GB2612315A

GB2612315A - Method for testing an exhaust gas after treatment device

Info

Publication number: GB2612315A
Application number: GB2115414.1A
Authority: GB
Inventors: A Marszalek Gary
Original assignee: Daimler Truck AG
Current assignee: Daimler Truck Holding AG
Priority date: 2021-10-27
Filing date: 2021-10-27
Publication date: 2023-05-03
Also published as: GB202115414D0

Abstract

The invention relates to a method for testing an exhaust gas after treatment device (10, figure 1) for an internal combustion engine. The exhaust gas after treatment device (10) and at least one sound transducer device (18) is provided. The sound transducer device (18) is operated such that the sound transducer device (18) provides low frequency effect sound pressure levels which are fed into the exhaust gas after treatment device (10) to simulate acoustical exhaust events of the internal combustion engine thereby exciting the exhaust gas after treatment device (10).

Description

METHOD FOR TESTING AN EXHAUST GAS AFTER TREATMENT DEVICE

FIELD OF THE INVENTION

[0001] The invention relates to a method for testing an exhaust gas after treatment device (ATD) for an internal combustion engine, in particular for a vehicle.

BACKGROUND INFORMATION

[0002] US 2013/0275055 Al shows an integrity monitoring system for monitoring integrity of at least a part of a stationary structure. Furthermore, RU 205 132 044 A shows a mechanical action test for space vehicles. Moreover, RU 2 716 889 Cl shows a vibrio acoustic research of vehicles.

SUMMARY OF THE INVENTION

[0003] It is an object of the present invention to provide a method by which exhaust gas after treatment devices for internal combustion engines, in particular of vehicles, may be tested particularly advantageously.

[0004] This object is solved by a method having the features of patent claim 1. Advantageous embodiments with expedient developments of the invention are indicated in the other patent claims.

[0005] The invention relates to a method for testing an exhaust gas after treatment device for an internal combustion engine, in particular of a vehicle. The exhaust gas after treatment device is also referred to as an exhaust system. For example, the exhaust gas after treatment device may be configured as a diesel exhaust system such that, for example, said internal combustion engine may be configured as a diesel engine. In the method, the exhaust gas after treatment device is provided. Moreover, in the method, at least one sound transducer device is provided. The sound transducer device is also referred to as an electrical acoustic transducer and configured to convert an audio signal, in particular an electrical audio signal, into at least one corresponding sound and thus at least one sound pressure level. In the method, the sound transducer device is operated such that the sound transducer device provides low frequency effect (LFE) sound pressure levels (SPL) which are fed into the exhaust gas after treatment device to simulate acoustical exhaust events of the internal combustion engine thereby exciting the exhaust gas after treatment device. For example, the sound transducer device is operated by an electronic control unit which, for example, provides at least one signal, in particular at least one electrical signal, to operate the sound transducer device. For example, said signal provided by the electronic control unit may be said audio signal which is converted into said low frequency effect sound pressure levels by the sound transducer device. By the method, an analysis of at least one structural component of the exhaust gas after treatment device may be performed using acoustical energy excitation. By the method according to the present invention, the exhaust gas after treatment device may be tested particularly advantageously. For example, the electronic control unit comprises at least one audio amplifier which is also referred to as an amplifier. For example, said amplifier provides said signal for operating the sound transducer device. Moreover, for example, the electronic control unit comprises a computer for generating the signal and/or for generating a further signal from which the signal for operating the sound transducer device may result.

[0006] Further advantages, features, and details of the invention derive from the following description of a preferred embodiment as well as from the drawings. The features and feature combinations previously mentioned in the description as well as the features and feature combinations mentioned in the following description of the figures and/or shown in the figures alone can be employed not only in the respectively indicated combination but also in any other combination or taken alone without leaving the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The novel features and characteristic of the disclosure are set forth in the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate exemplary embodiments and together with the description, serve to explain the disclosed principles. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the figures to reference like features and components. Some embodiments of system and/or methods in accordance with embodiments of the present subject matter are now described below, by way of example only, and with reference to the accompanying figures.

[0008] Fig. 1 shows a schematic perspective view of an exhaust gas after treatment device for an internal combustion engine.

[0009] Fig. 2 shows a schematic perspective view of a sound transducer device for testing the exhaust gas after treatment device.

[0010] Fig. 3 shows a schematic sectional view of the sound transducer device.

[0011] In the figures the same elements or elements having the same function are indicated by the same reference signs.

DETAILED DESCRIPTION

[0012] In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration". Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

[0013] While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawing and will be described in detail below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.

