No abstract

Focused on the problem of unbalanced propellant consumption in parallel tanks of propulsion system, a squeeze-type regulation method based on the gas law method was discussed in the paper. Taking the tank system as the research object, the thermodynamic models under isothermal, adiabatic and other conditions were given and the factors affecting the uncertainty of the model were analysed. The results show that the measurement uncertainty of the model mainly comes from the pressure measurement accuracy and the volume measurement accuracy. The model was applied to different cases and the influence law of different tank parameters on the model uncertainty was studied. It is found that under the premise of the fixed pressure difference of the parallel tanks, the uncertainty of the regulation model is almost linear with the regulation amount. In addition, the relative uncertainty of the model can be reduced effectively by improving the pressure difference of the parallel tanks. The accuracy of the regulation model can reach to 7.7%, which can meet the requirements for on-orbit use.

This is an investigation into the effect of spatially nonuniform temperature fields on the undamped, free vibration characteristics of the wire electrode in the wire electro-discharge machining (EDM) process. In particular, a nonlinear multi-mode structural model is developed for the translating wire along with a thermal model which accounts for heat input (from sparking), axial conduction, radial convection, and energy storage. The two models are then coupled through the internal thermal stress terms of the structural model. Using these combined models, an eigenvalue analysis is performed to examine the behavior of the natural frequencies (Im(λ)) as a function of the transport speed. It is shown that both divergence and Hopf bifurcations occur in this system. Specifically, the system is unstable at low transport speeds due to thermal buckling, stable at intermediate speeds, and unstable at high speeds due to a series of transport instabilities. Furthermore, it is shown that the frequency loci for a given mode decreases as the input discharge energy and, hence, the mean wire temperature are increased. This lowers the critical transport speed associated with the transport instability.