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SAE AIR6504 describes a method for assessing size dependent particle losses in asampling and measurement system of specified geometry utilizing the non-volatile PM (nvPM) mass and numberconcentrations measured at the end of the sampling system.1 The penetration functions of the sampling and measurementsystem 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 areconsidered in this method2 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 numberconcentrations to account for the system losses facilitating estimation of the nvPM mass and number at the engine exhaustnozzle exit plane. As the particle losses are size dependent, the magnitude of correction factors can vary as a function ofmany factors including combustor technology and engine operating condition.
Implementation of the nvPM sampling and measurement system for aircraft engine testing, as per AIR6037, requires asample line of up to 35 m and includes several sampling and measurement system components, which result in significantparticle loss on the order of 50% for nvPM mass and 90% for nvPM number.
The system loss correction factors are estimated based on a model with the following inputs and assumptions: engineexhaust exit plane nvPM have a lognormal distribution, known size dependent values of nvPM effective density andgeometric standard deviation, a minimum particle size cut-off of 10 nm, and no coagulation.
Product Details
- Published:
- 10/10/2017
- Number of Pages:
- 70
- File Size:
- 1 file , 5.1 MB
