Aerospace Research - ISTC Funded Projects 1994-2009

along with a flow rate approaching the
designed value and a full pressure recovery
coefficient being quite high. The porous bleed
permitted the increase of the airflow rate in
the model with sidewalls to be more than
doubled. This flow rate was more than 30%
higher than the airflow rate in the model
without sidewalls. It was also found that the
downstream porous bleed was the most
efficient. The upstream bleed closing exerted
virtually no effect on the airflow rate and did
not entail reduction in the flow rate. The
efficiency of the porous bleed increased with
the flow Mach number. At the same time, it
was found that, after inlet start, porous bleed
closing did not result in the inlet nonstart,
i. e., the inlet remained in the started state.
It was natural that the inlet flow rate increased
when the boundary layer bleed was closed.
Concurrently, the pressure distribution over
the model channel walls and Pitot pressure
fields in the typical channel cross sections
behind the inlet throat, airflow rate and full
pressure recovery coefficient were measured.
Evidently, modification of the geometrical
configuration of the model or shape of
the boundary layer bleed entailed a significant
change in the pressure distribution in
the model channel. The pressure distributions
in the models with and without side
walls, being compared, showed that the
inlet start was accompanied by a decrease
of the static pressure in the channel and
corresponding increase of the airflow rate
owing to the absence of a shock wave at the
inlet entrance and side spreading reduction.
Enhancement of Flight Performance, Economy and Efficiency
Fig. 18: Photo of the model with starting device
It should be noticed that the pressure
distribution differed not only quantitatively
but also qualitatively in the case of inlet
nonstart. Such a difference in the pressure
distributions at the inlet nonstart was typical
at any Mach number studied.
Tests with the inlet were carried out using 0,
2, and 4 degree angles of attack (Figs. 18
and 19). The measurement results have
revealed that at any Mach number the air flow
rates and full pressure recovery coefficients
were smaller for 0 degree angle of attack.
This was caused by the decreasing angle of
compression on the first compression surface
and by corresponding reduction of the
entrapped jet in the undisturbed stream.
The effect of the position of the cowl leading
edge on the varying air was studied (Fig. 20).
The upstream movement of the cowl resulted
in more air captured and more intense inner
compression, i.e., the mass flow rate and total
pressure recovery coefficient increased
(Fig. 21). It is evident that in this case there
was a certain optimum position of the cowl
leading edge, which would provide inlet start
and maximum value of the airflow rate and full
pressure recovery coefficients.
The model tests in hot­shot wind tunnel
IT­302M were conducted at Mach numbers
ranging from 5 to 8 within the range
of Reynolds numbers from 5 · 10 6 to 30 · l0 6 .
The main goal of the investigations of the inlet
model was to check the adequacy of results
of tests in different wind tunnels, to obtain
the experimental data at Mach numbers from
5 to 8, to ascertain the inlet start (nonstart)
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