(19) TZZ ¥_T (11) EP 2 772 438 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int Cl.: of the grant of the patent: B64D 41/00 (2006.01) 20.01.2016 Bulletin 2016/03 (21) Application number: 14154763.8 (22) Date of filing: 11.02.2014 (54) Auxiliary power units (APUs) and methods and sy stems for activation and deactivation of a load compressor therein Hilfskraftquellen (APUs) und Verfahren und Systeme zur Aktivierung und Deaktivierung eines Lastverdichters darin Unités de puissance auxiliaire (APU) et procédés et systèmes pour l’activation et la désactivation d’un compresseur de charge dans celles-ci (84) Designated Contracting States: (72) Inventors: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB • Jan, David K. GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO Morristown, NJ New Jersey 07962-2245 (US) PL PT RO RS SE SI SK SM TR • Zollars, Christopher Morristown, NJ New Jersey 07962-2245 (US) (30) Priority: 28.02.2013 US 201313781239 (74) Representative: Houghton, Mark Phillip (43) Date of publication of application: Patent Outsourcing Limited 03.09.2014 Bulletin 2014/36 1 King Street Bakewell, Derbyshire DE45 1DZ (GB) (73) Proprietor: Honeywell International Inc. Morris Plains, NJ 07950 (US) (56) References cited: EP-A2- 2 347 956 GB-A- 2 076 897 US-A- 4 091 613 Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 2 772 438 B1 Printed by Jouve, 75001 PARIS (FR) 1 EP 2 772 438 B1 2 Description position. [0004] In a conventional operating APU, the activated TECHNICAL FIELD load compressor is engaged with the operating APU en- gine and the deactivated load compressor is disengaged [0001] The present invention generally relates to aux- 5 from the operating APU engine. The load compressor iliary power units ("APU"s), and more particularly relates may be engaged with and disengaged from the operating to methods and systems for activation and deactivation APU engine via one or more friction clutches. Unfortu- of a load compressor therein. nately, friction clutches that have been used to engage the load compressor with the operating APU engine and BACKGROUND 10 disengage the load compressor therefrom tend to be heavy and have less than ideal reliability in APUs due to [0002] An operating aircraft auxiliary power unit (APU) high rotational speeds. High rotational speeds impose provides energy for functions other than propulsion. An high inertial loading, leading to excessive temperatures APU generally consists of a gas turbine engine (herein- and accelerated wear and failure of the friction clutch after referred to as an "APU engine), a generator, and a 15 components, leading to clutch failures. In addition, oil- load compressor (LC). Before the main propulsion en- cooled friction clutches impose oil cooling system pen- gines are started, the APU engine is started, generally alties. Dynamic disconnect clutches can also be used for by a battery or hydraulic accumulator and fuel. The op- disengaging the load compressor in the operating APU, eratingAPU provides auxiliary electrical powerand pneu- but can only disengage at speed and cannot re-engage matic power to the aircraft while the main propulsion en- 20 until the APU is shut down, thereby limiting operational gines are shut down, such as during aircraft ground op- flexibility. A relevant disclosure of an APU can be found erations and provides backup electrical and pneumatic in EP 2 347 956. power for in-flight operations. The operating APU sup- [0005] Accordingly, it is desirable to provide auxiliary plies the electrical power via the generator which is driven power units and methods and systems for activation and by the operating APU engine. The activated load com- 25 deactivation of a load compressor therein. In addition, it pressor in the operating APU supplies the pneumatic is also desirable to provide auxiliary power units in which power for various aircraft systems and functions. These the load compressor therein may be selectively engaged systems and functions may vary, and may include the with and disengaged to the operating APU engine without aircraft environmental control system (ECS), the cabin a friction clutch, thereby resulting in a more lightweight pressure control system, and/or main propulsion engine 30 and less complex APU, lower inertial loading and greater start (MES) air. APU reliability. It is also desirable to provide methods [0003] APU efficiency is generally reported in terms of and systems to selectively disengage the load compres- specific fuel consumption (SFC), the mass of fuel con- sor from the operating APU engine when pneumatic pow- sumed per unit of energy output. Continued operation of er is not needed, thereby improving aircraft fuel economy the load compressor when pneumatic power is not need- 