Optimization of Air Distribution in a Preliminary Design Stage of an Aero-Engine Combustor

Abstract

The design of a modern aero-engine combustor is strongly driven by severe emission regulations. The paper describes an automated preliminary aero-thermal design process for a rich-burn combustor by combining different low fidelity analysis tools in order to speed up the preliminary design loop and provide improved combustor designs. Design evaluation is performed by a knowledge-based preliminary design tool coupled with a network solver. The preliminary design tool provides a 2D geometry model and cooling layout based on industrial in-house design rules. The 1D network solver then calculates the air distribution inside the combustor for two state-of-the-art combustor cooling schemes, i.e., single skin cooling and double skin tiled cooling. The computed air distribution is subsequently used to predict emissions which are minimized by using a genetic multi-objective optimization algorithm. As a result, better designs are obtained with the prescribed approach compared to a human reference design. Nomenclature, c i,j = flow/geometry specific constants λ = node mass source afr 1 = air-fuel-ratio of injector ρ = fluid density afr 2 = air-fuel-ratio at primary zone exit Indices c = port style • cc = combustor chamber cb = circumferential blockage factor • i,o = inner/inlet, outer/outlet f r = radial factor • m = middle d = diameter • p = port h, h = height, constraint vector • pp,sp = primary/secondary ports l = length • pz,sz = primary/secondary zones = mass flow • 3 = compressor exit n = number • 4 = turbine entry p = pressure • TO = take-off conditions p = parameter vector Abbreviations r = radius CFD = computationalsfluid dynamics s i,j = flow direction at node i,j NO x = nitrogen oxides v = velocity NSGA-II = non-dominated sorting V = volume genetic algorithm-II α = combustor cant angle SN = smoke number

Component-Specific Preliminary Engine Design Taking into Account Holistic Design Aspects

“…In order to influence the combustor outline and to optimize the efficiency and emission index, flow settings concerning the internal air distribution will be varied. Relevant design parameters are the air-to-fuel-ratios at injector r a f ,in and primary zone exit r a f ,pz , length of primary and secondary combustion zones represented by the relative position of the related mixing ports (γ pp , γ sp ), and the style of the primary and secondary mixing ports (s pp , s sp ) similar to [18]. The air-to-fuel ratios are related to the local mass flows at the injector, as well as primary zone exit, and are normalized by the fuel mass flow.…”

“…), and the style of the primary and secondary mixing ports ( , ) similar to [18]. The air-to-fuel ratios are related to the local mass flows at the injector, as well as primary zone exit, and are normalized by the fuel mass flow.…”

Coupled flow network model and CFD analysis for a combined impingement and film cooled gas turbine nozzle guide vane

“…Che et al [12] made calculations for both steady and transient state problems by using the component method and network method toward series and parallel networks. They showed that the whole engine model simulated by the component method is suitable for observing the safety of engine influenced by the dynamic characteristic of the secondary air system Angersbach and Bestle [13] described an automated preliminary aero-thermal design process for a rich burn combustor by combining preliminary design tool, 2D geometry model coupled with a 1D network solver in order to speed up the preliminary design loop and provide improved combustor designs. The 1D network solver then would calculate the air distribution inside the combustor for two different combustor cooling schemes.…”