Towards Plasma Assisted Stabilization of a Natural Gas Burner Using Nanosecond Pulsed Discharges

This study investigates the stability limits of a benchtop combustor and the potential use of plasma-assisted combustion (PAC) to improve flame stability and emissions characteristics. Baseline flame stability (without plasma) using natural gas was studied in the open-flame configuration across a wide range of equivalence ratios (ϕ = 0.27–0.87) and thermal input powers (25–100 kBTU/hr). Flame dynamics were assessed using imagery, acoustic, and emission measurements. Results showed that in lean conditions blowout was never observed. Instead, lean flames tend to transition to a low-intensity pilot flame that remains present over the entire lean operating regime. This behavior reflects the burner’s staged design, whereby fuel is injected into a rich primary zone and entrains air through a series of ports upstream of the igniter. For a fixed equivalence ratio, increasing the burner power resulted in a noticeable decrease in flame intensity and sound power. This was accompanied by an increase in CO emissions, suggesting a reduction in combustion efficiency. In parallel with the experimental baseline, plasma kinetic simulations using ZDPlasKin were performed to evaluate the chemical kinetics induced by the nanosecond repetitively pulsed discharge in air. Key species for combustion performance, such as O₃, NO, and free electrons, are reported for a range of reduced electric fields (E/N=200-400 Td). These simulations demonstrated that higher reduced electric fields produce significantly larger electron number densities and enhance NO dominated chemistry over O3, providing insight into how PAC may shift stability limits and emissions once implemented on the physical combustor. Overall, this study provides valuable baseline performance metrics of the benchtop test burner before future experimental implementation of PAC.