(19) TZZ¥ Z¥_T (11) EP 3 205 838 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) Int Cl.: 16.08.2017 Bulletin 2017/33 F01D 19/02 (2006.01) F02C 7/18 (2006.01) (21) Application number: 17155894.3 (22) Date of filing: 13.02.2017 (84) Designated Contracting States: (72) Inventors: AL AT BE BG CH CY CZ DE DK EE ES FI FR GB • PECH, John T. GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO Canton, CT Connecticut 06019 (US) PL PT RO RS SE SI SK SM TR • SPIERLING, Todd A. Designated Extension States: Rockford, IL Illinois 61109 (US) BA ME Designated Validation States: (74) Representative: Stevens, Jason Paul MA MD Dehns St Bride’s House (30) Priority: 12.02.2016 US 201662294548 P 10 Salisbury Square London (71) Applicant: Hamilton Sundstrand Corporation EC4Y 8JD (GB) Charlotte, NC 28217-4578 (US) (54) GAS TURBINE ENGINE MOTORING SYSTEM FOR BOWED ROTOR ENGINE STARTS (57) An engine starting system 100 for a gas turbine nected to at least one of the rotational components, the engine 250 is provided. The engine starting system 100 permanent magnet alternator 500 being configured to comprising: a gas turbine engine 250 including rotational rotate the rotational components; and a motor controller components comprising an engine compressor 256, an 420 in electronic communication with the permanent engine turbine 258, and a rotor shaft 259 operably con- magnet alternator, 500 the motor controller 420 being necting the engine turbine 258 to the engine compressor configured to command the permanent magnet alterna- 256, wherein each rotational component is configured to tor 500 to rotate the rotational components at a selected rotate when any one of the rotational components is ro- angular velocity for a selected period of time. tated; a permanent magnet alternator 500 operably con- EP 3 205 838 A1 Printed by Jouve, 75001 PARIS (FR) 1 EP 3 205 838 A1 2 Description communication with the permanent magnet alternator, the motor controller being configured to command the BACKGROUND permanentmagnet alternator to rotate the rotational com- ponents at a selected angular velocity for a selected pe- [0001] The embodiments herein generally relate to gas 5 riod of time. turbine engines and more specifically, systems and [0006] In addition to one or more of the features de- method for cooling gas turbine engines. scribed above, or as an alternative, further embodiments [0002] Aircraft gas turbine engines are being designed of the engine starting system may include an accessory with tighter internal clearances between engine cases gearbox operably connecting the permanent magnet al- and blades of the compressor and turbine to increase 10 ternator to at least one of the rotational components. efficiency and reduce fuel burn. These tighter clearances [0007] In addition to one or more of the features de- can result in compressor blade tips and turbine blade tips scribed above, or as an alternative, further embodiments rubbing on the engine cases if the engine core bows as of the engine starting system may include where the per- it cools down between flights and an engine start is at- manent magnet alternator is configured to generate elec- tempted. 15 tricity when the rotational components are rotating under [0003] After engine shutdown, the main shafts, com- power of the gas turbine engine. pressor disks, turbine disks and other parts with large [0008] In addition to one or more of the features de- thermal mass cool at different rates. The heat rises to scribed above, or as an alternative, further embodiments the top of the engine allowing the lower portions of these of the engine starting system may include: an air turbine parts to become cooler than the upper portions. This20 starter comprising a turbine wheel including a hub inte- causes blade tip clearance between the engine case and grally attached to a turbine rotor shaft and a plurality of blades of the compressor and turbine to decrease as the turbineblades extending radially from the hub,the turbine engine shafts and cases bow temporarily due to uneven rotor shaft being operably connected to at least one of thermal conditions. This does not present a problem for the rotational components and configured to rotate the the engine unless an engine start is attempted while the 25 rotational components when air flows through the turbine bowed condition exists. To address this engine manu- blades and rotates the turbine wheel. facturers have found that motoring the engine at relatively [0009] In addition to one or more of the features de- low speed for a period of time prior to engine start allow scribed above, or as an alternative, further embodiments the parts to achieve uniform thermal conditions and elim- of the engine starting system may include: an auxiliary inate the bowed condition restoring blade tip to engine 30 power unit fluidly connected to the air turbine starter and case clearances. electrically