GB2194292A - High bypass ratio counterrotating turbofan engine - Google Patents

Description

GB2194292A 1 SPECIFICATION ating combustion gases. Pressurized air from

compressor 18 is mixed with fuel in combus High bypass ratio counterrotating turbofan tor 20 and ignited, thereby generating com engine bustion gases. Some work is extracted from 70 these gases by high pressure turbine 22 This invention relates to gas turbine engines which drives compressor 18. The remainder and, in particular, is concerned with the type of the combustion gases are discharged from

of engine disclosed in patent specifications the gas generator 16 through strut 26 of sup

Nos. G132 129 502A and GB2 174 762A. port member 28 and into power turbine 30.

The specifications disclose an engine inciud- 75 Power turbine 30 includes a first annular ing a counterrotating turbofan driven by a drum rotor 32 rotatably mounted by suitable counterrotating power turbine. A feature of bearings 34 to frame hub member 36. First the engine is the configuration of the power rotor 32 includes a plurality of first turbine turbine and the ratio of the mean flowpath blade rows 38 extending radially inwardly radius of such turbine to the mean flowpath 80 therefrom and axially spaced.

radius of the gas generator. This is required in Power turbine 30 also includes a second part to ensure lower fan tip speed and/or annular drum rotor 40 disposed radially in higher turbine blade speed. wardly of first rotor 32 and first blade rows Under certain design conditions, it may be 38. Second rotor 40 includes a plurality of desirable to reduce the mean flowpath radius 85 second turbine blade rows 42 extending radi of the power turbine. According to one em- ally outwardly therefrom and axially spaced.

bodiment of the engine, such a reduction in Second rotor 40 is rotatably mounted to first the mean flowpath radius of the power turbine shaft 44 by differential bearings 46.

would increase the fan tip speed thereby re- Each of the first and second turbine blade ducing the efficiency of the engine. 90 rows 38 and 42 comprises a plurality of cir- Accordingly, it is an object of the present curnferentially spaced turbine blades, with the invention to provide a new and improved high first blade rows 38 interdegetated and alter bypass ratio counterrotating turbofan engine. nately spaced with respective ones of the sec- In accordance with the present invention, ond blade rows 42. Combustion gases flowing the engine comprises a gas generator effective 95 through the blade rows 38 and 42 drive first for generating combustion gases, a power tur- and second rotors 32 and 40 in counterrotat bine, a fan section, and a booster compres- ing directions. The rotors rotate at substan sor. The power turbine includes first and sec- tially the same speed.

ond drive shafts, respectively. The fan section Fixedly attached to first and second rotors includes a first fan blade row connected to 100 32 and 40 are first and second drive shafts the first drive shaft and a second fan com- 44 and 48, respectively. Thus, first and sec pressor includes a first compressor blade row ond rotors 32 and 40 are effective for driving connected to the first drive shaft and a see- first and second drive shafts 44 and 48 re ond compressor blade row connected to the spectively. Drive shafts 44 and 48 are coaxi second drive shaft. 105 ally disposed relative to center line 12 of en- In the drawings: gine 10 and extend forward through gas gen Figure I is a schematic view of a high by- erator 16.

pass ratio counterrotating turbofan engine ac- Engine 10 further comprises a forward fan cording to one form of the present invention, section 52. Fan section 52 is disposed radially and 110 inwardly of annular fan duct 54 which is Figure 2 is a schematic view of a booster suitably secured by strut 56 to casing 14. Pan compressor for a high bypass ratio turbofan section 52 includes a first fan blade row 58 engine according to another form of the pre- connected to the forward end 60 of first drive sent invention. shaft 44. Similarly, fan section 52 includes a 115 second fan blade row 62 connected to the DETAILED DESCRIPTION OF THE INVENTION forward end 64 of second drive shaft 48.

