An ultra-low emission combustor concept based on ``flameless oxidation'' is demonstrated in this paper for aviation kerosene. Gas emission and size and number of nanoparticles using scanning mobility particle sizing (SMPS) measurements are carried out at the combustor outlet, revealing simultaneously soot-free and single-digit NO levels for \textcolor{black}{operation at atmospheric conditions}. Such performance, achieved with direct spray injection of the fuel without any external preheating or prevaporisation, is attributed to the combustor's unique mixing configuration. The combustor consists of azimuthally arranged fuel sprays at the upstream boundary and reverse-flow air jets injected from downstream. This creates locally sequential combustion, good mixing with hot products, and a strong whirling motion that increases residence time and homogenises the mixture. Under ideal conditions, a clean, bright-blue kerosene flame is observed, free of soot luminescence. Although soot is intermittently formed during operation around optimal conditions, high-speed imaging of the soot luminescence shows that particles are subjected to long residence times at O$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$-rich conditions and high temperatures, which likely promotes their oxidation. As a result, only nanoparticles in the 2-10 nm range are measured at the outlet under all tested conditions. The NO emissions and completeness of the combustion are strongly affected by the splitting of the air flow. Numerical simulations confirm the trend observed in the experiment and provide more insight into the mixing and air dilution.