Experimental Characterization of Loss Mechanism During Probe-Based NVPM Measurements

Abstract Soot emissions significantly impact global climate and human health. Consequently, it is of paramount importance to consider soot emissions throughout the development of aviation engines. In order to measure non-volatile particulate matter (nvPM), it is essential to transport the aerosol through lines to the measurement device. This inevitably leads to losses of particles. These losses are currently corrected in applications by ICAO regulations in ARP 6320, which pertain to measurements behind a complete engine. This paper explores the applicability of these regulations to other scenarios, particularly measurements directly behind the combustion chamber. The conditions here differ significantly from those behind the engine, with much higher particle concentrations and different pressure and temperature conditions. This paper presents experiments characterizing line losses due to diffusion and thermophoresis. The experiment utilizes soot generators which are capable of producing soot concentrations that are consistent and reproducible. With varying sampling line lengths, the associated diffusion losses are quantified. In another experiment, the generated aerosols were preheated to different temperatures and thermophoretic effects were measured with a cooled sampling probe. Two different concentrations of soot were investigated, one reflecting the conditions typical of engine testing and the other aligning with those of combustion chamber testing. The particle sizes used in these investigations correspond to those common in combustion chamber tests.