Study on Strength and Life of Anisotropic Single Crystal Blade - Part Ⅱ: Experimental Research

The single crystal blade is one of the key technologies for improving the performance, durability and reliability of aero-engines and ground gas-turbine engines. However, the anisotropic mechanical properties of the single crystal material makes a great deal of difficulties on the development and the application of the single crystal blade, which is a challenge for the engineering application of the single crystal superalloy and the theoretic bases of the application. Some researches on the strength analysis and the life prediction of the anisotropic single crystal blade were carried out by the authors' research team. They are as follows. The crystallographic constitutive models for the plastic and the creep behaviors and the method of the rupture life prediction were established and verified. The tensile or the creep experiments for DD3 single crystal alloy with different orientations under different temperatures and different tensile rates or under different temperatures and different stress levels were carried out. The experimental data and the anisotropic properties at intermediate and high temperatures revealed by the experiments are significant for the application of the single crystal alloy. In addition, the experimental research for a kind of single crystal blade was also made. As the application of the researches the strength analysis and the life prediction were carried out for the single crystal blade of a certain aeroengine. In this part, the experimental research work is describled, and the constitutive models and applications have been described in part I.

Radiation heat transfer model for complex superalloy turbine blade in directional solidification process based on finite element method

For the sake of a more accurate shell boundary and calculation of radiation heat transfer in the Directional Solidification(DS) process, a radiation heat transfer model based on the Finite Element Method(FEM)is developed in this study. Key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also stated. In order to analyze the effect of withdrawing rate on DS process,the solidification processes of a complex superalloy turbine blade in the High Rate Solidification(HRS) process with different withdrawing rates are simulated; and by comparing the simulation results, it is found that the most suitable withdrawing rate is determined to be 5.0 mm·min^(-1). Finally, the accuracy and reliability of the radiation heat transfer model are verified, because of the accordance of simulation results with practical process.

Numerical simulation of a rotary engine primary compressor impacted by bird

In order to examine the process of a rotary engine primary compressor impacted by bird, a finite element model of a bird impacted on plate is developed with the explicit code PAM-CRASH. The smooth particles hydrodynamic （SPH） method is used to simulate the bird because of the SPH method showing no signs of instability and correctly modeling the breaking-up of the bird into particles. Good agreement between the simulation results and experimental results indicates that the numerical method of bird strike used in the present paper is reasonable. Then a rotary engine primary compressor impacted by three different configurations bird named straight-ended cylinder bird, quadrangular bird, hemispherical-ended bird are investigated using the numerical simulation method. It is found that the whole process of bird strike sustained about 3.5 ms and the bird is slashed by blade during the strike. The geometry configuration of bird affected the displacement and von Mises stress of some blades severely, just because the breaking bird＇s mass is affected by the bird＇s configuration. In the event of bird striking on the site of＂up＂some blades may develop plastic deformation and it is very adverse for the safety work of the engine.

Numerical Investigation on Super-cooled Large Droplet Icing of Fan Rotor Blade in Jet Engine

Icing(or ice accretion) is a phenomenon in which super-cooled water droplets impinge and accrete on a body.It is well known that ice accretion on blades and vanes leads to performance degradation and has caused severe accidents.Although various anti-icing and deicing systems have been developed,such accidents still occur.Therefore,it is important to clarify the phenomenon of ice accretion on an aircraft and in a jet engine.However,flight tests for ice accretion are very expensive,and in the wind tunnel it is difficult to reproduce all climate conditions where ice accretion can occur.Therefore,it is expected that computational fluid dynamics(CFD),which can estimate ice accretion in various climate conditions,will be a useful way to predict and understand the ice accretion phenomenon.On the other hand,although the icing caused by super-cooled large droplets(SLD) is very dangerous,the numerical method has not been established yet.This is why SLD icing is characterized by splash and bounce phenomena of droplets and they are very complex in nature.In the present study,we develop an ice accretion code considering the splash and bounce phenomena to predict SLD icing,and the code is applied to a fan rotor blade.The numerical results with and without the SLD icing model are compared.Through this study,the influence of the SLD icing model is numerically clarified.