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In Folge der Verschärfung der gesetzlichen Abgasnormen wurden für direkt-einspritzende Benzinmotoren Partikelfilter notwendig. Zur Beladungsüberwachung können aufgrund stark unterschiedlicher Rahmenbedingungen die aus Dieselmotoren bekannten Systeme, wie dem Differenzdrucksensor, nur eingeschränkt übernommen werden. Ein hochfrequenzbasiertes Verfahren koppelt mittels Antennen elektromagnetische Wellen in das Filtergehäuse ein, deren Ausbreitungsverhalten durch die dielektrischen Eigenschaften des eingelagerten Rußes beeinflusst wird. Hierdurch kann bei Auswertung von Transmissionsdämpfung oder Resonanzfrequenzen die Rußbeladung direkt detektiert werden.
In order to comply with future emission regulations, the use of particulate filters in vehicles with direct injection gasoline engines is essential. The current amount of soot and ash in the filter is calculated by a soot load model in the electronic control unit in combination with a differential pressure sensor determining the pressure drop over the particulate filter. Active regeneration is initiated if the calculated amount of soot or the measured differential pressure is too high. This is associated with additional fuel consumption. An on-board diagnosis for the particulate filter is currently not part of the Euro 6d emission standard. For future exhaust emission standards, on-board diagnosis or active monitoring of the particulate filter is conceivable. One of the benefits of monitoring is the fact that unnecessary active regenerations can be avoided. As a result, there is no additional fuel consumption due to misinterpretations of the amount of soot in the filter. For active monitoring of the particulate filter, a radiofrequency (RF-) sensor, that detects the soot loading of the filter with electromagnetic waves directly, can be used. Such a system has the advantage that by utilizing the filter as a sensor more precise information about the current state of the filter, e.g. a possible damage, can be provided. Worst-case considerations of filter damages, tested at an engine test bench show the advantages which are entailed by a system like that. By means of partial regeneration of the particulate filter it is demonstrated how the remaining amount of soot in the filter can be detected in a better way in comparison to the differential pressure sensor by using the RF-sensor.
In recent years, particulate filters have become mandatory in almost all gasoline-powered vehicles to comply with emission standards regarding particulate number. In contrast to diesel applications, monitoring gasoline particulate filters (GPFs) by differential pressure sensors is challenging due to lower soot masses to be deposited in the GPFs. A different approach to determine the soot loading of GPFs is a radio frequency-based sensor (RF sensor). To facilitate sensor development, in previous work, a simulation model was created to determine the RF signal at arbitrary engine operating points. To ensure accuracy, the exact dielectric properties of the soot need to be known. This work has shown how small samples of soot-loaded filter are sufficient to determine the dielectric properties of soot itself using the microwave cavity perturbation method. For this purpose, mixing rules were determined through simulation and measurement, allowing the air and substrate fraction of the sample to be considered. Due to the different geometry of filter substrates compared to crushed soot samples, a different mixing rule had to be derived to calculate the effective filter properties required for the simulation model. The accuracy of the determined mixing rules and the underlying simulation model could be verified by comparative measurements on an engine test bench.
Gasoline particulate filters (GPFs) are an appropriate means to meet today's emission standards. As for diesel applications, GPFs can be monitored via differential pressure sensors or using a radio-frequency approach (RF sensor). Due to largely differing soot properties and engine operating modes of gasoline compared to diesel engines (e.g., the possibility of incomplete regenerations), the behavior of both sensor systems must be investigated in detail. For this purpose, extensive measurements on engine test benches are usually required. To simplify the sensor development, a simulation model was developed using COMSOL Multiphysics((R)) that not only allowed for calculating the loading and regeneration process of GPFs under different engine operating conditions but also determined the impact on both sensor systems. To simulate the regeneration behavior of gasoline soot accurately, an oxidation model was developed. To identify the influence of different engine operating points on the sensor behavior, various samples generated at an engine test bench were examined regarding their kinetic parameters using thermogravimetric analysis. Thus, this compared the accuracy of soot mass determination using the RF sensor with the differential pressure method. By simulating a typical driving condition with incomplete regenerations, the effects of the soot kinetics on sensor accuracy was demonstrated exemplarily. Thereby, the RF sensor showed an overall smaller mass determination error, as well as a lower dependence on the soot kinetics.
