Hydraulic Pressure Source Model

Using the hydraulic pressure source model of Figure 2 and the usual network equations, it is apparent that the hydraulic pressure source model yields a pressure-volume equation... 

Constant excitations to a system are represented by an effort or a flow source that provides an output of constant value. In the incremental bond graph these sources are replaced by sources of value zero. If a constant excitation, however, is to be considered uncertain, its source may be replaced in the incremental bond graph by a source modulated by the nominal value. For instance, let Se En represent a constant voltage or constant hydraulic pressure supply. If there is a relative uncertainty 8e = AE/E , then the constant effort source may be replaced in the incremental bond graph by an effort source MSe SsEn modulated by the nominal effort E obtained from the bond graph with nominal parameters. If the internal structure and the parameters of the device are known that provides the excitation and if possible disturbances acting on the device can be modelled, then an incremental bond graph model can be constructed that accounts for the uncertainty of the excitation. 

Figure 4 shows an image of the developed stabiliser trim control and actuation system model. It contains two instances of the drive channel model depicted by Figure 5. Each channel consists of a control computer, a hydraulic valve, motor and brake (FOB) that are electrically activated. The channels are connected to different electric (DCl, 2) and hydraulic (Pressure 1, 2) sources. Each computer is connected to the trim switches (Upl, 2 and Downl, 2), and to the other channel computer for coordination of active or stand-by status. The model interface and connection types are as defined in Table 1.

We consider the problem of liquid and gas flow in micro-channels under the conditions of small Knudsen and Mach numbers that correspond to the continuum model. Data from the literature on pressure drop in micro-channels of circular, rectangular, triangular and trapezoidal cross-sections are analyzed, whereas the hydraulic diameter ranges from 1.01 to 4,010 pm. The Reynolds number at the transition from laminar to turbulent flow is considered. Attention is paid to a comparison between predictions of the conventional theory and experimental data, obtained during the last decade, as well as to a discussion of possible sources of unexpected effects which were revealed by a number of previous investigations. 

PEM resistance in operational PEFC as a function of the fuel cell current density, comparing experimental data (dots) and calculated results from a performance model based on the hydraulic permeation model for various applied gas pressure differences between anode and cathode compartments. (Reprinted from S. Renganathan et al. Journal of Power Sources 160 (2006) 386-397. Copyright 2006, with permission from Elsevier.)... 

The numerical solution method for the above fluid-solid coupling model is an iterative computation process. To reduce the computational complexity, the solid deformation and fluid flow are regarded as two coupled equation systems, solved by FEM. The equilibrium in solid matrix is solved using Eq.(6) with an added coupling item apS j and the pore pressure is treated as an equivalent initial stress term. The flow equation (5) is solved with an added term of volume strain, reflecting the effect of solid deformation on fluid flow. It can be treated as a source or converge. In each iterative loop, the solid matrix deformation is solved firstly. The stress and strain results are then taken as inputs for the flow calculation with modified hydraulic parameters. After flow model is solved, the pore pressure values are transferred into solid matrix deformation model and begins next iterative loop. In this way, the flow and deformation of oil reservoir can be simulated. 

When the inlet assumptions state that water is entering the GDL at its interface with the catalyst layer, further clarification must be made between what has been called the uniform flux assumption and the uniform pressure assumption. The imiform flux assumption includes an individual source of liquid water for every inlet throat along the GDL/catalyst layer interface, while the uniform pressure assumption includes only a single source of liquid water that is connected to each inlet throat along the GDL/catalyst layer interface. Pltysically, the uniform pressure assumption assumes that there is a water cluster outside the GDL with negligible hydraulic resistance from one side to the other. Due to the microstracture of the catalyst layer, this scenario would approximate reality only if a pocket of liquid water could form between the catalyst layer and the GDL. Conversely, the uniform flux assumption assumes no hydraulic connectivity outside of the GDL between inlet locations. A compromise between these two assumptions was made by Hinebaugh and Bazylak in a 2D stmctured pore network model of GDL invasion, where the first row of pores and throats within the GDL is initialized as fully saturated. Similar to the uniform flux assumption, a liquid water source was... 

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