Advanced Materials Research Vols. 516-517

Abstract: The rapid spreading of poisonous smoke is the main reason which causes death in ship fires. Ships always have long tunnels to traveling passengers or cargos. Because of their longness and straightness, smoke diffuses rapidly. Fire doors are used to stop the smoke from spreading into other parts in vessels. When the fire doors are closed, the way for evacuation is also closed. So it’s important for the professionals to develop a kind of smoke-preventing device which can let people pass by when stopping the smoke. The air curtain is a kind of smoke isolating device which is used to decrease the heat exchange in supermarket or freezer. This paper analyzes flow field, the heat control and the smoke isolating ability of air curtain used in the ships’ long tunnels with different jet angles and initial velocities. At last, a suitable angle is proposed.

Abstract: The application of separated over-fire air (SOFA) in coal-fired boiler results in significant decrease of NOx emission but increases the trend of fireside water wall high temperature corrosion and incomplete combustion of pulverized coal. In order to meet the balance between low NOx emission and high boiler thermal efficiency, the main factors of air staging including SOFA flow, SOFA jet velocity and SOFA jet height were experimented on a 600MWe boiler. At the same time, the main components of flue gas beside the water wall were measured to evaluate the trend of high temperature corrosion. By comprehensive analysis, the optimum running mode of SOFA is concluded: (a) 75% of normal SOFA flow is suggested to reduce the trend of high temperature corrosion; (b) higher SOFA velocity is better for higher boiler thermal efficiency; (c) higher SOFA jet height is beneficial to the reduction of NOx emission.

Abstract: In this paper, a thermal protection system (TPS) of opposing jet combined with a forward-facing cavity in hypersonic flow was investigated numerically. The flow field parameters and heat flux distribution along the outer body surface are obtained. The thermal protection efficiency of the combined TPS and the single opposing jet TPS was compared. The numerical results shows that this combined TPS has a good effect on cooling the nose of hypersonic vehicle. The recirculation region plays an pivotal role for the reduction of heat flux. The exist of the cavity strengthen the cooling efficiency.

Abstract: In this study, a process model for thermal balance calculation of sludge drying-incineration system was constructed by spreadsheet software. Auxiliary fuel and total energy consumption of sludge drying-incineration and sludge direct incineration was calculated respectively. The result indicated that sludge moisture content of 60 wt.% was recommended for incineration, and that sludge drying-incineration consumed much less energy than sludge direct incineration when sludge moisture content was higher than 60 wt.%. The process model was proved to be high efficient, convenient and user-friendly in this study.

Abstract: This paper presented the numerical simulations on Multiple Ground Heat Exchangers. The two coupled solutions were solved iteratively at each time step, and the simulated ground temperature was calibrated using a cylindrical source model by adjusting the grid spacing and adopting a load factor of 1.047 in the difference equation. With constant load applied to a single tube. The ground temperature profiles were not similar at different distances from the tube. The introduction of time schedule revealed a discrepancy between the load applied to the ground heat exchanger and that transferred from the tube to the ground, which was usually assumed to be the same when using analytical models. Hence, in designing a large Ground source heat pump system, the present method should give more precise results in dynamic simulation.

Abstract: In order to overcome the difficulty of easily falling into the local minimum solution during the optimization process of heat exchanger network which is not considered fixed investment costs, an innovative method was presented. The total areas of local minimum solution were distributed equally, and then the distributed areas were assigned to initial areas for further optimization. The better local minimum solution was sought out after jumping out of local minimum solution. Through some case study, it presents that this optimization method is able to obtain better optimization results which is more suitable to industrial applications.

Abstract: Aiming at high power consumption by auxiliaries of circulating fluidized bed (CFB) boiler, combustion tests were carried out on a 300MW inferior anthracite fired CFB boiler to decrease the bed material inventory via energy saving combustion technologies for CFB boiler based on fluidization reconstruction. The effects of fluidization reconstruction on boiler performance improvement were analyzed. Application practices show that after fluidization reconstruction, the power consumed by auxiliaries of the CFB boiler decreases obviously. Auxiliary power ratio of the 300MW boiler unit has been reduced from 6.1% to 4.3%. The erosion of boiler heating surface has been alleviated obviously.

Abstract: Rules for non-orthogonal borders of irregular domain is the thorny issues when using analytical method for solving mathematical and physical equations. On the basis of solution in the form of separated variables, the border of arbitrary shape with non-orthogonal boundary will be separated into a limited number of discrete points, and then direct assignment for the form solution at each of the discrete points on the border according to boundary conditions, at every discrete points on the border can establish an equation. If the number of discrete points on the border is the same with truncated series after retained series, all coefficients of the form solution can be determined and the problem solved. This paper use Laplace equation as an example to illustrate Collocation Trefftz Method can solve certain steady-state heat conduction problems within non-orthogonal border and irregular domain.

Abstract: Rules for nonlinear borders of irregular domain is the thorny issues when using analytical method for solving mathematical and physical equations. On the basis of solution in the form of separated variables, the border of arbitrary shape with non-orthogonal boundary will be separated into a limited number of discrete points, and then direct assignment for the form solution at each of the discrete points on the border according to boundary conditions, at every discrete points on the border can establish an equation. If the number of discrete points on the border is equal with truncated series after retained series, all coefficients of the form solution can be determined and the problem solved. This paper use Laplace equation as an example to illustrate Collocation Trefftz Method can solve certain steady heat conduction problems within irregular domain with non-linear border.

Abstract: In order to enlarge the operating range at HCCI mode and explore the scientific methods to realize the ultra-low emission with DME as alternative fuel. Experimental investigation on the realization of PCCI-DI combustion is carried out on a single cylinder and naturally aspirated direct injection diesel engine. The method to achieve the PCCI-DI mode is that feeding part of DME into intake pipe to produce Pre-mixed homogeneous mixture and injecting the other part of the DME fuel into the combustion chamber by the original fuel injection device in the late stage of compression stroke. Results indicate that the engine can be operated at a wider range of speeds and loads at PCCI-DI mode. The brake thermal efficiency increases and NO_x emission reduces. However, HC and CO emission increase. It is also indicated from experiments that NO_x, HC and CO emission increase with an increase of DME premixed quantity. Furthermore, the optimum fuel supply advance angle for PCCI-DI mode could be delayed 6~8 °CA on the base of DME DI mode.