FR2665485A1 - GAS TURBINE ENGINE. - Google Patents

Abstract

This engine comprises two compressors (4, 6), a combustion chamber (8), a turbine (10) to drive the two compressors (4, 6), two orientable outlet nozzles (12, 14) for the first compressor ( 4), two air inlets (18) and two adjustable outlet nozzles (20, 22) for the second compressor (6). The outlet nozzles (12, 14) are disposed adjacent to the air inlets (18) and may be oriented between a first position in which the flow from the first compressor (4) exhausts to ambient air and a second position in which they coincide with the air inlets (18) and in which the flow from the first compressor (4) flows into the second compressor (6). The outlet nozzles (12, 14) are also provided with means for varying their outlet section when they are in a position other than the second position.

Description

Gas turbine engine.

  The present invention relates to gas turbine engines with variable cycle and in particular to gas turbine engines provided with orientable outlet orifices to give an airplane provided with such an engine an aptitude to carry out a flight.

  vertical or short takeoffs and landings (Adav, Adac).

  Variable cycle motors are generally presented in US Patents 3,913,321 or 4,038,818 (assigned to ROLLS ROYCE LIMITED) In general, these motors include a first axial flow compressor and a central motor

  comprising, in series for the flow, a second installation

  compressor combustion, and turbines for

  drag the first and second compressors The motors are capable of operating in two distinct modes These modes are in fact a "flow in series" mode and a "flow in parallel" mode In the flow mode in series the first and the second compressor are connected in series for flow and all the output flow from the first compressor supercharges the second compressor In the "parallel flow" mode, the output flow from the first compressor is prevented from supercharging the second compressor and

  it is evacuated to ambient air either by a bypass duct or by adjustable or fixed exhaust nozzles, and simultaneously an auxiliary air intake is opened so as to allow air to enter the second compressor.

  Variable-cycle engines of the type described above offer numerous advantages, in particular for an aircraft requiring take-off and vertical landing possibilities and also for supersonic forward flight. The efficiency of the engine can be optimized during take-off and vertical landing and flight. subsonic during parallel flow mode and optimized in forward supersonic flight: during series flow mode So, for vertical flight, the proven benefits of engines such as the Pegasus35 engine from Rolls Royce Limited (used to drive the Marrier AV 8 A British Aerospace or the AV 8 B British Aerospace / Mc Donnell Douglas can be operated while allowing efficient use of the engine in the serial flow mode for

supersonic flight.

  To allow the outlet flow from the first compressor to be selectively redirected for the series or parallel operating modes, it is usual to provide a bypass valve downstream of the first compressor

  but upstream of the second compressor.

  Examples of such deflection valves are described

  described in the above-mentioned patents The problems associated with such deflection valves reside in their complexity, weight, cost and disruptive effect on the thermodynamic cycle of the engine during the transition period from the

  serial flow mode to parallel flow mode.

  In general, the disruption to flow is due to the slow speed of actuation of the flaps and doors of the deflection valve and to the fact that many moving parts such as the doors and flaps are positioned in the path

  air flow and must be operated at the same time.

  An object of the present invention is to provide a variable cycle motor of the type described above with deflection valve means which are simple to operate, light in weight, relatively inexpensive and providing a relatively clear flow path for both

operating modes.

  The invention as claimed provides a substantially unrestricted flow path from the first compressor to the nozzles or to the inlet of the second compressor

  and uses the adjustable nozzles as deflection valves.

  This eliminates the need for additional bypass valves

heavy and costly.

  Figures 1 and 2 are respectively a plan view in partial section and a side elevation view of an engine constructed according to the present invention, showing the

engine in one configuration.

  Figures 3 and 4 are views of the engine of Figures

  1 and 2 in a second configuration.

  Figure 5 is a schematic view of a known mechanism for varying the angles of a number of rows of blades

  of stator of one of the compressors of the engine of Figures 1 to 4.

  Figure 6 is a schematic view of the mechanism for varying the outlet section of the front nozzles of the engine

of Figures 1 to 4.

  Figure 7 is a view of a modified air intake for the engine of Figure 1, allowing the aircraft to fly in flight

  front without supercharging of the central engine.

  With general reference to Figures 1 to 4 first, a gas turbine engine (12) for driving an aircraft

  so as to give it an aptitude for takeoff and landing

  sage short or vertical, includes a first compressor (4), a second compressor (6), a combustion chamber (8) and a turbine (10) to drive the compressors The flow

  air from the atmosphere enters the first com-

  presser (4) and escapes via two adjustable nozzles (12,14) The air flow enters the second compressor (6) through two inlets (16,18) arranged (as will be described with more details below) adjacent to the adjustable nozzles (12,14) and escapes via the combustion chamber

  (8) and the turbine (10) by two adjustable nozzles (20,22).

