Aircraft auxiliary power unit

Patent metadata

Field	Value
Publication number	US-2021122488-A1
Application number	US-202017061079-A
Country	US
Kind code	A1
Filing date	Oct 1, 2020
Priority date	Oct 23, 2019
Publication date	Apr 29, 2021
Grant date	—

Abstract

An auxiliary power unit ( 10 ) for an aircraft ( 1 ) comprises a gas turbine engine comprising an engine core ( 12 ). The engine core comprises a core compressor ( 14 ) and core turbine ( 18 ) coupled by a core shaft ( 24 ). The auxiliary power unit further comprises a load spool comprising a load compressor ( 30 ), a load turbine ( 20 ) and a permanent magnet electric machine ( 28 ), each being coupled by a load shaft ( 26 ). The load shaft ( 26 ) and core shaft ( 24 ) are configured to rotate independently of one another.

First claim

1 . An auxiliary power unit for an aircraft comprising;
a gas turbine engine comprising an engine core comprising a core compressor and core turbine coupled by a core shaft; a load spool comprising a load compressor, a load turbine and a permanent magnet electric machine, each being coupled by a load shaft; wherein the load shaft and core shaft are configured to rotate independently of one another.

2 . An auxiliary power unit according to claim 1 , wherein the permanent magnet electric machine is directly coupled to the load turbine by the load shaft, such that the load turbine and electric machine rotate at the same speed.

3 . An auxiliary power unit according to claim 1 , wherein the auxiliary power unit comprises a power electronics unit coupled to the electric machine.

4 . An auxiliary power unit according to claim 3 , wherein the power electronics unit comprises a first AC to DC converter configured to convert AC electrical power output from the electric machine to DC electrical power.

5 . An auxiliary power unit according to claim 4 , wherein the first AC to DC converter is bi-directional, and is configured to convert DC electrical power to AC electrical output to the electric machine.

6 . An auxiliary power unit according to claim 4 , wherein the power electronics unit comprises a DC to DC voltage converter configured to convert DC voltage output from the first AC to DC converter to a different voltage.

7 . An auxiliary power unit according to claim 6 , wherein the voltage converter is configured to output DC power at approximately 24 Volts.

8 . An auxiliary power unit according to claim 4 , wherein the power electronics unit comprises a first DC to AC converter configured to convert DC electrical power output from the rectifier to AC electrical power.

9 . An auxiliary power unit according to claim 8 , wherein the first DC to AC converter is configured to output AC electrical power at 115 Volts RMS, and may be configured to output AC electrical power at approximately 400 Hz.

10 . An auxiliary power unit according to 8 , wherein the DC to AC converter is bi-directional, and is configured to convert AC electrical power to DC electrical power.

11 . An auxiliary power unit according to claim 1 , wherein the core compressor comprises an axial compressor section upstream of a centrifugal compressor, each coupled to the core shaft.

12 . An auxiliary power unit according to claim 1 , wherein the load compressor comprises variable inlet guide vanes.

13 . An auxiliary power unit according to claim 1 , wherein the auxiliary gas turbine engine comprises an accessory drive coupled to the core shaft.

14 . An auxiliary power unit according to claim 1 , wherein the gas turbine engine comprises a clutch configured to selectively couple the core shaft and load shaft.

15 . An aircraft comprising a main propulsive gas turbine engine and an auxiliary power unit according to claim 1 .

16 . A method of operating an auxiliary power system according to claim 1 , the method comprising:
providing electric power to the permanent magnet electric machine, to drive the electric machine as a motor, such that the electric machine drives the load compressor, to provide compressed air to the aircraft.

Assignees

• Rolls Royce Plc
• Rolls Royce Corp

Inventors

• Swain Daniel
• Stieger Rory D
• Taylor Mark D

Classifications

• H02J2105/32

  for aircrafts · CPC title

• B64F1/34

  for starting propulsion plant · CPC title

• B64D41/00 Primary

  Power installations for auxiliary purposes · CPC title

• H02J4/00 Primary

  Circuit arrangements for mains or distribution networks not specified as AC or DC; Circuit arrangements for mains or distribution networks combining AC and DC sections or sub-networks (arrangements using intermediate DC-AC-DC conversion H02J1/002; arrangements using high-voltage DC [HVDC] links H02J3/36) · CPC title

• Y02T50/80

  Energy efficient operational measures, e.g. ground operations or mission management · CPC title