Sascha Zur

Multi-Level MDO of a Long-Range Transport Aircraft Using a Distributed Analysis Framework

DLRs work on developing a distributed collaborative MDO environment is presented. A multi-level Approach combining high-fidelity MDA for aerodynamics and structures with conceptual aircraft design methods is employed. Configuration-specific sizing loads are evaluated and used for sizing the structure. A gradient-free optimization algorithm is used to optimize the fuel burn of a generic long-range wide-body transport aircraft configuration with 9 shape parameters. The results show a truly multidisciplinary improvement of the modified design. The result of a gradient-free high-fidelity MDO with preselected load cases and five shape parameters is also presented, comparing a full mission analysis with results for the Breguet range equation.

A Stochastic Reliability Model for Application in a Multidisciplinary Optimization of a Low Pressure Turbine Blade Made of Titanium Aluminide

CURRENTLY, THERE ARE A LOT OF RESEARCH ACTIVITIES DEALING WITH TITANI-UM ALUMINIDE (TIAL) AS A NEW MATERIAL FOR LOW PRESSURE TURBINE (LPT) BLADES. EVEN THOUGH THE SCATTER IN MECHANICAL PROPERTIES OF SUCH AN INTERMETALLIC ALLOY IS MORE DISTINCTIVE AS IN CONVENTIONAL METALLIC ALLOYS, STOCHASTIC INVESTIGATIONS ON TIAL ARE VERY RARE. FOR THIS REASON, WE ANALYZED THE SCATTER IN STATIC AND DYNAMIC ME-CHANICAL PROPERTIES OF THE CAST ALLOY TI-48AL-2CR-2NB. IT WAS FOUND THAT THIS ALLOY SHOWS A SIZE EFFECT IN STRENGTH WHICH IS LESS PRONOUNCED THAN THE SIZE EFFECT OF BRITTLE MATERIALS. A WEAKEST-LINK APPROACH IS ENHANCED FOR DESCRIBING A SCALABLE SIZE EFFECT UNDER MULTIAXIAL STRESS STATES AND IMPLEMENTED IN A POSTPROCESSING TOOL FOR RELIABILITY ANALYSIS OF REAL COMPONENTS. THE DEVELOPED RELIABIL-ITY TOOL WAS INTEGRATED INTO A MULTIDISCIPLINARY OPTIMIZATION OF THE GEOMETRY OF A LPT BLADE. SOME PROCESSES OF THE OPTIMIZATION WERE DISTRIBUTED IN A WIDE AREA NETWORK, SO THAT SPECIALIZED TOOLS FOR EACH DISCIPLINE COULD BE EMPLOYED. THE OPTIMIZATION RESULTS SHOW, THAT IT IS POSSIBLE TO INCREASE THE AERODYNAMIC EFFICIENCY AND THE STRUCTURAL MECHANICS RELIABILITY AT THE SAME TIME, WHILE ENSURING THE BLADE CAN BE MANUFACTURED IN AN INVESTMENT CASTING PROCESS.

Distributed Multidisciplinary Optimization of a Turbine Blade Regarding Performance, Reliability and Castability

Modern aero-engine blades are optimized for high perfor- mance and long service life, but manufacturing requirements are not considered adequately during the design process. Thus, time- consuming, iterative re-designs become necessary until a pro- ducible component evolves. The multidisciplinary design opti- mization method presented in this paper addresses not only the aerodynamic efficiency and structural reliability of a new turbine blade, but also ensures the castability of the design and thereby accelerates the entire design process and reduces the time-to- production. Because real casting process simulations are very time-intensive, they were substituted by checks of experimentally and numerically validated geometrical constraints. Different engineering tools were assembled in a joint process chain using an integration framework, which manages and distributes the calculations and hence the workload in a shared network. Based on a preliminary design of a new turbine section, the selected initial low pressure turbine blade was neither castable nor reliable. The multidisciplinary optimization achieved a blade design that satisfies the requirements for a successful casting process, has a low failure probability and, although not as high as from a pure aerodynamic optimization, exhibits an efficiency improvement.