Exploring the impact of spray and atomisation properties on nvPM emissions produced by an RQL research combustor

This is the authors' abstract. We don't add key points for this paper.

Concerns surrounding the impact of harmful emissions from aircraft are driving increased adoption of Sustainable Aviation Fuel (SAF) by the aviation industry. In addition to reducing lifecycle CO2 emissions, significant reductions in non-volatile Particulate Matter (nvPM) emissions are achievable for SAF compared to conventional aviation fuels, which have previously been observed to correlate with higher Fuel Hydrogen Content (FHC). However, reductions in nvPM are not consistent across all engine power conditions, with the largest benefits observed at lower power conditions. This prompts questions about the fundamental mechanisms affecting nvPM formation in gas turbine engines operating with different fuels. Towards better understanding these mechanisms, this study explores the influence of fuel atomisation quality on nvPM formation rates. The emissions produced by the combustion of several aviation fuels (including conventional Jet A-1, SAF, and SAF/Jet A-1 blends) in a small-scale Rich-Quench-Lean (RQL) research combustor were characterised using a regulatory nvPM sampling and measurement system. A design feature of the combustor allowed atomisation quality to be varied independently of primary zone equivalence ratio, with reduced atomisation quality resulting in consistently higher nvPM emissions. Measured nvPM EImass and EInumber showed evidence of a fuel dependency, whereby emissions from higher FHC fuels appeared to be less affected by atomisation changes. Sauter Mean Diameters (SMD) were estimated for the fuel sprays produced during emissions measurements, using an atomiser-specific empirical correlation, derived from independent laser-based spray benchmarking experiments conducted at ambient conditions. Using this correlation, it was predicted that small increases in SMD of 3-4 μm (~5-6%) resulted in nvPM increases of up to 108% EImass and 87% EInumber.