système de prélèvement à volume constant

CONT: Motor vehicle exhaust is a complex mixture of unburned fuel, combustion products (including a high water vapor content), and intake air that exits the tail pipe at high temperatures. In simulated driving conditions on the dynamometer, the volume of the exhaust emitted from the tail pipe is continually changing depending on where in the driving cycle the vehicle is (for example, during acceleration, during deceleration, at constant speed, or at idle). To quantitatively determine emission rates from vehicles, we use a constant volume sampling system, which maintains a constant total flow rate of vehicle exhaust plus dilution air. With a CVS system, as exhaust flow increases, such as during heavy acceleration, the dilution air is automatically decreased and the sampling source is representative of exhaust variations. This CVS system provides the source for all exhaust samples collected (regulated and unregulated).