Measuring and testing – Gas analysis – Solid content of gas
Patent
1984-08-27
1986-02-04
Kreitman, Stephen A.
Measuring and testing
Gas analysis
Solid content of gas
340627, G01N 2716
Patent
active
045677506
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a process and a device for detection and/or measuring the particle content in gases, in particular in exhaust gases of fossil fuels, like the soot concentration in the exhaust gas of Diesel motors and the like, of the genus stated in the preamble of claim 1.
The degree of blackening of a soot filter being admitted by the exhaust gas is used and evaluated as the measurement for the soot concentration in a known process of this type for determining the soot concentration in exhaust gases of internal combustion engines or oil burning installations. However, it is a prerequisite of such a process that the filter is free from soot at the outset of the measuring process. The filter must then be either cleaned or replaced by a new filter after the measuring process. For cleaning purposes the filter is frequently heated thus burning off the soot layer.
The replacing as well as the cleaning of the filter is not only very cumbersome, but it also requires considerable installation time. Therefore, the known process is only used in the stationary operation, for example, for adjusting the motor at the motor manufacturing plant or in oil burning installations.
SUMMARY OF THE INVENTION
The object of the invention is to provide a process which the invention and in accordance with the characterizing is suitable to be used in the nonstationary operation, for example, in the vehicle itself.
In the process of the invention two electrical heating faces (11, 12) are provided as sensor and arranged in two parallel bridge branches of a Wheatstone bridge circuit, one heating face (11) is constantly so preheated that the particle deposition on its surface is at a minimum, the voltage or current, or the increase in voltage or current are measured in a diagonal branch of the Wheatstone bridge circuit during a heating time period, and a warning signal or a measuring value for the particle content is derived from the voltage or current maximum or the steepness of the voltage or current increase.
The process in accordance with the invention uses the fact that the removal of the particle deposition, like soot and the like, on the sensor is an endothermic process, that is, it consumes heat. Therefore. the heat energy which is required for heating the heating face for removing the particle deposition must be higher on a heating face which is covered with a particle deposition than with a clean surface. Therefore, in accordance with the process of the invention the hitherto additionally required cleaning procedure of the sensor is used for measuring the particle content. Due to this timely coupling of burning free the sensor and the measuring procedure, the total measuring time required is considerably shortened, in such a manner that one can obtain from the measuring a controller output for a constant control procedure for setting the engine. Measurements have shown that when using platinum coils as heating faces the normal voltage or current maximum in accordance with the invention is traversed in less than 50 ms. Therefore, the measuring procedure can be performed automatically and constantly with a small period cycle which provides the prerequisite for the nonstationary application of the process in the vehicle itself, for example, and also offers the possibility for controlling the motor setting.
The device of the invention includes two electrical heating faces (11, 12) provided as a sensor and arranged in two parallel bridge branch of a Wheatstone bridge circuit, one heating face is constantly so preheated that the particle deposition on its surface is at a minimum, means is provided for measuring the voltage or current, or the increase in voltage or current in a diagonal branch of the Wheatstone bridge circuit (17) during a heating time period, and means is provided for deriving signal or a measuring value for the particle content from the voltage or current maximum or the steepness of the voltage or current increase.
In accordance with advantageous embodiment of the device the
REFERENCES:
patent: 2702471 (1955-02-01), Vonnegut
patent: 3986386 (1976-10-01), Beltzer et al.
Kreitman Stephen A.
Robert & Bosch GmbH
Striker Michael J.
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