Tianyi Zhao

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.