GB2257752A

GB2257752A - Gas turbine inlet particle separator.

Info

Publication number: GB2257752A
Application number: GB9115625A
Authority: GB
Inventors: Robert Bounden; Roy Sanders
Original assignee: British Aerospace PLC
Current assignee: BAE Systems PLC
Priority date: 1991-07-19
Filing date: 1991-07-19
Publication date: 1993-01-20
Also published as: GB9115625D0

Abstract

A gas turbine engine (1) in a helicopter has an air intake separator (4) from which separated particles are removed by an ejector (5), driven by high pressure gas supplied by an auxiliary power unit (6). The invention provides a reduction in fuel and main engine power consumption compared with known systems which drive the ejector (5) with gas bled from the main engine (1). Valve (9) enables ejector (5) to be switched off during high flying, when the separator is not needed. <IMAGE>

Description

AIRCRAFT ENGINES This invention relates to improvements in aircraft engines and is especially applicable to rotary wing aircraft.

Gas turbine engines fitted to helicopters, for example, can be suseptible to the ingestion of solid particles. The likelihood of this ingestion and subsequent damage to the engine is maximised when the helicopter is in close proximity to the ground, during take-off or landing for example.

Known techniques for preventing damage to an engine by ingested particles rely on the provision of an inlet particle separator (IPS) which is attached to the engine inlet, in front of the engine's compressor.

A particular form of IPS utilises ballistic trajectory focussing of solid particles, said particles being collected in a peripheral chamber, scavenged by an ejector and finally discharged with the engine exhaust gases.

The ejector in the known IPS arrangement is driven by a high pressure air supply bled off from the engine.

An IPS is required to operate at any time when the engine is likely to ingest debris i.e. at low level and slow speed or in sand-laden air. These are flight regimes where engine power requirements are at a maximum and, disadvantageously, known IPS systems consume typically 3% of engine power. In the known systems, the IPS is operational at all times.

Often, helicopters are fitted with an auxiliary power unit (APU) whose functions include supplying high pressure air for starting a main engine, driving an electrical power generator and providing high pressure air for the environmental control system.

This invention provides a method of obtaining inlet particle separation from a gas turbine engine air intake, said engine being provided with an inlet particle separator and ejector, in which the ejector is driven by high pressure fluid supplied from an auxiliary power unit.

By using an APU instead of the main engine to drive the ejector, the invention results in an improvement in the maximum power available from the main engine. Other benefits which accrue from the invention are improved main engine life, reduced fuel consumption and reduced maintenance.

Since the ejector is driven via a supply line remote from the main engine, fluid supplied to it will be cooler, therefore the invention provides the easily realised option of incorporating a switch in the supply line so that the IPS may be turned off when not required. Alternatively, the IPS could be switched off by shutting down the APU.

An embodiment of the invention will now be described by way of example only with reference to the drawing which illustrates schematically a method of inlet particle separation in accordance with the invention.

A gas turbine engine 1 installed in a helicopter (not shown) has an inlet 2 and an exhaust duct 3. An inlet particle separator (IPS) 4 is attached to the engine's inlet 2. Connected to the IPS 4 is an ejector 5 through which solid particles are ejected, thus by-passing the engine 1.

An auxiliary power unit (APU) 6 comprising a single-spool gas turbine engine is also installed in the helicopter remote from engine 1. The APU 6 is provided with a bleed port 7 via which is supplied high pressure gas for starting the main engine 1. Gas from this bleed port 7 is tapped off into a conduit 8 which connects the APU with the ejector 5. A valve 9 is installed in the conduit for controlling gas flow to the ejector 5.

In operation, the pilot starts up the main engine 1, prior to take-off, using the high pressure gas supply from the APU 6. With the valve 9 in the open position, gas is also supplied to the ejector 5. As the main engine 1 becomes operational, debris from the ground enters the IPS 4 and is forced to follow a high curvature path which terminates in a peripheral plenum chamber forming an outer part of the IPS 4. The action of the ejector 5 driven by high pressure gas from the APU 6 results in the extraction of the debris from the plenum chamber and its subsequent ejection.

After take-off and when the helicopter is clear of the ground such that ingestion of particles is unlikely, the pilot closes the valve 9. Alternatively if operational circumstances permit, the pilot may shut down the APU 6, thus conserving fuel, which the APU 6 would otherwise consume. The APU 6 and ejector 5 are re-activated whenever ingestion of debris is likely.

If the helicopter is provided with more than one main engine each incorporating an IPS and ejector, then an equivalent number of gas supplies from the APU is provided, each driving an ejector on each engine.

Claims

1. A method of obtaining inlet particle separation from a gas turbine engine air intake, said engine being provided with an inlet particle separator and ejector, in which the ejector is driven by high pressure fluid supplied from an auxiliary power source.

2. A method according to claim 1 in which means are provided for controlling the supply of high pressure fluid from the auxiliary power unit to the ejector.

3. A method of obtaining inlet particle separation from a gas turbine engine air intake substantially as hereinbefore described with reference to the drawing.