GB2198228A

GB2198228A - An auxiliary gas turbine plant for supplying cabin air in an aircraft

Info

Publication number: GB2198228A
Application number: GB08722757A
Authority: GB
Inventors: Karl-Heinz Collin
Original assignee: Kloeckner Humboldt Deutz AG
Current assignee: Kloeckner Humboldt Deutz AG
Priority date: 1986-09-29
Filing date: 1987-09-28
Publication date: 1988-06-08
Anticipated expiration: 2007-09-28
Also published as: FR2604480A1; GB8722757D0; DE3633090A1; GB2198228B

Abstract

An auxiliary gas turbine plant 4 drives a work turbine 8 connected to an air supply device 10. The turbine plant takes its air supply 3 from a cabin 1 supplied by the device 10. The gas turbine is preferably a two shaft plant. <IMAGE>

Description

An auxiliary gas turbine plant This invention relates to an auxiliary gas turbine plant for use in aircraft wherein a work turbine of the plant is arranged to drive at least one air-supply device.

An auxiliary gas turbine plant serving to start an aircraft's propulsion unit or units and to operate its ancilliary equipment is known from DE-OS-23 25 592. The plant remains in operation throughout the entire flight of the aircraft so as to supply, for example, conditioned air to the cabin. The air required for operating the auxiliary gas turbine plant is tapped from the compressor(s) of the main propulsion unit(s). A disadvantage of such an arrangement is that the main propulsion unit(s) must be operated, especially at high altitudes, at a higher performance level than flying conditions actually call for, and this merely for supplying sufficient air to the auxiliary gas turbine plant.This is particularly the case when, after the aircraft has reached its ceiling altitude and has started to descend, the main propulsion unit(s) require to be operated, merely for aerating the cabin, at a higher performance level than the flying conditions demand.

It is also known to supply the auxiliary gas turbine plant exclusively with air drawn from the atmosphere. Even this arrangement however necessitates operating the auxiliary turbine plant with increasing flight altitude at an increased performance level, the reason being that the air pressure in the cabin must be kept constant but that the auxiliary turbine plant's output drops as a result of the decreasing air density.

It is therefore an aim of the present invention to increase the power output of an auxiliary gas turbine plant at high altitudes.

This aim is achieved, in accordance with the invention, by arranging for the auxiliary gas turbine plant to suck in air from, and at the pressure level prevailing in, the aircraft's cabin and release it into the atmosphere through the work turbine. This measure considerably increases the auxiliary turbine plant's power output compared with that of an auxiliary turbine plant which is supplied with air drawn from the atmosphere. If an attempt were made to achieve an output of the same magnitude by the use of an auxiliary gas turbine plant arranged to suck in air from the atmosphere, such an auxiliary turbine plant would have to be dimensioned for a performance level which, depending on the flight altitude, is up to five times greater than that required for its operation at ground level.Leaving out of account the enormous turbine weight this would entail, the plant would still have to be kept in operation, even when little use if made of it, because a wide operating range has to be covered.

The auxiliary gas turbine plant is constructed, in one preferred embodiment of the invention, as a two-shaft arrangement.

It is advantageous if a gas generator turbine is operated at a constant level. This does not pose any problem in the present instance as the pressure of the cabin air which is supplied to a compressor of the generator turbine in the plant is constant. Any adjustment necessitated by the prevailing atmospheric pressure is effected, according to the invention, by the work turbine which is the only one to operate in different partial-load regions. Such a control permits the generator turbine of the plant to always work at its best operating level.

Further improvements provided by the invention for an auxiliary gas turbine plant will become evident from the following description of the accompanying drawings, which illustrate an example of a plant in accordance with the invention. In the drawings Figures 1 to 7 show, by means of charts, different effects on the power consumption of an air-supply device and include performance charts of a conventional auxiliary gas turbine plant and that of a plant according to the invention; and Figure 8 illustrates how an auxiliary gas turbine plant according to the invention is connected to the cabin of an aircraft.

The graph of Figure 1 represents the rate of increase of the air-supply device's power consumption in relation to the flight altitude. It is evident that this rate increases with increasing altitude.

