【作者】 李琦；

【导师】 刘魁星；

【作者基本信息】 天津大学 ， 工程硕士（专业学位）， 2020， 硕士

【摘要】 变风量空调系统自20世纪60年代中期问世以来,以其节能、舒适、灵活等特点在美国、欧洲、日本等发达国家和地区进行了应用尝试和推广普及,其在美国高层建筑中的使用率可达90%以上。但变风量空调系统及其控制技术在我国的应用效果并不理想。由于变风量空调结构及控制方法较为复杂,其运行中故障隐蔽,而目前国内对于既有系统的故障诊断主要集中于硬件故障诊断,对控制逻辑设计问题及人员操作不当引发的故障研究较少。同时,变风量空调系统各参数之间存在不同程度的耦合关系,易造成系统水力失调从而达不到预期控制效果。本文首先介绍变风量空调系统的硬件组成、系统结构及控制方法,从系统结构及工作原理的角度出发总结归纳变风量空调系统运行可能产生的各类硬件软件故障;阐述系统各监控参数状态与故障类型的联系,说明各类故障下的参数表现;形成“硬件故障诊断—控制逻辑诊断—人为操作诊断”的变风量空调系统故障诊断方法。随后,探究影响变风量空调系统控制效果的因素。从系统水力特性、控制参数、控制方法三个方面出发,利用Trnsys、Matlab、Flowmaster仿真软件建立变风量空调系统模型,量化分析各因素对流量分配和温度控制的影响。探究发现,各末端所受影响主要来自所处之路其他末端阀门调节,影响程度约达18.75%,来自其他支路末端的影响仅约0.82%。控制参数方面,PID参数选择对系统稳定性和快速性有明显影响,控制周期增长可使系统稳定性增强,但快速性减弱。控制方法方面,受自身设计制约,定静压法和总风量法对负荷波动较大的工况控制失效。变静压法可较好适应各工况变化,但其根据末端阀位变频的控制方法使系统波动较大。定静压、变静压、总风量三种方法对与设计负荷不符的工况温度可控时长占比分别为35.51%、75.45%、43.21%。基于对变风量空调系统控制效果影响因素的研究,提出一种基于模糊控制和通风网络的新型控制方法。对变风量空调系统的控制结构进行调整,在此基础上采用通风网络计算系统管网流量分配,引入模糊控制计算末端需求风量。利用变风量空调系统仿真实验平台仿真软件对比定静压控制法、变静压控制法、总风量法与通风网络法对于变风量空调系统的控制效果。评价指标包括温度可控时长占比及系统能耗。实验表明,设计负荷工况下,本文所提新型控制方法温度可控时长占比为100%,较定静压法、总风量法分别节能18.23%、11.42%。在负荷波动工况下温度可控时长占比93.33%,优于变静压法的75.45%,且二者能耗水平相似。更多还原

【Abstract】 Since its advent in the mid-1960s,the variable air volume air conditioning system has been tried and popularized in developed countries and regions such as the United States,Europe,and Japan due to its energy saving,comfort,and flexibility,and its utilization rate in high-rise buildings in the United States Up to 90%.However,the application effect of variable air volume air conditioning system and its control technology in China is not ideal.Due to the complicated structure and control method of variable air volume air conditioners,the faults are concealed during operation.At present,the domestic fault diagnosis for existing systems is mainly focused on hardware fault diagnosis,and there are few studies on faults caused by control logic design problems and improper personnel operation.At the same time,there are different degrees of coupling relationship between the parameters of the variable air volume air conditioning system,which is easy to cause the system hydraulic imbalance and fail to achieve the expected control effect.This article first introduces the hardware composition,system structure and control method of the variable air volume air conditioning system.From the perspective of the system structure and working principle,it summarizes various hardware and software failures that may occur during the operation of the variable air volume air conditioning system;The type of connection explains the parameter performance under various types of faults;it forms the fault diagnosis method of VAV air-conditioning system based on "hardware fault diagnosis-control logic diagnosis-human operation diagnosis".Then,explore the factors that affect the control effect of the variable air volume air conditioning system.Starting from the three aspects of system hydraulic characteristics,control parameters,and control methods,Trnsys,Matlab,and Flowmaster simulation software are used to establish a variable air volume air conditioning system model to quantitatively analyze the impact of various factors on flow distribution and temperature control.The investigation found that the impact of each end is mainly from the valve adjustment of the other end of the road,the degree of impact is about 18.75%,and the influence from the other branch ends is only about0.82%.In terms of control parameters,the selection of PID parameters has a significant impact on the stability and rapidity of the system.The increase of the control period can enhance the stability of the system,but the rapidity decreases.In terms of control methods,subject to its own design constraints,the static pressure method and the total air volume method have failed to control the conditions with large load fluctuations.The variable static pressure method can better adapt to changes in various working conditions,but its control method based on the frequency conversion of the terminal valve position makes the system fluctuate greatly.The three methods of constant static pressure,variable static pressure,and total air volume account for 35.51%,75.45%,and 43.21% of the temperature controllable durations that are inconsistent with the design load.Based on the research on the influencing factors of the control effect of variable air volume air conditioning system,a new control method based on fuzzy control and ventilation network is proposed.The control structure of the variable air volume air conditioning system is adjusted,on this basis,the ventilation network calculation system pipe network flow distribution is adopted,and fuzzy control is introduced to calculate the terminal demand air volume.The control effect of variable static air pressure control method,variable static pressure control method,total air volume method and ventilation network method on variable air volume air conditioning system was compared by using simulation software of variable air volume air conditioning system simulation experiment platform.The evaluation indicators include the proportion of temperature controllable duration and system energy consumption.Experiments show that under the design load condition,the new control method proposed in this paper accounts for 100% of the temperature controllable time,which is 18.23% and 11.42% less energy than the static pressure method and the total air volume method.Under load fluctuation conditions,the temperature controllable duration accounted for 93.33%,which was better than 75.45% of the variable static pressure method,and the energy consumption levels of the two were similar..更多还原