文档介绍：THE THERMODYNAMIC PROPERTIES OF
HIGH TEMPERATURE AIR
JOHN S. EVANS
Plasma Applications Section
Langley Research Center, NASA
The thennodynamic properties of air which are important for analysis of
the aerodynamic and heat transfer problems encountered under reentry
conditions are reviewed. The changes induced in gas properties by the shock
wave associated with a high speed object in the atmosphere are discussed,
including the effect of chemical reactions and ionization.
This talk is entitled “The Thermodynamic Properties of High Tempera-
ture Air”. The reason for choosing to discuss this subject as part of a con-
ference on reentry dynamics is that knowledge of the thermodynamic
properties of gases is quite important to aerodynamic calculations of such
things as drag, lift, and heat transfer. This is especially true at the high
speeds characteristic of bodies reentering the earth‘s atmosphere from space,
for at these high speeds the temperature of the air flowing over the body is
-measured in thousands ofdegrees Kelvin. At such temperatures the thexmo-
dynamic properties (such as pressure, density, temperature, enthalpy, and
entro y) and the functions of their derivatives (such as sound speed and
spec’lg c heat) are quite different from their room temperature values. More-
over, there may be regions of the flow in which thermodynamic equilibrium
is absent. This latter feature leads to the idea of “relaxation zones” in which
the properties are seeking the equilibrium values but have not yet attained
them.
Figure 1 illustrates the large changes that occur in the -
position of air as the temperature increases. It is taken from an NACA
paper by Moeckel and Westonl and gives the position of
air at a density of times that at sea level-corresponding to an altitude
somewhat greater than 300,000 feet. Note the appearance of new chemical
species as the temperature increases. Diatomic oxyg