On-road Emissions Patterns Identified By PEMS
Nearly all modern engines, when tested new and according to the accepted testing protocols in a laboratory, produce relatively low emissions well within the set standards. As all individual engines of the same series are supposed to be identical, only one or several engines of each series get tested. The tests have shown that:
- The bulk of the total emissions can come from relatively short high-emissions episodes
- Emissions characteristics can be different even among otherwise identical engines
- Emissions outside of the bounds of the laboratory test procedures are often higher than under the operating and ambient conditions comparable to those during laboratory testing
- Emissions deteriorate significantly over the useful life of the vehicles
- There are large variances among the deterioration rates, with the high emissions rates often attributable to various mechanical malfunctions
These findings are consistent with published literature, and with the data from a myriad of subsequent studies. They are more applicable to spark-ignition engines and considerably less to diesels, but with the regulation-driven advances in diesel engine technology (comparable to the advances in spark-ignition engines since 1970’s) it can be expected that these findings are likely to be applicable to the new generation diesel engines. Since 2000, multiple entities have utilized PEMS data to measured in-use, on-road emissions on hundreds of diesel engines installed in school buses, transit buses, delivery trucks, plow trucks, over-the-road trucks, pickups, vans, forklifts, excavators, generators, loaders, compressors, locomotives, passenger ferries, and other on-road, off-road and non-road applications. All the previously listed findings were demonstrated; in addition, it was noticed that extended idling of engines can have a significant impact on the emissions during subsequent operation.
Also, PEMS testing identified several engine “anomalies” where fuel-specific NOx emissions were two to three times higher than expected during some modes of operation, suggesting deliberate alterations of the engine control unit (ECU) settings. Such data set can be readily used for developing emissions inventories, as well as to evaluate various improvements in engines, fuels, exhaust after-treatment and other areas. (Data collected on “conventional” fleets then serves as “baseline” data to which various improvements are compared.) This data set can also be examined for compliance with not-to-exceed (NTE) and in-use emissions standards, which are ‘US-based’ emission standards that require on-road testing.
Read more about this topic: Portable Emissions Measurement System
Famous quotes containing the words patterns and/or identified:
“For the man who should loose me is dead,
Fighting with the Duke in Flanders,
In a pattern called a war.
Christ! What are patterns for?”
—Amy Lowell (1874–1925)
“Linguistically, and hence conceptually, the things in sharpest focus are the things that are public enough to be talked of publicly, common and conspicuous enough to be talked of often, and near enough to sense to be quickly identified and learned by name; it is to these that words apply first and foremost.”
—Willard Van Orman Quine (b. 1908)