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It is important to understand the influence of gas transport properties on the process of urea gas decomposition in the modeling of a urea-SCR system. The purpose of this study is to find the gas transport property that exerts the strongest influence on the process of urea gas decomposition in a urea-SCR system using a three-dimensional model with the laminar flow of incompressible viscous gas at a steady-state condition by the SIMPLE algorithm. It is found that the gas transport properties which have the strongest influence on the process of urea gas decomposition in a urea-SCR system are the density and molecular diffusivity. It is also found that the influence of density is stronger than the molecular diffusivity at low temperature ranges. In contrary, the molecular diffusivity has stronger influence at high temperature ranges comparing with the density.

A comprehensive three-dimensional modeling for a single channel of SCR monolith reactor is performed with the laminar flow of viscous gas by the SIMPLE algorithm. The main advantage of this modeling approach is that the processes in the gas phase, washcoat layer and solid substrate are calculated simultaneously by a three-dimensional steady-state simulation. The detailed simulation of SCR monolith reactor may help to understand the complex interactions between various physical and chemical processes that occur in the reactor channel. The washcoat layer is represented by a porous medium. The non-isothermal diffusion and reaction processes are calculated in the waschoat layer by suppressing the convective term of the species transport equation. The effects of pore diffusion and mass transfer on the gas phase which usually lumped into the gas-solid mass and heat transfer coefficients are directly calculated by this fully distributed model.

A three-dimensional model with the laminar flow of an incompressible viscous gas at a steady-state is developed to simulate a urea-SCR system by the SIMPLE algorithm. A porous medium coated by a metal-oxide-based catalyst is considered in this study. The flow field and chemical reactions inside the reactor are calculated simultaneously by a porous medium approach. In a urea-SCR modeling, the gas transport properties exist as parameters in each of the conservation equations. The evaluations of density, diffusion coefficients, viscosities, thermal conductivities and specific heats are required to select the most suitable gas transport properties in a numerical modeling of a multi-component gaseous mixture and chemically reacting flow.

Selective catalytic reduction (SCR) and diesel particulate filter (DPF) as a compact system are used to reduce NOx and soot emissions, respectively. The aim of this study is to develop a SCR catalytic filter device for reducing simultaneously NOx and soot emissions from a combustor. In order to attain the optimal NOx conversion, the amount of ammonia must be managed to the amount of NOx on catalyst surface. If the amount of ammonia is higher than that of NOx, ammonia slip will be presented. Therefore, the uniform ammonia distribution around the catalyst is one of the challenges for the SCR application. Temperature is also a sensitive parameter in the reaction rate of NOx with ammonia. In this paper, the heating effect on the gaseous flow in the SCR catalytic filter device is studied with the uniformity of ammonia distribution. As a result, it is found that the temperature around catalytic filters is lower at Re = 4255 than that at Re = 64.

Minimizing the cylinder wear and the consumption rate of cylinder oil in a large two-stroke diesel engine is of great economic importance. A motor-driven cylinder lubricator for Sulzer RT-flex large two-stroke diesel engines developed by authors is in need of mounting a quill system to lubricate cylinder parts for smoother operation. In order to apply a common-rail lubricating system to the developed cylinder lubricator as the second research step, the mechanical quill system with a progressively quantitative distributor is improved in the electronically controlled quill system with an accumulating distributor. In this study, the effects of lubricator motor speed, plunger stroke and cylinder back pressure on oil feed rate, maximum discharge and delivery pressures are experimentally investigated by using the electronically controlled quill system with an accumulating distributor in the developed cylinder lubricator.

The effects of recirculated exhaust gas on the wear of piston and piston rings were investigated by the experiment with a two-cylinder, four-cycle, indirect injection diesel engine operating at 75% load and 1600 rpm. For the purpose of comparison between the wear rates of the two cylinders with and without EGR, the recirculated exhaust gas was sucked into one of two cylinders after the soot contents in exhaust emissions were removed by an intentionally designed cylinder-type scrubber equipped with 6 water injectors (A water injector has 144 nozzles of 1.0 mm diameter), while only the fresh air was inhaled into the other cylinder. These experiments were carried out with the fuel injection timing fixed at 15.3° BTDC.

The effects of recirculated exhaust gas on the characteristics of NOx and soot emissions under a wide range of engine loads are experimentally investigated using a four-stroke, four-cylinder, indirect injection, water-cooled marine diesel engine operating at two engine speeds. The aim of this study is to develop the EGR control system for reducing NOx and soot emissions simultaneously in diesel engines. The EGR system is used to reduce NOx emissions. And a novel diesel soot-removal device with a cylinder-type scrubber for the experiment system is specially designed and manufactured to reduce soot contents in the recirculated exhaust gas to the intake system of the engine. It is found that NOx emissions decrease markedly, especially at higher loads, while soot emissions increase owing to the drop of intake and exhaust oxygen concentrations, and the rise of equivalence ratio as the EGR rate is elevated.