Engine A B C D Total airflow relative to datum 1.5 2.0 2.5 3.0 Design A,at beginning of study,= 0.5 1.0 1.5 2.0 Cruise Operating A,resulting from 0.291 0.762 1.240 1.716 optimum matching Cruise Thrust (1bf) 14500 14520 14410 14260 Cruise SFC relative to datum 0,990 0.972 0.967 0.970 Take-off operating入，resulting from 0.049 0.459 0.885 1,314 optimum matching Dry take-off thrust (1bf) 48280 50150 51370 53850 Dressed engine weight relative to datum 1.458 1.678 1.817 1,986 A=Bypass ratio A*=Design bypass ratio Quoted Cruise Mach 2.0,ISA 50C,53 000 ft Quoted Take-off 250 kt,ISA 100C,900 ft Quoted weight includes bypass duct,excludes mixer and primary nozzle Reheat for take-off if required Datum is Olympus 593 Mk 610 Table 2-Performance and Weight of Turbofan Family take-off.This variation of bypass ratio In order to provide British Aerospace is a natural feature of the layout described with a purejet tend point!for their where the fan and the remainder of the core studies,a further engine was considered. compression are on different spools and The leading particulars of this engine are nozzle variation is provided. It enables given in Table 3,and are based on a pro- the fan to be matched at high pressure ratio posal for a 15%flow increase over the for take-off.In contrast a turbojet,with- current engine.This is obtained by a mod- out the facility for allowing a sizeable ification to the first three stages of the quantity of LP compressor delivery air to current LP compressor.This modification bypass the HP system at cruise,needs to has been rig tested to show the required be matched at a low LP compressor pressure flow increase,and an earlier version has ratio at take-off to avoid LP compressor surge at cruise. Since the fan engines are matched at a Object: high fan pressure ratio at take-off rela- To provide BAe with "end point"for calcu- tive to a turbojet,the core has a rela- lations. tively higher degree of supercharge,and hence although the design core flow at Chosen Engine: cruise of the family of fan engines is the same as the olympus 593,the take-off core High temperature version of 1976 Olympus flow is some 30%to 40%higher.As a con- 593 Mk 622 proposal.Take-off airflow 15% sequence the dry take-off thrust is con- above Mk 610. siderably higher than would be given by an Olympus 593 turbojet operating at the same Leading Particulars: temperature.The necessity for reheat Cruise Mach 2.0 1SA+50C,53000ft boost at take-off is therefore minimised or TET 16000K eliminated,with consequent advantages in simplification of control equipment and Thrust 129801bf improved pollution characteristics. This SFC 1.034 x Datum also permits a shorter and hence lighter Take-ofE-250Kt,ISA+100℃，900ft exhaust system design.Eliminating reheat TET 17000K at take-off facilitates the use of ejector- type noise suppressors,as these would not Dry Thrust 377801bf easily withstand the peaky temperatures Reheated Thrust 49 300 1bf (18000K Reheat) involved in afterburner operation. Bare Engine Weight Plus Dressings 1.046 ×Datum(Datum is O1 ympus593Mk610） A more detailed discussion of the match- ing of the olympus 593 and various turbo- fan layouts has'been given by the authors 3. Table 3-Turbojet (=O)EngineEnqine A B C D I Quoted weight includes bypass duct, excludes mixer and primary nozzle ~ 1.0 1.5 2.0 ~ ____ Design A , at beginning of study, = A * 0.5 Cruise Operating h , resulting from 0.291 0.762 1.240 1.716 optimum matching . Cruise Thrust. (lbf) 14 500 14 520 14 410 14 260 0.990 0.972 0.967 0.970 __ ~~ ... ~ . .. Cruise SFC relative to datum optimum matching Dry take-off thrust (lbf) 48 280 50 150 51 370 53 850 Dressed engine weight relative to datum 1.458 1.678 1.817 1.986 ~ _________ Take-off operating A , resulting from 0.049 0.459 0.885 i.314 - ~- .~ ~ Reheat for take-off if required Datum is Olympus 593 Mlc 610 Table 2 - Performance and Weight of Turbofan take-off. This variation of bypass ratio is a natural feature of the layout described where the fan and the remainder of the core compression are on different spools and nozzle variation is provided. It enables the fan to be matched at high pressure ratio for take-off. In contrast a turbojet, with￾out the facility for allowinq a sizeable quantity of LP compressor deiivery air to bypass the HP system at cruise, needs to be matched at a low LP compressor pressure ratio at take-off to avoid LP compressor surge at cruise. Since the fan engines are matched at a high fan pressure ratio at take-off rela￾tive to a turbojet, the core has a rela￾tively higher degree of supercharge, and hence although the design core flow at cruise of the family of fan engines is the same as the Olympus 593, the take-off core flow is some 30% to 40% higher. As a con- sequence the dry take-off thrust is con￾siderably higher than would be given by an Olympus 593 turbojet operating at the same temperature. The necessity for reheat boost at take-off is therefore minimised or eliminated, with consequent advantages in simplification of control equipment and improved pollution characteristics. This also permits a shorter and hence lighter exhaust system design. Eliminating reheat at take-off facilitates the use of ejector￾type noise suppressors, as these would not easily withstand the peaky temperatures involved in afterburner operation. A more detailed discussion of the match￾ing of the Olympus 593 and various turbo￾fan layouts has been given by the authors3 Family In order to provide British Aerospace with a purejet 'end point' for their studies, a further engine was considered. The leading particulars of this engine are given in Table 3,and are based on a pro￾posal for a 15% flow increase over the current engine. This is obtained by a mod￾ification to the first three stages of the current LP compressor. This modification has been rig tested to show the required flow increase, and an earlier version has w: To provide BAe with "end point" for calcu￾lations. 3hosen Enqine: Hiah temDerature version of 1976 01vmDuS 593 Mk 6'22 proposal. above Mk 610. Take-off airfiow 154 -eadincr Particulars: Cruise - Mach 2.0 ISA + 5OC, 53 000 ft TET 1600°K Thrust 12 980 lbf SFC 1.034 x Datum rake-off - 250 Kt, ISA + 10°C, 900 ft TET 170O0K Dry Thrust 37 780 lbf Reheated Thrust 49 300 lbf (18000K Reheat) aare Enqine Weioht Plus Dressinqs 1.046 x Datum (Datum is Olympus 593 Mk 610) Table 3 - Turbojet (A= 0) Encline 4