been run on an engine to demonstrate a 10% flow increase.The choice for this study Condition 1 2 3 of a high temperature version of this engine rather than the basic olympus 593 Mach number 2.0 1.2 0,93 0.50 was dictated by a desire to meet a take-off thrust of around 50 000 1b within a reheat Altitude（ft) 53000 40000 25000 15000 temperature of 1800K. Assumed 0.9371 0.9858 0,99 0.99 The relative weights of these engines are intake PRF shown on Figure 4 as a function of flow increase over the Olympus 593.Also shown Net thrust 14610 19430 11980 9940 is the effect of scaling up the turbojets. (1bf) It will be seen that to increase flow by increasing bypass ratio is 'a considerably Relative lighter route than scaling up an engine. importance in 73,8% 10.3% 6.6% 9.2% mission fuel Condition 1:supersonic acceleration and 20n cruise Condition 2: transonic acceleration RESSED Condition 3: ENSINE diversion cruise WEICHT Condition 4:hold 乳A7ME 心Y 5 Table 4 Flight Conditions for Mission Fuel Calculation (ISA 50C) 卜/25 OWER L4WS4kE 4材-2口 1550 SOT LINE CONSISTENT WITH ⊙7九RET产 FI0 32 OF SAE 75/056 a格3 ▲my9pEs9is 10 5 20 25 30 COWEPALANT L 4s% 550K57 7龙LA/RFLOW RELA7e7DMMP然B93 15s0 元B2F4ND SOT Fig 4. Estimated Weight of Engines for ICAO Studies 2 It is of interest to compare the results of powerplant plus fuel weight calculations MEW DTZOM for the family of engines studied with the - -- results of earlier parametric studies such as Figure 3 which are based on simple cycle calculations and weight formulae. 2 OPERATINS CRUISE PYAASS RATO 05 格 The engines have been scaled to the common cruise thrust requirement of the Fig 5. Comparison of ICAO Study Engines 700 000 1b TOGW;4200 nm range,Mach 2.0 with Original Parametric Studies cruise aircraft model described in Reference 3.The internal engine perfor- Take-off and flyover noise estimates have mance was evaluated at the flight condi- been made for the family of engines by a tions listed in Table 4 to determine the Rolls-Royce method,The results are shown fuel weight for a typical mission. The for typical thrust levels on Figure 6 and relative importance of each flight condi- Figure 7 as a function of mass flow relative tion in determining mission fuel weight is to Olympus 593.Noteworthy is the diminish- also given in Table 4. ing return of increasing mass flow at the flyover condition.The actual noise scales The full line of Figure 5 shows the have been omitted,as this and other methods results of a parametric study similar to are being reviewed by the ICAO Working Group Figure 3 and in fact using identical noise sub-group,and it would be undesirable assumptions to Figure 32 of Reference 4, to pre-empt the conclusion of the sub-group. except that a 1600 K TET (1550K stator outlet temperature)has been used.The By combining Figures 6 and 7 with the individually plotted points show the mission calculation it is possible to results for the family of engines here relate powerplant plus fuel weight described.The datum is the current with total air flow and noise level,as Olympus 593 scaled to suit the new aircraft shown on Figure 8,Figure 8 also shows the model.It will be seen that the trends of benefit to be obtained from increasing the earlier parametric study are closely cruise TET beyond the Class II level to confirmed by the current more detailed 1700K together with an increase of around evaluation. 3%in HP spool rpm.This corresponds to
been run on an engine to demonstrate a 10% flow increase. The choice for this study of a high temperature version of this engine rather than the basic Olympus 593 was dictated by a desire to meet a take-off thrust of around 500000 lb within a reheat temperature of 1800 K. - The relative weights of these engines are shown on Figure 4 as a function of flow increase over the Olympus 593. Also shown is the effect of scaling up the turbojets. It will be seen that to increase flow by increasing bypass ratio is a considerably lighter route than scaling up an engine. Fig 4. Estimated Weight of Engines for ICAO - Studies It is of interest to compare the results of powerplant plus fuel weight calculations for the family of engines studied with the results of earlier parametric studies such as Figure 3 which are based on simple cycle calculations and weight formulae. The engines have been scaled to the common cruise thrust requirement