(180ae) Preliminary Evaluation of Gaseous Emissions from a Lean Premixed Prevaporized Combustor Designed for CIVIL Supersonic Transport

The global push for greener aviation technologies has revived interest in civil supersonic transport (CST), a domain historically limited by environmental and regulatory constraints. While modern CST concepts promise faster intercontinental travel, they must meet increasingly stringent emissions standards to be viable. One critical concern is the generation of gaseous pollutants, such as nitrogen oxides (NOₓ), carbon monoxide (CO), unburnt hydrocarbons (UHC), and carbon dioxide (CO₂), from high-temperature combustion processes typical in supersonic engines. To address this, lean premixed pre-vaporized (LPP) combustion has emerged as a promising approach to improve combustion efficiency and lower emissions. However, experimental data on gaseous emissions under CST-relevant conditions remain sparse. This study, supported by the NASA-ULI initiative and aligned with FAA/ICAO regulatory frameworks, seeks to fill this gap by characterizing the gaseous emissions from a newly fabricated LPP combustor designed for CST applications using the CAI 600 gas bench, an ancillary instrument used in conjunction the nvPM measuring North American Reference System (NARS). The results highlight the influence of fuel-to-air ratio (FAR) on emissions characteristics, with NOₓ formation increasing at higher temperatures and pressures. Similarly, CO₂ and CO levels are reduced at low-temperature/ low-FAR combustion conditions, with CO being drastically minimized. However, UHC maintains relative stability over the tested operating conditions. These findings provide valuable insights into the trade-offs between combustion efficiency and emissions, supporting the development of cleaner CST propulsion systems and future regulatory compliance. Further studies will expand testing to optimize combustor design across diverse flight regimes.