GB2069612A - Gas Turbine Power Plant - Google Patents

Abstract

Known reheated aircraft gas turbine power plants are constructed in a way which does not allow for separation of the reheat equipment from the primary engine during aircraft flight. A weight and drag penalty is thus incurred, when reheat is not being used. This specification describes a gas turbine power plant (10) including a reheat pipe (22) which is fastened to the downstream end of the primary power plant nozzle at (18), and to the power plant supporting pylon (12), at (24), by catches (44, 60 and 62 not shown) which can be released by actuation of rams (40, 68 and 70 not shown). Take off can be boosted and then the reheat pipe (22) detached, to reduce weight and drag at cruise. <IMAGE>

Description

SPECIFICATION Gas turbine power plant This invention relates to a gas turbine power plant of the kind used for the propulsion of aircraft.

Presently known power plants of the kind which propel aircraft, have effectively either a single combustor stage to enable a once only expansion of gases, or two combustor stages, the second of which provides a further gas expansion or reheat stage and includes a thrust nozzle.

The reheat stage where fitted, provides a temporary booster facility which enables higher speeds to be attained over short periods, than would be available without such equipment. It further makes available, more thrust which may be used to assist take off of an aircraft having power plants which include reheat equipment.

A drawback of the known arrangements is that, the reheat equipment, which is of considerable weight and creates an increase in the overall length of the power plant and therefore, an increase in skin friction drag, has to be carried throughout the flight of the aircraft, even though it is required to be used for only a very small portion of the aircraft flight time. Such penalties are too severe, for the equipment to be considered for use on power plants for commercial aircraft.

The present invention seeks to provide an aircraft gas turbine power plant having improved booster means.

According to the present invention, an aircraft gas turbine power plant comprises in flow series, a compressor, a first combustor stage, a turbine, a first propulsion nozzle and a conduit containing a second combustor stage and propulsion nozzle, the second combustor stage including its own fuel feed means, the conduit with its contents being detachably attached at its upstream end to the structure forming the first propulsion nozzle and intermediate its length to a nylon by means of which the power plant is connected to an aircraft such that the conduit may be discarded during flight of an aircraft propelled by said gas turbine power plant.

The invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side elevation of a gas turbine power plant according to an embodiment of the present invention, Figure 2 is an enlarged, cross sectional part view on line 2-2 of Fig. 1, and Figure 3 is an enlarged part view on line 3-3 of Fig. 1.

In Fig. 1 a gas turbine power plant 10 is shown suspended via a pylon 12, from beneath the wing 1 4 of an aircraft.

Gas turbine power plant 10 is encased in a streamlined cowl 1 6 in known manner and, in the present example, includes a ducted fan (not shown) upstream of a compressor, combustor and turbine, none of which are shown, but which are arranged in conventional manner with respect to each other.

The duct (not shown) of the ducted fan (not shown) terminates in a propulsion nozzle the outlet plane of which is indicated by the numeral 1 8. Similarly the core gas generator which drives the ducted fan (not shown) terminates in a propulsion nozzle the outlet of which terminates in the plane indicated by numeral 20.

A conduit 22 is arranged coaxially with gas turbine power plant 10 and has its upstream end fastened to that part of the structure of the gas turbine power plant 10, which forms the ducted fan propulsion nozzle, the join being in the region of nozzle outlet plane 1 8.

The fastening means will be described later in this specification.

Conduit 22 is further supported from pylon 12, by means 24 which will also be described later in this specification.

Conduit 22 contains reheat gutter 26 which in operation receive fuel from a store (not shown) in the aircraft via a fuel pump and fuel control unit in a housing 28, affixed to the outer surface of conduit 22.

Conduit 22 terminates in a propulsion nozzle 30, which emits gases generated by the mixing of fuel from reheat gutters 26 with fan air expelled from the nozzle of the ducted fan (not shown) and hot gases expelled from the core gas generator (not shown), and igniting the mix.

