Integrated turboramjet engine

A change-over arrangement for an integrated turboramjet engine has a guide ring which can be displaced in the axial direction and an annular cone which can be displaced against the guide ring. In the turbo-operation, the annular cone is in its front position and the guide ring is in its rear position closing off a ram air inlet duct, and in the ramjet operation, the annular cone, in its rear position, closes off the turbo-inlet duct, and the guide ring opens up the ram air inlet duct. As a result, a low-loss introduction of the air current can take place into the turbo-inlet duct or into the ram air inlet duct, without, at the same time, requiring disadvantageous enlargements of the diameter of the outer casing of the engine.

BACKGROUND AND SUMMARY OF THE INVENTION 
The invention relates to an integrated turboramjet engine for a hypersonic 
airplane having a common air inlet for the turbo-circuit and the ramjet 
circuit. An annular turbo-inlet duct and a ram air inlet duct which 
concentrically surrounds this turbo-inlet duct are provided. On the 
exterior side the ram air inlet is delimited by an engine casing. An inlet 
cone and movable devices for the deflecting of the air current from the 
common air inlet into one of the two inlet ducts is provided. 
Endeavors are taking place to develop hypersonic airplanes which can take 
off and land on normal airports and develop cruising speeds of several 
Mach. Hypersonic airplanes of this type may be used either as fast 
long-distance transport planes or as normally starting space tugs. The 
achievable Mach numbers range between Mach 4 and 8 at flying altitudes of 
approximately 30 km. 
Engines for propelling such airplanes must meet a number of requirements 
which cannot be reached by means of conventional engine concepts. Thus, a 
sufficient power output must take place at low flying speeds below Mach 1 
up to the peak speeds. For this purpose, it was suggested to provide 
combined turboramjet engines which at low flying speeds operate as a gas 
turbo-engine with or without an afterburner and, above a certain flying 
speed, operate as ramjet engines (RAM-operation). 
A construction of such engines provides that a gas turbo-engine is equipped 
on both sides with flaps, and an afterburner downstream of the gas turbine 
is simultaneously used as a ramjet burner chamber. For this purpose, an 
annular ram air duct is provided concentrically outside the gas turbine 
through which, during ramjet operation, the inflowing air is guided 
directly into the combustion chamber while bypassing the gas turbine. For 
this purpose, movable guide plates are provided in the area of the inlet 
duct and behind the turbine, these guide plates selectively guiding the 
air current either into the concentrically interior turbo-inlet duct and 
thus through the gas turbine core engine, or into the concentrically 
exterior ram air inlet duct. 
It is a considerable problem in the case of such change-over engines that 
the outside diameter of the engine must be kept as small as possible. Its 
minimum measurement is determined by the cross-sections of the two inlet 
ducts as well as the inside diameter required in the hub area for the core 
engine. 
A conceivable, constructively very simple possibility for the alternative 
acting upon the inlet ducts consists of providing an axially slidable 
guide plate ring which, in a first position, closes off the ram air inlet 
duct and in a second position closes off the turbo-inlet duct. However, 
this type of a solution has the disadvantage that the inlet duct carry out 
up complex courses and an outside diameter of the engine is required which 
exceeds the minimum diameter. Such enlargements of the diameter which are 
in the range of several decimeters, at high speeds, because of the 
enlarged cross-sectional surface, result in an increased flow resistance. 
It is therefore an object of the present invention to develop a turboramjet 
engine of the above-mentioned type such that a deflection of the air 
current into the two inlet ducts is possible without the requirement of an 
enlargement of the outside diameter of the engine. 
According to the invention, this object is achieved by means of an 
arrangement, wherein the devices for the deflecting of the air current 
comprise a guide ring which can be displaced in the axial direction along 
the engine casing for the closing-off of the ram air duct as well as an 
annular cone which is disposed radially inside with respect to the guide 
ring and can be displaced in the opposite direction for the closing-off of 
the turbo-inlet duct, the contour of the guide ring forming the duct wall 
and the annular cone having a construction which is advantageous with 
respect to the flow. 