35 and reducing undesirable air emissions and to selectively ed (but the APU is still operating, albeit in "generator- engage with the operating APU engine when pneumatic only mode" to provide electrical power) results in a par- power is needed, thereby maintaining operational flexi- asitic loss of fuel as well as undesirable air emissions. bility. Furthermore, other desirable features and charac- Therefore, it is beneficial to be able to deactivate the load teristics of the present invention will become apparent compressor in the operating APU when pneumatic power 40 from the subsequent detailed description of the invention is not needed, but to be able to (re)activate the load com- and the appended claims, taken in conjunction with the pressor in the operating APU when pneumatic power accompanying drawings and this background of the in- (auxiliary air) is needed. In a typical aircraft, for example, vention. an APU Master Switch is turned to the "Start" position to initiate the APU start and is released to the "Run" position, 45 BRIEF SUMMARY which is the normal operating mode for an "operating APU". When the APU Master Switch is turned to the "Off" [0006] The present invention in its various aspects is position, the auxiliary air is automatically shut off and the as set out in the appended claims. Auxiliary power units APU shuts down. When the APU Master Switch is in the are provided. In accordance with one exemplary embod- "Run" position and an APU Air switch is turned "ON", the 50 iment, the auxiliary power unit includes a load compres- load compressor may be activated to provide com- sor having an impeller, an APU engine, a coupling mem- pressed air (hereinafter "load compressor" or "LC" air) to ber, pre-spinning means, and an APU controller. APU the various aircraft systems and functions. When the engine is adapted to be mechanically engaged to load APU Air switch is turned "Off", the APU air shutoff valve compressor to drive load compressor to provide pneu- closes to isolate the APU from the aircraft pneumatic sys- 55 matic power and to be disengaged when the need for tem, and the load compressor is deactivated to standby pneumatic power ceases. Coupling member couples mode. The APU Master switch turned to the "Off" position load compressor and APU engine and is configured to will shut down the APU regardless of the APU AIR switch be controllably moved between an engaged position in 2 3 EP 2 772 438 B1 4 which the APU engine is mechanically engaged with the preceding background. load compressor, and a disengaged position, in which the APU engine is disengaged from the load compressor. BRIEF DESCRIPTION OF THE DRAWINGS APU controller is operably coupled to load compressor, APU engine, coupling member, and pre-spinning means 5 [0010] The present invention will hereinafter be de- and adapted to receive and be responsive to rotational scribed in conjunction with the following drawing figures, speed signals for controlling movement of coupling mem- whereinlike numerals denote likeelements, andwherein: ber between engaged and disengaged positions. [0007] Methods are provided for activation and deac- FIG. 1 is a simplified schematic diagram of an ex- tivation of a load compressor in an operating auxiliary 10 emplary APU in a system for performing the method power unit (APU) in accordance with yet another exem- of FIG. 4, the encircled region illustrating a load com- plary embodiment of the present invention. The method pressor coupled to a gearbox via a coupler, accord- comprises selectively engaging a load compressor with ing to exemplary embodiments; an APU engine and selectively disengaging the load compressor from the operating APU engine to deactivate 15 FIG. 2A is a sectional view of the load compressor the load compressor. The step of selectively engaging a engaged with the APU engine (more specifically, the load compressor comprises pre-spinning an impeller of load compressor input shaft is engaged with the the load compressor to a rotational speed setpoint with gearbox output shaft via the coupler comprising a compressor discharge bleed air; and mechanically en- clutchless coupling member and a coupling member gaging the load compressor with the operating APU en- 20 actuator) of the exemplary APU of FIG. 1, according gine when a rotational speed of the impeller reaches the to exemplary embodiments; rotational speed setpoint. [0008] Systems are provided for activation and deac- FIG. 2B is a sectional view similar to FIG. 2A, illus- tivation of a load compressor in an operating auxiliary trating the load compressor disengaged from the op- power unit (APU) in accordance with yet another exem- 25 erating APU engine (more specifically, the load com- plary embodiment of the present invention.