Based on the fact that the pressure loads generated in hydrogen combustion process may jeopardize the integrity of the containment during severe accident, and the changing rate as well as the maximum value of the pres...
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In this study, the mechanisms that cause heat split, a specific phenomenon in dual-cooled annular fuel elements, were investigated. On the basis of thermal resistance analysis, the developing process of heat split phe...
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In this study, the mechanisms that cause heat split, a specific phenomenon in dual-cooled annular fuel elements, were investigated. On the basis of thermal resistance analysis, the developing process of heat split phenomenon was summarized. It was found that thermal expansion, fuel densification, swelling, creep, relocation and fission gas release are the original parameters driving the development of heat split. Due to these factors, thermal resistances for heat flux to internal and external channels change with the operating time, which results in heat split. Furthermore, the theoretical simulation on heat split was performed by FROBA-ANNULAR, which is a coupled thermal–mechanical analysis code for dual-cooled annular fuel elements. Key parameters at different burnup stages, including gap size, gap conductance, temperature profile, coolant flux and heat flux were obtained. The calculation result shows that the fraction of heat flux to the internal cooling channel experiences complicated variation at the range of 32.9–39.7%. In addition, it was found that heat split does not match with the coolant split, especially at the lower burnup stage. Asymmetric heat transfer occurred because of the imbalance between heat split and coolant split, resulting in a substantial asymmetric temperature profile. Furthermore, heat split exerts an influence on DBNRs of inner and outer channels, although the computational values were still within the allowable limits.
AThis paper presents a study of multi-objective path planning. The goal is to find paths and meanwhile minimize multiple conflicting performance indices. Terrain information is well known priori. The algorithm about c...
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AThis paper presents a study of multi-objective path planning. The goal is to find paths and meanwhile minimize multiple conflicting performance indices. Terrain information is well known priori. The algorithm about cell mapping method is presented as follows: Constructing cell space converts continuous domain into discrete domain and all cells are stratified. Then transfer indices data from inner layer to outer layer. Next evolution all over the space is proposed for finding all cells' complete Pareto front. Subsequently covering region of optimal paths can be obtained. The indices information are stored in database. Finally a global information database about Pareto front is constructed by the cell mapping method. All cells have complete Pareto front and the number of corresponding optimal paths can be read from the Database. Covering region of optimal paths is presented. Case studies are presented to demonstrate the method.
The common rail fuel injection technology is widely applied in diesel engines to reduce PM and NO emissions. Proper control of common rail pressure can lead to better fuel combustion efficiency and lower emissions. Th...
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The common rail fuel injection technology is widely applied in diesel engines to reduce PM and NO emissions. Proper control of common rail pressure can lead to better fuel combustion efficiency and lower emissions. The dynamics of the common rail system is usually complex, nonlinear and time varying. It is important to develop a reliable model of the common rail system in order to design optimal controls that are effective for different operational conditions including the start, idle and acceleration. In this study, we develop a model of the common rail system from experimental data. The model encompass several subsystems including the high-pressure pump and fuel injector. With the help of the model, we present a two-level multi-objective optimal control design. First, optimal common rail pressure profiles for various operational conditions are developed by minimizing the fuel combustion and emission, while maximizingthe power output. Second, the time varying common rail pressure profiles are tracked by a nonlinear feedback control. The nonlinear feedback control is optimally design to meet the objectives of minimum integrated tracking error and control energy. The performance of the proposed optimal control design is tested through simulation and experiments.
Engineering structures are often designed and optimized to meet multiple and possibly conflicting objectives such as the minimum weight and maximum strength. The merit of multiobjective optimization is to obtain a wid...
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Engineering structures are often designed and optimized to meet multiple and possibly conflicting objectives such as the minimum weight and maximum strength. The merit of multiobjective optimization is to obtain a wide range of choices of structural design so that the best trade-off among different objectives can be achieved. This paper presents a multi-objective optimization of elastic beams for minimum radiated sound power and weight. The transfer matrix method is used to compute the structural and acoustic responses of the beam accurately andefficiently. Both Euler-Bernoulli and Timoshenko models are considered. The multi-objective particle swarm optimization technique is applied to search the Pareto optimal solutions representing various compromises between the weight and sound radiation. Several constraints are imposed, which substantially reduce the volume fraction of feasible solutions in the design space. Two cases of elastic beams with different boundary conditions are studied to demonstrate the multi-objective optimal designs of the structure. We have discovered that when the practical constraints such as the smoothness and lower bound of the fundamental frequency of the structure are imposed, the feasible solutions can be found only in a very small subset of the design space. Numerical results of multi-objective optimal design of non-uniform beams with two different boundary conditions are presented. We have shown that the optimized non-uniform beam indeed has smaller radiated sound power and radiation efficiency in the targeted frequency range as compared with the uniform beam of the same mass.
Saving energy without causing discomfort and without demanding human intervention is the need of the day. It is important to develop sensor systems which not only satisfy user requirements, but also take energy consum...
ISBN:
(纸本)9781450342636
Saving energy without causing discomfort and without demanding human intervention is the need of the day. It is important to develop sensor systems which not only satisfy user requirements, but also take energy consumption into consideration. In this demo, we present the sensing subsystems of a Smart Academic Environment, based upon the core concept of 'Observability' [1] which -- while satisfying user needs -- helps to reduce the number of sensors required.
According to former study on oxygen diffusion, Nb-Zr solid reaction and Uo2-zr solid reaction, models of oxidation, solid reaction in fuel meat and relocation of molten fuel meat are developed based on structure and m...
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ISBN:
(纸本)9781510811843
According to former study on oxygen diffusion, Nb-Zr solid reaction and Uo2-zr solid reaction, models of oxidation, solid reaction in fuel meat and relocation of molten fuel meat are developed based on structure and material properties of Uo2-zr plate. The new models can supply theoretical elements for safety analysis of core assembled with dispersion plate-type fuel under severe accident.
A coupled neutronics/thermal-hydraulics three dimensional code system SNTA is developed for SCWR core steady state analysis by modular coupling the improved neutronics nodal methodological code and SCWR thermal-hydrau...
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A 3rd generation reactor called HuaLong is developed by China National Nuclear Corporation (CNNC). S econdary passive system (PRS) is designed to remove the residual heat during 72 hours after the reactor trips. To ve...
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ISBN:
(纸本)9781510811843
A 3rd generation reactor called HuaLong is developed by China National Nuclear Corporation (CNNC). S econdary passive system (PRS) is designed to remove the residual heat during 72 hours after the reactor trips. To verify the ability of PRS system, the test facility ESPRIT is built in Chengdu which is 1:1 in heigh t and 1/62.5 in power. Tests are consisted by three Steady-states and one transient. One model of RELAP5 mod3.2 is developed and used to simulate the steady and transient tests. The results of RJELAP5 show con sistent with facility results, but the early phenomenon during transients is different between RELAP5 and tests as RELAP5 underestimates the direct-contact condensation power.
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