E-FIELD Flames

The objective of this investigation is to better understand the relationship between electric field voltage and chemi-ion current, analyze the dynamic response of flames to electric field changes, evaluate soot formation, and characterize stabilized near-limit lifted flames.

The E-FIELD flames experiment investigates how electric fields influence the behavior of laminar diffusion flames in microgravity. This unique environment is ideal for isolating electric field effects from buoyancy forces. The experiment is conducted with gas-fueled flames, both with and without a coflow of air. In the former case, the tests are conducted using the same coflow burner used by the Coflow Laminar Diffusion (CLD) Flame experiment. An electric field is generated by creating a high voltage (up to 10 kV) differential between the burner and a flat circular mesh suspended above (i.e., downstream of) the burner. Measurements, as a function of the field strength and fuel, are taken of the ion current through the flame and the flame’s response time to electric forcing. The gas-jet burner is used to create a small, focused flame for detailed ion-driven convection studies while the coflow burner surrounds the fuel jet with a weak synthetic air flow to enable flame stability and soot behavior analysis. A high-voltage copper mesh electrode positioned above the burner tip generated an electric field with controlled polarity and strength. The electric field interacts with ions generated through chemi-ionization during combustion, driving ion-driving convection and influencing flame behavior. Methane and ethylene were used as fuels and diluted with nitrogen to control flame strength. Dilution levels were varied to explore a range of combustion dynamics, from highly stable to near-extinction flames. Voltage-current curves were recorded to assess the relationship between electric field strength and chemi-ion current, revealing ion-driven convection effects. High-resolution cameras captured flame shape, luminosity, and soot distribution. Spectral imaging with filters measures chemiluminescent emissions and soot volume fraction. There were thermopile detectors to measure flame radiant emissions. All experiments were conducted in the combustion integrated rack (CIR). Tests were administered with Glenn Research Center (GRC) directing astronaut actions. Parameters such as fuel flow rate, coflow velocity, and field polarity are were varied to isolate specific effects on ion production, flame stability, and soot behavior.

The application of electric fields in microgravity environments will significantly influence laminar diffusion flames by enabling precise manipulation of flame stability, soot behavior, and combustion dynamics through ion-driven convection and chemi-ionization processes.

The E-FIELD Flames research is not being conducted to serve any space applications, but it is possible that its findings could aid the development of future space-based combustion devices (e.g., for solid waste processing). The use of electric fields to control flames can reduce the production of harmful pollutants in practical terrestrial combustion. The combustion of fossil fuel is the primary human source of greenhouse gas and acid rain and furthermore creates soot, which can be beneficial but is also a health hazard. Combustion using electrical fields may also allow for more efficient combustion, reducing fuel consumption in addition to unwanted emissions.