Zhu Jiaqi

Application of conjugate heat transfer and fluid network analysis to improvement design of turbine blade with integrated cooling structures

A combination of fluid network analysis method with conjugate heat transfer are applied to the improvement design of the integrated cooling structures in a high-performance turbine blade, coupled with the 3D viscous solver for the gas flow field. By comparison with the experimental results of open literatures, the methodology developed is numerically validated. For a high-pressure turbine rotor blade, it is used to rapidly predict and evaluate the aerodynamic and heat transfer performances of its integrated inner cooling structures. According to the computation results, three ways are definitely proposed for the improvement design, including the adjustment of the coolant flow mass entering into the front and rear cavities in a more appropriate flow mass ratio, the improvement of the turning geometries in serpentine channels to minimize the inner coolant flow resistance, and the adjustment of the local cooling structure dimension according to the high temperature region on outer surface of blade. Through the verification of the fully 3D conjugate heat transfer simulation for the fields of gas flow, solid blade and coolant flow, it shows that the maximum temperature on rotor blade surface is reduced obviously, the temperature distribution becomes more uniform after improvement, and the inlet parameters of cooling cavities are matched more reasonably. It is concluded that in this paper the fluid network combined with conjugate heat transfer significantly shortens the aerodynamic and heat transfer design cycle for the turbine blade with integrated cooling structures.

First-principles studies of the vibrational properties of amorphous carbon nitrides

Raman spectra of amorphous carbon nitride films (a-C:N) resemble those of typical amorphous carbon (a-C), and no specific features in the spectra are shown due to N doping. The present work provides a correlation between the microstructure and vibrational properties of a-C:N films from first principles. The six periodic model structures of 64 atoms with various mass densities and nitrogen contents are generated by the liquid-quench method using Car?Parinello molecular dynamics. By using Raman coupling tensors calculated with the finite electric field method, Raman spectra are obtained. The calculated results show that the vibrations of C=N could directly contribute to the Raman spectrum. The similarity of the Raman line shapes of N-doped and N-free amorphous carbons is due to the overlapping of C=N and C=C vibration bands. In addition, the origin of characteristic Raman peaks is also given.

The research progress about the effect of carrier concentration and mobility on the infrared transparent properties and conductive properties of oxide thin films

Due to the high visible transmittance and conductivity, transparent conductive films caused more and more attention. However, according to the Drude’s theory, there still exist some doubts about the possibility of infrared transparent conductive film. It is the fact that, due to the electrical and optical properties determined by carrier concentration, the contradiction between the wide-range infrared transmission and high conductivity is difficult to coordinate. In this paper, firstly, according to interaction between electrons and photons, we explored the key of confliction between electrical and optical properties, and also discovered the feasibility of infrared transparent conductive films. Through theoretical analysis, we found the reasons of contradiction of electrical and optical properties. Secondly, by summarizing and analyzing the photoelectrical properties of the conventional transparent conductive oxide films, we put forward the relationship among free-electrical, mobility, plasma wavelength and conductivity properties. Lastly, as the result of our research, if the film has the wide-range infrared transmission and high conductivity properties at same time, the effect of carrier concentration and mobility on plasma wavelength is not overlooked.