass flow and a base temperature of less than 900 degrees Celsius, particularly at least in the first part of the operating range, during the aging phase. If the base temperature is stable, at least in the excessive range, the second combustion chamber, or in particular several combustion chambers of the internal combustion engine, is preferably briefly shut off. This leads to the high peak temperature in the catalytic converter, at least in the first part of the operating range. During the shut-off of the second combustion chamber, only air is passed through it, without introducing fuel into the second combustion chamber and without burning fuel in the second combustion chamber.

[0057] This results in the second combustion chamber operating with excess air. This excess air is counteracted, and specifically regulated, by enriching the mixture in the operating, first combustion chamber. Enriching the mixture in the operating, first combustion chamber means that it is run rich, i.e., with a rich air-fuel ratio. This allows the exhaust gas to be supplied as a lean mixture overall, even during the second part of the aging phase. Consequently, the internal combustion engine as a whole, i.e., holistically and thus globally considered, can be operated with a lean air-fuel ratio throughout the second part of the aging phase.The enrichment of the first combustion chamber results in excess, i.e., unburned hydrocarbons contained in the exhaust gas, which are burned in or on the catalyst, in particular in or on the first part of the catalyst, due to the aforementioned exotherms, and thereby the24-3927 PIF.

[0058] 15

[0059] The aforementioned peak temperature in the catalyst, especially at least in the first sub-section, will cause this.

[0060] In the event that the aforementioned excess air from the exclusion of the second combustion chamber is insufficient to generate the desired high peak temperature, the following, for example, can be provided: The test bench has, for instance, an exhaust gas tract through which the exhaust gas flows, in which the catalyst is located, so that during the aging phase and preferably also during the regeneration phase, the exhaust gas is routed through the exhaust gas tract and thus through the catalyst. It is possible to introduce air as secondary air into the exhaust gas tract at an inlet point located downstream of the combustion chambers and upstream of the catalyst, bypassing, in particular all, the combustion chambers. The secondary air is supplied, for example, by a compressed air source and / or delivered by means of a pump, which may be electrically operated.Thus, secondary air is introduced into the exhaust system at the inlet point, bypassing the combustion chambers of the internal combustion engine, and consequently into the exhaust gas flowing through the exhaust system. As a result, the oxygen contained in the secondary air can combust with the excess hydrocarbons in the catalyst, achieving a beneficially high peak temperature. Secondary air can be used or introduced into the exhaust system particularly when the excess air resulting from the deactivation of the second combustion chamber is insufficient to generate a sufficiently high peak temperature. In such cases, the mixture in the operating, fired primary combustion chamber should be enriched to ensure that the exhaust gas passing through the catalyst is lean overall.

[0061] Since the formation of the second combustion chamber is carried out at least once, preferably several times, during the second part of the aging phase, the second part of the aging phase constitutes a high-temperature component of the aging phase. With regard to the process as a whole, the aging phase constitutes a high-temperature component because the catalyst is aged advantageously during and through the aging phase, particularly compared to the regeneration phase. In the first part of the aging phase, for example, a target operating point is set such that the exhaust gas mass flow has a base temperature that is stabilized, so that during the first part, the exhaust gas mass flow maintains a base temperature that is at least substantially constant for several seconds. Subsequently, the second part 24-3927 PIF

[0062] 16

[0063] The aging phase is carried out so that the second combustion chamber is deactivated. This deactivation of the second combustion chamber lasts, for example, several seconds. Between two deactivations of the second combustion chamber, there is a waiting period of several seconds, during which the deactivation of the second combustion chamber is, in particular, completely suspended. This prevents excessively high temperatures of the exhaust gas and the catalytic converter, thus avoiding undesirable damage to the catalytic converter.To precisely control the aging of the catalyst and / or to monitor its oxygen storage capacity, a measurement is performed after each aging phase. This measurement measures emissions in the exhaust gas downstream of the catalyst and / or the catalyst's oxygen storage capacity. The measurement can be taken after the aging phase and before the regeneration phase, or after the aging phase and after the regeneration phase. Based on this measurement, the current state of aging of the catalyst is determined and evaluated. If, for example, the current state of aging is determined to be within the limit for catalyst performance, the process is terminated.If, for example, it is determined that the current aging state of the catalyst does not yet correspond to the limiting catalyst state, the process is continued, in particular until the current aging state of the catalyst corresponds to the limiting catalyst state.

[0064] Further features of the invention will become apparent from the claims, the figure, and the figure description. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the figure description and / or shown in the figure alone, are not only usable in the combinations specified, but also in other combinations or on their own.

[0065] Further details of the invention will become apparent from the following description of a preferred embodiment with the accompanying drawing. Figure 1 shows a partial schematic and cutaway side view of a test rig by means of which a method for the targeted aging of a catalyst is carried out.