The graph of Figure 2 represents the rate of cabin air-flow at ground level relative to flight altitude.

The graph of Figure 3 represents the pressure rate of the air-supply device in relation to the flight altitude.

The line 1 in Figure 4 represents the "load-compression pressure", line 2 the cabin pressure, and line 3 the atmospheric pressure, all relative to the flight altitude.

The graph of Figure 5 represents the atmospheric temperature relative to the flight altitude.

The broken line 1 in Figure 6 represents the specific fuel consumption of an auxiliary gas turbine plant operating with air drawn from the atmosphere, while the other line in Figure 6 represents that of an auxiliary turbine plant according to the invention operating with air drawn from the cabin, both in relation to the flight altitude. Both characteristic lines relate to auxiliary gas turbine plants wherein the air-throughput of each at ground level is 1 kg/sec.

The performance characteristic 1 in Figure 7 represents the performance required of the air-supply device in relation to the flight altitude. It is evident that the required performance of the device - which determines the pressure in the cabin of the aircraft - rises the higher the flight altitude. However the output of a conventional auxiliary gas turbine plant operating with atmospheric air drops considerably with increasing altitude - as shown by the characteristic 2. It has been assumed that the performance at zero altitude - i.e., operation at ground level - of a conventionally-operated auxiliary gas turbine plant, as represented by the characteristic 2, is the same as that of the auxiliary turbine plant operated in accordance with the invention and indicated by the performance characteristic 3.It is evident from the performance chart that a conventionally-operated auxiliary turbine plant already fails to provide the required output at a flight altitude of substantially 6 km. If one wished to ensure that a conventionally-operated auxiliary turbine plant is, at a maximum flight altitude of 45,000 feet, still capable of providing a sufficient output, its output at ground level would have to be substantially five times that of an auxiliary turbine plant operated in accordance with the invention. The characteristic 3a represents the performance of an auxiliary turbine plant operated in accordance with the invention and assumes losses through leaks from the cabin of substantially 30%. In this case, the auxiliary turbine plant's output just provides the power required by the air-supply device at the assumed maximum flight altitude of 45,000 feet. The shaded area between the characteristics 1 and 3a represents an output potential which, if the auxiliary turbine is operated in accordance with the invention, may be tapped as additional, for example electric, power and be used to operate other equipment.

The pressure prevailing in the cabin 1 (Figure 8) of an aircraft corresponds to the characteristic 2 in Figure 4. It has to be assumed that a certain amount of the air escapes as a leakage flow into the surroundings, that is to say, into the atmosphere. This leakage flow is denoted by the arrow 2. The air flow denoted by the arrow 3 is extracted from the cabin 1 for operating the auxiliary gas turbine plant 4. The air flow 3 is fed to a compressor 5 of the auxiliary turbine plant 4 and hence ducted to a combustion chamber 6. The gas flow from the chamber 6 is piped to a gas generator turbine 7 for the purpose of driving the latter. The generator turbine 7 is connected by a shaft 13 to the compressor 5 for the purpose of driving it. A gas flow 3' emerging from the generator turbine 7 is fed to a work turbine 8 and, since the latter is arranged independently from the shaft 13, drives it. The gas flow 3' egressing from the work turbine 8 is discharged into the atmosphere. The work turbine 8 is connected by a shaft 9 to and drives an air-supply device 10. This device 10 is constructed as a compressor which sucks in air from the atmosphere and feeds the sucked-in mass flow 11 to an air conditioner 12 from which the mass flow 11 reaches the interior of the cabin 1.

Claims

1. An auxiliary gas turbine plant for use in aircraft wherein a work turbine of the plant is arranged to drive at least one air-supply device, in which the auxiliary gas turbine plant is arranged to suck in air from, and at the pressure level prevailing in, the aircraft cabin while the gas flow egressing from the work turbine is arranged to be discharged into the atmosphere.

2. An auxiliary gas turbine plant according to claim 1, in which the auxiliary gas turbine plant is constructed as a two-shaft arrangement.

3. An auxiliary gas turbine plant substantially as described herein with reference to the accompanying drawings.