Influence Of Thermal Distortions Research Articles

Thermo-hydrodynamic characteristics of spiral groove gas face seals operating at low pressure

Thermo-hydrodynamic behaviors of spiral groove gas face seals are investigated for the cases of low seal pressure. Pressure and temperature fields of gas film are calculated, and then influence of thermal distortion on seal performance are analyzed. It is found that spiral grooves lead to complex film temperature distributions and rotational speed results in the increase of whole film temperature. But the shear heat and pumping effect of spiral grooves have little influence on film temperature gradient along the leakage direction. The face thermal distortion, forming divergent clearance along the leakage direction, makes the opening force decrease and the leakage increase. A higher seal pressure and clearance will result in a larger thermal distortion. And the rotational speed may enhance the face thermal distortion further in some low pressure cases.

Influence of Thermal Distortion of Mirrors in Laser Resonators on Laser Modes

Taking into account the thermal absorption of laser light on laser mirror surface, the thermal deformation of the mirror substrate was analyzed. Influence of the thermal distortions of the mirror substrate on the laser resonant modes was calculated. The expressions for the field distributions of transverse laser modes with perturbation methods were derived. By comparing them with the elegant Hermite-Gaussian modes where there were no thermal distortions, the intensity profiles of the transverse laser modes versus the amount of the thermal deformation were obtained. The results show that the larger the thermal distortions of mirrors are, the wider the intensity profiles of the fundamental mode become, and the smaller the peak intensity becomes. Meanwhile, the high-order modes will be induced.