[0014] The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion so that a setup, device or method that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or device or method. In other words, one or more elements in a system or apparatus preceded by "comprises" or "comprise" does not or do not, without more constraints, preclude the existence of other elements or additional elements in the system or method.

[0015] In the following detailed description of the embodiment of the disclosure, reference is made to the accompanying drawing that forms part hereof, and in which is shown by way of illustration a specific embodiment in which the disclosure may be practiced. This embodiment is described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.

[0016] Fig. 1 shows in a schematic perspective view an exhaust gas after treatment device 10 for an internal combustion engine configured to drive a vehicle such as, for example, a commercial vehicle. For example, the internal combustion engine, which is not shown, is configured as a diesel engine such that, for example, the exhaust gas after treatment device 10 is configured as a diesel exhaust system. The exhaust gas after treatment device 10 is configured for an after treatment of exhaust gas of the internal combustion engine. Thus, the exhaust gas may flow through the exhaust gas after treatment device 10. In the embodiment shown in Fig. 1, the exhaust gas after treatment device 10 comprises at least one housing 12 which may be made of a metallic material. Moreover, for example, the exhaust gas after treatment device 10 comprises at least one exhaust gas after treatment element which may be arranged in the housing 12. For example, the exhaust gas after treatment element may be configured as or may comprise at least one catalytic converter. For example, the exhaust gas after treatment device 10, in particular the housing 12, comprises an inlet 14 through which the exhaust gas may flow. Thus, via the inlet 14, the exhaust gas may flow into the exhaust gas after treatment device 10.

[0017] In the following, a method for testing the exhaust gas after treatment device 10 will be described. In the method, the exhaust gas after treatment device 10 is provided. As shown in Fig. 1, for example, the exhaust gas after treatment device 10 is arranged in a chamber 16 which may be a chamber of a test rig. Moreover, in the method, at least one sound transducer device 18 (Fig. 2) is provided. For example, there may be four sound transducer devices 18. Furthermore, in said method, the sound transducer device 18 is operated such that the sound transducer device 18 provides low frequency effect (LFE) sound pressure levels (SPL) which are fed into the exhaust gas after treatment device 10 to simulate acoustical exhaust events of the internal combustion engine thereby exciting the exhaust gas after treatment device 10. In the embodiment shown in the Fig., the low frequency effect sound pressure levels provided by the sound transducer device 18 are fed into the exhaust gas after treatment device 10, in particular into the housing 12, via the inlet 14. Moreover, in the embodiment shown in the Figs., the low frequency effect sound pressure levels are guided from the sound transducer device 18 to the inlet 14 and thus to the exhaust gas after treatment device 10 via a pipe 21. For example, the pipe 21 is connected with both the inlet 14 and the sound transducer device 18, in particular an outlet 20 of the sound transducer device 18 which may provide the sound pressure levels via the outlet 20.

[0018] For example, the at least one sound transducer device 18 is operated by an electronic control unit 22 comprising a computer 24 and an amplifier 26. The computer 24 generates or provides a first signal, in particular a first electrical signal. For example, the first signal is a first audio signal. The amplifier 26 receives the first signal provided by the computer 24. Moreover, the amplifier 26 provides a second signal which may be a second electrical signal. For example, the second signal may be a second further audio signal. The second signal results from the first signal provided by the computer 24. By the second signal provided by the amplifier 26, the sound transducer device 18 is operated such that, for example, the sound transducer device 18 converts the second signal into the low frequency effect sound pressure levels (i.e. into sound which is fed into the exhaust gas after treatment device, in particular the housing 12, via the inlet 14).

[0019] Standard practice to evaluate and test component devices for vibration and resonance response is to use electro dynamic shakers (EDS) or other mechanical tables designed to produce vibratory motion in multiple axis. Furthermore, such standard methods are not very accurate for heavy devices like exhaust gas after treatment devices (ATD) which can weigh in excess of 600 pounds. An energy required to shake such massive devices under test (DUT) for hundreds of hours is quite expensive. Exciting the DUT using acoustical pressure such as said low frequency effect sound pressure levels provided by the sound transducer device 18 is more accurate and more energy efficient. In other words, said low frequency effect sound pressure levels provided by the sound transducer device 18 by operating the sound transducer device 18 may form an acoustical pressure which is fed into the exhaust gas after treatment device 10 via the pipe 21 and the inlet 14 thereby exciting the exhaust gas after treatment device 10.