[0066] Fig. 1 shows a schematic sectional view of a test rig 1 for the targeted aging of a catalyst 2. Based on Fig. 1, a 24-3927 PIF

[0067] 17

[0068] A method for the targeted aging of catalyst 2 is described, wherein the catalyst 2 is selectively aged using the test rig 1. In this method, the test rig 1 comprises the catalyst 2 and an internal combustion engine 3, also referred to as an internal combustion engine or combustion power unit, which is shown schematically. The test rig 1 also includes an exhaust system 4 in which the catalyst 2 is arranged.

[0069] In this process, the internal combustion engine 3 has at least or exactly two combustion chambers, namely a first combustion chamber 5 and a second combustion chamber 6. The process involves repeatedly performing an aging phase, specifically by carrying out several successive aging phases. During the aging phase, the internal combustion engine 3 is operated under fire, resulting in an overall lean exhaust gas. For this purpose, during the aging phase, the internal combustion engine 3 is operated with a lean air-fuel ratio overall, and thus globally. The term "global" with regard to the air-fuel ratio means that the internal combustion engine 3 is operated with a lean air-fuel ratio overall, and thus globally.The term "lean exhaust gas" refers to the fact that the exhaust gas has a composition resulting from the fact that the internal combustion engine 3 is operated under lean conditions overall. During the aging phase, the exhaust gas from the internal combustion engine 3 forms a mass flow, also referred to as the first exhaust gas mass flow, which is routed through the exhaust system 4 and thus through the catalyst 2.

[0070] In the embodiment shown in Fig. 1, the catalyst 2 has, in particular, exactly, two sub-sections, namely a first sub-section T1 and a second sub-section T2. ​​It can be seen that, in the direction of flow of the exhaust gas mass flow through the catalyst 2, sub-section T2 is arranged downstream of sub-section T1. In the embodiment shown in Fig. 1, sub-sections T1 and T2 are completely spaced apart from each other in the direction of flow of the exhaust gas mass flow through the catalyst 2, so that, in the direction of flow of the exhaust gas mass flow through the catalyst 2, a length region L is arranged between sub-sections T1 and T2, which is completely free of components that are catalytically active for post-treatment of the exhaust gas. In contrast, sub-sections T1 and T2 have catalytically active components, in particular a 24-3927 PIF.

[0071] 18

[0072] A catalytically active coating is applied, wherein the catalytically active components are catalytically active for the post-treatment of the exhaust gas. This means that the catalytically active components catalytically induce and / or support chemical reactions by which components contained in the exhaust gas, such as carbon monoxide, unburned hydrocarbons, nitric oxide, and nitrogen dioxide (or nitrogen oxides in general), are converted into carbon dioxide, water, and, in particular, pure nitrogen. This conversion is also referred to as conversion. The performance or capability of the catalyst 2 to carry out this conversion is also referred to as conversion performance or conversion capability. Furthermore, the catalyst 2 has an ability, also referred to as oxygen storage capacity (OSC), to store any oxygen that may be contained in the exhaust gas.The oxygen storage capacity is achieved, for example, by the aforementioned catalytically active components and / or other components.

[0073] Alternatively, it would be conceivable that sections T1 and T2 connect directly to each other, so that, in the direction of flow of the exhaust gas mass flow through catalyst 2, no length section is arranged between sections T1 and T2 that is completely free of components catalytically active for conversion. However, in the present case, length section L is completely free of components catalytically active for conversion.

[0074] During the aging phase, for example, the exhaust gas mass flow is lower than a limit value, and therefore an advantageously low exhaust gas mass flow. The limit value is, for example, 1000 kilograms per hour.

[0075] During the first part of the aging phase, the internal combustion engine 3 is operated with combustion, specifically by firing the first combustion chamber 5 and the second combustion chamber 6. This results in the internal combustion engine 3 providing an overall lean exhaust gas, thus operating with a lean air-fuel ratio. The overall lean exhaust gas forms the exhaust mass flow, which has a base temperature of less than 900 degrees Celsius during this first part and is passed through the exhaust tract 4 and the catalyst 2. During the second part of the aging phase, which directly follows the first part, the internal combustion engine 3 is operated with combustion, specifically by firing the first combustion chamber 5 and operating the second combustion chamber 6 without combustion. This is also referred to as the silencing or silencing of the 24-3927 PIF.

