Abstract. In this paper, the stresses of plate-fin structures at the different operation parameters were analyzed in actual operation process of LNG plate-fin heat exchanger based on finite element method and thermal elastic theory. Stress characteristics of plate-fin structures were investigated at the different operation parameters of that. The results show that the structural failure of plate-fin structures is mainly induced by the maximum shear stress at the brazing filler metal layer between plate and fin while by the maximum normal stress in the region of brazed joint near the fin side. And a crack would initiate in brazed joint near the fin side. The maximum normal stress is also main factor to result in the structural failure of plate-fin structures at the different temperature difference (between Natural Gas (NG) and Mixture Refrigerant (MR)), MR temperature and NG pressure of LNG heat exchanger. At the same time, the peak stresses obviously increase as the temperature difference, MR temperature and NG pressure increase. These results will provide some constructive instructions in the safe operation of LNG plate-fin heat exchanger in a large-scale LNG cold-box.
The density of supercritical CO2 is calculated by Peng-Robinson state equation. Through comparing with the experimental values, it is founded that the calculation results are very similar with experimental values, which indicates that Peng-Rob inson state equation is an ideal method for forecasting the density of supercritical CO2.
Discloses the variation of the thermal stress of the ingot heating process to cylindrical body ingot, for example, the thermal stress change in the heating process of the modeling obtained the variation of the axial, tangential and radial thermal stress,the research results provide a theoretical basis for the corresponding set of process parameters.
In this study, a robust model predictive controller is designed for the trajectory tracking problem of non-holonomic constrained wheeled mobile robot based on an elliptic invariant set approach. The controller is based on a time-varying error model of robot kinematics and uses linear matrix inequalities to solve the robust tracking problem taking uncertainties into account. The uncertainties are modelled by linear fractional transform form to contain both parameter perturbations and external disturbances. The control strategy consists of a feedforward term that drives the centre of the ellipse to the reference point and a feedback term that converges the uncertain system state error to the equilibrium point. The strategy stabilises the nominal system and ensures that all states of the uncertain system remain within the ellipsoid at each step, thus achieving robust stability of the uncertain system. Finally, the robustness of the algorithm and its resistance to disturbances are verified by simulation and experiment.
Supercritical CO2 is nontoxic, nonflammable, noncorrosive, inexpensive, and does not generate any additional toxic or hazardous wastes. In this article, the fluidic parameters of supercritical CO2 and water fluidic are calculated by related equations. The results show that the fluidic impact force of supercritical CO2 fluidic is higher than water fluidic, which indicates that using supercritical CO2 fluidic to dispose the obsolete propellant is possible.
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