Investigation of Low Emission Reverse Flow Combustors

Abstract

Combustion of hydrocarbon fuels has been a major source of energy for many industries, including transportation, power generation, and heating. However, their combustion is associated with the emission of pollutants such as NOx, CO, unburned hydrocarbons, and soot, which can have detrimental impacts on the environment. In recent studies, Peripheral Vortex Reverse Flow (PVRF) and Stagnation Point Reverse Flow (SPRF) combustors have been demonstrated to result in low pollutant emissions. In these reverse flow combustors, the flow reverses to emit on the same side as the air/fuel injection port, with the PVRF combustor consisting of a single exhaust that generates a strong peripheral vortex inside the combustor, while the SPRF combustor has two exhaust ports that form recirculation from both sides. This study investigates the performance of Compressed Natural Gas (CNG) fueled PVRF and SPRF combustors, each operating at a heat load of 6.25 kW, in premixed and non-premixed modes. The experiments were conducted to measure NOx and CO emissions within global operational limits, as well as to identify reaction zones through CH* chemiluminescence imaging. Numerical simulations were carried out using RANS with global chemical kinetic mechanisms to estimate flow dynamics and gas recirculation patterns. Very low emission levels, less than or equal to 5 ppm of NOx at an equivalence ratio of 0.6, were observed for both SPRF and PVRF combustors in both non-premixed and premixed modes. The trends for NOx and CO concerning the equivalence ratio were also similar for both PVRF and SPRF combustors. Notably, the PVRF combustor exhibited slightly lower NOx emissions in the non-premixed mode compared to the premixed mode. The numerical simulations found a higher recirculation ratio for the PVRF combustor compared to the SPRF combustor. Additionally, the location of the reaction zone exhibited significant variation between premixed and non-premixed modes for both combustors. Show more