Bi-objective optimization of pylon-engine-nacelle assembly: weight vs. tip clearance criterion

Abstract

A realistic application of advanced structural and multi-objective optimization for the design of a fully assembled aircraft powerplant installation is presented. As opposed to the classical design process of powerplant installation that does not consider the influence of pylon sizing over engine efficiency, we develop in the present a fully integrated approach where both pylon and compressor intercase are designed at once. The main objective is to consider the impact of weight over tip clearance performance criterion and see how these two objectives are antagonistic. In this work, we perform in the same design session tasks traditionally devoted to the airframe manufacturer and aero-engine manufacturer. The overall weight of the assembly is minimized with respect to Specific Fuel Consumption (SFC) criterion. One interesting aspect of the process is that SFC criterion is based on highly proprietary models and its simulation and call within an optimization process is made available through the development of a webservice. One major phenomenon to consider in both pylon and engine design is Fan Blade Off (FBO) event, i.e. the sudden release of a blade. This event causes high impact loads and must be considered carefully in the design. Such a simulation is not an easy task and several nonlinear phenomena must be addressed (e.g. rotordynamics), not to mention the integration of this nonlinear dynamic response in a static structural optimization process. This article describes how the design of the full assembly is performed taking into account both objectives. Such a problem lies in multi-objective optimization field and then we describe the method we use to solve such a problem. The simulation of an FBO post-impact rotor dynamics is also described and we end up with the final results that show the influence of pylon-engine weight sizing over SFC.

Some considerations regarding the use of multi-fidelity Kriging in the construction of surrogate models

“…The first of these engineering test problems is a simpler multi-fidelity version of the high pressure compressor optimization taken from Bettebghor et al [1]. In this optimization the specific fuel consumption (SFC) of the engine is optimized by altering the location of the thrust linkages on the exterior of the high pressure compressor casing, shown in Figure 30.…”

“…A high fidelity transient thermo-mechanical analysis of the engine can be performed taking approximately 6 days or a low fidelity steady-state mechanical analysis, as used by Bettebghor et al [1], can be performed in 1/30 th the time. In both cases the displacements around the circumference of the casing for each compressor stage are extracted and with a fixed set of rotor platform displacements used to calculate the tip clearance of the compressor.…”

“…Table 1 presents the r 2 correlation between the adiabatic efficiencies, massflow rates and pressure ratios obtained from the cheap and expensive simulations 1 . These results indicate that there is a very good correlation between the design metrics obtained from the cheap and expensive simulations.…”

“…Such multi-fidelity approaches have been successfully employed throughout the literature in the design optimization of airfoils [17,24,26], wings [3], compressor rotors [2], combustors [25] and the creation of aerodynamic models [7,[9][10][11]26]. 1 An example of single and multi-fidelity Kriging [5] Figure 1 is a simple example, recreated from Forrester et al [5], of the advantages that multi-fidelity Kriging can offer if used to create a surrogate model. A Kriging model constructed from a four point design of experiments (DoE) of the expensive function (f e (x)) is illustrated by the dashed line.…”

Co-Creation in Complex Supply Chains: The Benefits of a Value Driven Design Approach

“…The authors have extensively used Vanguard Studio (http://www.vanguardsw.com/), a commercial software package dedicated to graphical and hierarchical model development, to implement such a black box concept in the optimization of pylon-engine-nacelle assemblies (Bettebghor et al 2013). An important feature of Vanguard Studio is the automatic web deployment capability, which allows model developers to publish their models on the server, so that they can be viewed and run by other users through a standard browser.…”