Lili Gu

We analyze theoretically the thermal effect on the dynamics of a damped-cantilever Timoshenko beam structure, which is featured with cross-sectional temperature gradients. The thermal effect is incorporated in the dynamic model via the temperature-dependent elastic modulus and the temperature-gradient-induced thermal force. The inhomogeneous boundaries introduced by the thermal moment are handled by decomposing the total displacement into static and dynamic displacements. In the end, numerical results based on the analytical solutions are given for a better understanding of the thermal effect on the dynamic behaviors. The solutions reveal the circumstances in which thermal eigenvalues should be considered together with the cross-sectional temperature gradients in predicting thermal vibrations. Moreover, the results also highlight the role of axial temperature gradients on the dynamic response induced by equivalent shearing forces.

This paper presents a study of the heat transfer influence on the centrifugal compressor performance. The compressor
studied in this paper is based on the scale-up of a turbocharger compressor equipped with a shroudless impeller. To
account for the heat transfer effect, a conjugate heat transfer analysis is performed with computational fluid dynamics
techniques. The heat transfer phenomena not only externally but also internally are investigated at the design point. The
grids adopted in the study are verified at the baseline, with an excellent agreement found between numerical simulations
and measurements. The results provide an insight into the dependence of the heat transfer influences on the heat flux
paths. The path of the external heat flux passing through the impeller shaft is found to have a great impact on the
compressor performance. The study of internal heat transfer shows that the shroud surface dominates the internal heat
transfer effect on the efficiency loss. Furthermore, the heat transfer influence is also investigated on the compressor
performance at other operating points. The results imply a positive potential margin for the improvement of compressor
efficiency by means of heat transfer control.

We present an analytical analysis of a continuous rotor shaft subjected to universal temperature gradients. To this end, an analytical model is derived to investigate the generic thermal vibrations of rotor structures. The analytical solutions are obtained in a rotating frame and include parameters related with both the thermal environment and the rotor dynamic structures. This provides an insight into the mechanisms for the rotor thermal vibration. Furthermore, numerical results based on the analytical solutions are given. An index denoting the temperature gradients is proposed for the occasions with
nonlinear cross-sectional temperature distributions. Finally, the factors influencing the thermal vibrations are analyzed. The results show that the thermal vibration is affected by
many factors including the shaft size, rotational speeds, heating locations, critical speed, etc. Moreover, it is investigated how the convection coefficient and the heat conductivity influence the thermal vibrations in order to provide an insight into the management of thermal vibrations from the perspective of thermal aspects.