plateau. I will take thls opportunity to chal-
lengeanddispel that thoughtfor thosewhofeel
that to be the case. I believe that significant
technologicaladvancesare yet to bemade. In
somecasesthese advances, If achieved, could be
considered as breaking tecnnologlcal barriers,
with potential payoffs making them revolutionary
in nature. I realize that most people vlew the
advances In turbomachlnery technology as evolu-
tionary, and to a large extent they have been.
Coupled with the potentla] to significantly
Impact the present state of compressor technology
are the strong needs and unique opportunities to
do so. Historically. the technology has been
driven by a need for enhanced capabIIitles to
meet the requirements of advanced aircraft mis-
sions. As we approach the 21st century, advanced
aircraft missions wlth demanding propulsion sys-
tem requirements are being considered for both
subsonic and supersonic flight. Examples are
ultra-hlgh-bypass-ratlo turbofan engines for
advanced subsonic transports and advanced super-
sonic propulsion systems for long-range super-
sonic transports.
The purpose of thls paper is flrst to brlefly
review the most significant technological advances
to date and then, wlth history as a background,
to project a bright view of the future that
reflects the need and plans to further advance
compression system technology. In tracing the
history of compressor development for aircraft
propulslon systems, selected examples are noted
to help portray the advances In technologies that
have taken place. The examples chosen were llm-
ited to those available in the open literature.
Many different examples exist, but out of the
need fcr brevity, only a few were chosen. If I
have left out your favorite examples, I
apologize.
In looking to the future I discuss some con-
cepts now being studied at the Lewis Research
Center that I believe have the potential for slg-
nlflcantly impacting the design and performance
of future compressor and engine systems for
selected aircraft applications. One such con-
cept being studied for supersonic flight Is the ,
processing of the flow supersonically through
the fan stage at supersonic flight speeds, thus
reducing the need for a long, heavy supersonic
inlet.
The status of transltlonlng from an emplrl-
cally derived design system to a computatlonally
oriented system Is highlighted and includes an
experimental program being pursued at the Lewis
Research Center to enhance thls process. And
last, I present a view of the future In which I
believe there wlll be a strengthening of the
synergisms between deslgn systems and designers
of the various turbomachlnery components, whether
it be pumps or turbines for rocket engines: com-
pressors, fans, propellers, or turbines for air-
breathing engines; axial, mixed flow, or radial;
single stage or multistage; large or small.
The coalescence of several technologles has
normally resulted in the largest overall advance-
ments in the various components of the gas tur-
bine engine. This has been especially true for
2
the compressor. However, this paper emphasizes
the advances In compressor aerodynamlcs, both
steady and unsteady, since the malor Improvements
in compressor performance have come about through
advances in the aerodynamic design. In compari-
son, the turbine advancements have come about
prlmarlly from the applicatlon of advanced high-
temperature materials coupled with advances In
turblne cooling technology.
HISTORICAL PERSPECTIVE
A historlcal perspective on the design and
development of compressors for alrcraft gas tur-
bine engines must start wlth the Whittle and
von Ohaln engines, It Is interestlng to note
that Whlttle's 1930 patent dlsclosure (Flg. I)
showed two axlal-flow compressor stages followed
by a centrifugal stage, a configuration common
In the smaller gas turblne engines of today.
However, In hls 1939 patent disclosure (Fig. 2)
he showed a double-entry, slngle-stage centrifu-
gal. Hls W-I and W-2 engines Incorporated the
double-entry concept. A cutaway vlew of a
General Electrlc early prototype turbojet based
on Whlttle's W-2 design Is shown In Fig. 3. The
double-entry impeller can be seen in the figure.
Tests of Whittle's W-I engine began In 1941, and
on May 15, 1941, he brought Britaln Into the jet
age when his W-I engine propelled the G1oster
E.28/39 aircraft on Its flrst flight.
Dr. yon Ohaln designed and bullt three dlf-
ferent engines, culmlnating In the He.S.3B
englne, which on August 27, 1939, propelled the
He 178 aircraft on the world's first Jet-
propelled flight. Thls engine incorporated a
slngle-stage centrlfugal. Two years later he
developed the He.S.8A engine for the He 280 alr-
craft, the first Jet flghter aircraft. A cut-
away vlew of thls engine Is shown In Fig. 4. The
compressor conslsted of a single axlal-flow rotor
followed by a centrlfugal stage. Later, he
Exhaustnozzle(iet)
/-Combustionchamber \
y/ ,/-Fuelspraynozzle \
lurbine --_ ....
r_(
F_aust-"nozzle(jet>_
Figure 1. - 1930 Patent disclosure by Whlttle.