Jili Zhang

Study on the Performance of Sleeve Regulating Valve Based on the Valve Admittance Function

This paper presents a novel methodology to study the characteristic of the sleeve electric two-way regulating valves, applied in the HVAC systems. In this paper, the valve admittance is introduced by comparative analysis with electric circuit system. Experimental tests are proposed to obtain the valve admittance by measuring the differential pressure of the valve and the flow rate. Then, the relationship between valve admittance and valve opening is modeled. Based on established models and pipe network models, which have been applied in various flow water cycling systems, the working performance of the regulating valve throughout most of the plug travel was theoretically studied. This method was demonstrated by applying it to the test rig to provide predictive control of the flow rate. The results showed that the relative error was less than 2% with only one or two regulating processes.

Development of a distributed artificial fish swarm algorithm to optimize pumps working in parallel mode

The existing control systems for the parallel pumps in HVAC systems are mostly based on a centralized structure in which all the data from sensors and control instructions are processed by a master controller. This structure has somehow limited the stability, expandability, and the universality of the control system. The strategies are always case by case, ones which cannot be easily transplanted to other systems and when some devices are out-of-order the entire control system will be influenced. In the current article, a distributed control structure has been proposed for the parallel pumps in which the master controller is replaced by several independent distributed controllers cooperating together to handle the global task. An evolutionary algorithm artificial fish swarm algorithm has been transplanted to the proposed structure to optimize the pumps working in parallel mode. Simulation studies have been conducted based on the models of a physical pump system and the performance of the proposed algorithm is compared with other common heuristic algorithms in both effect and stability. The results show that distributed artificial fish swarm algorithm has inherited the characters of artificial fish swarm algorithm and it is more efficient in the calculation.

A distribute and self-tuning wireless environment monitoring system for buildings based on the Wi-Fi Direct technology

As the quality of building energy management systems has been taken seriously by more and more people, finding an efficient way to gather and release information for the system is of great importance. Compared with the wired monitoring system, the wireless system has many advantages, such as flexibility and economy, when applied in buildings. However, most wireless monitoring systems are composed of nodes with different functions and the communication protocols are not standard or transparent, which, therefore, is difficult to track the malfunctions and complicated for unprofessional users. In order to promote standardization of wireless networks applied in buildings and making it easier to manage and extend, the current article has developed a self-organized wireless network based on the Wi-Fi Direct technology to monitor the environment for large-scale buildings. In this network, all the nodes are identical in function and the communication is based on the Transmission Control Protocol/Internet Protocol. A distribute data processing mechanism to rectify the outliers is utilized in the network. The performance of the proposed network has been testified through both simulations and experiments. The results have shown that the proposed monitoring system has advantages, such as dynamic in structure, easy to extend, transparent in communication, and distributed in data processing.

Prediction of pollutants dispersion patterns around two adjacent urban road tunnels

Abstract Road tunnels have recently become prevalent in urban areas of China. In areas adjacent to these tunnels, air quality and human health are important public health concerns. As such, assessing pollutant dispersion and decay rates around tunnel portals in the surrounding environment is an important field of study. This study established a three-dimensional computational fluid dynamics (CFD) model containing two adjacent urban road tunnels, to estimate pollution dispersion characteristics outside the tunnels. The results indicate that, when pollutants were exhausted from the portals only, crossflow between the two adjacent tunnels was quite severe. The highest carbon monoxide (CO) concentration was nearly 50 ppm, exceeding the 10 ppm limit National Standard in China for 1 h exposure when exhaust shafts are absent. When shafts exhausted 80% of the pollutants from the tunnel portal, crossflow between the adjacent tunnels decreased to 10-50% of that without shafts. The simulation results demonstrate that the combination of shafts and portals was an effective and energy-saving strategy to exhaust pollution from adjacent super-long urban road tunnels. These findings increase our fundamental understanding and provide guidelines for evaluating pollutant exposure risk around tunnel portals, the design of tunnel exhaust shafts, and environmental planning purposes in urban environments. GRAPHICAL ABSTRACT