Measuring and testing – Gas analysis
Reexamination Certificate
1999-12-16
2001-09-04
Williams, Hezron (Department: 2856)
Measuring and testing
Gas analysis
C073S023310, C073S118040
Reexamination Certificate
active
06282944
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an apparatus and a process for the analysis of exhaust gas components from an internal combustion engine.
BACKGROUND
Apparatus and processes for the measurement of exhaust gas components of internal combustion engines have been known for a long time. In the so-called CVS (Constant Volume Sampling) process, the exhaust gas produced during a test is introduced into the intake flow of a constantly transporting conveyor. The conveyor has a transport capacity, which lies clearly above the maximum exhaust gas volume flow of the vehicle engine under full load. The volume difference that occurs between the exhaust gas quantity and the conveyor capacity is equilibrated by intake of filtered fresh air that fulfills the dual functions of providing exhaust gas dilution and constant gas/air volume flow rate. Samples are taken and collected in sample bags from the exhaust gas air mixture during the entire test with uniform volume flow. The concentrations of pollutants and carbon dioxide are measured in the samples prepared in this way. However, a problem arises in that the emissions of modern engines and vehicles are becoming increasingly smaller. The measured concentrations often approach the detection limits of the analytical technique, so that the results of analysis are unreliable. One remedy is to make the dilution ratio smaller and thus the concentration of exhaust gas in the bags will be higher. This procedure is limited by the water concentration that also increases. Condensation of water in the exhaust bags and in the lines leading therein as well as in the analysis lines, however, must be avoided, since this leads to the falsification of the measurement results (several pollutants are soluble in water and also precipitate therein). This problem is eliminated at the present time by heating the exhaust gas sample bag, sample lines leading thereto from the CVS, as well as the analysis lines.
In heating the sample gas, there is now the problem that in order to avoid condensate, the entire device including the exhaust bag, the sampling lines and the analysis lines must be heated. This extensive heating and temperature regulation plus monitoring are time-consuming and expensive. Since any cold spots in the piping system must be avoided, all valves, for example, must also be at an elevated temperature, which requires an increased expenditure for insulation. The operating costs are also considerable, due to the high consumption of electrical power involved in the heating. In addition, there is no flexibility in the construction of the complete test stand.
SUMMARY OF THE INVENTION
An object of the invention is to provide an apparatus and a process for the analysis of exhaust gas components, which avoid the above-noted disadvantages.
This object is achieved by arranging the sample bag in a gas-tight, pressure resistant container which is maintained under vacuum.
Because the sample bag is arranged in a gas-tight and pressure-resistant container, which is under a vacuum, the vacuum also prevails in the connection lines leading to flow limiters, which are disposed directly at the place of sampling. Due to the reduction in pressure as compared to conventional processes, condensation is avoided in an effective and cost-favorable way.
In order to be able to measure the vacuum in the container, a pressure sensor is assigned to the container. In this way, the vacuum in the container is kept constant during the sampling and thus during the associated filling of the sample bags. A pressure regulator in the vacuum conveyor line is controlled by the pressure sensor to regulate admission of fresh air to maintain the desired vacuum pressure.
In order to avoid unnecessary lines and to make the device as flexible as possible, the pressure sensor, the pressure regulator, valves and also the vacuum conveyor may be arranged directly at the container.
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Ladas & Parry
Pierburg AG
Wiggins David J.
Williams Hezron
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