A Study of Ion Concentration Fluctuations in Turbulent Diffusion Flames using Correlation Techniques

  • William G. Roberts

Student thesis: Doctoral ThesisDoctor of Philosophy


An investigation of the interaction between chemistry
and turbulence has been made by studying the effects of
non equilibrium ion chemical kinetics in a turbulent diffusion
flame. In such a system the charged species undergo a
chemical reaction concurrently with turbulent mixing. Where the
chemical reaction rate is greater than the appropriate mixing
rate it has been theoretically predicted that a measurable
difference should exist between the statistical functions used
to describe the fluctuating species concentration field and
that of a chemically inert constituent.

Experimental evidence for this phenomenon has been
established by sampling the local ion concentration fluctuations
in a turbulent diffusion flame, of nozzle Reynolds
number 1.0 x 10 *4 using a stationary electrostatic probe. The
random positive ion saturation current collected by the probe
was analysed to determine its auto correlation function. The
ionisation field was generated by seeding the flame with
acetylene and other metal salt solutions preselected on the
basis of their Damkohler number values in the flame.

Studies have also been conducted to map the flame determining
both autocorrelation and cross correlation functions to
obtain further information for the interaction phenomenon and
of the structure of the ion concentration field throughout the
Date of Award1973
Original languageEnglish


  • Ion concentration
  • fluctuations
  • turbulent diffusion flames
  • correlation techniques

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