The principal advantage of the invention is that despite the fact that the 
minimum diameter defined by the inlet ducts is maintained, a deflection of 
the air current into the two inlet ducts is possible, in which case, at 
the same time, a low-loss housing contour of the flow ducts can be 
achieved. In addition, by means of this arrangement, a maintaining of the 
engine output is also achieved in the critical moment of the change-over 
from the turbo-operation to the ramjet operation in that the approaching 
air, in a targeted and continuous manner, can be deflected from one inlet 
duct in connection with the closing device behind the turbine into the 
other inlet duct. Additional advantages of the invention are the short 
installation length of the closing device and the short strokes of the 
adjusting arrangements. Also, during the ramjet operation, good cooling 
possibilities exist for the thermally stressed inlet cone and the annular 
cone by means o film cooling as a result of the blowing-in of cold air. 
In an advantageous further development of the invention, the guide ring has 
an approximately conically tapering front side and a connecting 
approximately conically tapering rear side. The guide ring is therefore 
constructed to be approximately wedge-shaped, in which case the front side 
is shaped out for forming an aerodynamically advantageous flow contour of 
the turbo-inlet duct during the turbo-operation In this operating 
condition, the guide ring is in its axial rear position, and its front 
side is advantageously shaped such that the wall contour from the outside 
casing to the intermediate casing, which at the same time also represents 
the outer boundary of the turbo-inlet duct, causes the lowest possible 
flow losses. The rear side of the guide ring is developed such that, while 
interacting with the annular cone, during the ramjet operation, it defines 
an annular duct connected with a ram air inlet duct. For this purpose, the 
rear side is preferably constructed to be conical. 
During the ramjet operation, the guide ring is in its axially frontal 
position, in which case, at the same time, the annular cone is arranged 
slightly behind and radially inside the guide ring. In this case, the rear 
side of the guide ring defines the frontal section of the exterior wall of 
the ram air inlet duct. At the same time, the annular cone is shaped such 
that a continuous flow course is possible from the inlet cone to the 
intermediate casing. 
The ring edge between the front side and the rear side of the guide ring is 
also shaped such that during the ramjet operation a flow loss occurs in 
this area that is as low as possible. 
Another advantageous development of the invention consists of the fact that 
the frontal axial position of the annular cone is fixed in such a manner 
that the annual duct formed between the annular cone and the inlet cone 
has at least the cross-section of the ram air inlet duct. This arrangement 
has the advantage that during the changing-over from the turbo-operation 
to the ramjet operation, after the opening of the ram air inlet duct, 
sufficient air can be admitted to the ram air inlet duct by the advancing 
of the guide ring. 
A further development according to the invention provides that, for the 
changing-over from the turbo-operation to the ramjet operation, the guide 
ring can first be slid from an axially rear position toward the front, and 
subsequently, the annular cone is displaced from an axially frontal 
position toward the rear. Approximately at the same time with the 
advancing of the guide ring, a closing flap will close arranged downstream 
of the core engine so that no more air is taken into the turbo-inlet duct; 
i.e with the advancing of the guide ring, the ram air inlet duct is opened 
up and the approaching air is guided into it. Then the annular cone is 
moved from a frontal position toward the rear and, in its end position, 
closes off the turbo-inlet duct completely. 
As an alternative, it is also possible to carry out the two movements of 
the guide ring and the annular cone in opposing directions not 
successively but partly or completely simultaneously. As a result, the 
change-over time from the turbo-operation to the ramjet operation and vice 
versa can be advantageously shortened. 
The annular cone preferably has the continuation of the contour of the 
inlet cone and, if required, may have a bend, preferably a convex bend 
viewed from the inflow direction, if the inlet cone has a bend of this 
shape. 
The annular cone can be moved axially by means of adjusting devices, in 
which case, at the same time, the axial guiding and locking in certain 
positions will take place. 
Other objects, advantages and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS 
FIG. 1 is an axial view of an integrated turboramjet engine 1 which can be 
changed over from the turbo-operation to the ramjet operation. It 
comprises essentially a gas turbine 2 with injection arrangements 3 which 
operate as an afterburner injection arrangement in the turbo-operation and 
as ramjet injection arrangements in the ramjet operation, in which case 
the ram air, by way of the annular duct 4, while bypassing the gas turbine 
2, is supplied directly to an afterburner pipe arranged behind the 
injection arrangements 3. 
The gas turbine 2 comprises a 6-stage compressor 5 behind which a 
combustion chamber 6 and a single-stage turbine 7 is connected. The 
compressor 5 and the turbine 7 are connected with one another by means of 
a common shaft 8. It is also possible to construct the engine as two- or 
three-shaft engine according to the requirements, without leaving the 
scope of the invention. The weight forces and the gas forces generated in 
the gas turbine 2, by way of several supporting ribs 9a, 9b distributed 
over the circumference are guided to the engine casing 10 which, in turn, 
is fastened to the airplane. 
