Part I:

The work reported in our recent letter has been extended to radio frequency fields using, for simplicity, the thermocouple method alone. The apparatus used was that described in Ref. 1. The nigh voltage supply was replaced by a radio frequency, generator giving a field strength of 1 kV rms cm-1 at 6 MHz.

The burning velocities obtained again showed no appreciable variation. For stoichiometric ethylene/air and ethane/air flames they were 68.5 and 42.0 cm s-1 respectively with an rms variation of 1%. Values obtained with dc (including zero) fields were 67.9 and 41.6 cm s-1 with rms variations of 3.4 and 5.3%, compared with the estimated experimental errors of 2.8 and 4.5% respectively [1].

Part II:

As regards dc fields, the suggestion that the small changes in heat transfer prior to blowoff were due to flow modifications around the periphery, induced by forces acting on the ions, was tested optically. Because of the high sensitivity required, double exposure laser interferometry was used. The presence of such a small effect is shown in Fig. 1.