Exhaustive test for diesel vehicles
Environmental Science and Technology v.35, i.3 1feb01
This new Australian test’s ability to instantaneously evaluate emissions from diesel vehicles has earned it international attention.
Australia’s environmental protection agency is pilot-testing a new method for evaluating diesel vehicle emissions. The technique, which uses laser light-scattering photometry to give on-the-spot pollutant readings, has attracted international attention, thanks to its speed and low cost.
Although smog tests that use chassis dynamometers to simulate real-world driving conditions are routinely used to evaluate emissions from in-use, gasoline-powered vehicles, this is the first major demonstration project that allows these popular tests to target diesel cars and trucks. The new method, which can determine exhaust NOx and particulates in only 10 minutes in a drive-up testing station, “represents the holy grail that diesel emissions people have been looking for,” claims Steve Brown, the New South Wales state manager for Parsons Australia, the engineering firm that developed the test.
“A lot of people have been talking about measuring particulate emissions from in-use [diesel] vehicles, but no one has actually been able to do it [until now],” agrees Don Chernich, manager of the Heavy Duty Diesel section for the California Air Resources Board (CARB), which is currently studying this type of test to meet the state’s regulatory obligation to limit diesel emissions. “It’s very likely that we’ll go to some type of real-time testing . . . . Being able to verify that vehicles are properly maintained and not tampered with is something that we’re very concerned with,” adds Mark Burnitzki, an air pollution specialist with CARB.
The Australian test combines three existing technologies: laser light-scattering photometry, which measures the amount of dust in ambient air; a system for measuring the exhaust mass flow of the vehicle being tested; and a chassis dynamometer programmed to simulate driving conditions in Australia. Brown estimates that this equipment will cost about $200,000 (U.S.), which he says is an order of magnitude lower than other equipment capable of performing the same measurements.
The Australian government expects to use the new test to support the National Environmental Protection Measure that the country is developing to combat NOx and particulate emissions from diesel engines, according to Vicki Ratliff, assistant director of the Air Quality Section for Environment Australia. The regulations should be finalized by next June, according to government sources.
The new test is superior to the “10-s visible smoke” test, which is currently used in Australia to evaluate emissions. Comparisons with benchmark tests show that in a group of 500 vehicles, the visible smoke test identified up to 30% of high-polluting vehicles, whereas the new test pinpointed 70–80% of the high polluters, says Ratliff.
According to Chernich, the light-scattering photometry results must still be correlated with the benchmark test of collecting particulates from a car or truck’s exhaust on a gravimetric filter and measuring the mass. “With any type of optical measurement, you have the problem of the particles reacting differently depending upon how big and what shape they are and how much water there is. But any existing particulate-matter measuring technology is problematic in one way or another, including the existing reference method,” Burnitzki adds. —KELLYN S. BETTS
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