Thermodynamic correction of particle concentrations measured by underwing probes on fast flying aircraft
Thermodynamic correction of particle concentrations measured by underwing probes on fast flying aircraft
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DOI：
10.5194/amt-9-5135-2016
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发表时间：
2015-12
影响因子：
3.8
通讯作者：
R. Weigel;P. Spichtinger;C. Mahnke;M. Klingebiel;A. Afchine;A. Petzold;M. Krämer;A. Costa;
中科院分区：
文献类型：
--
作者：
R. Weigel;P. Spichtinger;C. Mahnke;M. Klingebiel;A. Afchine;A. Petzold;M. Krämer;A. Costa;
摘要。在飞机上用翼下探针测量颗粒浓度时，仪器体上游的空气压缩对测量结果的影响是飞行速度的函数。特别是，对于快速飞行的飞机，必须考虑空气样本量的压缩。因此，需要一个校正程序来将测量到的颗粒数浓度与通常适用于不同仪器的环境条件进行反转，以获得可比较的结果。在发生颗粒检测的压缩区域（即在实际测量条件下），空气样品的压力和温度与距离飞机一定距离的环境（未受干扰）条件相比有所增加。将测量的数字密度按环境条件缩放的常规程序假定，每个时间间隔探测的空气量由飞机速度（真空气速度，TAS）决定。然而，配备皮托管的粒子成像仪器测量每个翼下探针的探针空气速度（PAS），显示PAS值系统地低于TAS值。我们得出的结论是，PAS和TAS之间的偏差主要是由探测空气样品的压缩引起的。根据2014年德国湾流G-550 （HALO -高空远程）研究飞机在两次任务中的测量结果，我们开发了一种程序，使用热力学方法将测量的颗粒浓度校正为环境条件。根据所提供的公式，相应的浓度校正因子ξ适用于每个翼下探头的高频测量，每个翼下探头都配备了自己的空气速度传感器（例如皮托管）。对于风速（即TAS）在60 ~ 250 m s−1之间，ξ值为1 ~ 0.85。对于单个机翼位置的不同仪器，计算出的ξ值表现出很强的一致性，这允许将ξ参数化为当前HALO翼下探头配置的TAS函数。云粒子对环境条件和测量条件之间空气速度变化的适应能力取决于云粒子的惯性作为粒径（直径Dp）的函数。建议的液云滴惯性校正系数μ (Dp)在1 （Dp）之间
Abstract. Particle concentration measurements with underwing probes on aircraft are impacted by air compression upstream of the instrument body as a function of flight velocity. In particular, for fast-flying aircraft the necessity arises to account for compression of the air sample volume. Hence, a correction procedure is needed to invert measured particle number concentrations to ambient conditions that is commonly applicable to different instruments to gain comparable results. In the compression region where the detection of particles occurs (i.e. under factual measurement conditions), pressure and temperature of the air sample are increased compared to ambient (undisturbed) conditions in certain distance away from the aircraft. Conventional procedures for scaling the measured number densities to ambient conditions presume that the air volume probed per time interval is determined by the aircraft speed (true air speed, TAS). However, particle imaging instruments equipped with pitot tubes measuring the probe air speed (PAS) of each underwing probe reveal PAS values systematically below those of the TAS. We conclude that the deviation between PAS and TAS is mainly caused by the compression of the probed air sample. From measurements during two missions in 2014 with the German Gulfstream G-550 (HALO – High Altitude LOng range) research aircraft we develop a procedure to correct the measured particle concentration to ambient conditions using a thermodynamic approach. With the provided equation, the corresponding concentration correction factor ξ is applicable to the high-frequency measurements of the underwing probes, each of which is equipped with its own air speed sensor (e.g. a pitot tube). ξ values of 1 to 0.85 are calculated for air speeds (i.e. TAS) between 60 and 250 m s−1. For different instruments at individual wing position the calculated ξ values exhibit strong consistency, which allows for a parameterisation of ξ as a function of TAS for the current HALO underwing probe configuration. The ability of cloud particles to adopt changes of air speed between ambient and measurement conditions depends on the cloud particles' inertia as a function of particle size (diameter Dp). The suggested inertia correction factor μ (Dp) for liquid cloud drops ranges between 1 (for Dp