In the position shown in FIG. 1, the turboramjet engine 1 is in the 
turbo-operation; i.e., the air approaching in the common air inlet 11 is 
guided into the turbo-air inlet duct 12 and leaves the gas turbine 2 at 
the gas turbine outlet 13 while flowing around the injection arrangement 3 
and flowing into the afterburner pipe 33. 
For the changing-over from the shown turbo-operation to the ramjet 
operation, a guide ring 14 and an annular cone 15, in the area of the air 
inlet 11, are displaced axially against one another in such a manner that 
the turbo-air inlet duct 12 is closed and a ram air inlet duct 16 is 
opened up which is arranged concentrically outside this turbo-air inlet 
duct 12. As a result, the air current arriving in the air inlet 11, while 
bypassing the gas turbine 2, by way of the ram air inlet duct 16 and duct 
4, is supplied directly to the afterburner pipe 3. At the same time, 
during the ramjet operation, a closing ring 17 is slid axially toward the 
rear against the position shown in FIG. 1, and as a result, closes off the 
gas turbine outlet 13. 
The interaction of the guide ring 14 and the annular cone 15 according to 
the invention is shown in FIGS. 2 and 3 in an enlarged representation for 
the ramjet operation and for the turbo-operation. 
In the position shown in FIG. 2, the turboramjet engine 1 is in the ramjet 
operation s that the turbo-air inlet duct 12 is closed off by means of the 
annular cone 15. At the same time, the ram air inlet duct 16 is connected 
with the common air inlet 11. For this purpose, the guide ring 14 is moved 
into its axial frontal end position. The annular cone 15 has a shape which 
aerodynamically represents a continuation of an inlet cone 18 which guides 
the air jet in the area of the air inlet 11. In this case, the annular 
cone, on the interior side, rests sealingly against the inlet cone 18 and, 
on the exterior side, against the intermediate casing 19 which separates 
the turbo-air inlet duct 12 from the ram air inlet duct 16 which surrounds 
it radially. By means of an adjusting arrangement 20, the annular cone 15, 
if required, can be displaced from an axial rear end position toward the 
front and is also held and guided by this adjusting arrangement 20. These 
adjusting arrangements 20 are supported in the inlet cone 18. As an 
alternative, it is also possible to house these adjusting arrangements in 
the intermediate housing 19 and to connect them with the rear edge of the 
annular cone 15 by means of rods as shown in FIG. 4. The latter 
arrangement will be particularly advantageous if the intermediate casing 
19 has a sufficient thickness. 
In the shown position, the front edge 21 sealingly ends at the engine 
casing 10. The rear edge 22 sealingly rests against an annular molded body 
23. The rear side of the guide ring 14 has such a shape that, together 
with the molded body 23, it permits a low-loss introduction of the air 
current located at the air inlet 11 into the ram air inlet duct 16. The 
guide ring 14 can be moved axially in the opposite direction to the 
annular cone 15 by means of the guide ring adjusting arrangement 25, while 
being guided along the molded body 23. In this case, the two adjusting 
arrangements 20 and 25 can be operated independently of one another. 
As an alternative, it is also possible to leave the molded body 23 out 
completely and to construct the guide ring 14 correspondingly longer. This 
arrangement has the disadvantage, however, that the radially exterior row 
9b of supporting ribs must be displaced axially to the rear, and thus a 
less advantageous guiding of the gas forces and of the weight forces takes 
place from the gas turbine 2 into the engine casing 10. In the ramjet 
operation, all movable parts, thus particularly the guide ring 14 and the 
annular cone 15, are firmly braced and have a sealing effect, and all 
propulsion and guiding elements, particularly the adjusting arrangements 
20, 25 and the push rods 27 and holding struts 26 are housed in a sealed 
and thermally protected manner in order to prevent that they are acted 
upon by the hot approaching air of approximately 2,200 K. 
The guide ring adjusting arrangement which, at the same time, serves the 
axial guiding and fixing is housed in the molded body 23 and is sealed off 
against hot air. 