Owing to increasingly stringent emission limits, particulate filters have become mandatory for gasoline-engine vehicles. Monitoring their soot loading is necessary for error-free operation. The state-of-the-art differential pressure sensors suffer from inaccuracies due to small amounts of stored soot combined with exhaust gas conditions that lead to partial regeneration. As an alternative approach, radio-frequency-based (RF) sensors can accurately measure the soot loading, even under these conditions, by detecting soot through its dielectric properties. However, they face a different challenge as their sensitivity may depend on the engine operation conditions during soot formation. In this article, this influence is evaluated in more detail. Various soot samples were generated on an engine test bench. Their dielectric properties were measured using the microwave cavity perturbation (MCP) method and compared with the corresponding sensitivity of the RF sensor determined on a lab test bench. Both showed similar behavior. The values for the soot samples themselves, however, differed significantly from each other. A way to correct for this cross-sensitivity was found in the influence of exhaust gas humidity on the RF sensor, which can be correlated with the engine load. By evaluating this influence during significant humidity changes, such as fuel cuts, it could be used to correct the influence of the engineon the RF sensor.
To reduce particulate emissions, the use of particulate filters in diesel engines is meanwhile state of the art, while the integration of such systems in gasoline engines is now also necessary in order to comply with today's regulations. Over its lifetime, a gasoline particulate filter (GPF) collects ash components of fuel, lubrication oil, and materials originating from the catalytic coating and from engine abrasion. In the development and application process, synthetic ashing from GPFs is challenging. The ash of the lubrication oil can be increased in various ways, like oil-doped fuel, a separate oil burner, or changes in the piston-cylinder system of the engine. However, these methods show major disadvantages. For this reason, an improved approach is presented in this study, which allows a quick response to changes in combustion (e.g., engine knocking) and producing ash, which is more realistic due to its primary particle size and the density of ash plugs, in a shorter time. Therefore, an approach to accelerate ash loading by active oil injection using a multi-point injection (MPI) system is introduced. With the help of this methodology, an ashing capacity of 1.21 g/h is implemented, which is a high rate compared to other investigations. The primary particle size (evaluated by means of a transmission electron microscope), is in the same size range as those detected at the full-load curve during regular operation. A computer tomographic (CT) analysis of the incinerated particulate filter also shows that a very high density of ash plugs can be realized, which has also been found in the literature for real applications. In addition, with the help of a mass spectrometer (MS) and an intermediate weighing of the particulate filter, the current ash loading of the GPF could be determined with an accuracy of 1%.
Forschungsbericht 2017
(2017)
In der Ausgabe 5/2008 von „Gesundheits- und Sozialpolitik“ wurden erste Ergebnisse der zweiten Versichertenbefragung der Kassenärztlichen Bundesvereinigung (KBV) vorgestellt. Der Fokus der Darstellung lag im ersten Teil auf dem Inanspruchnahmeverhalten und der Zufriedenheit der Versicherten mit der ärztlichen Versorgung, wobei der Aspekt der Wartezeiten auf einen Termin und in der Arztpraxis ausführlich behandelt wurde. Insgesamt ist eine hohe Inanspruchnahme der haus- und fachärztlichen ambulanten Versorgung zu konstatieren sowie eine überwiegende Zufriedenheit mit der ärztlichen Betreuung. Die Ergebnisse zu den Wartezeiten auf einen Arzttermin spiegeln im Vergleich zu öffentlich geführten Debatten ein differenziertes Bild wider. Im zweiten Teil werden folgende Fragen vertiefend diskutiert: Welche Kriterien sind neben der fachlichen Kompetenz (für die Versicherten) für die Wahl der Arztpraxis relevant? Welche Bedeutung haben Gütesiegel als Qualitätsmarker für die Versicherten? Welche Erfahrungen haben die Versicherten mit Änderungen in der Medikamentenverordnung gemacht? Nehmen die Versicherten an Hausarztmodellen teil und wie bewerten sie die Versorgungsqualität? Welche Akzeptanz haben unterschiedliche Wahltarife bei den gesetzlich Versicherten?
