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Procedure for the Calculation of non-volatile Particulate Matter Sampling and Measurement System Penetration Functions and System Loss Correction Factors 非挥发性颗粒物取样和测量系统穿透功能和系统损失修正系数的计算程序
发布日期: 2022-06-24
SAE AIR6504描述了一种用于评估空气中尺寸相关颗粒损失的方法 使用非挥发性PM(nvPM)质量和数量的规定几何形状的取样和测量系统 在取样系统末端测量的浓度。1采样和测量的穿透功能 系统可通过测量或分析计算方法确定。损耗机制包括热泳(其尺寸依赖性非常弱)和尺寸依赖性损耗 本方法2考虑了由于测量误差和方法假设引起的不确定性。该系统损失评估的结果允许开发nvPM质量和数量的估计修正系数 用于解释系统损失的浓度,有助于估算发动机排气处的nvPM质量和数量 喷嘴出口平面。由于颗粒损失取决于尺寸,因此修正系数的大小可能随尺寸的变化而变化 许多因素包括燃烧室技术和发动机运行条件。按照AIR6037的要求,为飞机发动机测试实施nvPM采样和测量系统需要 采样线高达35米,包括多个采样和测量系统组件,可产生显著的 nvPM质量的颗粒损失约为50%,nvPM数量的颗粒损失约为90%。系统损耗修正系数是根据具有以下输入和假设的模型估算的: 发动机 排气出口平面nvPM具有对数正态分布、已知的nvPM有效密度和尺寸相关值 几何标准偏差,最小粒径截止值为10 nm,无凝结。
SAE AIR6504 describes a method for assessing size dependent particle losses in a sampling and measurement system of specified geometry utilizing the non-volatile PM (nvPM) mass and number concentrations measured at the end of the sampling system.1 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 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 number concentrations to account for the system losses facilitating estimation of the nvPM mass and number at the engine exhaust nozzle exit plane. As the particle losses are size dependent, the magnitude of correction factors can vary as a function of many factors including combustor technology and engine operating condition.Implementation of the nvPM sampling and measurement system for aircraft engine testing, as per AIR6037, requires a sample line of up to 35 m and includes several sampling and measurement system components, which result in significant particle 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: engine exhaust exit plane nvPM have a lognormal distribution, known size dependent values of nvPM effective density and geometric standard deviation, a minimum particle size cut-off of 10 nm, and no coagulation.
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