of the 700 000 lb TCGW; 4200 nm range, Mach 2.0 cruise aircraft model described in Reference 3. The internal engine,perfor- mance was evaluated at the flight conditions listed in Table 4 to determine the fuel weight for a typical mission. The relative importance of each flight condition in determining mission fuel weight is also given in Table 4. The full line of Figure 5 shows the results of a parametric study similar to Figure 3 and in fact using identical assumptions to Figgre 32 of Reference 4, except that a 1600 K TET (155OoK stator outlet temperature) has been used. The individually plotted points show the ,results for the famil'y of engines here described. The datum is the current Olympus 593 scaled to suit the new aircraft model. It will be seen that the trends of the earlier parametric study are closely Eonfirmed by the current more detailed evaluation. J ~ Condition Mach number Altitude (ft) Assumed intake PRF Net thrust (lbf) Relative importance in mission fuel 73.8% 10.3% 6.6% ~ ILL 4 _____ 0.50 15 O( __ ~ 0.99 ~ 9940 ~ 9.2% .- Condition 1: sunersonic acceleration and cruise Condition 2: transonic acceleration Condition 3: diversion cruise Condi.tion 4: hold Table 4 - Fliqht Conditions for Mission Fuel Calculation (ISA + 50CL Fig 5. Comparison of ICAO Study Engines with Original Parametric Studies Take-off and flyover noise estimates have been made for the family of engines by a Rolls-Royce method. The results are shown for typical thrust levels on Figure 6 and Figure 7 as a function of mass flow relative to Olympus 593. Noteworthy is the diminishing return of increasing mass flow at the flyover condition. The actual noise scales tiave been omitted, as this and other methods are being reviewed by the ICAO Working Group noise sub-group, and it would be undesirable to pre-empt the conclusion of the sub-group. By combining Figures 6 and 7 with the mission calculation it is possible tb relate powerplant plus fuel maight with total air flow and noise level, as shown on Figure 8. Figure 8 also .shows the benefit to be obtained from increasing cruise TET beyond the Class I1 level to 1700 K together with an increase of around 3% in, HP spool rpm. This corresponds to 5
MACH 03 ISA 10%C 6…40H公2必 DECREASING MOISE SdB ITERVLS- 名Edit时 SCALED 595 心老 62 X7a北RFLOW RELA公和PS53 Fig 6. AST Take-off (Sideline)Noise-Four Fig 8. Payload Total Airflow and Noise Engines,2310 ft Slant Range Comparison 175 ALTITUDE Integrated Aircraft/Engine Study POUR ENGINE FREE FIELD .Whilst the mission fuel plus powerplant weight studies outlined above can give the relative merits of self-consistent engine proposals,for accurate assessments there is no substitute for a combined aircraft/ engine study where the aircraft design can be modified and optimised in accordance with the characteristics of the powerplants, which can also be tailored to the specific aircraft. 25 As mentioned earlier,British Aerospace have been conducting such studies 20 EPNdB 30 as part of their contribution to the work +©% of the ICAO Parametric Study sub-group,and 2时 some preliminary results have been published in Reference 5. TAM NET7HRT=CO他E4落T包) The British Aerospace project assessment programme used for these studies can handle Fig 7.AST Cutback (Flyover)Noise a range of aircraft geometries,mission ranges,passenger payloads and engine Iturning up the tapt on each engine of the designs. Noise at each of three measuring family. The increased cruise thrust capa- points defined by ICAO 1971 Annex 16,based bility gives a smaller engine,but it on measured Concorde noise levels,is calcu- should be noted that the transonic regime lated, The noise calculations are in the will require a proportionately higher TET course of being checked by methods proposed increase to give the thrust. If this is by the ICAO noise sub-group,and the noise not practical,some reheat may be required scale has been omitted,l0dB bandwidth and the benefit of increased TET will be intervals being shown on the curves to indi- eroded,Furthermore,it must be remembered cate trends.No special silencing means, that the benefits of increased TET can also apart from the use of acoustic liners,has be eroded by a higher replacement cost for been assumed for these curves. hot end parts. Figures 9 and 10 reproduced from Reference 5 show the results of the cal- Figure 8 also shows