Fig. 1 shows a gas turbine engine 10 ac- - Each of the first and second fan blade rows cording to one embodiment of the present in- 58 and 62 comprises a plurality of circumfer vention. Engine 10 includes a longitudinal cen- entially spaced fan blades. Fan blade rows 58 ter line axis 12 and an annular casing 14 dis- 120 and 62 are counterrotating which provides a posed coaxially about axis 12. Engine 10 also relatively high fan efficiency and propulsive includes a core gas generator engine 16 which efficiency with generally low absolute tip includes a compressor 18, a combustor 20, speed on each fan blade row. The fan blade and a high pressure turbine 22, either single rows 58 and 62 extend radially outwardly to or multiple stage, all arranged coaxially about 125 the fan duct 54.

the longitudinal axis or center line 12 of en- It should be appreciated that the counterro- gine 10 in serial, axial flow relationship. An tating fan blade row 62 serves to remove the annular drive shaft 24 fixedly interconnects swirl or circumferential component of air im compressor 18 and high pressure turbine 22. parted by the counterrotating fan blade row The gas generator 16 is effective for gener- 130 58. In this way struts 56 is not an outlet 2 GB2194292A 2 guide vane in the sense that no swirl need be It should be appreciated that in the present taken out by the struts. Therefore only a rela- engine 10 there is basically a separate core tively small -number of struts 56 are required engine 20 in the center with two ccounter to support duct 54. rotating turbines at one end and two counter- The struts 56 are positioned axially forward 70 rotating fans at the other end. The counterro- of the core engine 20. This allows support of tating turbines and fans are not intermingled the engine 10 at a location as close to fan with the center core engine.

blade rows 58 and 62 as possible. In order to achieve thrust reversal, a stan- Engine 10 further comprises a booster com- dard thrust reversal unit can be included in the pressor 66. Booster compressor 66 includes a 75 system. Alternately, a variable pitch mecha first annular rotor 68 including a plurality of nism can be provided, as is known in the art, first compressor blade rows 70 extending ra- and incorporated within the system.

dially outwardly therefrom and axially spaced. It will be understood that the dimensions Booster compressor 66 also includes a sec- and proportional and structural relationships ond annular rotor disposed radially outwardly 80 shown in the drawings are illustrated by way of rotor 68 and first compressor blade rows of example only and those illustrations are not 70. Rotor 72 includes a plurality of second to be taken as the actual dimensions or pro compressor blade rows 74 extending radially portional structural relationships used in the inwardly therefrom and axially spaced. Rotor counterrotating turbofan engine of the present 68 is fixedly attached to fan blade row 58 85 invention.

and a forward end 60 of first drive shaft 44. Numerous modifications, variations, and full Similarly rotor 72 is fixedly attached to fan and partial equivalents can be undertaken blade ro 62 and the forward end 64 of sec- without departing from the invention as limited ond drive shaft 48. only by the spirit and scope of the appended Each of the first and second compressor 90 claims.

blade rows 70 and 74 comprises a plurality of

Claims (1)

1. circumferentially spaced compressor blades, CLAIMS with the first blade

   rows 70 alternately 1. A gas turbine engine comprising:

   spaced with respective ones of the second a unitary gas generator effective for generat- blade rows 74. Compressor blade rows 70 95 ing combustion gases; and 74 are counterrotating and located in the a power turbine aft of said gas generator core duct 76 leading into compressor 18 of including first and second counterrotatable tur gas generator 16. bine blade rows effective for rotating first and The counterrotating booster compressor 66 second drive shafts, respectively; provides a significant pressure rise to air en- 100 a fan section forward of said gas generator tering the core gas generator 16. An advan- including a first fan blade row connected to tage of having the fan blade row and the said first drive shaft and a second fan blade compressor blade rows driven by the same row connected to said second drive shaft; and drive shaft is that energy is optimally ex- a booster compressor forward of said gas tracted from power turbine 30. Without the 105 generator including a first compressor blade booster compressor stages being driven by row connected to said first drive shaft and a the power turbine from shafts 44 and 48, a second compressor blade row connected to separate compressor with an additional shaft said second drive shaft.

   and drive turbine would be required. Further- 2. A gas turbine engine comprising:

