Spray-wall interaction

Han Z, Xu Z, Trugui N (2000) Spray/wall interaction models for multidimensional engine simulation. International Journal of Engine Research 1(1) 127-146. 

Kuhnke D (2004) Spray/Wall-Interaction Modelling by Dimensionless Data Analysis, PhD Thesis, Darmstadt University of Technology, Darmstad. 

D. Stanton, A. Lippert, R. D. Reitz, and C. J. Rutland. Influence of Spray-Wall Interaction and Fuel Films on Cold Starting in Direct Injection Diesel Engines. SAE Paper, 982584, 1998. 

F. Birkhold, U. Meingast, P. Wassermann, and O. Deutschmann. Analysis of the injection of urea-water-solution for automotive scr denox-systems Modeling of two-phase flow and spray/wall-interaction. SAE Technical Papers, 2006. cited By (since 1996)24. 

The boundary conditions for the spray equations specify the droplet-wall interactions, as well as the mass flow rate and the droplet distribution function at the nozzle exit. Additional details and references can be found in Ref. [4]. 

Keywords Atomization Correlations DepositiOTi E>rop Interaction Heat transfer Impinging spray Liquid deposition Multiple drop impacts Secondary thermodynamics Spray Spray-wall impact Statistics... 

Figure 25.11 Flow pattern and spray pattern in a test set-up for the determination of droplet-wall interactions.

The shielding blanket is composed of water-cooled steel modules, which are directly supported by the vacuum vessel and are effective in moderating the 14MeV neutrons, with a water-cooled copper mat bonded to the surface of the modules on the plasma side, and protected from interaction with the plasma by beryllium. Manufacturing considerations can be found elsewhere [48]. The first wall incorporates two start-up limiters located in two equatorial ports. With the aim to reduce cost and nuclear waste, the design includes a modular and separable first wall. This allows damaged or eroded blanket modules to be repaired inside the hot cell either by replacement of panels or by plasma spraying or other methods. 

Liquid fuel sprays are not yet fullj understood [310]. The atomization process of a liquid fuel jet [376 332 345 293 309], the turbulent dispersion of the resulting droplets [256 253 262 333 319], their interaction with walls [259 365], their evaporation and combustion [290] are phenomena occurring in LES at the subgrid scale and therefore require accurate modeling. 

Cross contamination encountered with desolvation systems has been greatly reduced by using a concentric sheath to prevent deposits on tube walls. It is important to note that nebulisers and spray chambers operate interactively and must be optimised as a unit rather than individually. There are, however, certain parameters that need to be considered in relation to the spray chamber ... 

In recent years a great many studies have reported on the dynamic systems where a drop of liquid is placed on a smooth solid surface. ° The system liquid drop-solid is a very important system in everyday life, for example, rain drops on tree leaves or other surfaces. It is also significant in all kinds of systems where a spray of fluid is involved, such as in sprays or combustion engines. The dynamics of liquid drop evaporation rate is of much interest in many phenomena. The liquid-solid interface can be considered as follows. Real solid surfaces are, of course, made up of molecules not essentially different in their nature from the molecules of the fluid. The interaction between a molecule of the fluid and a molecule of the boundary wall can be regarded as follows. The molecules in the solid state are not as mobile as those of the fluid. It is therefore permissible for most purposes to regard the molecules in the solid state as stationary. However, complexity arises in those liquid-solid systems where a layer of fluid might be adsorbed on the solid surface, such as in the case of water-glass. 

Shortening of high temperature interaction of a product (e.g., cooling of the spray-drying chamber walls, drying at a lower temperature in multistage systems). 

The remainder of the chapter focuses on the actual spray modeling. The exposition is primarily done for the RANS method, but with the indicated modifications, the methodology also applies to LES. The liquid phase is described by means of a probability density function (PDF). The various submodels needed to determine this PDF are derived from drop-drop and drop-gas interactions. These submodels include drop collisions, drop deformation, and drop breakup, as well as drop drag, drop evaporation, and chemical reactions. Also, the interaction between gas phase, liquid phase, turbulence, and chemistry is examined in some detail. Further, a discussion of the boundary conditions is given, in particular, a description of the wall functions used for the simulations of the boundary layers and the heat transfer between the gas and its confining walls. 

The description of a dispersed multiphase flow with chemical reactions leads to a complex system of differential and algebraic equations, which can only be solved by specifying appropriate boundary and initial conditions. For the gas phase equations, the boundary conditions are imposed on the gas velocity u, the temperature T, the turbulent kinetic energy k, and its dissipation e. The spray equations require conditions at the nozzle exit and for the interactions of the droplets with the walls. 

The source term in the film momentum equation is considered to account for the interaction between the impinging spray and the pre-existent liquid film. This is particularly important in SCR systems, since the spray axis is alway angled with respect to the normal direction of the pipe and mixer walls. For this reason, the contribution to the film momentum can be decomposed into two components one normal to the wall surface and the other one tangential (, laying on the same plane of the face representing the wall. The former can be included in the film pressure equation, since it acts as an increase of pressure due to the canceling of the momentum in that direction. The latter, instead, is considered in the momentum equation as follows (S u) ... 

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