The mass-flux fraction (or Hirschfelder-Curtiss variable or Kármán-Penner variable) is the ratio of mass-flux of a particular chemical species to the total mass flux of a gaseous mixture. It includes both the convectional mass flux and the diffusional mass flux. It was introduced by
Joseph O. Hirschfelder and
Charles F. Curtiss in 1948 and later by
Theodore von Kármán
Theodore von Kármán ( hu, ( szőllőskislaki) Kármán Tódor ; born Tivadar Mihály Kármán; 11 May 18816 May 1963) was a Hungarian-American mathematician, aerospace engineer, and physicist who was active primarily in the fields of aeronaut ...
and
Sol Penner
Stanford Solomon Penner (5 July 1921 – 15 July 2016) also known as Sol Penner, was a German-American scientist and engineer, a major figure in combustion physics, especially in rocket engines, and a founder of the Engineering program at Universit ...
in 1954. The mass-flux fraction of a species i is defined as
:
where
*
is the
mass fraction
*
is the mass average velocity of the gaseous mixture
*
is the average velocity with which the species i diffuse relative to
*
is the density of species i
*
is the gas density.
It satisfies the identity
:
similar to mass fraction, but, the mass-flux fraction can take both positive and negative values. This variable is used in steady, one-dimensional
combustion
Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combus ...
problems in place of mass fraction.
[Penner, S. S. (1957). Chemistry problems in jet propulsion (Vol. 1). Pergamon Press.] For one-dimensional (
direction) steady flows, the conservation equation for the mass-flux fraction reduces to
:
where
is the mass production rate of species i.
References
{{reflist, 30em
Chemical properties
Dimensionless numbers of chemistry
Combustion