  Referring now particularly to FIGS. 1 and 2, when the engine is asked to produce a vertical thrust on the airplane, that is to say a thrust normal to the axis of the engine, the nozzles (12, 14) and (20,22) are directed downwards as shown In this configuration, the air flow entering the first compressor comes from the atmosphere at the front of the engine and the flow leaving the first compressor s escapes to the atmosphere

  to produce a vertical thrust via the nozzles (12,14).

  The air flow entering the second compressor (6)

  comes from the atmosphere via the inputs (16,18) and 11 esc-

  pement of the second compressor is evacuated to the atmosphere via the combustion chamber (8) and the turbine (10) to produce a vertical thrust via the nozzles (20,22) In this way, the compressors (4) and (6) work in parallel, producing a large mass of flow at low

  speed, suitable for takeoff.

  Referring now particularly to FIGS. 3 and 4, when the engine must provide a forward thrust on the airplane, that is to say a thrust parallel to the axis of the engine, the nozzles (12,14) are oriented rearward as shown The inlets (16,18) are arranged relative to the nozzles (12,14) so that, in this configuration, each of the nozzles (12,14) coincides with a respective air inlet (16 , 18) In this configuration the inlet to the first compressor (4) comes from the atmosphere at the front of the engine and the flow from the first compressor escapes via the nozzles (12,14) in the inlets (16 , 18) to form the intake of the second compressor The flow, coming from the second compressor (6) escapes through the chamber (8) and the turbine (10) to produce a forward thrust via the nozzles (20,22) In this way, the compressors (4) and (6) work in series, producing a smaller mass flow. at high speed than when working in parallel, as in Figures 1 and 2, making this configuration suitable for horizontal flight at high speed. In order to allow a good transfer of the flow

  nozzles (12,14) at the inlets (16,18) when the compress-

  sors work in series, a resilient seal (24,26) is provided at the edge of each entry The seals (24,26) can be inflated and are inflated, as shown in Figures 2 and 4, to ensure the sealing between each inlet and its respective nozzle when the nozzle is in coincidence

with the entrance.

  It is necessary to reduce the outlet section of the nozzles (12,14), when they are moved outside of

  their position in which they coincide with the

  very (16,18), in order to increase the pressure drop a

  through them and optimize their function in this con-

  figuration Each nozzle (12,14) is fitted with a set of variable outlet guide fins (28,30) (see Fig 6)

  in place of the outlet guide fins (28,30) is con-

  controlled by a cam (32 a), a cam path (32 b), a bent lever (33), levers (35) and push rods (34) The fins (28, 30) guide the outlet nozzle reduce the outlet section of the nozzle as soon as the nozzles exit their position in which they coincide with the inlets (16,18) During the transition period from the rear position to the down position , the

  fins (28,30) can be deflected to fold the drain

  escaping from the nozzle backwards to give

  at the substantial rear component flow.

  It will be appreciated that the space formed between the first compressor (4) and the second compressor can be used to place bulky auxiliary elements of the engine.

  such as an oil tank (36).

  It will be appreciated that the central engine, that is to say the compressor (6), the combustion chamber (8) and the turbines (10) are designed so as to operate under conditions

  widely different flow rates.

  In an operating mode (the "serial flow" mode) the air inlet to the compressor (6) is supercharged by the compressor (4) In the "parallel flow" mode the air does not is not supercharged In order to maximize the thrust it is necessary to provide a compression ratio compressor

  higher, and avoid blockage of the compressor.

  Referring to Figure 5, the compressor (6) may be provided with variable stator vanes (38), each of which is pivotally mounted at its outer end on a lug (40) Levers (42) are designed to connect each lug (40) to a connection ring (40) There is a connection ring for each row of stator blades A beam (46) is provided and is mounted on a double pivot (48) of the type described in English Patent No. 1,511,723 The beam (46) comprises rods (50) mounted on universal joints (52) and the rods (50) are connected to the connecting rings (44) by universal joints (54) A motor (56), which actuates a drive screw (56 a) which screws into a nut (58) fixed on the end, which would otherwise be free, of the beam (46) is provided to move the beam ( 46) around the axes (60,64) and consequently rotate the connection rings (44) The blades (38) are connected es to the connecting rings by levers (66) and universal joints (68) A rotation of the rings (44) simultaneously causes the

  -rotation of roofs the stator vanes (38) in each row.

  this mechanism is fully described in the patent

English NI 1,511,723.

  In addition or as an alternative, the turbines may be provided with variable position guide vanes (70) in order to

  to control the flow through the turbines.