the effect of changing the weight fraction of the in- culations for fixed range and fixed payload takes,nacelles,and secondary nozzles of respectively for the engines discussed above. The engines are sized to the cruise the datum engine powerplant from the thrust requirement of each aircraft,and Concorde value to 0,6 of the Concorde reheat boost is assumed for take-off,where value,which would be more appropriate to necessary.As expected,the lower noise second generation axisymmetric pods. The levels require higher bypass ratios,and penalty for increased mass flow is result in increasing gross weight for a diminished.However,Figure 8 ignores given range and mission, installation loss,(eg skin friction etc) which will tend to offset this trend,as is A very significant feature of these shown in Figure 3.It should be noted that curves is how the lower bound tends to if this change in datum weight fraction become vertical for a given range and could be achieved without any structural or payload.Thus there is a minimum noise other weight penalty,an improvement in level that cannot be bettered at a given payload of 27%would be obtained. level of technology. 6
Fig 6. AST Take-off (Sideline) Noise -Four Engines, 2310 ft Slant Range a. W6,NE FEE WCLD N75 AL77WDE Fig 7. AST Cutback (Flyover) Noise 'turning up the zap' on each engine of the family. The increased cruise thrust capability gives a smaller engine, but it should be noted that the transonic regime will require a proportionately higher TET increase to give the thrust. If this is not practical, some reheat may be required and the benefit of increased TET will be eroded. Furthermore, it must be remembered that the benefits of increased TET can also be eroded by a higher replacement cost for hot end parts. Figure 8 also showsthe effect of changing the weight fraction of the intakes, nacelles, and secondary nozzles of the engine powerplant from the .Concorde value to 0.6 of the Concorde value, which would be more appropriate to second generation axisymmetric pods. The penalty for increased mass flow is diminished. However, Figure 8 ignores installation loss, (eg skin friction etc) which will tend to offset this trend, as is shown in Figure 3. It should be noted that if this change in datum weight fraction could be achieved without any structural or other weight penalty, an improvement in payload of 27% would be obtained. Fig 8. Payload Total Airflow and Noise Comparison Intearated Aircraft/Enqine Studv .Whilst the mission fuel plus powerplant weight studies outlined above can give the relative merits of self-consistent engine proposals, for accurate assessments there is no substitute for a combined aircraft/ engine study where the aircraft design can be modified and optimised in accordance with the characteristics of the powerplants, which can also be tailored to the specific aircraft. As mentioned earlier, British Aerospace have been conducting such studies as part of their contribution to the work of the ICAO Parametric Study sub-group, and some preliminary results have been published in Reference 5. ~ The British Aerospace project assessment programme used for these studies can handle a range of aircraft geometries, mission ranges, passenger payloads and engine designs., Noise at each of three measuring points defined by ICAO 1971 Annex 16, ba~sed on measured Concorde noise levels, is calculated. The noise calculations are in the course of being checked by methods proposed by the ICAO noise sub-group, and the noise scale has been omitted, lOdB bandwidth intervals being shown on the curves to indicate trends. No special silencing means, apart from the use of acoustic liners, has been assumed for these curves. Reference 5 show the results of the calculations for fixed range and fixed payload respectively for the engines discussed above. The engines are sized to the cruise thrust requirement of each aircraft, and I-eheat boost is assumed for take-off,where necessary. As expected, the lower noise levels require higher bypass ratios, and result in increasing gross weight for a given range and mission. Figures9and 10 reproduced from A very significant feature of these curves is how the lower bound tends to become vertical for a given range and level that cannot be bettered at a given level of technology. payload. Thus there is a minimum noise \