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28 results on '"Zhang, Junshen"'

19. A Health Status Assessment Method of Fluid Loop System Based on Hierarchical Multi-Information Fusion.

Author

Li, Rui, Zhang, Junshen, Fang, Hongzheng, and Zhang, Qing

Subjects
*DISTRIBUTION (Probability theory), *SUPPORT vector machines, *FAULT diagnosis, *FLUIDS, *MEMBERSHIP functions (Fuzzy logic)
Abstract

As a kind of thermal control device, fluid loop systems must operate with the demands of high safety, high reliability, and long life. In order to accurately assess the health status of fluid loop systems, a hierarchical multi-information fusion (HMIF) method is proposed in this paper. Considering that fluid loop systems generally have distinct structural hierarchies, the health evaluation process in this method is divided into three levels, which are the indicator level, the component level, and the system level. In the evaluation process, the health indices are, respectively, constructed to quantify the health status at the three levels. At the indicator level, One-Class support vector machine algorithm is used to obtain the distribution space of each state monitoring indicator under a normal state. The indicator-level health indices are evaluated by calculating the ratio of the data located in the distribution space to the overall data. At the component level, a fuzzy theory is used to calculate the health indices of the component level. Health indices at the indicator level are first converted to membership degree by membership degree function. Then, the evaluation fusion strategy is used to deduce the membership degree of the component level. The health indices at the component level are obtained from the mapping relationship between the membership degree and the health index. At the system level, an adaptive weight adjustment strategy is proposed to fuze all component-level health indices. Taking a practical fluid loop system as an example, health indices at the three levels evaluated by the HMIF method are compared with the actual status. The results indicate that the proposed method can correctly judge the health state of the system and provide a reference for the maintenance and fault diagnosis of fluid loop systems. [ABSTRACT FROM AUTHOR]

Published
2024
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25. Numerical Method and Its Application to Coupled System with Chemical Reaction, Fluid Flow and Heat Transfer: A Case Study of Shell-and-Tube Reactor

Author

Cheng Kang, Ke Wu, Xin Zhang, Chi Zhang, Zhang Junshen, and Kai Zhu

Subjects
Exothermic reaction, Thermal science, Computer science, Turbulence, business.industry, Baffle, Mechanics, Heat transfer coefficient, Computational fluid dynamics, Concentric tube heat exchanger, Inductor, Volumetric flow rate, Laminar flow reactor, Physics::Fluid Dynamics, Thermal, Heat exchanger, Heat transfer, Fluid dynamics, business, Reaction tube, Shell and tube heat exchanger
Abstract

A new method of collaborative simulation of chemical reaction, fluid flow and heat transfer based on OpenFOAM is proposed. Then a case study of shell-and-tube reactor for a single shell and several reaction tubes pass reactor with a variable number of baffles and turbulent flow is performed. The results are observed to be sensitive to the turbulence model selection. The best turbulence model among the ones considered is determined by comparing the CFD results of heat transfer coefficient, outlet temperature and pressure drop with the Bell -- CDelaware method results. For two baffle cut values, the effect of the baffle spacing to shell diameter ratio on the heat exchanger performance is investigated by varying flow rate. The temperature distribution of the reaction tube is influenced by thermal environment of both shell and tube side, and optimizing the fluid flow in shell side to conform to the exothermic characteristics of the reaction tube can effectively improve the temperature uniformity of the reaction tubes.

Published
2015

26. Adaptive Critic Design Based Control of Tunnel Ventilation System with Variable Jet Speed

Author

Zhang Junshen, Zhiyi Huang, Ke Wu, Kai Zhu, Xin Zhang, Chi Zhang, Cheng Kang, and Qinmin Yang

Subjects
Pollutant, Vehicle dynamics, Jet (fluid), Variable (computer science), Artificial neural network, Control theory, Computer science, Airflow, Energy consumption, Simulation
Abstract

In this paper, an adaptive critic design (ACD) based control algorithm is proposed for road tunnel ventilation systems with jet fans. Firstly, a comprehensive dynamic model is established for control purpose, which considers both the static and dynamic nonlinearities between the pollutant concentration and the jet speed or the air flow inside the tunnel. Vehicle speed and density are also integrated into the model as system external disturbances. To cope with the time-varying model parameters and unknown system uncertainties, one artificial neural network (NN) unit is employed in controlling the jet fans to regulate the pollutant concentration to a desired level, even in the presence of varying working conditions. An additional NN is utilized to approximate the cost-to-go function required for the performance optimization. The proposed scheme is also verified and compared with traditional control design in simulation environment. The simulation results substantiate the conclusion that the adaptive controller can achieve a better regulation performance along with less energy consumption.

Published
2015

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