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[0077] Combustion chamber 6, in particular referred to as cylinder deactivation. Thus, combustion chamber 6 is deactivated during the second part of the aging phase. During this second part of the aging phase, air is pumped through combustion chamber 6 without any fuel being introduced. As a result, the internal combustion engine 3 provides the overall lean exhaust gas during the second part of the aging phase, which forms the exhaust gas mass flow that is passed through the catalyst 2. The unfired operation of combustion chamber 6 during the second part of the aging phase results in an excess of air being provided, or caused, by combustion chamber 6 being at least partially compensated for by the fact that combustion chamber 5 is run rich, i.e., with a rich air-fuel ratio.The excess air results in oxygen being present in the exhaust gas, and the rich combustion of the combustion chamber 5 results in unburned hydrocarbons being present in the exhaust gas. These unburned hydrocarbons are oxidized, and thus combusted, in the catalyst 2 with the oxygen contained in the exhaust gas, causing a peak temperature in the catalyst 2 that is higher than the base temperature at least once during the second part of the aging phase. The peak temperature is greater than 900 degrees Celsius, and in particular greater than 1000 degrees Celsius. The process rapidly reduces the oxygen storage capacity of the catalyst 2, especially in the first section T1, to an initial target value, specifically to a minimum, without significantly reducing the conversion rate. By continuing the process, the conversion rate is then further reduced.Consequently, by continuing the process, the conversion rate can be specifically adjusted to a second target value. By adjusting the oxygen storage capacity to the first target value and the conversion rate to the second target value, catalyst 2 can be quickly, easily, and precisely brought into a so-called limiting catalyst state.

[0078] Preferably, a regeneration phase, in particular exactly one, is carried out between each aging phase. During the regeneration phase, the internal combustion engine 3 is operated under fire, thereby providing an overall rich exhaust gas. This means that during the regeneration phase, the internal combustion engine 3 is operated with a global rich air-fuel ratio. During the regeneration phase, the rich exhaust gas, also referred to as a second exhaust mass flow, forms a PIF

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[0080] Exhaust gas mass flow that is passed through the catalyst 2, i.e. through the exhaust tract 4 and the catalyst 2, and has a temperature that is less than 900 degrees Celsius.

[0081] In Fig. 1, an arrow 7 illustrates the direction of flow in which the exhaust gas and thus the respective exhaust gas mass flow is directed through the exhaust tract 4 and thus through the catalyst 2.

[0082] Figure 1 also shows a diagram 8. Diagram 8 has an abscissa 9, on which a path length, in particular through the catalyst 2, is plotted. On an ordinate 10 of diagram 8, the temperature of the exhaust gas, also referred to as the exhaust gas temperature, is plotted. A curve 11 of diagram 8 shows a temperature profile in the catalyst 2 during the silencing phase. It can be seen that the second part of the aging phase is a high-temperature phase, in which the high peak temperature in the catalyst 2 occurs.

[0083] Figure 12 illustrates a temperature profile in catalyst 2 during the saturation phase when the exhaust gas mass flow rate, which is passed through the exhaust tract 4 and thus through catalyst 2, is greater than the limit value. It can be seen that because the exhaust gas mass flow rate is lower than the limit value and therefore advantageously low, a very high temperature can be achieved in the first sub-section T1, particularly during the aging phase, and in this case, a higher temperature in sub-section T1 than in sub-section T2. ​​This allows the oxygen storage capacity, especially in the first sub-section T1, to be rapidly reduced, so that the oxygen storage capacity of catalyst 2, particularly in the first sub-section T1, can be reduced to the first target value very quickly without excessively reducing the overall conversion performance of catalyst 2.The background to this is that the first sub-area, T1, is monitored by OBD, which measures the oxygen storage capacity (OSO). Therefore, the OSO is reduced to a minimum value.

[0084] The overall conversion performance of catalyst 2 can be selectively reduced to the second target value after the oxygen storage capacity has been rapidly reduced to the first target value, simply by continuing the process after reducing the oxygen storage capacity to the first target value. Test rig 1 also includes a first lambda sensor 13 and a second 24-3927 PIF.