  In addition or as an alternative, the flow through the central motor can be controlled by means of variable section nozzles. Many well-known means are possible for varying the section of the nozzles. One of them can employ an asymmetrical arrangement of petals (not shown) or a two-dimensional nozzle using one or more displaceable plates (72) which can be moved to modify the section of the nozzle by means of a motor (73) which drives a screw jack by means of drive shafts

  hoses (76) and a gearbox (77).

  In addition or as an alternative, the inlet guide vanes (74) of the compressor (4) can be of variable geometry. The inlets (16) can be repositioned, as shown in Figure 7, so that the nozzles (12,14) are = turned to a position slightly towards

  the top when they must coincide with the entries (16,18).

  A subsonic cruising speed can be obtained, without supercharging the central engine, by rotating the nozzles (12,14) towards a position in which they evacuate towards the rear. If necessary, the outlet guide fins in the nozzles , 14) can be deflected to fold the flow backwards in order to increase the forward thrust In all positions of the nozzles (12,14) upwards until they coincide with the inlets (16 , 18), the outlet sections are reduced. In yet another embodiment (not shown) the air inlets (16) can be designed so as to allow a "bypass" or deflection mode of operation in which, when the nozzles (12, 14) are directed backwards (but not fully matching inlets (16)), part of the nozzle flow (12,14) is discharged into the central motor and part is discharged rearwards but not through the central motor In this case, a shutter shutter (not re-presented 15) would be provided at the edge of each inlet The shutter shutter would operate so as to close each inlet

  air (16) to a section equal to the section of each part of each nozzle (12,14) communicating directly with the interior of the air inlet.

Claims (10)

  1. Gas turbine engine comprising a first compressor (4); a second compressor (6); a combustion chamber (8); turbine means (10) for driving the first and second compressors; first inlet means for causing a flow to enter the first compressor (4); first outlet means (12,14) for evacuating the flow coming from the first compressor (4) second inlet means (16,18) to cause a flow to enter the second compressor (6>, and second means outlet (20,22) for discharging the flow from the second compressor (8) via the combustion chamber (8) and the turbine means (10), characterized in that the first outlet means (12,14) can be oriented between a first position in which the flow coming from the first compressor is evacuated to the ambient air and a second   position in which the first outlet means (12,14) coincide with the second inlet means (16,18) and the flow coming from the first compressor (4) flows into the second compressor (6).   2. Gas turbine engine according to claim 1, characterized in that resilient sealing means (24,26) are provided for sealing between the first outlet means (12,14) and the second means   input (16,18) when the first output means (12,14) are in the second position.   3. Gas turbine engine according to claim 2, characterized in that the resilient sealing means (24,26) are inflatable.   4 gas turbine engine according to claim 1, wherein the optimum flow of the working fluid to   through the engine is that for which the first outlet means (12,14) are in the second position and the first and second compressors (4,6) each rotate at a predetermined speed, characterized in that means for controlling the are provided to control the flow   working fluid through the first compressor (4), the second compressor (6) and the turbine means (10) to prevent blockage of the first (4) and second (6) compressors during operation at these speeds predetermined or below.   5 G gas turbine engine according to claim 4, characterized in that the control means comprise stator vanes (38), whose angle of attack is variable by   to change the flow through the engine.   6. Gas turbine engine according to claim 4, characterized in that the control means comprise means for varying the outlet section of the first outlet means (12,14) so as to produce a smaller outlet section when the first exit means (12,14) are in any position other than the second position.   7. Gas turbine engine according to claim 4, characterized in that the control means comprise means for varying the outlet section of the second output means (20,22).   8 gas turbine engine according to claim 1, characterized in that the first outlet means (12,14)   can be moved to a third position, inter-   medial between the first and the second position, in which the first outlet means (12,14) partially evacuate in the second air inlet means (16,18) and also backwards along the second means of 'air inlet (16,18), and in that sealing means are provided to limit the section of the second air inlet means (16,18) to a section equal to this part of the first means outlet (12,14) which discharges into the second means of entry.   9. gas turbine engine according to claim 1, characterized in ceqie the first outlet means (12,14)   can be moved to a third inter-   medial between the first and second positions, the first outlet means (12,14) discharging rearwards along the second air inlet means (16,18) but   not discharging into the second air inlet means.   10. Gas turbine engine according to claim 1, characterized in that the first outlet means (12,14)   are provided with a plurality of flow deflection fins-   ment extending across the flow path by the first outlet means (12,14), and in that the fins   are movable so as to deflect a flow of gas coming therefrom; first exit means (12,14), backwards during the period of passage of the first exit means10 (12,14) from their second position to their first position.