[0020] For example, the sound transducer device 18 may be designed as a custom tuned external front port band pass subvvoofer intended or configured to replicate a flat acoustical response over a range of fundamental frequencies found within engine exhaust events. Furthermore, for example, recording in situ exhaust sounds presented to the ATD (i.e. provided by the sound transducer device 18 and fed into the exhaust gas after treatment device 10), along with corresponding engine RPM time stamps, allows for a safe replication and playback of any desired vehicle/engine speed load condition. ATDs may then also be instrumented further for additional analysis or characterizations of troublesome harness areas. Such analysis in conjunction with application histograms may then be used to validate or predict intended product life of the exhaust gas after treatment device 10. Acoustical excitation is a more accurate representative and can efficiently excite to product motion in full three-dimensional space. It is also tremendously more energy efficient than shaking the entire device.

[0021] Fig. 3 shows one embodiment of the sound transducer device 18 in a schematic sectional view. As shown in Fig. 3, the sound transducer device 18 comprises an enclosure 28 which is also referred to as a housing. The enclosure 28 comprises a first chamber 30, which may be sealed, and a second chamber 32, which may be sealed. The enclosure 28 further comprises a pressure outlet 34 which may be the outlet 20. The pressure outlet 34 opens, at one of its ends, into the chamber 30 and at its other end into a surrounding 36 of the enclosure 28. In the embodiment shown in the Figs., the pressure outlet 34 opens, at its other end, into the pipe 21 such that the sound pressure levels provided by the sound transducer device 18 via the pressure outlet 34 are fed into the pipe 21 and guided by the pipe 21 to the inlet 14 and thus the exhaust gas after treatment device 10.

[0022] In the embodiment shown in Fig. 3, the sound transducer device 18 further comprises a first sound transducer 38 arranged in the chamber 30. Moreover, the sound transducer device 18 comprises a second sound transducer 40 arranged in the second chamber 32. As shown in Fig. 3, the respective sound transducer 38, 40 has a respective positive terminal + and a respective negative terminal -. In the embodiment shown in Fig. 3, the first sound transducer 38 is used or operated as an out of phase speaker, and the second sound transducer 40 is operated or used as an in phase speaker. In Fig. 3, the end at which the pressure outlet 34 opens into the chamber 30 is designated by El, whilst the other end is designated by E2. For example, the pressure outlet 34 may comprise a pipe 42 via which the sound transducer device 18 may provide the sound pressure levels. For example, the pressure outlet 34, in particular the pipe 42, bounds a channel through which the sound pressure levels may propagate such that the sound transducer device 18 may provide the sound pressure levels via said channel. For example, the pressure outlet 34, in particular the pipe 42 and in particular the channel, may have a diameter of four inches. Moreover, a distance between the end El and an inner surface 44 of a wall 46 of the enclosure 28 is designated by D. As shown in Fig. 3, the chamber 30 is at least partially and directly bounded by the inner surface 44.

[0023] The idea behind the method is to use low frequency effect (LFE) sound pressure levels (SPL) to simulate acoustical exhaust events normally produced by the internal combustion engine. These acoustical reproductions may excite natural resonances in the exhaust gas after treatment device 10 and its outer metal skin, duplicating true vibratory movements experienced by its components and relevant sub-assemblies. Example subassemblies of interest may be external brackets, sensors, associated harness wiring and their respective clipping points.

[0024] Numerous methods may generate acoustical operating signals for operating the sound transducer device 18, from a simple signal generator to actual sound recordings measured in conjunction with engine RPM (revolutions per minute) and loading conditions. To produce acoustical portions of exhaust events, a custom low frequency effect or subwoofer enclosure such as the enclosure 28 may be created. It was determined that a tuned enclosure is advantageous, with some form of acoustical wave guide to couple the sound pressure levels directly into the exhaust gas after treatment device or a device under test (DUT). For a simulation of a 6-cylinder-engine, an advantageous frequency in Hertz (Hz) may be based on firings per revolution: 3 R [0025] Hz -x Pm [0026] Such an acoustical driver producing a relatively flat frequency response over the engine operating RPM range has been found desirable. For example, a fourth order band pass enclosure as the enclosure 28 with a supportive driver response may be chosen. A fourth order band pass enclosure may consist of a sealed rear enclosure section and a ported front chamber section. With respect to the embodiment shown in Fig. 3, for example, said sealed rear enclosure section may be the chamber 32, and said ported front chamber section may be the chamber 30. The sealed rear enclosure is also referred to as or forms a rear sealed volume. The ported front chamber section is also referred to as or forms a front enclosure volume. The front chamber section is ported since the pressure outlet 34 which is also referred to as a port opens into both the chamber 30 and the surroundings 36 such that the surroundings 36 and the chamber 30 are fluidically connected by the pressure outlet 34. The rear sealed volume, along with the front enclosure volume and the port, may tune and shape a desired low frequency output response of the enclosure 28, said lower frequency output response being said lower frequency effect sound pressure levels. Excluding atmospheric conditions, port tuning influence comes from its diameter, length, shape and the speed of sound. For appearances and space savings, commercial ported LFE enclosures usually have these ports protrude internally to the enclosure. However, this is purely for appearance's sake and may technically extend externally just as effectively. Basically, the larger the port diameter, the longer the required length to achieve equivalent tuning response. Using enclosure simulation software, it was discovered that an enclosure may be designed meeting desired band pass criteria, along with a reasonable length of port for DUT coupling (i.e. for coupling or connecting the exhaust gas after treatment device 10 with the sound transducer device 18, in particular the pressure outlet 34 which also referred to as said port). For example, the design may support the use of a 48 inches long and 6 inches diameter exhaust pipe for use as a combined acoustic transmission waveguide and tuning element. Thus, for example, said 48 inches long and 6 inches diameter exhaust pipe may be the pipe 21. Minor imperfections in the overall response may also be compensated using a graphic equalization as compensation.

