Page 263 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Emitec Gesellschafl fur Emissionstechnologie - Dr. Ing. H.c.F. Porsche AG 245

3) forming a mean temperature value over the time interval fiom the temperature measured at
the plurality of measurement points
4) measuring the temperature of the catalytic converter honeycomb body over the time interval
at least at one measurement point forming an associated local temperature value. The
measurement can take place in a thin segment of said catalytic converter extending
perpendicular to the flow direction
5) monitoring the variations of the mean temperature value and the local temperature value
over time
6) deriving the indication as to the hnction of the catalytic converter only if the variations over
time of the mean temperature value and the local temperature value are below a
predetermined limit value
7) comparing the mean temperature value with the local temperature value for deriving an
indication as to the status of the catalytic converter

The temperature sensors are installed in a way similar to the one shown in fig. 103.

The method of DE4038829 (1992) is applied for a catalytic converter comprising: a) an inner
region, a jacket surface surrounding the inner region and being disposed approximately parallel
to the exhaust gas flow direction; b) the inner region conducting the exhaust gas flow through
the inner region in the given flow direction; and c) a reaction zone being defined as a part of
the inner region in which the catalyzed exothermic reaction predominantly takes place.

The method comprises the following steps:
1) measuring a distribution of temperature over the jacket surface along a measurement path
being aligned approximately parallel to the given flow direction. The measurement of
temperature can take place with one of the following ways (fig. 105):
a) by evaluating heat radiation originating at the jacket surface by imaging the heat
radiation originating at the jacket surface by means of an electronic image
processing device and a photographic device such that the temperature
distribution along the measurement path is displayed on an image obtained in the
imaging step, or
b) by means of a temperature sensor being located on and movable along the
measurement path, or
c) by means of a plurality of temperature sensors being disposed along the
measurement path
2) defining a limit value of a temperature deviation
3) determining the reaction zone by locating a segment of the measurement path at which the
temperature deviates by less than the limit value from a maximum value of the temperature
along the measurement path. This can be achieved by
a) covering the measurement path with a substrate having a color changing
under the influence of heat and detecting the reaction zone by evaluating
the color of the substrate (fig. 105). or
b) comparing the measured distribution of the temperature with a
multiplicity of predetermined standard distributions, for each of which
the reaction zone is known and determining the reaction zone by