Search Results

The accuracy of low-level emission measurements has become increasingly important, due to the development and implementation of SULEV and PZEV vehicles. One technique to test the low-level measurement performance of a CVS is to inject a known mass of a trace gas, such as propane, into the sample system and verify that substantially all of the mass injected is recovered, typically within 2% of the total injected mass. A Vehicle Exhaust Emission Simulator has been used to inject precise amounts of trace gases with a known accuracy in the range of 0.5% to 1.0%. Recoveries for propane, carbon monoxide, and carbon dioxide are typically 98% or higher, while recoveries for nitrogen oxide are sometimes as low as 95% to 96%. In other words, as much as 5% of the injected nitrogen oxide mass is not recovered by the CVS. This represents an unexpected loss of 3% to 4% of the injected nitrogen oxide.

The accuracy of low-level emission measurements has become increasingly important, due to the development and implementation of SULEV and PZEV vehicles. One technique to test the low-level measurement performance of a CVS is to inject a known mass of a trace gas, such as propane, into the sample system and verify that substantially all of the mass injected is recovered, typically within 2% of the total injected mass. A Vehicle Exhaust Emission Simulator has been used to inject precise amounts of trace gases with a known accuracy in the range of 0.5% to 1.0%. Recoveries for propane, carbon monoxide, and carbon dioxide are typically 98% or higher, while recoveries for nitrogen oxide are sometimes as low as 95% to 96%. In other words, as much as 5% of the injected nitrogen oxide mass is not recovered by the CVS. This represents an unexpected loss of 3% to 4% of the injected nitrogen oxide.

The accuracy of low-level emission measurements has become increasingly important, due to the development and implementation of ULEV, SULEV, and PZEV vehicles. Measurement of these decreasing levels of automotive emissions requires new sampling and measuring techniques. Several alternative emission sampling techniques have been investigated to minimize measurement variability and maximize system repeatability. An alternative technique to obtain accurate low-level emissions measurement from SULEV vehicles is the Bag Mini-Diluter, which uses a proportional signal from an Exhaust Volume Measurement Device to sample vehicle exhaust. Crucial to successful proportional sampling of vehicle exhaust flow is the performance of the Exhaust Flow Measurement Device. This study evaluates an Exhaust Volume Measurement Device commonly used with a Bag Mini-Diluter.