8G8 I e Sociey sa o e esosie o saemes o oiios aace i aes o i iscussio a meeigs o e Sociey o o is iisios o Secios o ie i is uicaios Discussion is printed Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1978/79726/V01BT02A096/2392448/v01bt02a096-78-gt-198.pdf by guest on 24 September 2021 Copyright © 1978 by ASME only if the ppr is published in an ASME journal or Proceedings. eease o geea uicaio uo eseaio u cei sou e gie o ASME e ecica iisio a e $.00 E COY auo(s $.0 O ASME MEMES 00 Mn rbfn Enn Mr Enr Effnt M. C. EMSWO MemASME M. A. IKI Geea Eecic Co Ciciai Oio A eiew o aso aica gas uie egie eeome a eouio uig e as wo ecaes is esee i ems o eegy cosumio e ieacio a eecs o cyce essue aio iig emeaue yass aio a comoe eiciecies o isae ue cosumio ae eiewe e ossiiiies o ue susaia imoeme i eegy eiciecy wi imoe oeaig ecoomics a wi imoe eiomea caaceisics ae ieiie a eauae aameic aa ae esee sowig ae-os i e aeas o eiciecy a ecoomics Eiomea cosieaios ae aso iscusse e aace o ese acos i a cos-eecie aace uoa is iscusse I cocusio oecios ae mae o e caaiiy o a aace uoa egie comae wi e goas esaise y ASA o ei Eegy Eicie Egie ogam e caaceisics o is moe eicie cos-eecie owe a a ca e oeaioa i e ae 19s ae sow i eaiosi o cue uoa egies Contributed by the Gas Turbine Division of The American Society of Mechanical Engineers for presentation at the Gas Turbine Conference & Products Show, London, England, April 9-13, 1978. Manuscript received at ASME Headquarters January 13, 1978. Copies will be available until January 1, 1979. E AMEICA SOCIEY O MECAICA EGIEES, UIE EGIEEIG CEE 35 EAS 4th SEE, EW YOK, .Y. 00 Mn rbfn Enn Mr Enr Effnt M C. EMSWO, M. A. IKI Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1978/79726/V01BT02A096/2392448/v01bt02a096-78-gt-198.pdf by guest on 24 September 2021 ABSTRACT Following the world fuel crisis in 1973, NASA initiated and funded a succession of important A review of transport aircraft gas turbine studies to identify advanced engine systems and engine development and evolution during the past technology that would provide the basis for another two decades is presented in terms of energy con- substantial step improvement in aircraft engine fuel sumption. The interaction and effects of cycle efficiency relative to current high bypass turbofans. pressure ratio, firing temperature, bypass ratio, These studies built on prior company work and con- and component efficiencies on installed fuel con- centrated on the payoff of advanced material tech- sumption are reviewed. nologies and on determining the most suitable and The possibilities for further substantial efficient engine configurations and cycles for com- improvement in energy efficiency with improved mercial transport applications. Two materials operating economics and with improved environ- studies were described in References 1 and 2 while mental characteristics are identified and evaluated. cycle and configuration work was described in Parametric data are presented showing trade-offs References 3 and 4. in the areas of efficiency and economics. Environ- Then followed the NASA Energy Efficient mental considerations are also discussed. The Engine Preliminary Design and Integration Studies, balance of these factors in a cost effective advanced which established a goal of at least 12% reduction turbofan is discussed. in fuel consumption at . 8 Mach, 10, 700M cruise and In conclusion, projections are made for the a reduction of at least 5% in DOC relative to a capability of an advanced turbofan engine compared modern operational high bypass turbofan. The base- with the goals established by NASA for their Energy line engine relative to which the NASA goals were to Efficient Engine Program. The characteristics of be achieved in the General Electric studies was the this more efficient, cost-effective powerplant, CF6-50C, which is currently in wide operational use. that can be operational in the late 1980's, are shown The more energy efficient turbofan described herein, in relationship to current turbofan engines. along with the evaluation ground rules and trends which led to its design selection, was derived from INTRODUCTION these studies. The report of these studies is in process and is expected to be published in mid-1978 The fuel consumption per pound of thrust of (Reference 5). US commercial jet engines improved in two major In this paper, we will examine the component steps since the first jet powered US commercial and system design choices that were available and the aircraft in the late 1950's. An improvement of 15% criteria applied to define an engine to meet the was obtained when the first low bypass turbofans improved efficiency and operating