Referring now to Fig. 2. Cowl 1 6 has a number of equi-angularly spaced depressions 32 at its nozzle end, which form local shoulders 34. Conduit 22 has a piston ring sealing arrangement 36 which fits into cowl 1 6 and carries a number of blocks 38 each of which, supports a respective ram and rod assembly 40.

Each block 38 has an extension 42, the free end of which has a link 44 pivotally attached thereto, intermediate the link ends.

The free end of each link locates in a respective depression 32 in abutting engagement with the shoulder 34. Cowl 1 6 and conduit 22 are thus axially aligned and locked against separation.

Streamlined pods 49 are afixed to conduit 22 and extend over the locking mechanism.

Conduit 22 is further supported from pylon 12, by a link structure 46 as shown in Fig. 3.

A plate 50 is positioned by dowelling 52 against the underside of pylon 1 2. Plate 52 has a local flange 54 to which one end of each of a pair of links 56 is pivotally attached.

The other ends of the links 56 are pivotally attached to a web 58 on conduit 22. Links 56 are aligned such that their longitudinal axes are tangential to the outer surface of conduit 22. The function of links 56 is to counter any tendency of conduit 22 to rotate about its axis.

Plate 50 is retained against pylon 12, by a pair of catches 60, 62 which are pivotally supported from extensions 64, 66 from pylon 1 2. A pair of rams 68, 70 are also supported from pylon 1 2 and connected via rods 72, 74 to respective catch ends.

The whole retention assembly is enclosed by the pylon streamlined skin 12a.

In operation of an aircraft which is propelled by a power plant of the kind described in this specification, the reheat equipment is activated so as to assist take off. When used in conjunction with a ducted fan gas turbine engine as described herein, the reheat can give a thrust boost of up to 50% of normal thrust i.e. thrust without reheat and in consequence, the take off run is ultra short.

On reaching cruise altitude, the catches 44, 60 and 62 are released by remote actuation of their respective rams 40, 68 and 70 and conduit 22 falls away, leaving the thrust nozzles of the fan and gas generator exposed.

The rams 40, 68 and 70 could be actuated hydraulically, fuel being the fluid used to generate the necessary forces, to maintain the respective catches in the conduit locked positions. Appropriate diversion of the fuel pressure on command from the pilot, would result in the releasing of the catches. The powering of rams in such a manner, is well known in the aircraft gas turbine art and avoids the necessity of providing extra tankage to hold hydraulic fluids. Weight and/or space volume are thereby kept to a minimum.

The fuel line connections from the aircraft tanks, to the reheat equipment, could be of the plug in type which is also well known in the aircraft gas turbine art, so as to simply pull apart on separation of conduit 22. Resiliently loaded stops would then move to block the aircraft mounted fuel line nozzles (not shown).

Although the invention has been described herein, as including a ducted fan with a gas turbine engine, the skilled man will realise, that a simple jet propulsion engine could also be provided with a discardable reheat system.

Similarly explosive bolts or other means which are capable of remote release, may be substituted for the rams and catches described herein.

Claims (5)

1. An aircraft gas turbine power plant comprising in flow series, a compressor, a first combustor, a turbine, a first propulsion nozzle and, a conduit containing a second combustor and propulsion nozzle, the second combustor including its own fuel feed means, the conduit with its contents being detachably attached at its upstream end to the structure forming the first propulsion nozzle, and intermediate its length to a pylon by means of which the power plant is connectable to an aircraft, such that the conduit may be deliberately discarded during flight of an aircraft propelled by said gas turbine power plant.
2. 2. An aircraft gas turbine power plant as claimed in claim 1 including a ducted fan upstream of the compressor.
3. 3. An aircraft gas turbine power plant as claimed in claim 1 or 2 wherein the conduit is detachably attached to the structure forming the first propulsion nozzle and intermediate its length to said pylon, by catches which are held in and moveable from, a conduit locking position by hydraulically operated rams.
4. 4. An aircraft gas turbine power plant as claimed in claim 3 wherein the power plant fuel is utilised for providing ram pressures.
5. 5. An aircraft gas turbine power plant substantially as described in this specification with reference to the drawings.