This new standard describes a method for assessing size dependent particle losses in a sampling and measurement system of specified geometry utilizing on the non-volatile PM (nvPM) mass and number concentrations measured at the end of the sampling system. The penetration functions of the sampling and measurement system may be determined either by measurement or by analytic computational methods. Loss mechanisms including thermophoretic (which has a very weak size dependence) and size dependent losses are considered in this method along with the uncertainties due to both measurement error and the assumptions of the method. The results of this system loss assessment allow development of estimated correction factors for nvPM mass and number concentrations to account for the system losses facilitating estimation of the nvPM mass and number at the engine exhaust nozzle exit plane.
The body of the ARP6481 details the recommended calculation method, uncertainties and limitations of the system loss correction factors. It explains, in detail, the required inputs and outputs from the supplied Excel® software tool.
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ARP6481 was developed by the SAE E-31 Aircraft Emissions Measurement committee. The E-31 committee addresses all facets of aircraft exhaust emissions measurement–tools, methods, processes, and equipment. It is responsible for standardizing measurement methods of emissions from aircraft, including isolated combustor systems. The group is comprised of four subcommittees dedicated to creating, preparing, and maintaining all relevant specifications, standards, and requirements for aircraft exhaust emissions measurement.
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