<DOC>
<DOCNO>
576
</DOCNO>
<TITLE>
viscous and inviscid stagnation flow in a dissociated hypervelocity free
 stream .
</TITLE>
<AUTHOR>
inger, g.r.
</AUTHOR>
<BIBLIO>
proc. 1962. heat transfer and fluid mech. inst .
</BIBLIO>
<TEXT>
high reynolds number hypersonic stagnation flow over a blunt-nosed body
in a nonequilibrium dissociated free stream is analyzed and compared to
a similar flow in an initially undissociated ambient gas . free stream
dissociation effects on various equilibrium stagnation flow properties
in air are presented as a function of the ambient atom mass fraction and
 dissociation energy for velocities ranging from 15,000 to 25,000 fps .
significant changes in the bow shock geometry, stagnation gas state, and
 boundary layer behavior are found when the free stream dissociation
involves more than 10( of the total energy . it is observed that for
large amounts of both atomic oxygen and nitrogen ahead of the body, the
equilibrium shock layer properties converge toward those pertaining to
chemically and vibrationally-frozen flow across the bow shock . moreover,
under certain conditions, the ionization level can be increased by
 an order of magnitude and the usual reduction in frozen boundary layer
heat transfer due to a highly-cooled noncatalytic surface can increase
from stall of adjacent stages .
the effects of compromises of stage matching to favor part-speed operation
were also considered . this phase of the study indicated that
such compromises would severely reduce the complete-compressor-stall
margin . furthermore, the low-speed stage stall problem is transferred
from the inlet stages to the middle stages, which are more susceptible
to abrupt-stall characteristics .
the analysis indicates that inlet stages having continuous performance
characteristics at their stall points are desirable with respect to
part-speed compressor performance . these characteristics must, however,
 be obtained when the stages are operating in the flow environment of
the multistage compressor . alleviation of part-speed operational problems
may also be obtained by improvement in either stage flow range or
stage loading margin .
the results of this analysis are only qualitative . the trends obtained,
 however, are in agreement with those obtained from experimental studies
 of high-pressure-ratio multistage axial-flow compressors, and the results
are valuable in developing an understanding of the off-design
problem . in addition to these stage-matching studies, a general discussion
of variable-geometry features such as air bleed and adjustable
 gas model . numerical solutions of non-equilibrium airflows with fully
coupled chemistry provide a preliminary verification of such scaling for
limit characteristics . the analysis indicated that all these problems
could be attributed to discontinuities in the performance characteristics
of the front stages . such discontinuities can be due to the type
 of stage stall or to a deterioration of stage performance resulting
blades is included .
</TEXT>
</DOC>
