The influence of coal-blending methods, such as out-furnace and in-furnace methods, on unburned carbon and NO emissions of blending coal combustion in a drop-tube furnace (DTF) has been analyzed using experimental and numerical approaches for binary coals (sub-bituminous and bituminous coals) used by Korean power plants. In the out-furnace method, as the blending ratio of sub-bituminous coal based on bituminous coal (SBR) increases up to 50%, the unburned carbon fraction gradually decreases. The worst condition is found at a SBR of 75%, which is caused by the occurrence of highly oxygen-deficient conditions in the furnace. Furthermore, the emission index of NO (EINO) is proportional to the SBR. In addition, the in-furnace blending method is applied using a modified DTF to improve the efficiency of unburned carbon fractions and the involvement of NO emissions. The results show that unburned carbon fractions as well as the EINO decrease over time because of improvements in oxygen deficiency and NO reduction mechanisms. The numerical modeling strongly supports these phenomena and provides insights into the mechanisms that affect the blending methods during the combustion of coal blends.
A gerotor pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, construction, and other various applications. In particular, the pump is an essential machine element that feeds lubricant oil in an automotive engine. The main components of the pump are the two rotors. Usually, the outer one is characterized by lobes with a circular shape, while the inner rotor profile is determined as a conjugate to the other. In this study, the design optimization has been carried out to determine the design parameters that maximize the specific flow rate and minimize the flow rate irregularity. The integrated system, which is composed of three main modules, has been developed through AutoLISP, Visual Basic language, and the CAD method, and considers various design parameters. An optimally designed model for a general type of gerotor pump has been generated and experimentally verified for its pump performances. Results obtained using the system enable the designer and manufacturer of the oil pump to be more efficient in this field.
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