In den letzten Jahren haben verschiedene Institutionen bevölkerungsrepräsentative Befragungen zur Bewertung von Einzelaspekten der Gesundheitsversorgung durchgeführt (Bertelsmann Gesundheitsmonitor, Commonwealth Fund, Gesundheitssurvey des Robert Koch-Instituts, BKK-Befragung, WIdO-monitor). Hierzu zählt auch die Kassenärztliche Bundesvereinigung (KBV), die im Jahr 2006 die Forschungsgruppe Wahlen Telefonfeld (FGW) in Mannheim beauftragte, repräsentativ gesetzlich und privat Versicherte zur Zufriedenheit mit der ambulanten Versorgung sowie zum Bedarf an neuen Dienstleistungsangeboten zu befragen (KBV 2006; Rieser 2006). Eine zweite Versichertenbefragung der KBV erfolgte im Zeitraum Mai und Juni 2008, wiederum von der FGW durchgeführt. Die Ergebnisse dieser repräsentativen Erhebung werden im Rahmen von zwei Artikeln in Gesundheits- und Sozialpolitik vorgestellt. Im Zentrum des hier vorliegenden ersten Beitrags stehen die Inanspruchnahme der ambulanten haus- und fachärztlichen Versorgung, die Erfahrungen mit Terminvergabe und Wartezeiten sowie die Bewertungen der Versorgung durch die Versicherten. Darüber hinaus wird die Bedeutung von Individuellen Gesundheitsleistungen (IgeL) in der ambulanten Versorgung gesetzlich Versicherter diskutiert. Der zweite Artikel wird sich schwerpunktmäßig mit den Qualitätskriterien für die Wahl eines Arztes, mit den Erfahrungen von Veränderungen in der Medikamentenverordnung sowie mit der Akzeptanz neuer Versorgungsformen und Wahltarife befassen.
Ältere Patienten und Frauen warten länger auf einen Arzttermin als junge Versicherte und Männer, gesetzlich Versicherte länger als Privatpatienten. Die meisten Patienten sind aber keineswegs unzufrieden. 90 Prozent bekommen entweder am selben Tag einen Termin oder halten die Wartezeit für angemessen.
Increasingly stringent emission limits have made particulate filters necessary for gasoline engines. Similar to diesel applications, gasoline particulate filters (GPFs) can be monitored by differential pressure measurement or by the radio-frequency-based filter diagnosis (RF sensor). In addition to measuring the soot loading, ash detection is critical for monitoring the GPF over the entire vehicle lifetime. Because the RF sensor detects the filter loading through a change in the dielectric properties of the GPF, it can detect not only soot but also ash. In diesel applications, the RF sensor has already demonstrated its potential for ash detection. To verify the feasibility of simultaneous ash and soot monitoring for GPFs, filters were loaded with ash on an engine test bench and measured on a lab test bench under defined synthetic exhaust gas conditions. By evaluating resonant modes, soot and ash could be clearly distinguished, as ash mainly affects the resonant frequency, while soot also changes the quality factor due to its high dielectric losses. However, higher soot loadings could not be detected by the resonant parameters, but instead by a frequency-averaged transmission signal. While the presence of ash caused an offset in this signal, its sensitivity to soot was not affected. Thus, the influence of ash can be corrected if the signal in the soot-free filter state is known, e.g., from the behavior of the resonant parameters. Therefore, even with a continuously increasing ash loading over the lifetime of a vehicle, an accurate soot detection is possible with the RF sensor.
Combined Ash and Soot Monitoring in Gasoline Particulate Filters with a Radio-Frequency-Based Sensor
(2022)
In recent years, it turned out that primarily the number of ultrafine particles and not their mass is relevant in terms of harmful health effects. Therefore, exhaust emission standards are constantly being tightened with regard to the particulate number. To meet the emission limits, particulate filters have become necessary for gasoline engines. Similar to diesel applications, gasoline particulate filters (GPFs) can be monitored via differential pressure measurement or via a radio-frequency approach (RF-sensor). The latter is based on the influence of the soot conductivity on the electromagnetic field. To control the GPF, ash detection is of crucial importance besides the soot load monitoring. With the differential pressure system, this is only possible with high uncertainties due to the low pressure increase caused by ash. The RF-sensor, however, has already demonstrated its potential for ash detection in diesel applications. In order to verify the applicability of the system for GPFs, filters were loaded via a method for fast ash loading. Thereby, it was shown that by evaluating resonant modes – especially the resonant frequency – the ash loading can easily be measured as long as the filter is soot-unloaded. In contrast, soot loading can be determined independently from this by considering a frequency-averaged transmission signal between the antennas of the RF-sensor. Using a setup for radio-frequency material characterization, the dielectric parameters of the generated ash were also measured. In comparison with the properties of the synthetic soot PrintexU, ash showed significantly lower dielectric losses. Thus, the evaluation of the loss-dependent quality factor, which is only possible at low soot loadings, allows a precise conclusion whether the filter is completely soot-free. Furthermore, using synthetic soot loading, it could be shown that soot detection via the averaged transmission signal is not affected by ash. In summary, it could be shown that with the RF-sensor, ash and soot can be simultaneously detected.