In-flight measurements of contrail ice nucleation on low particle emissions from modern engines and sustainable aviation fuels – the ECOCON experiment

我们建议测量现代稀燃发动机和可持续航空燃料(SAF)的年轻尾迹，以研究大幅减少的颗粒数排放对尾迹冰成核、尾迹特性及其气候影响的影响。航迹在航空对气候的影响中所占份额最大。在轨道上，冰晶是通过发射颗粒上的异质成核而形成的。非挥发性烟尘颗粒由于其相对较大的颗粒尺寸，是尾迹冰晶的主要凝结核(CN)。在目前的烟尘排放水平高于每公斤燃料10^14个颗粒的情况下，其他排放或环境气溶胶在尾迹冰成核过程中只起到很小的作用。但现代发动机技术和SAF承诺要低得多的烟尘排放水平。地面排放测试显示，分级稀燃发动机可以将非挥发性碳烟颗粒排放降低两到三个数量级，并提高总颗粒物排放。需要飞行中的数据，以便测量巡航高度的发动机颗粒排放，并调查常规煤油和SAF的微物理轨迹特性及其对大气辐射收支的影响。我们将回答这样一个问题，即在未来的轨道冰成核中，除了烟尘颗粒之外，CN类型的重要性越来越大，包括离子诱导的超细水相颗粒或环境气溶胶的成核。我们将进一步调查在什么排放水平和温度下，挥发性颗粒或周围气溶胶上的冰核将会起作用。为此，我们将在NASA领导的一项实验中执行和评估飞行中的轨迹测量。该实验将集中在现代稀燃燃烧系统的尾迹上。NASA的机载测量实验室DC-8将作为测量飞机。轨道冰颗粒浓度将使用快进光谱仪探测器(FFSSP)和云气溶胶和降水光谱仪(CAPS)进行测量。通过使用稀燃燃烧技术，并可能将其与100%SAF的燃烧相结合，我们预计每公斤燃料的碳烟排放量将低于1014个颗粒。这使我们有可能分析，挥发性气溶胶的激活是否有助于在低烟尘区域的轨迹上形成冰核。我们还计划用现场数据对轨道模型CoCiP进行评估，我们将从减少的排放中推导出轨道的辐射强迫和能量强迫。这一结果将为未来的气候友好型航空开辟道路。

We propose to measure young contrails from modern lean-burn engines and sustainable aviation fuels (SAF), to study the effects of strongly reduced particle number emissions on contrail ice nucleation, contrail properties and their climate impact. Contrails have the largest share in the climate impact of aviation. In contrails, ice crystals form by heterogenous nucleation on emitted particles. Due to their relatively large particle size, non-volatile soot particles serve as the main condensation nuclei (CN) for ice crystals in contrails. At current soot emission levels above 10^14 particles per kg fuel, other emitted or ambient aerosols only play a minor role in the contrail ice nucleation process. But modern engine technologies and SAF promise much lower soot emission levels. Ground emission tests revealed, that staged lean-burn engines can have by two to three orders of magnitude lower non-volatile soot particle emissions and higher total particle emissions. In-flight data are required in order to measure the engine particle emissions at cruise altitudes and to investigate microphysical contrail properties and their effect on the atmospheric radiation budget, both for conventional kerosene and for SAF. We will answer the question on the increasing importance of CN types other than soot particles in future contrail ice nucleation, including ion-induced nucleation of ultra-fine aqueous particles or ambient aerosols. We will further investigate at which emission levels and temperatures ice nucleation on volatile particles or ambient aerosol will kick in. To this end, we will perform and evaluate in-flight measurements of contrails during an experiment led by NASA. The experiment will focus on contrails from a modern lean-burn combustion system. The airborne measurement laboratory DC-8 by NASA will serve as the measuring aircraft. Contrail ice particle concentrations will be measured with the Fast Forward Spectrometer Probe (FFSSP) and the Cloud Aerosol and Precipitation Spectrometer (CAPS). By using the lean-burn combustion technology and possibly combining it with the burn of 100% SAF, we expect to achieve soot emissions below 10^14 particles per kg fuel. This gives us the possibility to analyse, whether the activation of volatile aerosol contributes to ice nucleation in contrails in the low soot regime. We also plan to evaluate the contrail model CoCiP with the in-situ data and we will derive the radiative forcing and energy forcing of contrails from reduced emissions. The results will shape the way for future climate friendly aviation.