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Zhou L.-L.,Nanjing University of Science and Technology | Yu Y.-G.,Nanjing University of Science and Technology | Cao Y.-J.,Northwest Institute of Mechanical and Electrical Engineering
Hanneng Cailiao/Chinese Journal of Energetic Materials

To research the influence of injection structure on gas-curtain generated by underwater launched gun, the three-dimensional unsteady mathematical model of multi gas jets in liquid tube was established, and the distribution of phase, pressure and velocity were numerical acquired. Numerical result indicates that after the injection of multi gas jets, Taylor cavities are formed in the liquid Tube. With the mixing process between the Taylor cavities and liquid medium, the multi gas jets merges and the gas-curtain is generated. During the merging process, the pressure in the flow field fluctuates and low-velocity vortex areas are formed on the gas-liquid interface. When the diameter of the slant nozzles increases from 1.5 mm to 2 mm, the reflux of the oblique jets is enhanced, which can result in the improvement of axial expansion performance of the side jets, and the drainage performance of gas-curtain is strengthened, the velocity of the liquid above the gas-curtain increases from 8.26 m·s-1 to 9.4 m·s-1 at 8 ms. © 2016, Editorial Board of Chinese Chinese Journal of Energetic Materials. All right reserved. Source

Liang T.,Xidian University | Liang T.,Northwest Institute of Mechanical and Electrical Engineering | Chen J.,Xidian University | Zhao H.,Hengyang Normal University
International Journal of Systems Science

In this article, by using the fractional order PIλ controller, we propose a simple and effective method to compute the robust stability region for the fractional order linear time-invariant plant with interval type uncertainties in both fractional orders and relevant coefficients. The presented method is based on decomposing the fractional order interval plant into several vertex plants using the lower and upper bounds of the fractional orders and relevant coefficients and then constructing the characteristic quasi-polynomial of each vertex plant, in which the value set of vertex characteristic quasi-polynomial in the complex plane is a polygon. The D-decomposition method is used to characterise the stability boundaries of each vertex characteristic quasi-polynomial in the space of controller parameters, which can obtain the stability region by varying λ orders in the range (0, 2). These regions of each vertex plant are computed by using three stability boundaries: real root boundary (RRB), complex root boundary (CRB) and infinite root boundary (IRB). The method gives the explicit formulae corresponding to these boundaries in terms of fractional order PIλ controller parameters. Thus, the robust stability region for fractional order interval plant can be obtained by intersecting stability region of each vertex plant. The robustness of stability region is tested by the value set approach and zero exclusion principle. Our presented technique does not require sweeping over the parameters and also does not need linear programming to solve a set of inequalities. It also offers several advantages over existing results obtained in this direction. The method in this article is useful for analysing and designing the fractional order PIλ controller for the fractional order interval plant. An example is given to illustrate this method. © 2013 Taylor & Francis Group, LLC. Source

Xie Q.,Shanghai JiaoTong University | Li Y.,Southwest University | Chen X.,Shanghai JiaoTong University | Hu J.,Northwest Institute of Mechanical and Electrical Engineering | And 2 more authors.
Journal of Power Sources

The phosphosilicate sol/sulfonated poly(ether ether ketone) (SPEEK) composite membranes are fabricated by using a simple mechanical mixing process. The performance of the composite membranes is investigated, including their morphology, thermal and mechanical properties, water adsorption and swelling ratio, proton conductivity and fuel cell performance. The composite membranes obtain the advantages of both components while avert their disadvantages, showing excellent comprehensive performance. The utilization of SPEEK endows the composite membranes with good mechanical properties even if the proportion of inorganic components in the membranes is as high as 40 wt.%. The incorporation of phosphosilicate sol not only enhances the dimensional and thermal stability of the composite membranes, but also improves their conductivity significantly. A maximum of proton conductivity of 0.138 S cm-1, higher than that of Nafion 212 membrane (0.124 S cm-1), is obtained from the composite membrane 6SPEEK/4(P-Si) under the conditions of 70 °C and 95% relative humidity, owing to its enhanced hygroscopicity and functional groups. Besides, a single fuel cell equipped with the composite membrane 7SPEEK/3(P-Si) releases a peak power density of 449.9 mW cm-2 at 60°C, higher than that of cells equipped with SPEEK and Nafion 212 membrane measured under the same conditions. © 2015 Elsevier B.V. Source

Jin S.,Polytechnic University of Mozambique | Su Y.,Northwest Institute of Mechanical and Electrical Engineering | Guo C.,Northwest Institute of Mechanical and Electrical Engineering
Zhongguo Jixie Gongcheng/China Mechanical Engineering

A new contact model among rough surfaces was presented based on fractal theory. Y-K fractal model was revised to include all of the elastic, elastic-plastic, and fully plastic deformation regimes for asperity of the fractal surfaces. The two dimensional Y-K model was extended to a new one for three dimensional fractal contact. It is shown that simulation results from revised fractal contact agree with test one better than Y-K contact model, especially under large load. Thus the presented revised fractal contact model can provide more reasonable method for the prediction of contact behaviors among rough surfaces with more accurate than that of Y-K model relatively. Source

Su Y.-W.,Northwest Institute of Mechanical and Electrical Engineering | Chen W.,Xian Jiaotong University | Guo C.-X.,Northwest Institute of Mechanical and Electrical Engineering
Mocaxue Xuebao/Tribology

Wear of clearance revolute joints is commonly coupled with mechanical dynamics. Winkler surface model is utilized to calculate joints reaction and contact pressure rather than Hertz model and finite element method (FEM) because Hertz model is not suitable for conformal contact. And FEM leads to the high computational cost. An analysis scheme of wear coupling with mechanical dynamics is established and validated by an exemplary crank slider mechanism with one clearance joint. Results show that wear prediction based Winkler's model can provide an acceptable accurate wear results compared with FEM although the later produces more accurate prediction. The proposed method is also an efficient tool for tribological design of mechanism with clearance joints. Source

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