Study on the optimization design of a civil turbofan engine

Abstract

This work presents an optimization design process for a high bypass unmixed turbofan engine. The optimization design process contains a constraint analysis model, a mission analysis model, an engine cycle parameter optimization model, an engine performance model and an emission prediction model. The constraint analysis model is provided to establish the relationship between thrust to weight ratio and wing loading at takeoff. The mission analysis model is adopted to calculate the aircraft takeoff weight, the maximum thrust at takeoff and the required thrust in cruise. The engine cycle parameter optimization model is based on the self-adaptive three times variation differential evolution (STTVDE) which is developed from the differential evolution algorithm to find the engine cycle parameters minimizing the specific fuel consumption in cruise. The high compressor exit temperature limit, combustor exit temperature limit, engnine size, engnine weight and turbine expansion ratio as well as required thrust in cruise and takeoff which calculated from the constraint analysis and the mission analysis are used as constraint parameters in the engine cycle parameter optimization model. The emission prediction model is used to calculate the landing takeoff (LTO) emission cycle for NO x , CO and UHC based on Boeing fuel flow methodology and T 3 -P 3 methodology. The engine performance model and the mission analysis model are employed to calculate the fuel consumption in the flight mission when engine cycle parameters are determined. Finally, five optimization cases are to be optimized, and their fuel consumptions are compared with each other in the mission analysis model. NomenclaturePropulsion and Energy Forum MFP = mass flow rate parameter m • = mass flow rate NO x = nitrous dioxide N = number n = load factor P = pressure q = dynamic pressure R = additional drage; range S = wing planform area T = temperature t = time; total UHC = unburned hydrocarbon u = total drag to thrust ratio V = velocity W = weight x = variable in function Geek letter α = installed thrust lapse β = instantaneous weight fraction γ = path angle θ = pitch angle ϑ = dimensionless temperature ratio (T/T Ref ) μ = coefficient of friction σ = standard deviation Γ = empty aircraft weight fraction Superscript -= average Subscripts C = constraint c = compressor cor = corrected mass flow rate e = empty f = fuel L = lower boundary p = payload pe = expendable payload pp = permanent payload Ref = reference SLS = sea level static th = throat TO = takeoff U = upper boundary V = variable 0 = upstream of an engine 3 = high pressure compressor exit section 4 = combustor exit section Abbreviations BPR = bypass ratio FAR = fuel air ratio HPCR = high pressure compressor pressure ratio HPT = high pressure turbine LPT = low pressure turbine IFPR = inner fan pressure ratio OFPR = outer fan pressure ratio American Institute of Aeronautics and Astronautics 2 Downloaded by PRINCETON UNIVERSITY on August 11, 2015 | http://arc.aiaa.org |