Abstract

The influence of electric fields on the stability and emissions of natural gas combustion was investigated at a seven-hole Bunsen burner at pressures p between 0.1 MPa and 1 MPa being representative for combtrstion processes in gas turbines, For the E-field generation a ring shaped high voltage electrode placecl above the burner head was used. Self-sustained gas discharge formation was avoided by keeping the spatial average of the reduced electric field below 40 Td (1 Td: 10^-21 Vm²). In this case we found that the reduced electrical current I/p is well described by a power law of the reduced voltage U/p with power 1.5. Due to the applied electric field the air number, at which lean blow off occurred, could be increased from 1.14 to 1.22 resulting in a decrease of nitric oxide emissions of more  thall 20%. At the same time the carbon monoxide emissions decreased by more than 90%. The electric power consumption for this effect was < 0.02% of the thermal power of the burner. Plasma combustion control was tested at a small scale atmospheric pressure laboratory set-up consisting of a single flame Bunsen type burner and an integrated gliding arc reactor cerltered in the cylindrica1 burner tube. Half of tire methane fuel was subjected to plasma indrrcecl partia1 oxidation resulting in formation of hydrogen, carbon morioxide, and small concentrations of by-products, whereas a very lean mixture of the renraining fuel with air was directly fed to the burner tube. An increase of the lean blow off air number from 1.6 to 2.0 was achieved. Further the fuel conversion was improved from 90% to 95%.