The liquid floated gyroscope (LFG) is a core instrument of the inertial navigation system, which is used to obtain the angular motion information of the carrier. Under the thermal effect of electronic components, the floating oil inside the instrument flows slowly, thereby introducing a viscous interference torque (VIT) acting on the floater surface, which will affect the output accuracy of the instrument. Since the magnitude of VIT is extremely small, there is currently no effective means to obtain its accurate value. Therefore, this work aims to combine the advantages of experiment and simulation, and then propose a feasible method to predict the VIT. Firstly, a gas-liquid-solid three-phase coupled heat transfer model of the LFG was established, and the relative error between the calculated temperature and the test temperature of the calibration point is 3.5%. The computational fluid dynamics (CFD) method was adopted to calculate the VIT under different oil temperature distributions, and the BP (back propagation) neural network algorithm was selected to build a network model between the temperature distribution and the VIT, and the model fitting accuracy was 0.99. Then, the actual temperature distribution of the gyro oil was obtained through experiments, which was taken as an input of the neural network to predict the VIT. The relative error between the predicted and simulation values under the same conditions was 4.18%. The proposed method provides a feasible scheme to predict the microscopic VIT that is difficult to measure, which provides a theoretical reference for the accuracy improvement of LFGs.
In order to analyze the dynamic behavior of the oil film in the herringbone gear meshing area under oil injection lubrication conditions more accurately, this paper proposed a thermal elastohydrodynamic lubrication (TEHL) analysis method, by combining the traditional TEHL calculation method with two-phase flow theory. Firstly, ANSYS/CFX 18.1 was used to determine the air content of the lubricating oil in the meshing zone under the injection condition. Then, considering the influence of air content on the rheological properties of lubricating oil, the traditional TEHL model was improved. On this basis, the influence of injection angle a1 on the oil fraction and the lubrication characteristics of the oil film was analyzed. This research can provide a feasible method for the analysis of the lubrication characteristics of herringbone gear.
The hemispherical dynamic pressure motor (HDPM) has the advantages of high speed, wear resistance and stability, which is widely used in inertial instruments to produce the gyroscopic effect. The ultra-thin gas film between the stator and rotor of the motor provides dynamic pressure lubrication and bearing capacity, whose dynamic characteristics determine the motor performance. However, the influence mechanism of some key factors such as ball center distance on the film characteristics is not clear, which has become the bottleneck restricting the performance improvement of HDPMs. Therefore, in this paper, a series of gas film similarity models were solved under different geometric and working parameters, and the influence law of the ball center distance, rotor displacement and stopping process on the aerodynamic characteristics was obtained, the results show that these primary parameters have significant effects on the pressure distribution, resistance moment and frictional heat of the ultra-thin gas film. This work can not only provide a theoretical basis for the aerodynamic performance optimization of HDPMs, but also serve as a reference for the design of other aerodynamic instruments.
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