economy goals were introduced in the early 1960's and the high noted above. bypass fans in the early 1970's were in turn 20% better than the low bypass fans. These improve- ENERGY EFFICIENT ENGINE DEFINITION ments in engines together with major improvements in aircraft efficiency have been the product of Since the design of a complete installed competitive pressures to produce more economical engine system is a complex iterative process, the and productive aircraft. Now the urgent realities nature and effect of the design choices that are of the world energy problem require major efforts available to improve overall engine performance are to further improve engine efficiency to conserve most easily understood when they are shown as energy in the National interests. This next major variations on a basic design. In this way, the effect step in power plant efficiency improvement must of the changes inherently has the proper impact on also improve operating costs to provide the incentive the merit of the end product. for its use in future transports. The basic engine cycle that is used here to 1 Mgr - Energy Efficient Engine Program, Fellow evaluate the design choices for a more fuel efficient ASME turbofan evolved during the NASA Energy Efficient 2 Gen Mgr - Advanced Engrg & Technology Programs 1 Engine studies noted above. Design studies of this 5 stage low pressure turbine. The 10 stage 23:1 engine were carried out for an engine having pressure ratio core compressor is driven by a 2 15, 900 Kg SLTO thrust. Important cycle para- stage turbine. The engine system and component meters for this engine are given in Table 1. design is discussed in more detail later. The currently operational engine used as a Table 1 - Energy Efficient Engine Cycle baseline for comparative system performance eval- Fan Pressure Ratio, Max. Climb 1. 71 uation in the General Electric Studies is the CF6-50C, Bypass Ratio " " 6. 1 shown in Figure 2 below (scaled to same Mx Cl Fn at Cycle Pressure Ratio " " 38 . 8 Mach 10, 700M as Figure 1). Cycle parameters Mixed Flow Exhaust - Bypass ratio set to for this engine are shown in Table 2. Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1978/79726/V01BT02A096/2392448/v01bt02a096-78-gt-198.pdf by guest on 24 September 2021 achieve desired mixing pressure match Table 2 - CF6-50C Cycle Turbine Rotor Inlet Temp 1360 C Hot Day T 0 Turbine Rotor Inlet Temp 1304 C Hot Day Mx Cl Fan Pressure Ratio, Mx. Cl 1.76 Turbine Rotor Inlet Temp 1260 C Hot Day Mx Cr Bypass Ratio, " i 4.2 Cycle Pressure Ratio, Mx Cl 32 The preliminary design of the installed Turbine Rotor In Temp, °C (Hot Day TO) 1316 engine which would operate with this cycle is shown Separate Flow Exhaust in Figure 1 below. The engine outer fan frame, inlet, and long duct mixed flow nacelle are made of This engine does not have an integrated inlet/ lightweight composite materials and are structurally nacelle structure. The fan and 3 stage booster integrated. Pylon mounted controls and accessories compressor are driven by a 4 stage low pressure have been considered to reduce nacelle drag. The turbine. The 14 stage 14:1 pressure ratio core fan and its quarter stage are directly driven by a compressor is driven by a 2 stage turbine. ig 1 Eegy eicie suy egie ig Geea Eecic C-5C 2 ENGINE TRADE FACTORS The design of an aircraft engine requires 7 balance and compromise of characteristics and 2.2 capabilities to obtain best overall system perform- SO US = 1575 KG 7 (35000 LBF) ance. Engine cost, maintenance cost, weight, life, reliability, safety and fuel consumption must be 600 YASS AIO quantitatively balanced or optimized throughout the 6 engine and system design to define the "right" 2.0 ss egie Downloaded from http://asmedigitalcollection.asme.org/GT/proceedings-pdf/GT1978/79726/V01BT02A096/2392448/v01bt02a096-78-gt-198.pdf by guest on 24 September 2021 Engine trade factors provide a rational 5 method of trading off the penalties and benefits re- 8 SEECE / sulting from any particular engine characteristics 1 15 1 17 1 in terms of overall benefit to a particular aircraft A / A MAY CIM and engine system. They are derived for commer- cial transport operations by creating a mathemati- ig 3 Eecs o a essue aio/yass cal model of the engine/aircraft system, embodying aio o a aiow a i iamee eegy eicie suy egie appropriate characteristics of mission and engine/ aircraft technology, and varying each significant design choice in turn to determine its impact on overall system performance, weight and cost. 2.6 Trade factors for advanced commercial B 5 SO US = 1575 KG aircraft and engine systems flying particular (35 missions is shown in Table 3.