   _more, if the booster compressor stages were 110 a gas generator including a core compres- non-existent, the engine would be limited in sor, combustor, and turbine in serial flow rela overall pressure ratio resulting in poorer effick tionship effective for generating combustion ency. The rotating booster gives sufficient gases; pressure 6se despite the slow fan speed. By an annular casing disposed coaxially about a having compresosr blade rows 70 and 74 115 center line of said engine; counterrotating, a lesser number of compres- a power turbine including first and second sor blade rows than that required for a single counterrotatable turbine blade rows effective low speed compressor driven from only one for rotating first and second drive shafts, re shaft is possible. spectively; Fig. 2 shows an alternative embodiment of 120 a fan section disposed within an annular fan fan section 52 and booster compressor 66. duct, said fan section including a first fan Booster compressor 66 is configured so that blade row connected to said first drive shaft rotor 68 is disposed radially outwardly from and a second fan blade row connected to said rotor 72. Thus, first compressor blade rows second drive shaft and located axially aft of 70 extend radially inwardly from rotor 68 and 125 said first row, each row comprising a plurality compressor blade rows 74,extend radially out- of blades extending until proximate said fan wardly from rotor 72. duct, said fan section being effective to pro- It will be clear to those skilled in the art duce a fan flow; and that the present invention is not limited ot he a booster compressor including a first com- specific embodiments illustrated herein. 130 pressor blade row connected to said first 3 GB 2 194 292A, 3 drive shaft and a second compressor blade 9. A gas turbine engine, as recited in claim row connected to said second drive shaft. 7, wherein said gas generator is non-interdigi- 3. A gas turbine engine, as recited in claim tated with said fan section, booster compres- 2 further comprising: sor and power turbine.

   a strut securing said duct to said casing and 70 10. A gas turbine engine, as recited in positioned axially forward of said core com- claim 7, wherein said first and second drive pressor. shafts rotate at approximately the same 4. A gas turbine engine, as recited in claim speeds.

   2, wherein said first and second counterrota- 11. A gas turbine engine substantially as table turbine blade rows rotate at substantial 75 hereinbefore described with reference to and equalspeeds. as illustrated in the drawings.

   5. A gas turbine engine comprising:

   a gas generator effective for generating Published 1988atThe Patent Office, State House, 66/71 High Holborn, London WC 1 R 4TP. Further copies may be obtained from combustion gases; The Patent Office, Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD.

   a power turbine including a first rotor having Printed by Burgess & Son (Abingdon) Ltd. Can. 1/87.

   a plurality of first turbine blade rows extending radially inwardly therefrom and a second rotor having a plurality of second turbine blade rows extending radially outwardly therefrom, said first and second turbine blade rows alter nating with each other and being interdigi tated, said first and second turbine rotors be ing counterrotatable and effective for driving first and second drive shafts, respectively; a fan section including a first fan blade row connected to said first drive shaft and a sec ond fan blade row connected to said second drive shaft; and a booster compressor including a first com- pressor blade row connected to said first drive shaft and a second compressor blade row connected to said second drive shaft.

   6. A gas turbine engine as recited in claim 5, wherein said gas generator is a separate unit from said power turbine fan sections and booster compressor.

   7. A gas turbine engine comprising:

   a gas generator effective for generating combustion gases; a power turbine including a first turbine ro- tor having a plurality of first turbine blade rows extending radially inwardly therefrom and a second turbine rotor having a plurality of second turbine blade rows extending radially outwardly therefrom, said first and second tur bine rotors being counterrotatable and effec tive for driving first and second drive shafts, respectively; a fan section including a first fan blade row connected to said first drive shaft and a sec ond fan blade row connected to said second drive shaft; and a booster compressor including a first compressor rotor connected to said first drive shaft having a plurality of first compressor blade rows extending radially outwardly there from, and a second compressor rotor con nected to said second drive shaft having a plurality of second compressor blade rows ex tending radially inwardly therefrom.

   8. A gas turbine engine, as recited inclaim 7, wherein said second fan blade row is lo cated axially aft of said first fan blade row, said fan section being effective to produce a fan flow.