Abstract:-The state of catalysts plays a key role in automotive exhaust gas aftertreatment. The soot or ash loading of Diesel particulate filters, the oxygen loading degree in three-way catalysts, the amount of stored ammonia in SCR catalysts, or the NO x loading degree in NO x storage catalysts are important parameters that are today determined indirectly and in a model-based manner with gas sensors installed upstream and/or downstream of the catalysts. This contribution gives an overview on a novel approach to determ… Show more
“…The wideband lambda probes or other exhaust gas sensors are also for research purposes only. Modified from [13]. Table 2 with C3H8 for detailed gas compositions.…”
Section: The Microwave Cavity Perturbation Techniquementioning
confidence: 99%
“…A typical general setup is shown in Fig. 1 (from [13]). The cavity resonator may be coupled to a source and a load via simple "antennas" (e.g.…”
Section: The Microwave Cavity Perturbation Techniquementioning
confidence: 99%
“…The microwave-based method (also called "microwave cavity perturbation method"), however, that allows for monitoring directly the oxygen loading state of TWCs without any electrical contacts has a higher potential [12,13]. The new method measures the electrical microwave properties (permittivity and conductivity) of the catalyst.…”
“…The wideband lambda probes or other exhaust gas sensors are also for research purposes only. Modified from [13]. Table 2 with C3H8 for detailed gas compositions.…”
Section: The Microwave Cavity Perturbation Techniquementioning
confidence: 99%
“…A typical general setup is shown in Fig. 1 (from [13]). The cavity resonator may be coupled to a source and a load via simple "antennas" (e.g.…”
Section: The Microwave Cavity Perturbation Techniquementioning
confidence: 99%
“…The microwave-based method (also called "microwave cavity perturbation method"), however, that allows for monitoring directly the oxygen loading state of TWCs without any electrical contacts has a higher potential [12,13]. The new method measures the electrical microwave properties (permittivity and conductivity) of the catalyst.…”
“…Studies with a combined system of a TWC-coated GPF on an engine dynamometer proved the system functionality under transient conditions within the European driving cycle (NEDC) [ 30 ]. In NO x reduction application, the storage state of lean NO x traps (LNT) was successfully monitored, but application to this catalyst type seems to suffer from a comparably small signal [ 32 , 33 ]. The potential of the RF technique to determine the NH 3 storage on SCR catalysts is presumed and is the focus of this paper.…”
The upcoming more stringent automotive emission legislations and current developments have promoted new technologies for more precise and reliable catalyst control. For this purpose, radio-frequency-based (RF) catalyst state determination offers the only approach for directly measuring the NH3 loading on selective catalytic reduction (SCR) catalysts and the state of other catalysts and filter systems. Recently, the ability of this technique to directly control the urea dosing on a current NH3 storing zeolite catalyst has been demonstrated on an engine dynamometer for the first time and this paper continues that work. Therefore, a well-known serial-type and zeolite-based SCR catalyst (Cu-SSZ-13) was investigated under deliberately chosen high space velocities. At first, the full functionality of the RF system with Cu-SSZ-13 as sample was tested successfully. By direct RF-based NH3 storage control, the influence of the storage degree on the catalyst performance, i.e., on NOx conversion and NH3 slip, was investigated in a temperature range between 250 and 400 °C. For each operation point, an ideal and a critical NH3 storage degree was found and analyzed in the whole temperature range. Based on the data of all experimental runs, temperature dependent calibration functions were developed as a basis for upcoming tests under transient conditions. Additionally, the influence of exhaust humidity was observed with special focus on cold start water and its effects to the RF signals.
“…More details on the microwave-based technique for catalyst monitoring can be found in Refs. [35][36][37][38]. For the studies reported in this text, only the magnitude of the reflection parameter, |S 11 | (plotted in dB;…”
Section: Experimental Setups and Preliminary Testsmentioning
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