Electric-Field Effects on Laminar Diffusion Flames (E-FIELD Flames)
The Electric-Field Effects on Laminar Diffusion Flames (E-FIELD Flames) experiment is conducted in the Combustion Integrated Rack (CIR) on the International Space Station, as part of the Advanced Combustion via Microgravity Experiments (ACME) project. In this experiment, an electric field with voltages as high as 10,000 volts is established between the burner and a mesh electrode. The motion of the charged ions, which are naturally produced within the flame, are strongly affected by a high-voltage electric field. The resulting ion-driven wind can dramatically influence the stability and sooting behavior of the flame. Measurements are made of electric-field strength, the ion current passing through the flame, and flame characteristics such as the size, structure, temperature, soot, and stability. Conducting the tests in microgravity allows for great simplifications in the analysis, enabling new understanding and the development of less polluting and more efficient combustion technology for use on Earth.
An electric field can strongly influence flames because of its effect on the ions present as a result of the combustion reactions. The induced ion wind can modify the flame shape, alter the soot and stability limits, and direct the heat transfer. The purpose of the Electric-Field Effects on Laminar Diffusion Flames (E-FIELD Flames) experiment is to gain an improved understanding of flame ion production and learn how the electric field can be used to control non-premixed flames. For example, electric fields can enable stable burner operation at fuel-lean conditions with reduced pollutant emission, i.e., where the flame is not reliably sustained without the electric field. The experiment contributes to our critical understanding of combustion processes in the presence of electric fields. 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 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.