The fracture splitting method is an innovative processing technique in the field of the automobile engine connecting rod (con/rod) manufacturing. Compared with traditional method, the technique has remarkable advantages. It can decrease manufacturing procedures, reduce equipment and tools investment and save energy. Hence the total production cost is greatly reduced. Furthermore, the technique can also improve product quality and bearing capability. It provides a high quality, high accuracy and low cost route for producing connecting rods (con/rods). The method has attracted extensive attention and has been used in some types of con/rods manufacturing. The process and its key factors such as materials, notches for fracture splitting, fracture splitting conditions and fracture splitting equipment are discussed in detail.
Non-isothermal reactive transport in complicated porous media is diverse in nature and industrial applications. There are challenges in the modelling of multiple physicochemical processes in multiscale pore structures with various length scales ranging from nanometres to micrometres. This study focuses on coke combustion during in situ crude oil combustion techniques. A micro-continuum model was developed to perform an image-based simulation of coke combustion through a multiscale porous medium. The simulation coupled weakly compressible gas flow, species transport, conjugate heat transfer, heterogeneous coke oxidation kinetics and structural evolution. The unresolved nanoporous coke region was treated as a continuum, for which the random pore model, permeability model and species diffusivity model were integrated as sub-grid models to account for the sub-resolution reactive surface area, Darcy flow and Knudsen diffusion, respectively. A Pe–Da diagram was provided to present five characteristic combustion regimes covering the ignition temperature and air flux in realistic field operations and laboratory measurements. The present model proved to achieve more accurate predictions of the feasible ignition temperature than previous models. Compared with the air flux of
$\phi \sim O\textrm{(1) s}{\textrm{m}^\textrm{3}}(\textrm{air})\;{({\textrm{m}^\textrm{2}}\ \textrm{h})^{ - 1}}$
in the field, the increasing air flux in the laboratory transformed the combustion regime from diffusion-limited to convection-limited, which led to an overpredicted burning temperature. Reactive fingering combustion was analysed to understand the potential risks in some experimental measurements. The findings provide a better understanding of coke combustion and can help engineers design sustainable combustion methods. The developed image-based model allows other types of multiscale and nonlinear reactive transport to be simulated.
Summary
The high temperature organic Rankine cycle (ORC) has recently attracted much interest for its excellent performance in renewable energy utilization and industrial waste heat recovery. The thermal stability of working fluids is the important property for fluid selection studies because of the possible decomposition at high temperatures. Siloxanes are good selections for high temperature ORCs in previous studies. However, study on the thermal stability of siloxanes for high temperature ORCs is scant. This paper studied the thermal stability of siloxanes, using hexamethyldisiloxane (MM) as a representative fluid. An experimental method with two test systems was designed to identify the compositions of decomposition products. Linear siloxanes, such as octamethyltrisiloxane (MDM), were found to be the main decomposition products of MM. The influences of pressure, temperature, and time on the decomposition were then determined experimentally. The decomposition mechanism of MM and the influences of the decomposition on ORCs were also analyzed based on the experimental results.
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