FIG. 3 shows the arrangement according to the invention in the 
turbo-operation; i.e., that the turbo-air inlet duct 12 is connected with 
the common air inlet 11, while the ram air inlet duct 16 is closed. For 
this purpose, the annular cone 15 is in a position which is moved axially 
toward the front in comparison to FIG. 2, which is carried out by means of 
the adjusting arrangement 20. The annular cone 15 is connected with the 
adjusting arrangement 20 by means of a row of radially aligned holding 
struts 26 which, in turn, are connected with axially movable push and 
guide rods 27. The push and guide rods 27 and the holding struts 26, in 
their cross-section, are constructed to be advantageous with respect to 
the flow, in which case, an increased bending strength can be achieved 
preferably by means of a drop-shaped cross-sectional profile in addition 
to a favorable flow contour. The inlet cone 18 has a number of axial 
grooves 28 into which the holding struts 26 can be moved in the ramjet 
operation in order to interfere as little as possible with the flow 
contour of the inlet cone 18. In the turbo-operation, the guide ring 14 is 
in its axial rear end position while at the same time the molded body 23 
is completely covered with respect to the air flow. In this case, the 
front side 29 of the guide ring 14 is shaped out such that a flow contour 
can be achieved from the interior side of the engine casing 10 to the 
intermediate casing 19 which is as favorable as possible. 
For this purpose, its upstream front section is shaped to be concave and 
its rear section is shaped to be convex. The contour is constructed to be 
such that the front side 29, together with the rear side of the inlet cone 
18, has a cross-section which narrows down from the air inlet 11 to the 
turbo-air inlet duct 12 in order to accelerate the flow and prevent flow 
separations. 
At the same time, the guide ring 14, on the interior side, has a sealing 
effect with respect to the intermediate casing 19, and, on the exterior 
side, has a sealing effect with respect to the turbine casing 10 in order 
to prevent that heating gases from the gas turbine outlet 13 flow back 
backwards by way of the duct 4 into the turbo-air inlet duct 12. The 
sealing of the guide ring 14 on the exterior side may also take place with 
respect to the molded body 23 in order to reduce the sealing forces. 
With respect to their length, the guide ring 14 and the molded body 23 are 
coordinated with one another in such a manner that the rear edge 22 of the 
guide ring 14 ends shortly in front of the supporting ribs 9b. These 
supporting ribs 9b, in turn, should be radially aligned with the 
supporting ribs 9a in order to ensure a load transmission that is as 
favorable as possible. Because of the high temperatures occurring in the 
ramjet operation, the engine casing 10 is constructed as an insulating 
casing which explains its large thickness. However, in the 
turbo-operation, such a thickness is not required so that the engine 
casing 10, without increasing the outside diameter, viewed from the 
interior may be concavely curved in area 30 in order to achieve an 
improved transition to the front side 29 of the guide ring 14 and permit 
an increased diameter of the inlet cone 18 while the flow cross-section is 
maintained at the same time. 
The axial front position of the annular cone 15 is advantageously selected 
such that the annular duct 31 defined between the annular cone 15 and the 
inlet cone 18 has a cross-section which corresponds at least to the 
cross-section of the ram air duct 16. In this case, the engine casing, the 
annular cone and the inlet cone are coordinated such that the conditions 
of the flow cross-sections from the annular duct between the engine casing 
and the annular cone to the annular duct are the same at the inlet and the 
outlet. This takes place in order to deflect the air current located in 
the annular duct 16 into the ram air inlet duct 16 during the change-over 
from the turbo-operation to the ramjet operation. The reason is that, for 
the change-over, the guide ring 14 is first pushed toward the front 
whereby the exterior ring duct 32 defined between the annular cone 15 and 
the engine casing 10 is increasingly closed. As a result, the ram air 
inlet duct 16 is opened at the same time so that the air current located 
in the interior annular duct 31 is deflected more and more from the 
turbo-air inlet duct 12 to the ram air inlet duct 16. After, 
simultaneously with the advancing of the guide ring 14, the closing ring 
17 (FIG. 1) of the ga turbine outlet 13 was pushed toward the rear and 
therefore the throughput through the gas turbine 2 was stopped, the air 
current is necessarily also deflected into the ram air inlet duct 16. By 
means of the subsequent moving-back of the annular cone 15, a contour from 
the inlet cone 18 to the exterior wall of the intermediate casing 19 is 
produced which is advantageous with respect to the flow. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.