connected to the permanent magnet alterna- [0004] The problem is how to motor the engine at very tor, the auxiliary power unit being configured to generate specific speeds for up to four minutes prior to engine electricity to power the permanent magnet alternator and start? Pneumatic or Air Turbine Starters are typically duty provide air to the air turbine starter to rotate the turbine cycle limited due to lubrication issues and heat dissipa- 35 blades. tion. Butterfly type start valves are typically solenoid ac- [0010] In addition to one or more of the features de- tuated and have diaphragms and linkage in the actuator scribed above, or as an alternative, further embodiments piston assembly that are prone to wear if they are being of the engine starting system may include: a starter air used to modulate and control starter speed. This type of valve fluidly connecting the auxiliary power unit to the air operation decreases the valve and start life significantly. 40 turbine starter, the starter air valve being configured to A more efficient method of motoring the gas turbine en- adjust airflow from the auxiliary power unit to the air tur- gine that does not cause excessive wear and tear is de- bine starter. sired. [0011] According to another embodiment, a method of assembling an engine starting system for a gas turbine BRIEF DESCRIPTION 45 engine is provided. The method of assembling compris- es: obtaining a gas turbine engine including rotational [0005] According to one embodiment, an engine start- components comprising an engine compressor, an en- ing system for a gas turbine engine is provided. The en- gine turbine, and a rotor shaft operably connecting the gine starting system comprises: a gas turbine engine in- engine turbine to the engine compressor, wherein each cluding rotational components comprising an engine50 rotational component is configured to rotate when any compressor, an engine turbine, and a rotor shaft operably one of the rotational components is rotated; operably connecting the engine turbine to the engine compressor, connecting a permanent magnet alternator to at least one wherein each rotational component is configured to ro- of the rotational components, the permanent magnet al- tate when any one of the rotational components is rotat- ternator being configured to rotate the rotational compo- ed; a permanent magnet alternator operably connected 55 nents; and electrically connecting a motor controller to to at least one of the rotational components, the perma- permanent magnet alternator, the motor controller being nent magnet alternator being configured to rotate the ro- configured to command the permanent magnet alterna- tational components; and a motor controller in electronic tor to rotate the rotational components at a selected an- 2 3 EP 3 205 838 A1 4 gular velocity for a selected period of time. gular velocity for a selected period of time. [0012] In addition to one or more of the features de- [0019] In addition to one or more of the features de- scribed above, or as an alternative, in further embodi- scribed above, or as an alternative, further embodiments ments of the method of assembling an engine starting of the method of cooling a gas turbine engine may in- system, the permanent magnet alternator is operably 5 clude: detecting a failure in a starter air valve prior to connected to at least one of the rotational components rotating the gas turbine engine with the permanent mag- through an accessory gearbox. net alternator, the starter air valve being fluidly connected [0013] In addition to one or more of the features de- to an air turbine starter and configured to provide air to scribed above, or as an alternative, in further embodi- the air turbine starter, wherein the air turbine starter is ments of the method of assembling an engine starting 10 operably connected to at least one of the rotational com- system, the permanent magnet alternator generates ponents and configured to rotate the rotational compo- electricity when the rotational components are rotating nents. under power of the gas turbine engine. [0020] In addition to one or more of the features de- [0014] In addition to one or more of the features de- scribed above, or as an alternative, further embodiments scribed above, or as an alternative, further embodiments 15 of the method of cooling a gas turbine engine may in- of the method of assembling an engine starting system clude: detecting when a temperature of the gas turbine may include: operably connecting an air turbine starter engine is less than a selected temperature; and display- to at least one of the rotational components, the air tur- ing a message on a cockpit display when the temperature bine starter comprising a turbine wheel including a hub of the gas turbine engine is less than a selected temper- integrally attached to a turbine rotor shaft and a plurality 20 ature.