[0027] It is a standard industry practice to evaluate components for vibratory profiling and resonant behavior using vibration tables or shake tables, capable of single or multiple degrees of freedom. However, as components or assemblies become increasingly more massive, like that of an exhaust gas after treatment device, accurate motion becomes near impossible to reproduce. Especially as desired frequencies increase. Shake all approaches also require enormous amounts of energy to approach desired movement. On the vehicle, ATDs are generally mounted to a vehicle-frame or hang from a frame rail but still experience higher frequency engine excitation. However, this engine excitation comes from acoustical coupling of exhaust events through the exhaust system, unlike the forcing of components directly mounted upon the engine. By the method, the same behavior effected or exited by a standard shake all approaches may be effected or excited acoustically. By using a custom LFE subwoofer such as the sound transducer device 18 to acoustically couple excitations to or into the ATD directly, it is possible to replicate exactly what occurs on a vehicle. By the method, it is possible to test and evaluate ATD harness robustness, in particular through playback of previously recorded vehicle data being forced upon the ATD via acoustical coupling. The harness, its associated brackets, sensors and fixing points may then all be instrumented and safely characterized and evaluated insight an environmental chamber. Legacy issues with ATD harnessing may usually be traced back to a root cause of movement, such as conductor insulation chaffing on conduits, brackets, etc. The contamination of dust, dirt or grime into wiring channels, only further accelerates wear. So instrumenting the harness at key areas and reproducing previously recorded vehicle data referenced to operating conditions (e.g. RPM, loading, the etc.), troublesome areas may be exposed. Problematic speed load conditions may then be targeted for a corrective action resolution. Knowing which RPM initiated undesirable result or movement, vehicle application histograms may next be utilized to determine operating time span within the application. Such knowledge may then be further scrutinized to assess product life, durability and/or expected life cycle. Assessments may also be quickly and safely performed at numerous temperature points, without the need of an actual vehicle.

List of Reference Signs exhaust gas after treatment device 12 housing 14 inlet 16 chamber 18 sound transducer device outlet 21 pipe 22 electronic control unit 24 computer 26 amplifier 28 enclosure first chamber 32 second chamber 34 pressure outlet 36 surroundings 38 first sound transducer second sound transducer 42 pipe 44 inner surface 46 wall D distance El end E2 end + positive terminal - negative terminal

Claims

CLAIMS1. A method for testing an exhaust gas after treatment device (10) for an internal combustion engine, comprising: providing the exhaust gas after treatment device (10); providing at least one sound transducer device (18); and operating the sound transducer device (18) such that the sound transducer device (18) provides low frequency effect sound pressure levels which are fed into the exhaust gas after treatment device (10) to simulate acoustical exhaust events of the internal combustion engine thereby exciting the exhaust gas after treatment device (10).
2. The method according to claim 1, wherein actual sound recordings measured at different revolutions and loads of the internal combustion engine are used to operate the sound transducer device (18).
3. The method according to claim 1 or 2, wherein the sound transducer device (18) comprises: an enclosure (28) comprising a first chamber (30), a second chamber (32), and a pressure outlet (34) which opens, at one of its ends (El, E2), into one of the chambers (30, 32) and, at its other end (E2), into a surroundings (36) of the enclosure (28); a first sound transducer (38) arranged in the first chamber (30); and a second sound transducer (40) arranged in the second chamber (32).
4. The method according to claim 3, wherein the first sound transducer (38) is operated as an out of phase speaker, and the second sound transducer (40) is operated as an in phase speaker.