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[0086] Lambda sensor 14. Using the respective lambda sensors 13 and 14, a specific parameter characterizing the residual oxygen content in the exhaust gas can be measured at measuring points M1 and M2, respectively. It can be seen that measuring point M1 is upstream of the catalyst 2 in the direction of the exhaust gas mass flow through the catalyst 2, while measuring point M2 is downstream of subsection T1 and upstream of subsection T2. ​​Thus, subsection T1 is, or forms, a so-called monitored volume of the catalyst 2, since the residual oxygen content in the exhaust gas is measured both at measuring point M1 (upstream of subsection T2) and at measuring point M2 (downstream of subsection T2). In contrast, sub-area T2 is or forms an unmonitored volume of catalyst 2, since downstream of sub-area T2 the residual oxygen content in the exhaust gas is not measured or cannot be measured.In particular, the oxygen storage capacity can be determined and thus measured by measuring and recording the measured quantity, since the measured quantity also characterizes the oxygen storage capacity. It is evident that the method enables zoned aging of the catalyst 2. Through the method, and especially through the aging phase and, in particular, through the exclusion of combustion chamber 6, the sub-area T1 can be subjected to high stress and significant aging, while the sub-area T2 is protected. This allows the oxygen storage capacity to be quickly reduced to the first target value, and especially to a minimum, without excessively reducing the conversion performance.Due to this initial protection of the rear, second sub-section T2 compared to the front, first sub-section T1, catalyst 2 still exhibits good overall conversion performance after the oxygen storage capacity has been reduced to the first target value. By continuing the process, the conversion performance can then be further reduced and, in particular, brought to the second target value. The process is thus carried out until the conversion performance reaches or falls below the second target value. At that point, both target values ​​are achieved through the oxygen storage capacity and the conversion performance, and catalyst 2 exhibits the desired limiting catalyst state.

[0087] Test rig 1, for example, has a measuring device (not shown in detail in Fig. 1) by means of which at least one further measurand can be measured and thus recorded, which characterizes the conversion performance. By measuring the further measurand, the further measurand and thus the conversion performance can be monitored, so that, for example, a time point can be determined.24-3927 PIF

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[0089] The process can be terminated, and catalyst 2 will exhibit the desired limiting catalyst state. 24-3927 PIF

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[0091] Reference symbol list

[0092] 1 test bench

[0093] 2 catalyst

[0094] 3 Internal combustion engine 4 Exhaust system

[0095] 5 first combustion chamber

[0096] 6 second combustion chamber

[0097] 7 Arrow

[0098] 8 Diagram

[0099] 9 Abscissa

[0100] 10 ordinates

[0101] 11 Course

[0102] 12 Course

[0103] 13 Lambda sensor

[0104] 14 Lambda sensor

[0105] L Length range

[0106] M1 measuring point

[0107] M2 measuring point

[0108] T1 first sub-area

[0109] T2 second sub-area

Claims

24-3927 PIF 24 Patent claims 1. Method for the targeted aging of a catalyst (2) by means of a test rig (1) comprising the catalyst (2) and an internal combustion engine (3), in which: - the internal combustion engine (3) has at least two combustion chambers (5, 6), namely a first combustion chamber (5) and a second combustion chamber (6); - an aging phase is carried out in which: o the internal combustion engine (3) is operated, whereby the internal combustion engine (3) provides an overall lean exhaust gas, which forms an exhaust gas mass flow that is passed through the catalyst (2); o during a first part of the aging phase, the internal combustion engine (3) is operated by firing the first combustion chamber (5) and the second combustion chamber (6), whereby the internal combustion engine (3) provides the overall lean exhaust gas, which forms the exhaust gas mass flow that has a base temperature of less than 900 degrees Celsius during the first part and is passed through the catalyst (2); and o during a second part of the aging phase the internal combustion engine (3) is operated by firing the first combustion chamber (5) and operating the second combustion chamber (6) unfired, whereby the internal combustion engine (3) provides the overall lean exhaust gas which forms the exhaust gas mass flow that is passed through the catalyst (2).

2. Method according to claim 1, characterized by the fact that During the aging phase, the exhaust gas mass flow is less than 1000 kilograms per hour.

3. Method according to claim 1 or 2, characterized by the fact that 24-3927 PIF 25 After the aging phase, a regeneration phase is carried out in which the internal combustion engine (3) is operated, whereby the internal combustion engine (3) provides an overall rich exhaust gas, which forms an exhaust gas mass flow that is passed through the catalyst (2) and has a temperature that is less than 900 degrees Celsius, the base temperature.

4. Method according to claim 3, characterized by the fact that During the regeneration phase, the internal combustion engine (3) is operated by firing the first combustion chamber (5) and the second combustion chamber (6).

5. Method according to claim 3 or 4, characterized by the fact that the temperature is at most 800 degrees Celsius.

6. Method according to any one of claims 3 to 5, characterized by the fact that The regeneration phase lasts at least two minutes.

7. Method according to any one of claims 3 to 6, characterized by the fact that The regeneration phase is shorter than the aging phase.

8. Method according to any one of claims 3 to 7, characterized by the fact that During the regeneration phase, an unfired operation of a combustion chamber of the internal combustion engine (3) is omitted.

9. Method according to any one of the preceding claims, characterized by the fact that The aging phase lasts at least 60 minutes.

10. Method according to any one of the preceding claims, characterized by the fact that-3927 PIF 26 The second part of the aging phase causes at least a temporary peak temperature of the catalyst of more than 1000 degrees Celsius.

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