Field of the Invention
The invention relates to a method for analyzing the exhaust gas of internal combustion engines which includes the cooling of the exhaust gas before analysis, the determination of the concentration of at least two different exhaust gas components in at least two separate analysis stages, or the determination of the concentration of a single exhaust gas component with at least two different cooling stages. The invention also relates to an exhaust gas cooler for a device for analyzing the exhaust gas of internal combustion engines, as well as a device for analyzing the exhaust gases of internal combustion engines that includes at least one cooler for the exhaust gas and an analyzer arrangement for determining the concentration of at least two different exhaust gas components in at least two separate analysis stages, or for determining the concentration of a single exhaust gas component with at least two different cooling stages.
The Prior Art
In order to measure exhaust gases of internal combustion engines, appropriate preparation of the exhaust gas is necessary. The state of the art here is hot measurement of exhaust gas or cold measurement via a gas cooler. When the exhaust gas is measured cold, then it is necessary to remove water vapor. In known devices, a cooler which cools the exhaust gas to a temperature between 5° C. and 10° C. is used for this purpose. This ensures that the water content in the exhaust gas does not affect the measurement, and prevents water and hydrocarbons with higher boiling points from condensing in the analyzers. The boiling point of the exhaust gas component nitrogen dioxide which is relevant to the measurement is 21.15° C.; further, in contrast to the other exhaust gas components, nitrogen dioxide has a higher solubility in the water which condenses in the gas cooler. Both lead to a loss of nitrogen dioxide in the gas cooler and therefore to a lower concentration in the analyzer.
The object of the present invention was therefore an improvement of the method and the device for analyzing the exhaust gas with which a higher measuring accuracy is guaranteed. A further object was the design of an exhaust gas cooler which enables more effective cooling of the exhaust gas.