A Parametric Design Method of Lobe Mixer

Abstract

The invention relates to the technical field of mixed air exhaust systems of aviation gas turbofan engines, and particularly to a parameterization design method of a lobe mixer. The method is especially suitable for use in parameterization design and parameter optimization of the novel lobe mixer. The invention aims to solve the problem that design difficulty of the pre-whirling-resistance lobe mixer is high, and achieve the purpose of parameterization design through using parameters to define geometry of the lobe mixer in a design process. The method includes the steps of parameterization design of a basic lobe mixer, parameterization showing of the basic lobe mixer, two-dimensional design of the target lobe mixer, three-dimensional design of the target lobe mixer, novel parameterization trailing edge modification of the target lobe mixer and the like. Curves to which the invention relates can be all of straight lines, parabolas, polynomial curves, Bezier curves, spline curves and Nurbs curves. The method has many advantages of simple and effective design, less control parameters, smooth curved surfaces and the like.

Description

technical field [0001] The present invention relates to the technical field of mixed exhaust system of aviation gas turbofan engine, especially relates to the matching technology of low-pressure turbine outlet of aero-engine and mixed exhaust system, the aerodynamic layout of ultra-compact, high-mixing efficiency and high-performance aero-engine exhaust system, especially the lobe mixing Parametric design of the device. Background technique [0002] The exhaust system of aviation gas turbine fan engine is divided into two forms: separate exhaust and mixed exhaust. For civil turbofan engines with large bypass ratio, the exhaust system usually adopts the form of separate exhaust, while for gas turbofan engines with small and medium bypass ratios, the exhaust system mostly adopts the hybrid exhaust system. [0003] Early mixed exhaust systems mostly used annular exhaust mixing pipes. For example, F100-PW-129 adopted a simple annular mixed exhaust type. This mixed exhaust layou...

AI Technical Summary

Problems solved by technology

However, the geometric structure of the lobe mixer is complex, which makes its design more difficult, and the influence of its parameters is not yet fully clear

In addition, due to the increase in the load of the low-pressure turbine stage, the outlet flow of the low-pressure turbine has a circumferential airflow angle. The conventional lobe mixer itself has a certain anti-pre-swirl ability, but the space for adapting to the upstream pre-swirl is very limited, more than 10 A low-pressure turbine outlet airflow angle of ° will cause flow separation on the lobe surface, and a recirculation zone will appear downstream of the central cone, which greatly increases the total pressure loss and thrust loss, which in turn increases the difficulty of matching the lobe mixer with the low-pressure turbine , especially matching with the high load low pressure turbine

[0005] In order to solve the problems existing in conventional lobe mixers, scholars have conceived a new type of anti-prerotation lobe mixer, which can solve the negative effects of upstream prerotation to a certain extent.

However, due to the more complex structure of the anti-pre-swirl lobe mixer, its design and optimization are extremely difficult, making it difficult to carry out research work on it, so that the matching law between the new anti-pre-swirl lobe mixer and the outlet airflow of the upstream low-pressure turbine is still unclear. Not clear, and the mode of action with the downstream mixing nozzle is not yet clear

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