To solve the dead⁃zone in the output flow curve of the proportional flow valve without displacement sensor,a dead⁃zone compensation approach is proposed in this paper.Instead of detection and feedback of the valve spo...To solve the dead⁃zone in the output flow curve of the proportional flow valve without displacement sensor,a dead⁃zone compensation approach is proposed in this paper.Instead of detection and feedback of the valve spool position,the proposed approach adopted the pressure drop across the valve metering orifice to accomplish the dead⁃zone compensation.The first step was to test and get the_(max)imum output flow,Q_(max),at a preset reference pressure drop,such asΔP_(0).The next step was to construct the target compensation flow curve,which is a line through(0,0)and(ΔP_(0),Q_(max)).Then a compensation law was designed to approach the target curve.However,the research results show that the above strategy caused over⁃compensation once the actual pressure drop deviated fromΔP_(0).Thus a correction coefficient,β,was presented to correct the initial compensation law as the pressure drop deviated fromΔP_(0).For example,the test results indicate that the corrected compensation approach could reduce the dead⁃zone from 53.9%to 3.5%at a pressure drop of 1 MPa;as the pressure drop was increased to 5 MPa,the dead⁃zone was reduced from 51.7%to 3.5%.Therefore,the following conclusions can be drawn:the proposed compensation approach is feasible,which can effectively reduce the dead⁃zone and improve the output flow static performance of the proportional flow valve without spool displacement feedback.展开更多
The carrier anaerobic baffled reactor (CABR),which combines with the characteristics of ABR and the advantages of biofilm reactor,is a suitable technology for decentralized domestic sewage treatment in rural areas of ...The carrier anaerobic baffled reactor (CABR),which combines with the characteristics of ABR and the advantages of biofilm reactor,is a suitable technology for decentralized domestic sewage treatment in rural areas of China.In order to improve the treatment efficiency and reduce the investment,it is essential to optimize the structure of CABR.On the basis of our study and analysis of hydromechanics and chemical reaction engineering,the CABR tended to show a state of plug flow as the number of compartments in the CABR increased.The CABRs had good structural performance,with a dead zone ranging from 8.04%—12.69% at the hydraulic retention time (HRT) of 48 h.In terms of chemical reaction engineering,the reaction rate of CABRs with 4,6,8 and 12 compartments were equivalent to that of the CSTRs of 148.35%,181.82%,175.40% and 185.81% times volume,respectively.When the effectiveness and capacity of the reactor were considered,a CABR with 6 compartments was found to be optimal.展开更多
在唐山电网电压无功优化闭环控制系统投运初期,发现了母线电压遥测刷新缓慢和跳变问题并导致相应厂站闭锁的情况,为提高自动电压控制(Automatic Voltage Control,AVC)闭环运行的可靠性,提出了解决方法。文章首先阐述了AVC系统应用情况,...在唐山电网电压无功优化闭环控制系统投运初期,发现了母线电压遥测刷新缓慢和跳变问题并导致相应厂站闭锁的情况,为提高自动电压控制(Automatic Voltage Control,AVC)闭环运行的可靠性,提出了解决方法。文章首先阐述了AVC系统应用情况,然后分析了导致AVC闭锁的遥测问题原因,提出解决问题的思路即建立遥测采集传输处理结构图,并结合唐山电网特点提出了遥测死区设置问题和处理跳变问题的措施和流程,最后通过实例分析对提出的方法进行了效果验证。展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.51775362 and 51805350)the Natural Science Foundation of Shanxi Province(Grant No.201801D221226).
文摘To solve the dead⁃zone in the output flow curve of the proportional flow valve without displacement sensor,a dead⁃zone compensation approach is proposed in this paper.Instead of detection and feedback of the valve spool position,the proposed approach adopted the pressure drop across the valve metering orifice to accomplish the dead⁃zone compensation.The first step was to test and get the_(max)imum output flow,Q_(max),at a preset reference pressure drop,such asΔP_(0).The next step was to construct the target compensation flow curve,which is a line through(0,0)and(ΔP_(0),Q_(max)).Then a compensation law was designed to approach the target curve.However,the research results show that the above strategy caused over⁃compensation once the actual pressure drop deviated fromΔP_(0).Thus a correction coefficient,β,was presented to correct the initial compensation law as the pressure drop deviated fromΔP_(0).For example,the test results indicate that the corrected compensation approach could reduce the dead⁃zone from 53.9%to 3.5%at a pressure drop of 1 MPa;as the pressure drop was increased to 5 MPa,the dead⁃zone was reduced from 51.7%to 3.5%.Therefore,the following conclusions can be drawn:the proposed compensation approach is feasible,which can effectively reduce the dead⁃zone and improve the output flow static performance of the proportional flow valve without spool displacement feedback.
文摘The carrier anaerobic baffled reactor (CABR),which combines with the characteristics of ABR and the advantages of biofilm reactor,is a suitable technology for decentralized domestic sewage treatment in rural areas of China.In order to improve the treatment efficiency and reduce the investment,it is essential to optimize the structure of CABR.On the basis of our study and analysis of hydromechanics and chemical reaction engineering,the CABR tended to show a state of plug flow as the number of compartments in the CABR increased.The CABRs had good structural performance,with a dead zone ranging from 8.04%—12.69% at the hydraulic retention time (HRT) of 48 h.In terms of chemical reaction engineering,the reaction rate of CABRs with 4,6,8 and 12 compartments were equivalent to that of the CSTRs of 148.35%,181.82%,175.40% and 185.81% times volume,respectively.When the effectiveness and capacity of the reactor were considered,a CABR with 6 compartments was found to be optimal.
文摘在唐山电网电压无功优化闭环控制系统投运初期,发现了母线电压遥测刷新缓慢和跳变问题并导致相应厂站闭锁的情况,为提高自动电压控制(Automatic Voltage Control,AVC)闭环运行的可靠性,提出了解决方法。文章首先阐述了AVC系统应用情况,然后分析了导致AVC闭锁的遥测问题原因,提出解决问题的思路即建立遥测采集传输处理结构图,并结合唐山电网特点提出了遥测死区设置问题和处理跳变问题的措施和流程,最后通过实例分析对提出的方法进行了效果验证。
