NASA-TN-D-7890-1975 A brief study of the effects of turbofan-engine bypass ratio on short and long-haul cruise aircraft《涡轮风扇发动机旁通比对短途和长途巡航飞机影响的简短研究》.pdf
《NASA-TN-D-7890-1975 A brief study of the effects of turbofan-engine bypass ratio on short and long-haul cruise aircraft《涡轮风扇发动机旁通比对短途和长途巡航飞机影响的简短研究》.pdf》由会员分享,可在线阅读,更多相关《NASA-TN-D-7890-1975 A brief study of the effects of turbofan-engine bypass ratio on short and long-haul cruise aircraft《涡轮风扇发动机旁通比对短途和长途巡航飞机影响的简短研究》.pdf(46页珍藏版)》请在麦多课文档分享上搜索。
1、A BRIEF STUDY OF THE EFFECTS OF TURBOFAN-ENGINE BYPASS RATIO ON SHORT- AND LONG-HAUL CRUISE AIRCRAFT Aruid L. Keith, Jr. Lungley Reseurch Center Humpton, Vu. 23665 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, 0. C. DECEMBER 1975 I Provided by IHSNot for ResaleNo reproduction or networki
2、ng permitted without license from IHS-,-,-TECH LIBRARY KAFB, NM 19. Security Classif. (of this report) 20. Security Classif. (of this page) Unclassified Unclassified I IIIII I I lllll I lllll Ill1 Ill 21. NO. of pages 22. Price 43 I $3.75 2 Government Accession No. I - - - 1 Report No NASA TN D-7890
3、 A BRIEF STUDY OF THE EFFECTS OF TURBOFAN- ENGINE BYPASS RATIO ON SHORT- AND LONG- - 4. Title and Subtitle HAUL CRUISE AIRCRAFT 7. Author(s) hid L. Keith, Jr. 9. Performing Organiation Name and Address NASA Langley Research Center Hampton, Va. 23665 2. Swnsoring Agency Name and Address National Aero
4、nautics and Space Administration Washington, D.C. 20546 _. 5 Supplementary Notes 3. Recipients Catalog No. .- 5. Report Date December 1975 6. Performing Organization Code 8. Performing Organization Report No. L-9898 .- 10. Work Unit No. 505-04-1 1-01 11. Contract or Grant No. ._ - 13. Type of Report
5、 and Period Covered Technical Note - - . -_- 14 Spomoring Agency Code 6 Abstract A brief study of the effects of turbofan-engine bypass ratio on Breguet cruise Large thrust lapse rates at high range and take-off distance for subsonic cruise aircraft has shown significant differ- ences between short-
6、 and long-haul aircraft designs. bypass ratios caused severe reductions in cruise range for short-haul aircraft because of increases in propulsion system weight. fraction (ratio of propulsion weight plus total fuel weight to gross take-off weight), are less sensitive to propulsion-system weight and,
7、 accordingly, were not significantly affected by bypass-ratio variations. Both types of aircraft have shorter take-off dis- tances at higher bypass ratios because of higher take-off thrust-weight ratios. Long-haul aircraft, with a higher fuel 7. Key-Words- (Suggested by Authoris) ) Bypass ratio Crui
8、se range Turbofan engine . 18. Distribution Statement Unclassified - Unlimited For ale by the National Technical Information Service, Springfield, Virginia 221 61 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-A BRIEF STUDY OF THE EFFECTS OF TURBOFA
9、N-ENGINE BYPASS RATIO ON SHORT- AND LONG-HAUL CRUISE AIRCRAFT Arvid L. Keith, Jr. Langley Research Center SUMMARY A brief study has been made of the effects of varying tui-ofan-engine “ypass ratios from 3 to 12 on the Breguet cruise range and balanced-field take-off distance of short- and long-haul
10、aircraft. These aircraft were assumed to cruise at a Mach number of 0.8 at an altitude of 11 000 m (36 089 ft). The study showed that the large thrust lapse rate of high - bypass -ratio engines caused severe reductions in the cruise range of short-haul air- craft (low ratio of propulsion weight plus
11、 fuel weight to gross take-off weight, called fuel fraction). This result was due to an increase in the propulsion weight of the high-bypass- ratio engines. Long-haul aircraft (higher fuel fraction) are less sensitive to increases in propulsion weight, and accordingly the net effects of increasing b
12、ypass ratio were not sig- nificant. Both types of aircraft had shorter take-off distances with increasing bypass ratio because of higher take-off thrust-weight ratios. INTRODUCTION Continued development of the turbofan engine has resulted in an increase in bypass ratio from low values (1 to 1.4) to
13、moderately high values (4 to 8); this has brought about significant improvements in subsonic aircraft cruise performance and reductions in aircraft noise. These moderately high-bypass-ratio engines have evolved through technological advances in overall pressure ratio, turbine inlet temperature, hot-
14、parts cooling, and materials. These engines provide (1) better cruise economy because of lower specific fuel consumption, (2) lower noise in and around the airport community because of lower core-engine and fan-jet velocities, and (3) shorter take-off distances and faster climbout because of the hig
15、her take-off thrust of engines that are sized for matching of cruise net thrust with cruise drag (hereinafter referred to as cruise thrust-drag matching or thrust-drag matched engines). Shorter take-off distances and faster climbout also reduce community noise. It has been suggested that engines wit
16、h bypass ratios even higher than those of present engines would provide further gains in cruise economy, shorter take-off distances, and lower noise. Lower cruise specific fuel consumption is inherent in higher bypass-ratio Provided by IHSNot for ResaleNo reproduction or networking permitted without
17、 license from IHS-,-,-1l111llII II I1 I1 Ill I I II cycles for basic engines of a given technology level. Thrust lapse rate, the rate at which engine net thrust decays with flight speed, is also a function of bypass ratio, and engines which are sized specifically for cruise thrust-drag matching will
18、 certainly produce increases in take-off thrust with increases in bypass ratio. Furthermore, with high bypass ratios, if the exhaust flow, which is at a lower velocity, could be directed over or through wing-flap systems to increase take-off lift coefficients, shorter take-off distances, faster clim
19、bout, and still lower noise could be realized. Short take-off and landing aircraft thus could be con- figured to meet noise requirements expected for future aircraft without sacrifices in flight performance. The potential improvements offered by high-bypass-ratio engines may not be fully realized, h
20、owever, because of aircraft installation effects. with bypass ratio, propulsion systems sized to provide cruise thrust-drag matching will become larger and heavier as bypass ratio is increased. Increases in propulsion-system weight would require either an increase in aircraft gross take-off weight t
21、o perform the same mission requirement or a displacement of fuel or payload for aircraft having the same gross weight. Performance losses due to engine-installation effects and propulsion-system cruise drag can reduce the advantage of lower cruise specific fuel consumption provided by the high-bypas
22、s- ratio engine; the lower fan pressure ratios of high-bypass-ratio engines of a given techno- logical level result in greater sensitivity to installation effects. Since thrust lapse rate increases Thus, it is not clear that the advantages of lower cruise specific fuel consumption, increased take-of
23、f thrust, lower noise, and possibly lift augmentation at take off, which are attributable to increases in bypass ratio, can be attained without important influences on overall aircraft flight efficiency and cruise range. The weight of the engine and propulsion package and the specific fuel consumpti
24、on are of great importance to short-haul aircraft, for which the total fuel is a relatively small fraction of gross take-off weight. haul aircraft, the weight of the engine and propulsion package is of lesser importance; cruise specific fuel consumption and propulsion-system drag are the more import
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